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2750 lines
79 KiB
2750 lines
79 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* fs/fs-writeback.c |
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* |
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* Copyright (C) 2002, Linus Torvalds. |
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* |
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* Contains all the functions related to writing back and waiting |
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* upon dirty inodes against superblocks, and writing back dirty |
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* pages against inodes. ie: data writeback. Writeout of the |
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* inode itself is not handled here. |
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* |
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* 10Apr2002 Andrew Morton |
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* Split out of fs/inode.c |
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* Additions for address_space-based writeback |
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*/ |
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|
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#include <linux/kernel.h> |
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#include <linux/export.h> |
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#include <linux/spinlock.h> |
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#include <linux/slab.h> |
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#include <linux/sched.h> |
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#include <linux/fs.h> |
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#include <linux/mm.h> |
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#include <linux/pagemap.h> |
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#include <linux/kthread.h> |
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#include <linux/writeback.h> |
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#include <linux/blkdev.h> |
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#include <linux/backing-dev.h> |
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#include <linux/tracepoint.h> |
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#include <linux/device.h> |
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#include <linux/memcontrol.h> |
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#include "internal.h" |
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|
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/* |
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* 4MB minimal write chunk size |
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*/ |
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#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_SHIFT - 10)) |
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|
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/* |
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* Passed into wb_writeback(), essentially a subset of writeback_control |
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*/ |
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struct wb_writeback_work { |
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long nr_pages; |
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struct super_block *sb; |
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enum writeback_sync_modes sync_mode; |
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unsigned int tagged_writepages:1; |
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unsigned int for_kupdate:1; |
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unsigned int range_cyclic:1; |
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unsigned int for_background:1; |
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unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */ |
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unsigned int auto_free:1; /* free on completion */ |
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enum wb_reason reason; /* why was writeback initiated? */ |
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|
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struct list_head list; /* pending work list */ |
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struct wb_completion *done; /* set if the caller waits */ |
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}; |
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|
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/* |
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* If an inode is constantly having its pages dirtied, but then the |
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* updates stop dirtytime_expire_interval seconds in the past, it's |
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* possible for the worst case time between when an inode has its |
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* timestamps updated and when they finally get written out to be two |
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* dirtytime_expire_intervals. We set the default to 12 hours (in |
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* seconds), which means most of the time inodes will have their |
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* timestamps written to disk after 12 hours, but in the worst case a |
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* few inodes might not their timestamps updated for 24 hours. |
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*/ |
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unsigned int dirtytime_expire_interval = 12 * 60 * 60; |
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|
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static inline struct inode *wb_inode(struct list_head *head) |
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{ |
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return list_entry(head, struct inode, i_io_list); |
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} |
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|
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/* |
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* Include the creation of the trace points after defining the |
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* wb_writeback_work structure and inline functions so that the definition |
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* remains local to this file. |
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*/ |
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#define CREATE_TRACE_POINTS |
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#include <trace/events/writeback.h> |
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|
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EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage); |
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|
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static bool wb_io_lists_populated(struct bdi_writeback *wb) |
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{ |
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if (wb_has_dirty_io(wb)) { |
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return false; |
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} else { |
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set_bit(WB_has_dirty_io, &wb->state); |
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WARN_ON_ONCE(!wb->avg_write_bandwidth); |
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atomic_long_add(wb->avg_write_bandwidth, |
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&wb->bdi->tot_write_bandwidth); |
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return true; |
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} |
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} |
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|
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static void wb_io_lists_depopulated(struct bdi_writeback *wb) |
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{ |
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if (wb_has_dirty_io(wb) && list_empty(&wb->b_dirty) && |
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list_empty(&wb->b_io) && list_empty(&wb->b_more_io)) { |
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clear_bit(WB_has_dirty_io, &wb->state); |
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WARN_ON_ONCE(atomic_long_sub_return(wb->avg_write_bandwidth, |
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&wb->bdi->tot_write_bandwidth) < 0); |
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} |
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} |
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|
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/** |
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* inode_io_list_move_locked - move an inode onto a bdi_writeback IO list |
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* @inode: inode to be moved |
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* @wb: target bdi_writeback |
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* @head: one of @wb->b_{dirty|io|more_io|dirty_time} |
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* |
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* Move @inode->i_io_list to @list of @wb and set %WB_has_dirty_io. |
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* Returns %true if @inode is the first occupant of the !dirty_time IO |
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* lists; otherwise, %false. |
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*/ |
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static bool inode_io_list_move_locked(struct inode *inode, |
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struct bdi_writeback *wb, |
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struct list_head *head) |
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{ |
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assert_spin_locked(&wb->list_lock); |
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|
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list_move(&inode->i_io_list, head); |
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|
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/* dirty_time doesn't count as dirty_io until expiration */ |
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if (head != &wb->b_dirty_time) |
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return wb_io_lists_populated(wb); |
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|
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wb_io_lists_depopulated(wb); |
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return false; |
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} |
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|
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static void wb_wakeup(struct bdi_writeback *wb) |
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{ |
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spin_lock_bh(&wb->work_lock); |
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if (test_bit(WB_registered, &wb->state)) |
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mod_delayed_work(bdi_wq, &wb->dwork, 0); |
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spin_unlock_bh(&wb->work_lock); |
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} |
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|
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static void finish_writeback_work(struct bdi_writeback *wb, |
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struct wb_writeback_work *work) |
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{ |
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struct wb_completion *done = work->done; |
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|
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if (work->auto_free) |
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kfree(work); |
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if (done) { |
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wait_queue_head_t *waitq = done->waitq; |
|
|
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/* @done can't be accessed after the following dec */ |
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if (atomic_dec_and_test(&done->cnt)) |
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wake_up_all(waitq); |
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} |
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} |
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|
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static void wb_queue_work(struct bdi_writeback *wb, |
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struct wb_writeback_work *work) |
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{ |
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trace_writeback_queue(wb, work); |
|
|
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if (work->done) |
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atomic_inc(&work->done->cnt); |
|
|
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spin_lock_bh(&wb->work_lock); |
|
|
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if (test_bit(WB_registered, &wb->state)) { |
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list_add_tail(&work->list, &wb->work_list); |
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mod_delayed_work(bdi_wq, &wb->dwork, 0); |
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} else |
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finish_writeback_work(wb, work); |
|
|
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spin_unlock_bh(&wb->work_lock); |
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} |
|
|
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/** |
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* wb_wait_for_completion - wait for completion of bdi_writeback_works |
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* @done: target wb_completion |
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* |
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* Wait for one or more work items issued to @bdi with their ->done field |
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* set to @done, which should have been initialized with |
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* DEFINE_WB_COMPLETION(). This function returns after all such work items |
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* are completed. Work items which are waited upon aren't freed |
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* automatically on completion. |
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*/ |
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void wb_wait_for_completion(struct wb_completion *done) |
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{ |
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atomic_dec(&done->cnt); /* put down the initial count */ |
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wait_event(*done->waitq, !atomic_read(&done->cnt)); |
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} |
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|
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#ifdef CONFIG_CGROUP_WRITEBACK |
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|
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/* |
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* Parameters for foreign inode detection, see wbc_detach_inode() to see |
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* how they're used. |
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* |
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* These paramters are inherently heuristical as the detection target |
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* itself is fuzzy. All we want to do is detaching an inode from the |
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* current owner if it's being written to by some other cgroups too much. |
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* |
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* The current cgroup writeback is built on the assumption that multiple |
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* cgroups writing to the same inode concurrently is very rare and a mode |
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* of operation which isn't well supported. As such, the goal is not |
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* taking too long when a different cgroup takes over an inode while |
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* avoiding too aggressive flip-flops from occasional foreign writes. |
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* |
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* We record, very roughly, 2s worth of IO time history and if more than |
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* half of that is foreign, trigger the switch. The recording is quantized |
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* to 16 slots. To avoid tiny writes from swinging the decision too much, |
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* writes smaller than 1/8 of avg size are ignored. |
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*/ |
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#define WB_FRN_TIME_SHIFT 13 /* 1s = 2^13, upto 8 secs w/ 16bit */ |
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#define WB_FRN_TIME_AVG_SHIFT 3 /* avg = avg * 7/8 + new * 1/8 */ |
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#define WB_FRN_TIME_CUT_DIV 8 /* ignore rounds < avg / 8 */ |
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#define WB_FRN_TIME_PERIOD (2 * (1 << WB_FRN_TIME_SHIFT)) /* 2s */ |
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|
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#define WB_FRN_HIST_SLOTS 16 /* inode->i_wb_frn_history is 16bit */ |
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#define WB_FRN_HIST_UNIT (WB_FRN_TIME_PERIOD / WB_FRN_HIST_SLOTS) |
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/* each slot's duration is 2s / 16 */ |
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#define WB_FRN_HIST_THR_SLOTS (WB_FRN_HIST_SLOTS / 2) |
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/* if foreign slots >= 8, switch */ |
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#define WB_FRN_HIST_MAX_SLOTS (WB_FRN_HIST_THR_SLOTS / 2 + 1) |
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/* one round can affect upto 5 slots */ |
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#define WB_FRN_MAX_IN_FLIGHT 1024 /* don't queue too many concurrently */ |
|
|
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/* |
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* Maximum inodes per isw. A specific value has been chosen to make |
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* struct inode_switch_wbs_context fit into 1024 bytes kmalloc. |
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*/ |
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#define WB_MAX_INODES_PER_ISW ((1024UL - sizeof(struct inode_switch_wbs_context)) \ |
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/ sizeof(struct inode *)) |
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|
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static atomic_t isw_nr_in_flight = ATOMIC_INIT(0); |
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static struct workqueue_struct *isw_wq; |
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|
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void __inode_attach_wb(struct inode *inode, struct page *page) |
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{ |
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struct backing_dev_info *bdi = inode_to_bdi(inode); |
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struct bdi_writeback *wb = NULL; |
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|
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if (inode_cgwb_enabled(inode)) { |
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struct cgroup_subsys_state *memcg_css; |
|
|
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if (page) { |
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memcg_css = mem_cgroup_css_from_page(page); |
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wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC); |
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} else { |
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/* must pin memcg_css, see wb_get_create() */ |
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memcg_css = task_get_css(current, memory_cgrp_id); |
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wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC); |
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css_put(memcg_css); |
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} |
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} |
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|
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if (!wb) |
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wb = &bdi->wb; |
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|
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/* |
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* There may be multiple instances of this function racing to |
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* update the same inode. Use cmpxchg() to tell the winner. |
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*/ |
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if (unlikely(cmpxchg(&inode->i_wb, NULL, wb))) |
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wb_put(wb); |
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} |
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EXPORT_SYMBOL_GPL(__inode_attach_wb); |
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|
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/** |
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* inode_cgwb_move_to_attached - put the inode onto wb->b_attached list |
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* @inode: inode of interest with i_lock held |
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* @wb: target bdi_writeback |
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* |
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* Remove the inode from wb's io lists and if necessarily put onto b_attached |
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* list. Only inodes attached to cgwb's are kept on this list. |
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*/ |
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static void inode_cgwb_move_to_attached(struct inode *inode, |
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struct bdi_writeback *wb) |
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{ |
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assert_spin_locked(&wb->list_lock); |
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assert_spin_locked(&inode->i_lock); |
|
|
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inode->i_state &= ~I_SYNC_QUEUED; |
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if (wb != &wb->bdi->wb) |
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list_move(&inode->i_io_list, &wb->b_attached); |
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else |
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list_del_init(&inode->i_io_list); |
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wb_io_lists_depopulated(wb); |
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} |
|
|
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/** |
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* locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it |
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* @inode: inode of interest with i_lock held |
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* |
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* Returns @inode's wb with its list_lock held. @inode->i_lock must be |
|
* held on entry and is released on return. The returned wb is guaranteed |
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* to stay @inode's associated wb until its list_lock is released. |
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*/ |
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static struct bdi_writeback * |
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locked_inode_to_wb_and_lock_list(struct inode *inode) |
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__releases(&inode->i_lock) |
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__acquires(&wb->list_lock) |
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{ |
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while (true) { |
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struct bdi_writeback *wb = inode_to_wb(inode); |
|
|
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/* |
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* inode_to_wb() association is protected by both |
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* @inode->i_lock and @wb->list_lock but list_lock nests |
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* outside i_lock. Drop i_lock and verify that the |
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* association hasn't changed after acquiring list_lock. |
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*/ |
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wb_get(wb); |
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spin_unlock(&inode->i_lock); |
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spin_lock(&wb->list_lock); |
|
|
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/* i_wb may have changed inbetween, can't use inode_to_wb() */ |
|
if (likely(wb == inode->i_wb)) { |
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wb_put(wb); /* @inode already has ref */ |
|
return wb; |
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} |
|
|
|
spin_unlock(&wb->list_lock); |
|
wb_put(wb); |
|
cpu_relax(); |
|
spin_lock(&inode->i_lock); |
|
} |
|
} |
|
|
|
/** |
|
* inode_to_wb_and_lock_list - determine an inode's wb and lock it |
|
* @inode: inode of interest |
|
* |
|
* Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held |
|
* on entry. |
|
*/ |
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static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode) |
|
__acquires(&wb->list_lock) |
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{ |
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spin_lock(&inode->i_lock); |
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return locked_inode_to_wb_and_lock_list(inode); |
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} |
|
|
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struct inode_switch_wbs_context { |
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struct rcu_work work; |
|
|
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/* |
|
* Multiple inodes can be switched at once. The switching procedure |
|
* consists of two parts, separated by a RCU grace period. To make |
|
* sure that the second part is executed for each inode gone through |
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* the first part, all inode pointers are placed into a NULL-terminated |
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* array embedded into struct inode_switch_wbs_context. Otherwise |
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* an inode could be left in a non-consistent state. |
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*/ |
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struct bdi_writeback *new_wb; |
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struct inode *inodes[]; |
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}; |
|
|
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static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) |
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{ |
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down_write(&bdi->wb_switch_rwsem); |
|
} |
|
|
|
static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) |
|
{ |
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up_write(&bdi->wb_switch_rwsem); |
|
} |
|
|
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static bool inode_do_switch_wbs(struct inode *inode, |
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struct bdi_writeback *old_wb, |
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struct bdi_writeback *new_wb) |
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{ |
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struct address_space *mapping = inode->i_mapping; |
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XA_STATE(xas, &mapping->i_pages, 0); |
|
struct page *page; |
|
bool switched = false; |
|
|
|
spin_lock(&inode->i_lock); |
|
xa_lock_irq(&mapping->i_pages); |
|
|
|
/* |
|
* Once I_FREEING or I_WILL_FREE are visible under i_lock, the eviction |
|
* path owns the inode and we shouldn't modify ->i_io_list. |
|
*/ |
|
if (unlikely(inode->i_state & (I_FREEING | I_WILL_FREE))) |
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goto skip_switch; |
|
|
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trace_inode_switch_wbs(inode, old_wb, new_wb); |
|
|
|
/* |
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* Count and transfer stats. Note that PAGECACHE_TAG_DIRTY points |
|
* to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to |
|
* pages actually under writeback. |
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*/ |
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xas_for_each_marked(&xas, page, ULONG_MAX, PAGECACHE_TAG_DIRTY) { |
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if (PageDirty(page)) { |
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dec_wb_stat(old_wb, WB_RECLAIMABLE); |
|
inc_wb_stat(new_wb, WB_RECLAIMABLE); |
|
} |
|
} |
|
|
|
xas_set(&xas, 0); |
|
xas_for_each_marked(&xas, page, ULONG_MAX, PAGECACHE_TAG_WRITEBACK) { |
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WARN_ON_ONCE(!PageWriteback(page)); |
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dec_wb_stat(old_wb, WB_WRITEBACK); |
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inc_wb_stat(new_wb, WB_WRITEBACK); |
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} |
|
|
|
if (mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) { |
|
atomic_dec(&old_wb->writeback_inodes); |
|
atomic_inc(&new_wb->writeback_inodes); |
|
} |
|
|
|
wb_get(new_wb); |
|
|
|
/* |
|
* Transfer to @new_wb's IO list if necessary. If the @inode is dirty, |
|
* the specific list @inode was on is ignored and the @inode is put on |
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* ->b_dirty which is always correct including from ->b_dirty_time. |
|
* The transfer preserves @inode->dirtied_when ordering. If the @inode |
|
* was clean, it means it was on the b_attached list, so move it onto |
|
* the b_attached list of @new_wb. |
|
*/ |
|
if (!list_empty(&inode->i_io_list)) { |
|
inode->i_wb = new_wb; |
|
|
|
if (inode->i_state & I_DIRTY_ALL) { |
|
struct inode *pos; |
|
|
|
list_for_each_entry(pos, &new_wb->b_dirty, i_io_list) |
|
if (time_after_eq(inode->dirtied_when, |
|
pos->dirtied_when)) |
|
break; |
|
inode_io_list_move_locked(inode, new_wb, |
|
pos->i_io_list.prev); |
|
} else { |
|
inode_cgwb_move_to_attached(inode, new_wb); |
|
} |
|
} else { |
|
inode->i_wb = new_wb; |
|
} |
|
|
|
/* ->i_wb_frn updates may race wbc_detach_inode() but doesn't matter */ |
|
inode->i_wb_frn_winner = 0; |
|
inode->i_wb_frn_avg_time = 0; |
|
inode->i_wb_frn_history = 0; |
|
switched = true; |
|
skip_switch: |
|
/* |
|
* Paired with load_acquire in unlocked_inode_to_wb_begin() and |
|
* ensures that the new wb is visible if they see !I_WB_SWITCH. |
|
*/ |
|
smp_store_release(&inode->i_state, inode->i_state & ~I_WB_SWITCH); |
|
|
|
xa_unlock_irq(&mapping->i_pages); |
|
spin_unlock(&inode->i_lock); |
|
|
|
return switched; |
|
} |
|
|
|
static void inode_switch_wbs_work_fn(struct work_struct *work) |
|
{ |
|
struct inode_switch_wbs_context *isw = |
|
container_of(to_rcu_work(work), struct inode_switch_wbs_context, work); |
|
struct backing_dev_info *bdi = inode_to_bdi(isw->inodes[0]); |
|
struct bdi_writeback *old_wb = isw->inodes[0]->i_wb; |
|
struct bdi_writeback *new_wb = isw->new_wb; |
|
unsigned long nr_switched = 0; |
|
struct inode **inodep; |
|
|
|
/* |
|
* If @inode switches cgwb membership while sync_inodes_sb() is |
|
* being issued, sync_inodes_sb() might miss it. Synchronize. |
|
*/ |
|
down_read(&bdi->wb_switch_rwsem); |
|
|
|
/* |
|
* By the time control reaches here, RCU grace period has passed |
|
* since I_WB_SWITCH assertion and all wb stat update transactions |
|
* between unlocked_inode_to_wb_begin/end() are guaranteed to be |
|
* synchronizing against the i_pages lock. |
|
* |
|
* Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock |
|
* gives us exclusion against all wb related operations on @inode |
|
* including IO list manipulations and stat updates. |
|
*/ |
|
if (old_wb < new_wb) { |
|
spin_lock(&old_wb->list_lock); |
|
spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING); |
|
} else { |
|
spin_lock(&new_wb->list_lock); |
|
spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING); |
|
} |
|
|
|
for (inodep = isw->inodes; *inodep; inodep++) { |
|
WARN_ON_ONCE((*inodep)->i_wb != old_wb); |
|
if (inode_do_switch_wbs(*inodep, old_wb, new_wb)) |
|
nr_switched++; |
|
} |
|
|
|
spin_unlock(&new_wb->list_lock); |
|
spin_unlock(&old_wb->list_lock); |
|
|
|
up_read(&bdi->wb_switch_rwsem); |
|
|
|
if (nr_switched) { |
|
wb_wakeup(new_wb); |
|
wb_put_many(old_wb, nr_switched); |
|
} |
|
|
|
for (inodep = isw->inodes; *inodep; inodep++) |
|
iput(*inodep); |
|
wb_put(new_wb); |
|
kfree(isw); |
|
atomic_dec(&isw_nr_in_flight); |
|
} |
|
|
|
static bool inode_prepare_wbs_switch(struct inode *inode, |
|
struct bdi_writeback *new_wb) |
|
{ |
|
/* |
|
* Paired with smp_mb() in cgroup_writeback_umount(). |
|
* isw_nr_in_flight must be increased before checking SB_ACTIVE and |
|
* grabbing an inode, otherwise isw_nr_in_flight can be observed as 0 |
|
* in cgroup_writeback_umount() and the isw_wq will be not flushed. |
|
*/ |
|
smp_mb(); |
|
|
|
if (IS_DAX(inode)) |
|
return false; |
|
|
|
/* while holding I_WB_SWITCH, no one else can update the association */ |
|
spin_lock(&inode->i_lock); |
|
if (!(inode->i_sb->s_flags & SB_ACTIVE) || |
|
inode->i_state & (I_WB_SWITCH | I_FREEING | I_WILL_FREE) || |
|
inode_to_wb(inode) == new_wb) { |
|
spin_unlock(&inode->i_lock); |
|
return false; |
|
} |
|
inode->i_state |= I_WB_SWITCH; |
|
__iget(inode); |
|
spin_unlock(&inode->i_lock); |
|
|
|
return true; |
|
} |
|
|
|
/** |
|
* inode_switch_wbs - change the wb association of an inode |
|
* @inode: target inode |
|
* @new_wb_id: ID of the new wb |
|
* |
|
* Switch @inode's wb association to the wb identified by @new_wb_id. The |
|
* switching is performed asynchronously and may fail silently. |
|
*/ |
|
static void inode_switch_wbs(struct inode *inode, int new_wb_id) |
|
{ |
|
struct backing_dev_info *bdi = inode_to_bdi(inode); |
|
struct cgroup_subsys_state *memcg_css; |
|
struct inode_switch_wbs_context *isw; |
|
|
|
/* noop if seems to be already in progress */ |
|
if (inode->i_state & I_WB_SWITCH) |
|
return; |
|
|
|
/* avoid queueing a new switch if too many are already in flight */ |
|
if (atomic_read(&isw_nr_in_flight) > WB_FRN_MAX_IN_FLIGHT) |
|
return; |
|
|
|
isw = kzalloc(sizeof(*isw) + 2 * sizeof(struct inode *), GFP_ATOMIC); |
|
if (!isw) |
|
return; |
|
|
|
atomic_inc(&isw_nr_in_flight); |
|
|
|
/* find and pin the new wb */ |
|
rcu_read_lock(); |
|
memcg_css = css_from_id(new_wb_id, &memory_cgrp_subsys); |
|
if (memcg_css && !css_tryget(memcg_css)) |
|
memcg_css = NULL; |
|
rcu_read_unlock(); |
|
if (!memcg_css) |
|
goto out_free; |
|
|
|
isw->new_wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC); |
|
css_put(memcg_css); |
|
if (!isw->new_wb) |
|
goto out_free; |
|
|
|
if (!inode_prepare_wbs_switch(inode, isw->new_wb)) |
|
goto out_free; |
|
|
|
isw->inodes[0] = inode; |
|
|
|
/* |
|
* In addition to synchronizing among switchers, I_WB_SWITCH tells |
|
* the RCU protected stat update paths to grab the i_page |
|
* lock so that stat transfer can synchronize against them. |
|
* Let's continue after I_WB_SWITCH is guaranteed to be visible. |
|
*/ |
|
INIT_RCU_WORK(&isw->work, inode_switch_wbs_work_fn); |
|
queue_rcu_work(isw_wq, &isw->work); |
|
return; |
|
|
|
out_free: |
|
atomic_dec(&isw_nr_in_flight); |
|
if (isw->new_wb) |
|
wb_put(isw->new_wb); |
|
kfree(isw); |
|
} |
|
|
|
/** |
|
* cleanup_offline_cgwb - detach associated inodes |
|
* @wb: target wb |
|
* |
|
* Switch all inodes attached to @wb to a nearest living ancestor's wb in order |
|
* to eventually release the dying @wb. Returns %true if not all inodes were |
|
* switched and the function has to be restarted. |
|
*/ |
|
bool cleanup_offline_cgwb(struct bdi_writeback *wb) |
|
{ |
|
struct cgroup_subsys_state *memcg_css; |
|
struct inode_switch_wbs_context *isw; |
|
struct inode *inode; |
|
int nr; |
|
bool restart = false; |
|
|
|
isw = kzalloc(sizeof(*isw) + WB_MAX_INODES_PER_ISW * |
|
sizeof(struct inode *), GFP_KERNEL); |
|
if (!isw) |
|
return restart; |
|
|
|
atomic_inc(&isw_nr_in_flight); |
|
|
|
for (memcg_css = wb->memcg_css->parent; memcg_css; |
|
memcg_css = memcg_css->parent) { |
|
isw->new_wb = wb_get_create(wb->bdi, memcg_css, GFP_KERNEL); |
|
if (isw->new_wb) |
|
break; |
|
} |
|
if (unlikely(!isw->new_wb)) |
|
isw->new_wb = &wb->bdi->wb; /* wb_get() is noop for bdi's wb */ |
|
|
|
nr = 0; |
|
spin_lock(&wb->list_lock); |
|
list_for_each_entry(inode, &wb->b_attached, i_io_list) { |
|
if (!inode_prepare_wbs_switch(inode, isw->new_wb)) |
|
continue; |
|
|
|
isw->inodes[nr++] = inode; |
|
|
|
if (nr >= WB_MAX_INODES_PER_ISW - 1) { |
|
restart = true; |
|
break; |
|
} |
|
} |
|
spin_unlock(&wb->list_lock); |
|
|
|
/* no attached inodes? bail out */ |
|
if (nr == 0) { |
|
atomic_dec(&isw_nr_in_flight); |
|
wb_put(isw->new_wb); |
|
kfree(isw); |
|
return restart; |
|
} |
|
|
|
/* |
|
* In addition to synchronizing among switchers, I_WB_SWITCH tells |
|
* the RCU protected stat update paths to grab the i_page |
|
* lock so that stat transfer can synchronize against them. |
|
* Let's continue after I_WB_SWITCH is guaranteed to be visible. |
|
*/ |
|
INIT_RCU_WORK(&isw->work, inode_switch_wbs_work_fn); |
|
queue_rcu_work(isw_wq, &isw->work); |
|
|
|
return restart; |
|
} |
|
|
|
/** |
|
* wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it |
|
* @wbc: writeback_control of interest |
|
* @inode: target inode |
|
* |
|
* @inode is locked and about to be written back under the control of @wbc. |
|
* Record @inode's writeback context into @wbc and unlock the i_lock. On |
|
* writeback completion, wbc_detach_inode() should be called. This is used |
|
* to track the cgroup writeback context. |
|
*/ |
|
void wbc_attach_and_unlock_inode(struct writeback_control *wbc, |
|
struct inode *inode) |
|
{ |
|
if (!inode_cgwb_enabled(inode)) { |
|
spin_unlock(&inode->i_lock); |
|
return; |
|
} |
|
|
|
wbc->wb = inode_to_wb(inode); |
|
wbc->inode = inode; |
|
|
|
wbc->wb_id = wbc->wb->memcg_css->id; |
|
wbc->wb_lcand_id = inode->i_wb_frn_winner; |
|
wbc->wb_tcand_id = 0; |
|
wbc->wb_bytes = 0; |
|
wbc->wb_lcand_bytes = 0; |
|
wbc->wb_tcand_bytes = 0; |
|
|
|
wb_get(wbc->wb); |
|
spin_unlock(&inode->i_lock); |
|
|
|
/* |
|
* A dying wb indicates that either the blkcg associated with the |
|
* memcg changed or the associated memcg is dying. In the first |
|
* case, a replacement wb should already be available and we should |
|
* refresh the wb immediately. In the second case, trying to |
|
* refresh will keep failing. |
|
*/ |
|
if (unlikely(wb_dying(wbc->wb) && !css_is_dying(wbc->wb->memcg_css))) |
|
inode_switch_wbs(inode, wbc->wb_id); |
|
} |
|
EXPORT_SYMBOL_GPL(wbc_attach_and_unlock_inode); |
|
|
|
/** |
|
* wbc_detach_inode - disassociate wbc from inode and perform foreign detection |
|
* @wbc: writeback_control of the just finished writeback |
|
* |
|
* To be called after a writeback attempt of an inode finishes and undoes |
|
* wbc_attach_and_unlock_inode(). Can be called under any context. |
|
* |
|
* As concurrent write sharing of an inode is expected to be very rare and |
|
* memcg only tracks page ownership on first-use basis severely confining |
|
* the usefulness of such sharing, cgroup writeback tracks ownership |
|
* per-inode. While the support for concurrent write sharing of an inode |
|
* is deemed unnecessary, an inode being written to by different cgroups at |
|
* different points in time is a lot more common, and, more importantly, |
|
* charging only by first-use can too readily lead to grossly incorrect |
|
* behaviors (single foreign page can lead to gigabytes of writeback to be |
|
* incorrectly attributed). |
|
* |
|
* To resolve this issue, cgroup writeback detects the majority dirtier of |
|
* an inode and transfers the ownership to it. To avoid unnnecessary |
|
* oscillation, the detection mechanism keeps track of history and gives |
|
* out the switch verdict only if the foreign usage pattern is stable over |
|
* a certain amount of time and/or writeback attempts. |
|
* |
|
* On each writeback attempt, @wbc tries to detect the majority writer |
|
* using Boyer-Moore majority vote algorithm. In addition to the byte |
|
* count from the majority voting, it also counts the bytes written for the |
|
* current wb and the last round's winner wb (max of last round's current |
|
* wb, the winner from two rounds ago, and the last round's majority |
|
* candidate). Keeping track of the historical winner helps the algorithm |
|
* to semi-reliably detect the most active writer even when it's not the |
|
* absolute majority. |
|
* |
|
* Once the winner of the round is determined, whether the winner is |
|
* foreign or not and how much IO time the round consumed is recorded in |
|
* inode->i_wb_frn_history. If the amount of recorded foreign IO time is |
|
* over a certain threshold, the switch verdict is given. |
|
*/ |
|
void wbc_detach_inode(struct writeback_control *wbc) |
|
{ |
|
struct bdi_writeback *wb = wbc->wb; |
|
struct inode *inode = wbc->inode; |
|
unsigned long avg_time, max_bytes, max_time; |
|
u16 history; |
|
int max_id; |
|
|
|
if (!wb) |
|
return; |
|
|
|
history = inode->i_wb_frn_history; |
|
avg_time = inode->i_wb_frn_avg_time; |
|
|
|
/* pick the winner of this round */ |
|
if (wbc->wb_bytes >= wbc->wb_lcand_bytes && |
|
wbc->wb_bytes >= wbc->wb_tcand_bytes) { |
|
max_id = wbc->wb_id; |
|
max_bytes = wbc->wb_bytes; |
|
} else if (wbc->wb_lcand_bytes >= wbc->wb_tcand_bytes) { |
|
max_id = wbc->wb_lcand_id; |
|
max_bytes = wbc->wb_lcand_bytes; |
|
} else { |
|
max_id = wbc->wb_tcand_id; |
|
max_bytes = wbc->wb_tcand_bytes; |
|
} |
|
|
|
/* |
|
* Calculate the amount of IO time the winner consumed and fold it |
|
* into the running average kept per inode. If the consumed IO |
|
* time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for |
|
* deciding whether to switch or not. This is to prevent one-off |
|
* small dirtiers from skewing the verdict. |
|
*/ |
|
max_time = DIV_ROUND_UP((max_bytes >> PAGE_SHIFT) << WB_FRN_TIME_SHIFT, |
|
wb->avg_write_bandwidth); |
|
if (avg_time) |
|
avg_time += (max_time >> WB_FRN_TIME_AVG_SHIFT) - |
|
(avg_time >> WB_FRN_TIME_AVG_SHIFT); |
|
else |
|
avg_time = max_time; /* immediate catch up on first run */ |
|
|
|
if (max_time >= avg_time / WB_FRN_TIME_CUT_DIV) { |
|
int slots; |
|
|
|
/* |
|
* The switch verdict is reached if foreign wb's consume |
|
* more than a certain proportion of IO time in a |
|
* WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot |
|
* history mask where each bit represents one sixteenth of |
|
* the period. Determine the number of slots to shift into |
|
* history from @max_time. |
|
*/ |
|
slots = min(DIV_ROUND_UP(max_time, WB_FRN_HIST_UNIT), |
|
(unsigned long)WB_FRN_HIST_MAX_SLOTS); |
|
history <<= slots; |
|
if (wbc->wb_id != max_id) |
|
history |= (1U << slots) - 1; |
|
|
|
if (history) |
|
trace_inode_foreign_history(inode, wbc, history); |
|
|
|
/* |
|
* Switch if the current wb isn't the consistent winner. |
|
* If there are multiple closely competing dirtiers, the |
|
* inode may switch across them repeatedly over time, which |
|
* is okay. The main goal is avoiding keeping an inode on |
|
* the wrong wb for an extended period of time. |
|
*/ |
|
if (hweight32(history) > WB_FRN_HIST_THR_SLOTS) |
|
inode_switch_wbs(inode, max_id); |
|
} |
|
|
|
/* |
|
* Multiple instances of this function may race to update the |
|
* following fields but we don't mind occassional inaccuracies. |
|
*/ |
|
inode->i_wb_frn_winner = max_id; |
|
inode->i_wb_frn_avg_time = min(avg_time, (unsigned long)U16_MAX); |
|
inode->i_wb_frn_history = history; |
|
|
|
wb_put(wbc->wb); |
|
wbc->wb = NULL; |
|
} |
|
EXPORT_SYMBOL_GPL(wbc_detach_inode); |
|
|
|
/** |
|
* wbc_account_cgroup_owner - account writeback to update inode cgroup ownership |
|
* @wbc: writeback_control of the writeback in progress |
|
* @page: page being written out |
|
* @bytes: number of bytes being written out |
|
* |
|
* @bytes from @page are about to written out during the writeback |
|
* controlled by @wbc. Keep the book for foreign inode detection. See |
|
* wbc_detach_inode(). |
|
*/ |
|
void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page, |
|
size_t bytes) |
|
{ |
|
struct cgroup_subsys_state *css; |
|
int id; |
|
|
|
/* |
|
* pageout() path doesn't attach @wbc to the inode being written |
|
* out. This is intentional as we don't want the function to block |
|
* behind a slow cgroup. Ultimately, we want pageout() to kick off |
|
* regular writeback instead of writing things out itself. |
|
*/ |
|
if (!wbc->wb || wbc->no_cgroup_owner) |
|
return; |
|
|
|
css = mem_cgroup_css_from_page(page); |
|
/* dead cgroups shouldn't contribute to inode ownership arbitration */ |
|
if (!(css->flags & CSS_ONLINE)) |
|
return; |
|
|
|
id = css->id; |
|
|
|
if (id == wbc->wb_id) { |
|
wbc->wb_bytes += bytes; |
|
return; |
|
} |
|
|
|
if (id == wbc->wb_lcand_id) |
|
wbc->wb_lcand_bytes += bytes; |
|
|
|
/* Boyer-Moore majority vote algorithm */ |
|
if (!wbc->wb_tcand_bytes) |
|
wbc->wb_tcand_id = id; |
|
if (id == wbc->wb_tcand_id) |
|
wbc->wb_tcand_bytes += bytes; |
|
else |
|
wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes); |
|
} |
|
EXPORT_SYMBOL_GPL(wbc_account_cgroup_owner); |
|
|
|
/** |
|
* inode_congested - test whether an inode is congested |
|
* @inode: inode to test for congestion (may be NULL) |
|
* @cong_bits: mask of WB_[a]sync_congested bits to test |
|
* |
|
* Tests whether @inode is congested. @cong_bits is the mask of congestion |
|
* bits to test and the return value is the mask of set bits. |
|
* |
|
* If cgroup writeback is enabled for @inode, the congestion state is |
|
* determined by whether the cgwb (cgroup bdi_writeback) for the blkcg |
|
* associated with @inode is congested; otherwise, the root wb's congestion |
|
* state is used. |
|
* |
|
* @inode is allowed to be NULL as this function is often called on |
|
* mapping->host which is NULL for the swapper space. |
|
*/ |
|
int inode_congested(struct inode *inode, int cong_bits) |
|
{ |
|
/* |
|
* Once set, ->i_wb never becomes NULL while the inode is alive. |
|
* Start transaction iff ->i_wb is visible. |
|
*/ |
|
if (inode && inode_to_wb_is_valid(inode)) { |
|
struct bdi_writeback *wb; |
|
struct wb_lock_cookie lock_cookie = {}; |
|
bool congested; |
|
|
|
wb = unlocked_inode_to_wb_begin(inode, &lock_cookie); |
|
congested = wb_congested(wb, cong_bits); |
|
unlocked_inode_to_wb_end(inode, &lock_cookie); |
|
return congested; |
|
} |
|
|
|
return wb_congested(&inode_to_bdi(inode)->wb, cong_bits); |
|
} |
|
EXPORT_SYMBOL_GPL(inode_congested); |
|
|
|
/** |
|
* wb_split_bdi_pages - split nr_pages to write according to bandwidth |
|
* @wb: target bdi_writeback to split @nr_pages to |
|
* @nr_pages: number of pages to write for the whole bdi |
|
* |
|
* Split @wb's portion of @nr_pages according to @wb's write bandwidth in |
|
* relation to the total write bandwidth of all wb's w/ dirty inodes on |
|
* @wb->bdi. |
|
*/ |
|
static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages) |
|
{ |
|
unsigned long this_bw = wb->avg_write_bandwidth; |
|
unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth); |
|
|
|
if (nr_pages == LONG_MAX) |
|
return LONG_MAX; |
|
|
|
/* |
|
* This may be called on clean wb's and proportional distribution |
|
* may not make sense, just use the original @nr_pages in those |
|
* cases. In general, we wanna err on the side of writing more. |
|
*/ |
|
if (!tot_bw || this_bw >= tot_bw) |
|
return nr_pages; |
|
else |
|
return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw); |
|
} |
|
|
|
/** |
|
* bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi |
|
* @bdi: target backing_dev_info |
|
* @base_work: wb_writeback_work to issue |
|
* @skip_if_busy: skip wb's which already have writeback in progress |
|
* |
|
* Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which |
|
* have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's |
|
* distributed to the busy wbs according to each wb's proportion in the |
|
* total active write bandwidth of @bdi. |
|
*/ |
|
static void bdi_split_work_to_wbs(struct backing_dev_info *bdi, |
|
struct wb_writeback_work *base_work, |
|
bool skip_if_busy) |
|
{ |
|
struct bdi_writeback *last_wb = NULL; |
|
struct bdi_writeback *wb = list_entry(&bdi->wb_list, |
|
struct bdi_writeback, bdi_node); |
|
|
|
might_sleep(); |
|
restart: |
|
rcu_read_lock(); |
|
list_for_each_entry_continue_rcu(wb, &bdi->wb_list, bdi_node) { |
|
DEFINE_WB_COMPLETION(fallback_work_done, bdi); |
|
struct wb_writeback_work fallback_work; |
|
struct wb_writeback_work *work; |
|
long nr_pages; |
|
|
|
if (last_wb) { |
|
wb_put(last_wb); |
|
last_wb = NULL; |
|
} |
|
|
|
/* SYNC_ALL writes out I_DIRTY_TIME too */ |
|
if (!wb_has_dirty_io(wb) && |
|
(base_work->sync_mode == WB_SYNC_NONE || |
|
list_empty(&wb->b_dirty_time))) |
|
continue; |
|
if (skip_if_busy && writeback_in_progress(wb)) |
|
continue; |
|
|
|
nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages); |
|
|
|
work = kmalloc(sizeof(*work), GFP_ATOMIC); |
|
if (work) { |
|
*work = *base_work; |
|
work->nr_pages = nr_pages; |
|
work->auto_free = 1; |
|
wb_queue_work(wb, work); |
|
continue; |
|
} |
|
|
|
/* alloc failed, execute synchronously using on-stack fallback */ |
|
work = &fallback_work; |
|
*work = *base_work; |
|
work->nr_pages = nr_pages; |
|
work->auto_free = 0; |
|
work->done = &fallback_work_done; |
|
|
|
wb_queue_work(wb, work); |
|
|
|
/* |
|
* Pin @wb so that it stays on @bdi->wb_list. This allows |
|
* continuing iteration from @wb after dropping and |
|
* regrabbing rcu read lock. |
|
*/ |
|
wb_get(wb); |
|
last_wb = wb; |
|
|
|
rcu_read_unlock(); |
|
wb_wait_for_completion(&fallback_work_done); |
|
goto restart; |
|
} |
|
rcu_read_unlock(); |
|
|
|
if (last_wb) |
|
wb_put(last_wb); |
|
} |
|
|
|
/** |
|
* cgroup_writeback_by_id - initiate cgroup writeback from bdi and memcg IDs |
|
* @bdi_id: target bdi id |
|
* @memcg_id: target memcg css id |
|
* @reason: reason why some writeback work initiated |
|
* @done: target wb_completion |
|
* |
|
* Initiate flush of the bdi_writeback identified by @bdi_id and @memcg_id |
|
* with the specified parameters. |
|
*/ |
|
int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, |
|
enum wb_reason reason, struct wb_completion *done) |
|
{ |
|
struct backing_dev_info *bdi; |
|
struct cgroup_subsys_state *memcg_css; |
|
struct bdi_writeback *wb; |
|
struct wb_writeback_work *work; |
|
unsigned long dirty; |
|
int ret; |
|
|
|
/* lookup bdi and memcg */ |
|
bdi = bdi_get_by_id(bdi_id); |
|
if (!bdi) |
|
return -ENOENT; |
|
|
|
rcu_read_lock(); |
|
memcg_css = css_from_id(memcg_id, &memory_cgrp_subsys); |
|
if (memcg_css && !css_tryget(memcg_css)) |
|
memcg_css = NULL; |
|
rcu_read_unlock(); |
|
if (!memcg_css) { |
|
ret = -ENOENT; |
|
goto out_bdi_put; |
|
} |
|
|
|
/* |
|
* And find the associated wb. If the wb isn't there already |
|
* there's nothing to flush, don't create one. |
|
*/ |
|
wb = wb_get_lookup(bdi, memcg_css); |
|
if (!wb) { |
|
ret = -ENOENT; |
|
goto out_css_put; |
|
} |
|
|
|
/* |
|
* The caller is attempting to write out most of |
|
* the currently dirty pages. Let's take the current dirty page |
|
* count and inflate it by 25% which should be large enough to |
|
* flush out most dirty pages while avoiding getting livelocked by |
|
* concurrent dirtiers. |
|
* |
|
* BTW the memcg stats are flushed periodically and this is best-effort |
|
* estimation, so some potential error is ok. |
|
*/ |
|
dirty = memcg_page_state(mem_cgroup_from_css(memcg_css), NR_FILE_DIRTY); |
|
dirty = dirty * 10 / 8; |
|
|
|
/* issue the writeback work */ |
|
work = kzalloc(sizeof(*work), GFP_NOWAIT | __GFP_NOWARN); |
|
if (work) { |
|
work->nr_pages = dirty; |
|
work->sync_mode = WB_SYNC_NONE; |
|
work->range_cyclic = 1; |
|
work->reason = reason; |
|
work->done = done; |
|
work->auto_free = 1; |
|
wb_queue_work(wb, work); |
|
ret = 0; |
|
} else { |
|
ret = -ENOMEM; |
|
} |
|
|
|
wb_put(wb); |
|
out_css_put: |
|
css_put(memcg_css); |
|
out_bdi_put: |
|
bdi_put(bdi); |
|
return ret; |
|
} |
|
|
|
/** |
|
* cgroup_writeback_umount - flush inode wb switches for umount |
|
* |
|
* This function is called when a super_block is about to be destroyed and |
|
* flushes in-flight inode wb switches. An inode wb switch goes through |
|
* RCU and then workqueue, so the two need to be flushed in order to ensure |
|
* that all previously scheduled switches are finished. As wb switches are |
|
* rare occurrences and synchronize_rcu() can take a while, perform |
|
* flushing iff wb switches are in flight. |
|
*/ |
|
void cgroup_writeback_umount(void) |
|
{ |
|
/* |
|
* SB_ACTIVE should be reliably cleared before checking |
|
* isw_nr_in_flight, see generic_shutdown_super(). |
|
*/ |
|
smp_mb(); |
|
|
|
if (atomic_read(&isw_nr_in_flight)) { |
|
/* |
|
* Use rcu_barrier() to wait for all pending callbacks to |
|
* ensure that all in-flight wb switches are in the workqueue. |
|
*/ |
|
rcu_barrier(); |
|
flush_workqueue(isw_wq); |
|
} |
|
} |
|
|
|
static int __init cgroup_writeback_init(void) |
|
{ |
|
isw_wq = alloc_workqueue("inode_switch_wbs", 0, 0); |
|
if (!isw_wq) |
|
return -ENOMEM; |
|
return 0; |
|
} |
|
fs_initcall(cgroup_writeback_init); |
|
|
|
#else /* CONFIG_CGROUP_WRITEBACK */ |
|
|
|
static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) { } |
|
static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) { } |
|
|
|
static void inode_cgwb_move_to_attached(struct inode *inode, |
|
struct bdi_writeback *wb) |
|
{ |
|
assert_spin_locked(&wb->list_lock); |
|
assert_spin_locked(&inode->i_lock); |
|
|
|
inode->i_state &= ~I_SYNC_QUEUED; |
|
list_del_init(&inode->i_io_list); |
|
wb_io_lists_depopulated(wb); |
|
} |
|
|
|
static struct bdi_writeback * |
|
locked_inode_to_wb_and_lock_list(struct inode *inode) |
|
__releases(&inode->i_lock) |
|
__acquires(&wb->list_lock) |
|
{ |
|
struct bdi_writeback *wb = inode_to_wb(inode); |
|
|
|
spin_unlock(&inode->i_lock); |
|
spin_lock(&wb->list_lock); |
|
return wb; |
|
} |
|
|
|
static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode) |
|
__acquires(&wb->list_lock) |
|
{ |
|
struct bdi_writeback *wb = inode_to_wb(inode); |
|
|
|
spin_lock(&wb->list_lock); |
|
return wb; |
|
} |
|
|
|
static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages) |
|
{ |
|
return nr_pages; |
|
} |
|
|
|
static void bdi_split_work_to_wbs(struct backing_dev_info *bdi, |
|
struct wb_writeback_work *base_work, |
|
bool skip_if_busy) |
|
{ |
|
might_sleep(); |
|
|
|
if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) { |
|
base_work->auto_free = 0; |
|
wb_queue_work(&bdi->wb, base_work); |
|
} |
|
} |
|
|
|
#endif /* CONFIG_CGROUP_WRITEBACK */ |
|
|
|
/* |
|
* Add in the number of potentially dirty inodes, because each inode |
|
* write can dirty pagecache in the underlying blockdev. |
|
*/ |
|
static unsigned long get_nr_dirty_pages(void) |
|
{ |
|
return global_node_page_state(NR_FILE_DIRTY) + |
|
get_nr_dirty_inodes(); |
|
} |
|
|
|
static void wb_start_writeback(struct bdi_writeback *wb, enum wb_reason reason) |
|
{ |
|
if (!wb_has_dirty_io(wb)) |
|
return; |
|
|
|
/* |
|
* All callers of this function want to start writeback of all |
|
* dirty pages. Places like vmscan can call this at a very |
|
* high frequency, causing pointless allocations of tons of |
|
* work items and keeping the flusher threads busy retrieving |
|
* that work. Ensure that we only allow one of them pending and |
|
* inflight at the time. |
|
*/ |
|
if (test_bit(WB_start_all, &wb->state) || |
|
test_and_set_bit(WB_start_all, &wb->state)) |
|
return; |
|
|
|
wb->start_all_reason = reason; |
|
wb_wakeup(wb); |
|
} |
|
|
|
/** |
|
* wb_start_background_writeback - start background writeback |
|
* @wb: bdi_writback to write from |
|
* |
|
* Description: |
|
* This makes sure WB_SYNC_NONE background writeback happens. When |
|
* this function returns, it is only guaranteed that for given wb |
|
* some IO is happening if we are over background dirty threshold. |
|
* Caller need not hold sb s_umount semaphore. |
|
*/ |
|
void wb_start_background_writeback(struct bdi_writeback *wb) |
|
{ |
|
/* |
|
* We just wake up the flusher thread. It will perform background |
|
* writeback as soon as there is no other work to do. |
|
*/ |
|
trace_writeback_wake_background(wb); |
|
wb_wakeup(wb); |
|
} |
|
|
|
/* |
|
* Remove the inode from the writeback list it is on. |
|
*/ |
|
void inode_io_list_del(struct inode *inode) |
|
{ |
|
struct bdi_writeback *wb; |
|
|
|
wb = inode_to_wb_and_lock_list(inode); |
|
spin_lock(&inode->i_lock); |
|
|
|
inode->i_state &= ~I_SYNC_QUEUED; |
|
list_del_init(&inode->i_io_list); |
|
wb_io_lists_depopulated(wb); |
|
|
|
spin_unlock(&inode->i_lock); |
|
spin_unlock(&wb->list_lock); |
|
} |
|
EXPORT_SYMBOL(inode_io_list_del); |
|
|
|
/* |
|
* mark an inode as under writeback on the sb |
|
*/ |
|
void sb_mark_inode_writeback(struct inode *inode) |
|
{ |
|
struct super_block *sb = inode->i_sb; |
|
unsigned long flags; |
|
|
|
if (list_empty(&inode->i_wb_list)) { |
|
spin_lock_irqsave(&sb->s_inode_wblist_lock, flags); |
|
if (list_empty(&inode->i_wb_list)) { |
|
list_add_tail(&inode->i_wb_list, &sb->s_inodes_wb); |
|
trace_sb_mark_inode_writeback(inode); |
|
} |
|
spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags); |
|
} |
|
} |
|
|
|
/* |
|
* clear an inode as under writeback on the sb |
|
*/ |
|
void sb_clear_inode_writeback(struct inode *inode) |
|
{ |
|
struct super_block *sb = inode->i_sb; |
|
unsigned long flags; |
|
|
|
if (!list_empty(&inode->i_wb_list)) { |
|
spin_lock_irqsave(&sb->s_inode_wblist_lock, flags); |
|
if (!list_empty(&inode->i_wb_list)) { |
|
list_del_init(&inode->i_wb_list); |
|
trace_sb_clear_inode_writeback(inode); |
|
} |
|
spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags); |
|
} |
|
} |
|
|
|
/* |
|
* Redirty an inode: set its when-it-was dirtied timestamp and move it to the |
|
* furthest end of its superblock's dirty-inode list. |
|
* |
|
* Before stamping the inode's ->dirtied_when, we check to see whether it is |
|
* already the most-recently-dirtied inode on the b_dirty list. If that is |
|
* the case then the inode must have been redirtied while it was being written |
|
* out and we don't reset its dirtied_when. |
|
*/ |
|
static void redirty_tail_locked(struct inode *inode, struct bdi_writeback *wb) |
|
{ |
|
assert_spin_locked(&inode->i_lock); |
|
|
|
if (!list_empty(&wb->b_dirty)) { |
|
struct inode *tail; |
|
|
|
tail = wb_inode(wb->b_dirty.next); |
|
if (time_before(inode->dirtied_when, tail->dirtied_when)) |
|
inode->dirtied_when = jiffies; |
|
} |
|
inode_io_list_move_locked(inode, wb, &wb->b_dirty); |
|
inode->i_state &= ~I_SYNC_QUEUED; |
|
} |
|
|
|
static void redirty_tail(struct inode *inode, struct bdi_writeback *wb) |
|
{ |
|
spin_lock(&inode->i_lock); |
|
redirty_tail_locked(inode, wb); |
|
spin_unlock(&inode->i_lock); |
|
} |
|
|
|
/* |
|
* requeue inode for re-scanning after bdi->b_io list is exhausted. |
|
*/ |
|
static void requeue_io(struct inode *inode, struct bdi_writeback *wb) |
|
{ |
|
inode_io_list_move_locked(inode, wb, &wb->b_more_io); |
|
} |
|
|
|
static void inode_sync_complete(struct inode *inode) |
|
{ |
|
inode->i_state &= ~I_SYNC; |
|
/* If inode is clean an unused, put it into LRU now... */ |
|
inode_add_lru(inode); |
|
/* Waiters must see I_SYNC cleared before being woken up */ |
|
smp_mb(); |
|
wake_up_bit(&inode->i_state, __I_SYNC); |
|
} |
|
|
|
static bool inode_dirtied_after(struct inode *inode, unsigned long t) |
|
{ |
|
bool ret = time_after(inode->dirtied_when, t); |
|
#ifndef CONFIG_64BIT |
|
/* |
|
* For inodes being constantly redirtied, dirtied_when can get stuck. |
|
* It _appears_ to be in the future, but is actually in distant past. |
|
* This test is necessary to prevent such wrapped-around relative times |
|
* from permanently stopping the whole bdi writeback. |
|
*/ |
|
ret = ret && time_before_eq(inode->dirtied_when, jiffies); |
|
#endif |
|
return ret; |
|
} |
|
|
|
#define EXPIRE_DIRTY_ATIME 0x0001 |
|
|
|
/* |
|
* Move expired (dirtied before dirtied_before) dirty inodes from |
|
* @delaying_queue to @dispatch_queue. |
|
*/ |
|
static int move_expired_inodes(struct list_head *delaying_queue, |
|
struct list_head *dispatch_queue, |
|
unsigned long dirtied_before) |
|
{ |
|
LIST_HEAD(tmp); |
|
struct list_head *pos, *node; |
|
struct super_block *sb = NULL; |
|
struct inode *inode; |
|
int do_sb_sort = 0; |
|
int moved = 0; |
|
|
|
while (!list_empty(delaying_queue)) { |
|
inode = wb_inode(delaying_queue->prev); |
|
if (inode_dirtied_after(inode, dirtied_before)) |
|
break; |
|
list_move(&inode->i_io_list, &tmp); |
|
moved++; |
|
spin_lock(&inode->i_lock); |
|
inode->i_state |= I_SYNC_QUEUED; |
|
spin_unlock(&inode->i_lock); |
|
if (sb_is_blkdev_sb(inode->i_sb)) |
|
continue; |
|
if (sb && sb != inode->i_sb) |
|
do_sb_sort = 1; |
|
sb = inode->i_sb; |
|
} |
|
|
|
/* just one sb in list, splice to dispatch_queue and we're done */ |
|
if (!do_sb_sort) { |
|
list_splice(&tmp, dispatch_queue); |
|
goto out; |
|
} |
|
|
|
/* Move inodes from one superblock together */ |
|
while (!list_empty(&tmp)) { |
|
sb = wb_inode(tmp.prev)->i_sb; |
|
list_for_each_prev_safe(pos, node, &tmp) { |
|
inode = wb_inode(pos); |
|
if (inode->i_sb == sb) |
|
list_move(&inode->i_io_list, dispatch_queue); |
|
} |
|
} |
|
out: |
|
return moved; |
|
} |
|
|
|
/* |
|
* Queue all expired dirty inodes for io, eldest first. |
|
* Before |
|
* newly dirtied b_dirty b_io b_more_io |
|
* =============> gf edc BA |
|
* After |
|
* newly dirtied b_dirty b_io b_more_io |
|
* =============> g fBAedc |
|
* | |
|
* +--> dequeue for IO |
|
*/ |
|
static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work, |
|
unsigned long dirtied_before) |
|
{ |
|
int moved; |
|
unsigned long time_expire_jif = dirtied_before; |
|
|
|
assert_spin_locked(&wb->list_lock); |
|
list_splice_init(&wb->b_more_io, &wb->b_io); |
|
moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, dirtied_before); |
|
if (!work->for_sync) |
|
time_expire_jif = jiffies - dirtytime_expire_interval * HZ; |
|
moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io, |
|
time_expire_jif); |
|
if (moved) |
|
wb_io_lists_populated(wb); |
|
trace_writeback_queue_io(wb, work, dirtied_before, moved); |
|
} |
|
|
|
static int write_inode(struct inode *inode, struct writeback_control *wbc) |
|
{ |
|
int ret; |
|
|
|
if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) { |
|
trace_writeback_write_inode_start(inode, wbc); |
|
ret = inode->i_sb->s_op->write_inode(inode, wbc); |
|
trace_writeback_write_inode(inode, wbc); |
|
return ret; |
|
} |
|
return 0; |
|
} |
|
|
|
/* |
|
* Wait for writeback on an inode to complete. Called with i_lock held. |
|
* Caller must make sure inode cannot go away when we drop i_lock. |
|
*/ |
|
static void __inode_wait_for_writeback(struct inode *inode) |
|
__releases(inode->i_lock) |
|
__acquires(inode->i_lock) |
|
{ |
|
DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC); |
|
wait_queue_head_t *wqh; |
|
|
|
wqh = bit_waitqueue(&inode->i_state, __I_SYNC); |
|
while (inode->i_state & I_SYNC) { |
|
spin_unlock(&inode->i_lock); |
|
__wait_on_bit(wqh, &wq, bit_wait, |
|
TASK_UNINTERRUPTIBLE); |
|
spin_lock(&inode->i_lock); |
|
} |
|
} |
|
|
|
/* |
|
* Wait for writeback on an inode to complete. Caller must have inode pinned. |
|
*/ |
|
void inode_wait_for_writeback(struct inode *inode) |
|
{ |
|
spin_lock(&inode->i_lock); |
|
__inode_wait_for_writeback(inode); |
|
spin_unlock(&inode->i_lock); |
|
} |
|
|
|
/* |
|
* Sleep until I_SYNC is cleared. This function must be called with i_lock |
|
* held and drops it. It is aimed for callers not holding any inode reference |
|
* so once i_lock is dropped, inode can go away. |
|
*/ |
|
static void inode_sleep_on_writeback(struct inode *inode) |
|
__releases(inode->i_lock) |
|
{ |
|
DEFINE_WAIT(wait); |
|
wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC); |
|
int sleep; |
|
|
|
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); |
|
sleep = inode->i_state & I_SYNC; |
|
spin_unlock(&inode->i_lock); |
|
if (sleep) |
|
schedule(); |
|
finish_wait(wqh, &wait); |
|
} |
|
|
|
/* |
|
* Find proper writeback list for the inode depending on its current state and |
|
* possibly also change of its state while we were doing writeback. Here we |
|
* handle things such as livelock prevention or fairness of writeback among |
|
* inodes. This function can be called only by flusher thread - noone else |
|
* processes all inodes in writeback lists and requeueing inodes behind flusher |
|
* thread's back can have unexpected consequences. |
|
*/ |
|
static void requeue_inode(struct inode *inode, struct bdi_writeback *wb, |
|
struct writeback_control *wbc) |
|
{ |
|
if (inode->i_state & I_FREEING) |
|
return; |
|
|
|
/* |
|
* Sync livelock prevention. Each inode is tagged and synced in one |
|
* shot. If still dirty, it will be redirty_tail()'ed below. Update |
|
* the dirty time to prevent enqueue and sync it again. |
|
*/ |
|
if ((inode->i_state & I_DIRTY) && |
|
(wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)) |
|
inode->dirtied_when = jiffies; |
|
|
|
if (wbc->pages_skipped) { |
|
/* |
|
* writeback is not making progress due to locked |
|
* buffers. Skip this inode for now. |
|
*/ |
|
redirty_tail_locked(inode, wb); |
|
return; |
|
} |
|
|
|
if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) { |
|
/* |
|
* We didn't write back all the pages. nfs_writepages() |
|
* sometimes bales out without doing anything. |
|
*/ |
|
if (wbc->nr_to_write <= 0) { |
|
/* Slice used up. Queue for next turn. */ |
|
requeue_io(inode, wb); |
|
} else { |
|
/* |
|
* Writeback blocked by something other than |
|
* congestion. Delay the inode for some time to |
|
* avoid spinning on the CPU (100% iowait) |
|
* retrying writeback of the dirty page/inode |
|
* that cannot be performed immediately. |
|
*/ |
|
redirty_tail_locked(inode, wb); |
|
} |
|
} else if (inode->i_state & I_DIRTY) { |
|
/* |
|
* Filesystems can dirty the inode during writeback operations, |
|
* such as delayed allocation during submission or metadata |
|
* updates after data IO completion. |
|
*/ |
|
redirty_tail_locked(inode, wb); |
|
} else if (inode->i_state & I_DIRTY_TIME) { |
|
inode->dirtied_when = jiffies; |
|
inode_io_list_move_locked(inode, wb, &wb->b_dirty_time); |
|
inode->i_state &= ~I_SYNC_QUEUED; |
|
} else { |
|
/* The inode is clean. Remove from writeback lists. */ |
|
inode_cgwb_move_to_attached(inode, wb); |
|
} |
|
} |
|
|
|
/* |
|
* Write out an inode and its dirty pages (or some of its dirty pages, depending |
|
* on @wbc->nr_to_write), and clear the relevant dirty flags from i_state. |
|
* |
|
* This doesn't remove the inode from the writeback list it is on, except |
|
* potentially to move it from b_dirty_time to b_dirty due to timestamp |
|
* expiration. The caller is otherwise responsible for writeback list handling. |
|
* |
|
* The caller is also responsible for setting the I_SYNC flag beforehand and |
|
* calling inode_sync_complete() to clear it afterwards. |
|
*/ |
|
static int |
|
__writeback_single_inode(struct inode *inode, struct writeback_control *wbc) |
|
{ |
|
struct address_space *mapping = inode->i_mapping; |
|
long nr_to_write = wbc->nr_to_write; |
|
unsigned dirty; |
|
int ret; |
|
|
|
WARN_ON(!(inode->i_state & I_SYNC)); |
|
|
|
trace_writeback_single_inode_start(inode, wbc, nr_to_write); |
|
|
|
ret = do_writepages(mapping, wbc); |
|
|
|
/* |
|
* Make sure to wait on the data before writing out the metadata. |
|
* This is important for filesystems that modify metadata on data |
|
* I/O completion. We don't do it for sync(2) writeback because it has a |
|
* separate, external IO completion path and ->sync_fs for guaranteeing |
|
* inode metadata is written back correctly. |
|
*/ |
|
if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) { |
|
int err = filemap_fdatawait(mapping); |
|
if (ret == 0) |
|
ret = err; |
|
} |
|
|
|
/* |
|
* If the inode has dirty timestamps and we need to write them, call |
|
* mark_inode_dirty_sync() to notify the filesystem about it and to |
|
* change I_DIRTY_TIME into I_DIRTY_SYNC. |
|
*/ |
|
if ((inode->i_state & I_DIRTY_TIME) && |
|
(wbc->sync_mode == WB_SYNC_ALL || |
|
time_after(jiffies, inode->dirtied_time_when + |
|
dirtytime_expire_interval * HZ))) { |
|
trace_writeback_lazytime(inode); |
|
mark_inode_dirty_sync(inode); |
|
} |
|
|
|
/* |
|
* Get and clear the dirty flags from i_state. This needs to be done |
|
* after calling writepages because some filesystems may redirty the |
|
* inode during writepages due to delalloc. It also needs to be done |
|
* after handling timestamp expiration, as that may dirty the inode too. |
|
*/ |
|
spin_lock(&inode->i_lock); |
|
dirty = inode->i_state & I_DIRTY; |
|
inode->i_state &= ~dirty; |
|
|
|
/* |
|
* Paired with smp_mb() in __mark_inode_dirty(). This allows |
|
* __mark_inode_dirty() to test i_state without grabbing i_lock - |
|
* either they see the I_DIRTY bits cleared or we see the dirtied |
|
* inode. |
|
* |
|
* I_DIRTY_PAGES is always cleared together above even if @mapping |
|
* still has dirty pages. The flag is reinstated after smp_mb() if |
|
* necessary. This guarantees that either __mark_inode_dirty() |
|
* sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY. |
|
*/ |
|
smp_mb(); |
|
|
|
if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) |
|
inode->i_state |= I_DIRTY_PAGES; |
|
|
|
spin_unlock(&inode->i_lock); |
|
|
|
/* Don't write the inode if only I_DIRTY_PAGES was set */ |
|
if (dirty & ~I_DIRTY_PAGES) { |
|
int err = write_inode(inode, wbc); |
|
if (ret == 0) |
|
ret = err; |
|
} |
|
trace_writeback_single_inode(inode, wbc, nr_to_write); |
|
return ret; |
|
} |
|
|
|
/* |
|
* Write out an inode's dirty data and metadata on-demand, i.e. separately from |
|
* the regular batched writeback done by the flusher threads in |
|
* writeback_sb_inodes(). @wbc controls various aspects of the write, such as |
|
* whether it is a data-integrity sync (%WB_SYNC_ALL) or not (%WB_SYNC_NONE). |
|
* |
|
* To prevent the inode from going away, either the caller must have a reference |
|
* to the inode, or the inode must have I_WILL_FREE or I_FREEING set. |
|
*/ |
|
static int writeback_single_inode(struct inode *inode, |
|
struct writeback_control *wbc) |
|
{ |
|
struct bdi_writeback *wb; |
|
int ret = 0; |
|
|
|
spin_lock(&inode->i_lock); |
|
if (!atomic_read(&inode->i_count)) |
|
WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING))); |
|
else |
|
WARN_ON(inode->i_state & I_WILL_FREE); |
|
|
|
if (inode->i_state & I_SYNC) { |
|
/* |
|
* Writeback is already running on the inode. For WB_SYNC_NONE, |
|
* that's enough and we can just return. For WB_SYNC_ALL, we |
|
* must wait for the existing writeback to complete, then do |
|
* writeback again if there's anything left. |
|
*/ |
|
if (wbc->sync_mode != WB_SYNC_ALL) |
|
goto out; |
|
__inode_wait_for_writeback(inode); |
|
} |
|
WARN_ON(inode->i_state & I_SYNC); |
|
/* |
|
* If the inode is already fully clean, then there's nothing to do. |
|
* |
|
* For data-integrity syncs we also need to check whether any pages are |
|
* still under writeback, e.g. due to prior WB_SYNC_NONE writeback. If |
|
* there are any such pages, we'll need to wait for them. |
|
*/ |
|
if (!(inode->i_state & I_DIRTY_ALL) && |
|
(wbc->sync_mode != WB_SYNC_ALL || |
|
!mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK))) |
|
goto out; |
|
inode->i_state |= I_SYNC; |
|
wbc_attach_and_unlock_inode(wbc, inode); |
|
|
|
ret = __writeback_single_inode(inode, wbc); |
|
|
|
wbc_detach_inode(wbc); |
|
|
|
wb = inode_to_wb_and_lock_list(inode); |
|
spin_lock(&inode->i_lock); |
|
/* |
|
* If the inode is now fully clean, then it can be safely removed from |
|
* its writeback list (if any). Otherwise the flusher threads are |
|
* responsible for the writeback lists. |
|
*/ |
|
if (!(inode->i_state & I_DIRTY_ALL)) |
|
inode_cgwb_move_to_attached(inode, wb); |
|
spin_unlock(&wb->list_lock); |
|
inode_sync_complete(inode); |
|
out: |
|
spin_unlock(&inode->i_lock); |
|
return ret; |
|
} |
|
|
|
static long writeback_chunk_size(struct bdi_writeback *wb, |
|
struct wb_writeback_work *work) |
|
{ |
|
long pages; |
|
|
|
/* |
|
* WB_SYNC_ALL mode does livelock avoidance by syncing dirty |
|
* inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX |
|
* here avoids calling into writeback_inodes_wb() more than once. |
|
* |
|
* The intended call sequence for WB_SYNC_ALL writeback is: |
|
* |
|
* wb_writeback() |
|
* writeback_sb_inodes() <== called only once |
|
* write_cache_pages() <== called once for each inode |
|
* (quickly) tag currently dirty pages |
|
* (maybe slowly) sync all tagged pages |
|
*/ |
|
if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages) |
|
pages = LONG_MAX; |
|
else { |
|
pages = min(wb->avg_write_bandwidth / 2, |
|
global_wb_domain.dirty_limit / DIRTY_SCOPE); |
|
pages = min(pages, work->nr_pages); |
|
pages = round_down(pages + MIN_WRITEBACK_PAGES, |
|
MIN_WRITEBACK_PAGES); |
|
} |
|
|
|
return pages; |
|
} |
|
|
|
/* |
|
* Write a portion of b_io inodes which belong to @sb. |
|
* |
|
* Return the number of pages and/or inodes written. |
|
* |
|
* NOTE! This is called with wb->list_lock held, and will |
|
* unlock and relock that for each inode it ends up doing |
|
* IO for. |
|
*/ |
|
static long writeback_sb_inodes(struct super_block *sb, |
|
struct bdi_writeback *wb, |
|
struct wb_writeback_work *work) |
|
{ |
|
struct writeback_control wbc = { |
|
.sync_mode = work->sync_mode, |
|
.tagged_writepages = work->tagged_writepages, |
|
.for_kupdate = work->for_kupdate, |
|
.for_background = work->for_background, |
|
.for_sync = work->for_sync, |
|
.range_cyclic = work->range_cyclic, |
|
.range_start = 0, |
|
.range_end = LLONG_MAX, |
|
}; |
|
unsigned long start_time = jiffies; |
|
long write_chunk; |
|
long wrote = 0; /* count both pages and inodes */ |
|
|
|
while (!list_empty(&wb->b_io)) { |
|
struct inode *inode = wb_inode(wb->b_io.prev); |
|
struct bdi_writeback *tmp_wb; |
|
|
|
if (inode->i_sb != sb) { |
|
if (work->sb) { |
|
/* |
|
* We only want to write back data for this |
|
* superblock, move all inodes not belonging |
|
* to it back onto the dirty list. |
|
*/ |
|
redirty_tail(inode, wb); |
|
continue; |
|
} |
|
|
|
/* |
|
* The inode belongs to a different superblock. |
|
* Bounce back to the caller to unpin this and |
|
* pin the next superblock. |
|
*/ |
|
break; |
|
} |
|
|
|
/* |
|
* Don't bother with new inodes or inodes being freed, first |
|
* kind does not need periodic writeout yet, and for the latter |
|
* kind writeout is handled by the freer. |
|
*/ |
|
spin_lock(&inode->i_lock); |
|
if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) { |
|
redirty_tail_locked(inode, wb); |
|
spin_unlock(&inode->i_lock); |
|
continue; |
|
} |
|
if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) { |
|
/* |
|
* If this inode is locked for writeback and we are not |
|
* doing writeback-for-data-integrity, move it to |
|
* b_more_io so that writeback can proceed with the |
|
* other inodes on s_io. |
|
* |
|
* We'll have another go at writing back this inode |
|
* when we completed a full scan of b_io. |
|
*/ |
|
spin_unlock(&inode->i_lock); |
|
requeue_io(inode, wb); |
|
trace_writeback_sb_inodes_requeue(inode); |
|
continue; |
|
} |
|
spin_unlock(&wb->list_lock); |
|
|
|
/* |
|
* We already requeued the inode if it had I_SYNC set and we |
|
* are doing WB_SYNC_NONE writeback. So this catches only the |
|
* WB_SYNC_ALL case. |
|
*/ |
|
if (inode->i_state & I_SYNC) { |
|
/* Wait for I_SYNC. This function drops i_lock... */ |
|
inode_sleep_on_writeback(inode); |
|
/* Inode may be gone, start again */ |
|
spin_lock(&wb->list_lock); |
|
continue; |
|
} |
|
inode->i_state |= I_SYNC; |
|
wbc_attach_and_unlock_inode(&wbc, inode); |
|
|
|
write_chunk = writeback_chunk_size(wb, work); |
|
wbc.nr_to_write = write_chunk; |
|
wbc.pages_skipped = 0; |
|
|
|
/* |
|
* We use I_SYNC to pin the inode in memory. While it is set |
|
* evict_inode() will wait so the inode cannot be freed. |
|
*/ |
|
__writeback_single_inode(inode, &wbc); |
|
|
|
wbc_detach_inode(&wbc); |
|
work->nr_pages -= write_chunk - wbc.nr_to_write; |
|
wrote += write_chunk - wbc.nr_to_write; |
|
|
|
if (need_resched()) { |
|
/* |
|
* We're trying to balance between building up a nice |
|
* long list of IOs to improve our merge rate, and |
|
* getting those IOs out quickly for anyone throttling |
|
* in balance_dirty_pages(). cond_resched() doesn't |
|
* unplug, so get our IOs out the door before we |
|
* give up the CPU. |
|
*/ |
|
blk_flush_plug(current); |
|
cond_resched(); |
|
} |
|
|
|
/* |
|
* Requeue @inode if still dirty. Be careful as @inode may |
|
* have been switched to another wb in the meantime. |
|
*/ |
|
tmp_wb = inode_to_wb_and_lock_list(inode); |
|
spin_lock(&inode->i_lock); |
|
if (!(inode->i_state & I_DIRTY_ALL)) |
|
wrote++; |
|
requeue_inode(inode, tmp_wb, &wbc); |
|
inode_sync_complete(inode); |
|
spin_unlock(&inode->i_lock); |
|
|
|
if (unlikely(tmp_wb != wb)) { |
|
spin_unlock(&tmp_wb->list_lock); |
|
spin_lock(&wb->list_lock); |
|
} |
|
|
|
/* |
|
* bail out to wb_writeback() often enough to check |
|
* background threshold and other termination conditions. |
|
*/ |
|
if (wrote) { |
|
if (time_is_before_jiffies(start_time + HZ / 10UL)) |
|
break; |
|
if (work->nr_pages <= 0) |
|
break; |
|
} |
|
} |
|
return wrote; |
|
} |
|
|
|
static long __writeback_inodes_wb(struct bdi_writeback *wb, |
|
struct wb_writeback_work *work) |
|
{ |
|
unsigned long start_time = jiffies; |
|
long wrote = 0; |
|
|
|
while (!list_empty(&wb->b_io)) { |
|
struct inode *inode = wb_inode(wb->b_io.prev); |
|
struct super_block *sb = inode->i_sb; |
|
|
|
if (!trylock_super(sb)) { |
|
/* |
|
* trylock_super() may fail consistently due to |
|
* s_umount being grabbed by someone else. Don't use |
|
* requeue_io() to avoid busy retrying the inode/sb. |
|
*/ |
|
redirty_tail(inode, wb); |
|
continue; |
|
} |
|
wrote += writeback_sb_inodes(sb, wb, work); |
|
up_read(&sb->s_umount); |
|
|
|
/* refer to the same tests at the end of writeback_sb_inodes */ |
|
if (wrote) { |
|
if (time_is_before_jiffies(start_time + HZ / 10UL)) |
|
break; |
|
if (work->nr_pages <= 0) |
|
break; |
|
} |
|
} |
|
/* Leave any unwritten inodes on b_io */ |
|
return wrote; |
|
} |
|
|
|
static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages, |
|
enum wb_reason reason) |
|
{ |
|
struct wb_writeback_work work = { |
|
.nr_pages = nr_pages, |
|
.sync_mode = WB_SYNC_NONE, |
|
.range_cyclic = 1, |
|
.reason = reason, |
|
}; |
|
struct blk_plug plug; |
|
|
|
blk_start_plug(&plug); |
|
spin_lock(&wb->list_lock); |
|
if (list_empty(&wb->b_io)) |
|
queue_io(wb, &work, jiffies); |
|
__writeback_inodes_wb(wb, &work); |
|
spin_unlock(&wb->list_lock); |
|
blk_finish_plug(&plug); |
|
|
|
return nr_pages - work.nr_pages; |
|
} |
|
|
|
/* |
|
* Explicit flushing or periodic writeback of "old" data. |
|
* |
|
* Define "old": the first time one of an inode's pages is dirtied, we mark the |
|
* dirtying-time in the inode's address_space. So this periodic writeback code |
|
* just walks the superblock inode list, writing back any inodes which are |
|
* older than a specific point in time. |
|
* |
|
* Try to run once per dirty_writeback_interval. But if a writeback event |
|
* takes longer than a dirty_writeback_interval interval, then leave a |
|
* one-second gap. |
|
* |
|
* dirtied_before takes precedence over nr_to_write. So we'll only write back |
|
* all dirty pages if they are all attached to "old" mappings. |
|
*/ |
|
static long wb_writeback(struct bdi_writeback *wb, |
|
struct wb_writeback_work *work) |
|
{ |
|
long nr_pages = work->nr_pages; |
|
unsigned long dirtied_before = jiffies; |
|
struct inode *inode; |
|
long progress; |
|
struct blk_plug plug; |
|
|
|
blk_start_plug(&plug); |
|
spin_lock(&wb->list_lock); |
|
for (;;) { |
|
/* |
|
* Stop writeback when nr_pages has been consumed |
|
*/ |
|
if (work->nr_pages <= 0) |
|
break; |
|
|
|
/* |
|
* Background writeout and kupdate-style writeback may |
|
* run forever. Stop them if there is other work to do |
|
* so that e.g. sync can proceed. They'll be restarted |
|
* after the other works are all done. |
|
*/ |
|
if ((work->for_background || work->for_kupdate) && |
|
!list_empty(&wb->work_list)) |
|
break; |
|
|
|
/* |
|
* For background writeout, stop when we are below the |
|
* background dirty threshold |
|
*/ |
|
if (work->for_background && !wb_over_bg_thresh(wb)) |
|
break; |
|
|
|
/* |
|
* Kupdate and background works are special and we want to |
|
* include all inodes that need writing. Livelock avoidance is |
|
* handled by these works yielding to any other work so we are |
|
* safe. |
|
*/ |
|
if (work->for_kupdate) { |
|
dirtied_before = jiffies - |
|
msecs_to_jiffies(dirty_expire_interval * 10); |
|
} else if (work->for_background) |
|
dirtied_before = jiffies; |
|
|
|
trace_writeback_start(wb, work); |
|
if (list_empty(&wb->b_io)) |
|
queue_io(wb, work, dirtied_before); |
|
if (work->sb) |
|
progress = writeback_sb_inodes(work->sb, wb, work); |
|
else |
|
progress = __writeback_inodes_wb(wb, work); |
|
trace_writeback_written(wb, work); |
|
|
|
/* |
|
* Did we write something? Try for more |
|
* |
|
* Dirty inodes are moved to b_io for writeback in batches. |
|
* The completion of the current batch does not necessarily |
|
* mean the overall work is done. So we keep looping as long |
|
* as made some progress on cleaning pages or inodes. |
|
*/ |
|
if (progress) |
|
continue; |
|
/* |
|
* No more inodes for IO, bail |
|
*/ |
|
if (list_empty(&wb->b_more_io)) |
|
break; |
|
/* |
|
* Nothing written. Wait for some inode to |
|
* become available for writeback. Otherwise |
|
* we'll just busyloop. |
|
*/ |
|
trace_writeback_wait(wb, work); |
|
inode = wb_inode(wb->b_more_io.prev); |
|
spin_lock(&inode->i_lock); |
|
spin_unlock(&wb->list_lock); |
|
/* This function drops i_lock... */ |
|
inode_sleep_on_writeback(inode); |
|
spin_lock(&wb->list_lock); |
|
} |
|
spin_unlock(&wb->list_lock); |
|
blk_finish_plug(&plug); |
|
|
|
return nr_pages - work->nr_pages; |
|
} |
|
|
|
/* |
|
* Return the next wb_writeback_work struct that hasn't been processed yet. |
|
*/ |
|
static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb) |
|
{ |
|
struct wb_writeback_work *work = NULL; |
|
|
|
spin_lock_bh(&wb->work_lock); |
|
if (!list_empty(&wb->work_list)) { |
|
work = list_entry(wb->work_list.next, |
|
struct wb_writeback_work, list); |
|
list_del_init(&work->list); |
|
} |
|
spin_unlock_bh(&wb->work_lock); |
|
return work; |
|
} |
|
|
|
static long wb_check_background_flush(struct bdi_writeback *wb) |
|
{ |
|
if (wb_over_bg_thresh(wb)) { |
|
|
|
struct wb_writeback_work work = { |
|
.nr_pages = LONG_MAX, |
|
.sync_mode = WB_SYNC_NONE, |
|
.for_background = 1, |
|
.range_cyclic = 1, |
|
.reason = WB_REASON_BACKGROUND, |
|
}; |
|
|
|
return wb_writeback(wb, &work); |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static long wb_check_old_data_flush(struct bdi_writeback *wb) |
|
{ |
|
unsigned long expired; |
|
long nr_pages; |
|
|
|
/* |
|
* When set to zero, disable periodic writeback |
|
*/ |
|
if (!dirty_writeback_interval) |
|
return 0; |
|
|
|
expired = wb->last_old_flush + |
|
msecs_to_jiffies(dirty_writeback_interval * 10); |
|
if (time_before(jiffies, expired)) |
|
return 0; |
|
|
|
wb->last_old_flush = jiffies; |
|
nr_pages = get_nr_dirty_pages(); |
|
|
|
if (nr_pages) { |
|
struct wb_writeback_work work = { |
|
.nr_pages = nr_pages, |
|
.sync_mode = WB_SYNC_NONE, |
|
.for_kupdate = 1, |
|
.range_cyclic = 1, |
|
.reason = WB_REASON_PERIODIC, |
|
}; |
|
|
|
return wb_writeback(wb, &work); |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static long wb_check_start_all(struct bdi_writeback *wb) |
|
{ |
|
long nr_pages; |
|
|
|
if (!test_bit(WB_start_all, &wb->state)) |
|
return 0; |
|
|
|
nr_pages = get_nr_dirty_pages(); |
|
if (nr_pages) { |
|
struct wb_writeback_work work = { |
|
.nr_pages = wb_split_bdi_pages(wb, nr_pages), |
|
.sync_mode = WB_SYNC_NONE, |
|
.range_cyclic = 1, |
|
.reason = wb->start_all_reason, |
|
}; |
|
|
|
nr_pages = wb_writeback(wb, &work); |
|
} |
|
|
|
clear_bit(WB_start_all, &wb->state); |
|
return nr_pages; |
|
} |
|
|
|
|
|
/* |
|
* Retrieve work items and do the writeback they describe |
|
*/ |
|
static long wb_do_writeback(struct bdi_writeback *wb) |
|
{ |
|
struct wb_writeback_work *work; |
|
long wrote = 0; |
|
|
|
set_bit(WB_writeback_running, &wb->state); |
|
while ((work = get_next_work_item(wb)) != NULL) { |
|
trace_writeback_exec(wb, work); |
|
wrote += wb_writeback(wb, work); |
|
finish_writeback_work(wb, work); |
|
} |
|
|
|
/* |
|
* Check for a flush-everything request |
|
*/ |
|
wrote += wb_check_start_all(wb); |
|
|
|
/* |
|
* Check for periodic writeback, kupdated() style |
|
*/ |
|
wrote += wb_check_old_data_flush(wb); |
|
wrote += wb_check_background_flush(wb); |
|
clear_bit(WB_writeback_running, &wb->state); |
|
|
|
return wrote; |
|
} |
|
|
|
/* |
|
* Handle writeback of dirty data for the device backed by this bdi. Also |
|
* reschedules periodically and does kupdated style flushing. |
|
*/ |
|
void wb_workfn(struct work_struct *work) |
|
{ |
|
struct bdi_writeback *wb = container_of(to_delayed_work(work), |
|
struct bdi_writeback, dwork); |
|
long pages_written; |
|
|
|
set_worker_desc("flush-%s", bdi_dev_name(wb->bdi)); |
|
current->flags |= PF_SWAPWRITE; |
|
|
|
if (likely(!current_is_workqueue_rescuer() || |
|
!test_bit(WB_registered, &wb->state))) { |
|
/* |
|
* The normal path. Keep writing back @wb until its |
|
* work_list is empty. Note that this path is also taken |
|
* if @wb is shutting down even when we're running off the |
|
* rescuer as work_list needs to be drained. |
|
*/ |
|
do { |
|
pages_written = wb_do_writeback(wb); |
|
trace_writeback_pages_written(pages_written); |
|
} while (!list_empty(&wb->work_list)); |
|
} else { |
|
/* |
|
* bdi_wq can't get enough workers and we're running off |
|
* the emergency worker. Don't hog it. Hopefully, 1024 is |
|
* enough for efficient IO. |
|
*/ |
|
pages_written = writeback_inodes_wb(wb, 1024, |
|
WB_REASON_FORKER_THREAD); |
|
trace_writeback_pages_written(pages_written); |
|
} |
|
|
|
if (!list_empty(&wb->work_list)) |
|
wb_wakeup(wb); |
|
else if (wb_has_dirty_io(wb) && dirty_writeback_interval) |
|
wb_wakeup_delayed(wb); |
|
|
|
current->flags &= ~PF_SWAPWRITE; |
|
} |
|
|
|
/* |
|
* Start writeback of `nr_pages' pages on this bdi. If `nr_pages' is zero, |
|
* write back the whole world. |
|
*/ |
|
static void __wakeup_flusher_threads_bdi(struct backing_dev_info *bdi, |
|
enum wb_reason reason) |
|
{ |
|
struct bdi_writeback *wb; |
|
|
|
if (!bdi_has_dirty_io(bdi)) |
|
return; |
|
|
|
list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node) |
|
wb_start_writeback(wb, reason); |
|
} |
|
|
|
void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi, |
|
enum wb_reason reason) |
|
{ |
|
rcu_read_lock(); |
|
__wakeup_flusher_threads_bdi(bdi, reason); |
|
rcu_read_unlock(); |
|
} |
|
|
|
/* |
|
* Wakeup the flusher threads to start writeback of all currently dirty pages |
|
*/ |
|
void wakeup_flusher_threads(enum wb_reason reason) |
|
{ |
|
struct backing_dev_info *bdi; |
|
|
|
/* |
|
* If we are expecting writeback progress we must submit plugged IO. |
|
*/ |
|
if (blk_needs_flush_plug(current)) |
|
blk_schedule_flush_plug(current); |
|
|
|
rcu_read_lock(); |
|
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) |
|
__wakeup_flusher_threads_bdi(bdi, reason); |
|
rcu_read_unlock(); |
|
} |
|
|
|
/* |
|
* Wake up bdi's periodically to make sure dirtytime inodes gets |
|
* written back periodically. We deliberately do *not* check the |
|
* b_dirtytime list in wb_has_dirty_io(), since this would cause the |
|
* kernel to be constantly waking up once there are any dirtytime |
|
* inodes on the system. So instead we define a separate delayed work |
|
* function which gets called much more rarely. (By default, only |
|
* once every 12 hours.) |
|
* |
|
* If there is any other write activity going on in the file system, |
|
* this function won't be necessary. But if the only thing that has |
|
* happened on the file system is a dirtytime inode caused by an atime |
|
* update, we need this infrastructure below to make sure that inode |
|
* eventually gets pushed out to disk. |
|
*/ |
|
static void wakeup_dirtytime_writeback(struct work_struct *w); |
|
static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback); |
|
|
|
static void wakeup_dirtytime_writeback(struct work_struct *w) |
|
{ |
|
struct backing_dev_info *bdi; |
|
|
|
rcu_read_lock(); |
|
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { |
|
struct bdi_writeback *wb; |
|
|
|
list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node) |
|
if (!list_empty(&wb->b_dirty_time)) |
|
wb_wakeup(wb); |
|
} |
|
rcu_read_unlock(); |
|
schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); |
|
} |
|
|
|
static int __init start_dirtytime_writeback(void) |
|
{ |
|
schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); |
|
return 0; |
|
} |
|
__initcall(start_dirtytime_writeback); |
|
|
|
int dirtytime_interval_handler(struct ctl_table *table, int write, |
|
void *buffer, size_t *lenp, loff_t *ppos) |
|
{ |
|
int ret; |
|
|
|
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
|
if (ret == 0 && write) |
|
mod_delayed_work(system_wq, &dirtytime_work, 0); |
|
return ret; |
|
} |
|
|
|
/** |
|
* __mark_inode_dirty - internal function to mark an inode dirty |
|
* |
|
* @inode: inode to mark |
|
* @flags: what kind of dirty, e.g. I_DIRTY_SYNC. This can be a combination of |
|
* multiple I_DIRTY_* flags, except that I_DIRTY_TIME can't be combined |
|
* with I_DIRTY_PAGES. |
|
* |
|
* Mark an inode as dirty. We notify the filesystem, then update the inode's |
|
* dirty flags. Then, if needed we add the inode to the appropriate dirty list. |
|
* |
|
* Most callers should use mark_inode_dirty() or mark_inode_dirty_sync() |
|
* instead of calling this directly. |
|
* |
|
* CAREFUL! We only add the inode to the dirty list if it is hashed or if it |
|
* refers to a blockdev. Unhashed inodes will never be added to the dirty list |
|
* even if they are later hashed, as they will have been marked dirty already. |
|
* |
|
* In short, ensure you hash any inodes _before_ you start marking them dirty. |
|
* |
|
* Note that for blockdevs, inode->dirtied_when represents the dirtying time of |
|
* the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of |
|
* the kernel-internal blockdev inode represents the dirtying time of the |
|
* blockdev's pages. This is why for I_DIRTY_PAGES we always use |
|
* page->mapping->host, so the page-dirtying time is recorded in the internal |
|
* blockdev inode. |
|
*/ |
|
void __mark_inode_dirty(struct inode *inode, int flags) |
|
{ |
|
struct super_block *sb = inode->i_sb; |
|
int dirtytime = 0; |
|
|
|
trace_writeback_mark_inode_dirty(inode, flags); |
|
|
|
if (flags & I_DIRTY_INODE) { |
|
/* |
|
* Notify the filesystem about the inode being dirtied, so that |
|
* (if needed) it can update on-disk fields and journal the |
|
* inode. This is only needed when the inode itself is being |
|
* dirtied now. I.e. it's only needed for I_DIRTY_INODE, not |
|
* for just I_DIRTY_PAGES or I_DIRTY_TIME. |
|
*/ |
|
trace_writeback_dirty_inode_start(inode, flags); |
|
if (sb->s_op->dirty_inode) |
|
sb->s_op->dirty_inode(inode, flags & I_DIRTY_INODE); |
|
trace_writeback_dirty_inode(inode, flags); |
|
|
|
/* I_DIRTY_INODE supersedes I_DIRTY_TIME. */ |
|
flags &= ~I_DIRTY_TIME; |
|
} else { |
|
/* |
|
* Else it's either I_DIRTY_PAGES, I_DIRTY_TIME, or nothing. |
|
* (We don't support setting both I_DIRTY_PAGES and I_DIRTY_TIME |
|
* in one call to __mark_inode_dirty().) |
|
*/ |
|
dirtytime = flags & I_DIRTY_TIME; |
|
WARN_ON_ONCE(dirtytime && flags != I_DIRTY_TIME); |
|
} |
|
|
|
/* |
|
* Paired with smp_mb() in __writeback_single_inode() for the |
|
* following lockless i_state test. See there for details. |
|
*/ |
|
smp_mb(); |
|
|
|
if (((inode->i_state & flags) == flags) || |
|
(dirtytime && (inode->i_state & I_DIRTY_INODE))) |
|
return; |
|
|
|
spin_lock(&inode->i_lock); |
|
if (dirtytime && (inode->i_state & I_DIRTY_INODE)) |
|
goto out_unlock_inode; |
|
if ((inode->i_state & flags) != flags) { |
|
const int was_dirty = inode->i_state & I_DIRTY; |
|
|
|
inode_attach_wb(inode, NULL); |
|
|
|
/* I_DIRTY_INODE supersedes I_DIRTY_TIME. */ |
|
if (flags & I_DIRTY_INODE) |
|
inode->i_state &= ~I_DIRTY_TIME; |
|
inode->i_state |= flags; |
|
|
|
/* |
|
* If the inode is queued for writeback by flush worker, just |
|
* update its dirty state. Once the flush worker is done with |
|
* the inode it will place it on the appropriate superblock |
|
* list, based upon its state. |
|
*/ |
|
if (inode->i_state & I_SYNC_QUEUED) |
|
goto out_unlock_inode; |
|
|
|
/* |
|
* Only add valid (hashed) inodes to the superblock's |
|
* dirty list. Add blockdev inodes as well. |
|
*/ |
|
if (!S_ISBLK(inode->i_mode)) { |
|
if (inode_unhashed(inode)) |
|
goto out_unlock_inode; |
|
} |
|
if (inode->i_state & I_FREEING) |
|
goto out_unlock_inode; |
|
|
|
/* |
|
* If the inode was already on b_dirty/b_io/b_more_io, don't |
|
* reposition it (that would break b_dirty time-ordering). |
|
*/ |
|
if (!was_dirty) { |
|
struct bdi_writeback *wb; |
|
struct list_head *dirty_list; |
|
bool wakeup_bdi = false; |
|
|
|
wb = locked_inode_to_wb_and_lock_list(inode); |
|
|
|
inode->dirtied_when = jiffies; |
|
if (dirtytime) |
|
inode->dirtied_time_when = jiffies; |
|
|
|
if (inode->i_state & I_DIRTY) |
|
dirty_list = &wb->b_dirty; |
|
else |
|
dirty_list = &wb->b_dirty_time; |
|
|
|
wakeup_bdi = inode_io_list_move_locked(inode, wb, |
|
dirty_list); |
|
|
|
spin_unlock(&wb->list_lock); |
|
trace_writeback_dirty_inode_enqueue(inode); |
|
|
|
/* |
|
* If this is the first dirty inode for this bdi, |
|
* we have to wake-up the corresponding bdi thread |
|
* to make sure background write-back happens |
|
* later. |
|
*/ |
|
if (wakeup_bdi && |
|
(wb->bdi->capabilities & BDI_CAP_WRITEBACK)) |
|
wb_wakeup_delayed(wb); |
|
return; |
|
} |
|
} |
|
out_unlock_inode: |
|
spin_unlock(&inode->i_lock); |
|
} |
|
EXPORT_SYMBOL(__mark_inode_dirty); |
|
|
|
/* |
|
* The @s_sync_lock is used to serialise concurrent sync operations |
|
* to avoid lock contention problems with concurrent wait_sb_inodes() calls. |
|
* Concurrent callers will block on the s_sync_lock rather than doing contending |
|
* walks. The queueing maintains sync(2) required behaviour as all the IO that |
|
* has been issued up to the time this function is enter is guaranteed to be |
|
* completed by the time we have gained the lock and waited for all IO that is |
|
* in progress regardless of the order callers are granted the lock. |
|
*/ |
|
static void wait_sb_inodes(struct super_block *sb) |
|
{ |
|
LIST_HEAD(sync_list); |
|
|
|
/* |
|
* We need to be protected against the filesystem going from |
|
* r/o to r/w or vice versa. |
|
*/ |
|
WARN_ON(!rwsem_is_locked(&sb->s_umount)); |
|
|
|
mutex_lock(&sb->s_sync_lock); |
|
|
|
/* |
|
* Splice the writeback list onto a temporary list to avoid waiting on |
|
* inodes that have started writeback after this point. |
|
* |
|
* Use rcu_read_lock() to keep the inodes around until we have a |
|
* reference. s_inode_wblist_lock protects sb->s_inodes_wb as well as |
|
* the local list because inodes can be dropped from either by writeback |
|
* completion. |
|
*/ |
|
rcu_read_lock(); |
|
spin_lock_irq(&sb->s_inode_wblist_lock); |
|
list_splice_init(&sb->s_inodes_wb, &sync_list); |
|
|
|
/* |
|
* Data integrity sync. Must wait for all pages under writeback, because |
|
* there may have been pages dirtied before our sync call, but which had |
|
* writeout started before we write it out. In which case, the inode |
|
* may not be on the dirty list, but we still have to wait for that |
|
* writeout. |
|
*/ |
|
while (!list_empty(&sync_list)) { |
|
struct inode *inode = list_first_entry(&sync_list, struct inode, |
|
i_wb_list); |
|
struct address_space *mapping = inode->i_mapping; |
|
|
|
/* |
|
* Move each inode back to the wb list before we drop the lock |
|
* to preserve consistency between i_wb_list and the mapping |
|
* writeback tag. Writeback completion is responsible to remove |
|
* the inode from either list once the writeback tag is cleared. |
|
*/ |
|
list_move_tail(&inode->i_wb_list, &sb->s_inodes_wb); |
|
|
|
/* |
|
* The mapping can appear untagged while still on-list since we |
|
* do not have the mapping lock. Skip it here, wb completion |
|
* will remove it. |
|
*/ |
|
if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) |
|
continue; |
|
|
|
spin_unlock_irq(&sb->s_inode_wblist_lock); |
|
|
|
spin_lock(&inode->i_lock); |
|
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) { |
|
spin_unlock(&inode->i_lock); |
|
|
|
spin_lock_irq(&sb->s_inode_wblist_lock); |
|
continue; |
|
} |
|
__iget(inode); |
|
spin_unlock(&inode->i_lock); |
|
rcu_read_unlock(); |
|
|
|
/* |
|
* We keep the error status of individual mapping so that |
|
* applications can catch the writeback error using fsync(2). |
|
* See filemap_fdatawait_keep_errors() for details. |
|
*/ |
|
filemap_fdatawait_keep_errors(mapping); |
|
|
|
cond_resched(); |
|
|
|
iput(inode); |
|
|
|
rcu_read_lock(); |
|
spin_lock_irq(&sb->s_inode_wblist_lock); |
|
} |
|
spin_unlock_irq(&sb->s_inode_wblist_lock); |
|
rcu_read_unlock(); |
|
mutex_unlock(&sb->s_sync_lock); |
|
} |
|
|
|
static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr, |
|
enum wb_reason reason, bool skip_if_busy) |
|
{ |
|
struct backing_dev_info *bdi = sb->s_bdi; |
|
DEFINE_WB_COMPLETION(done, bdi); |
|
struct wb_writeback_work work = { |
|
.sb = sb, |
|
.sync_mode = WB_SYNC_NONE, |
|
.tagged_writepages = 1, |
|
.done = &done, |
|
.nr_pages = nr, |
|
.reason = reason, |
|
}; |
|
|
|
if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info) |
|
return; |
|
WARN_ON(!rwsem_is_locked(&sb->s_umount)); |
|
|
|
bdi_split_work_to_wbs(sb->s_bdi, &work, skip_if_busy); |
|
wb_wait_for_completion(&done); |
|
} |
|
|
|
/** |
|
* writeback_inodes_sb_nr - writeback dirty inodes from given super_block |
|
* @sb: the superblock |
|
* @nr: the number of pages to write |
|
* @reason: reason why some writeback work initiated |
|
* |
|
* Start writeback on some inodes on this super_block. No guarantees are made |
|
* on how many (if any) will be written, and this function does not wait |
|
* for IO completion of submitted IO. |
|
*/ |
|
void writeback_inodes_sb_nr(struct super_block *sb, |
|
unsigned long nr, |
|
enum wb_reason reason) |
|
{ |
|
__writeback_inodes_sb_nr(sb, nr, reason, false); |
|
} |
|
EXPORT_SYMBOL(writeback_inodes_sb_nr); |
|
|
|
/** |
|
* writeback_inodes_sb - writeback dirty inodes from given super_block |
|
* @sb: the superblock |
|
* @reason: reason why some writeback work was initiated |
|
* |
|
* Start writeback on some inodes on this super_block. No guarantees are made |
|
* on how many (if any) will be written, and this function does not wait |
|
* for IO completion of submitted IO. |
|
*/ |
|
void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) |
|
{ |
|
return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason); |
|
} |
|
EXPORT_SYMBOL(writeback_inodes_sb); |
|
|
|
/** |
|
* try_to_writeback_inodes_sb - try to start writeback if none underway |
|
* @sb: the superblock |
|
* @reason: reason why some writeback work was initiated |
|
* |
|
* Invoke __writeback_inodes_sb_nr if no writeback is currently underway. |
|
*/ |
|
void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) |
|
{ |
|
if (!down_read_trylock(&sb->s_umount)) |
|
return; |
|
|
|
__writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason, true); |
|
up_read(&sb->s_umount); |
|
} |
|
EXPORT_SYMBOL(try_to_writeback_inodes_sb); |
|
|
|
/** |
|
* sync_inodes_sb - sync sb inode pages |
|
* @sb: the superblock |
|
* |
|
* This function writes and waits on any dirty inode belonging to this |
|
* super_block. |
|
*/ |
|
void sync_inodes_sb(struct super_block *sb) |
|
{ |
|
struct backing_dev_info *bdi = sb->s_bdi; |
|
DEFINE_WB_COMPLETION(done, bdi); |
|
struct wb_writeback_work work = { |
|
.sb = sb, |
|
.sync_mode = WB_SYNC_ALL, |
|
.nr_pages = LONG_MAX, |
|
.range_cyclic = 0, |
|
.done = &done, |
|
.reason = WB_REASON_SYNC, |
|
.for_sync = 1, |
|
}; |
|
|
|
/* |
|
* Can't skip on !bdi_has_dirty() because we should wait for !dirty |
|
* inodes under writeback and I_DIRTY_TIME inodes ignored by |
|
* bdi_has_dirty() need to be written out too. |
|
*/ |
|
if (bdi == &noop_backing_dev_info) |
|
return; |
|
WARN_ON(!rwsem_is_locked(&sb->s_umount)); |
|
|
|
/* protect against inode wb switch, see inode_switch_wbs_work_fn() */ |
|
bdi_down_write_wb_switch_rwsem(bdi); |
|
bdi_split_work_to_wbs(bdi, &work, false); |
|
wb_wait_for_completion(&done); |
|
bdi_up_write_wb_switch_rwsem(bdi); |
|
|
|
wait_sb_inodes(sb); |
|
} |
|
EXPORT_SYMBOL(sync_inodes_sb); |
|
|
|
/** |
|
* write_inode_now - write an inode to disk |
|
* @inode: inode to write to disk |
|
* @sync: whether the write should be synchronous or not |
|
* |
|
* This function commits an inode to disk immediately if it is dirty. This is |
|
* primarily needed by knfsd. |
|
* |
|
* The caller must either have a ref on the inode or must have set I_WILL_FREE. |
|
*/ |
|
int write_inode_now(struct inode *inode, int sync) |
|
{ |
|
struct writeback_control wbc = { |
|
.nr_to_write = LONG_MAX, |
|
.sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE, |
|
.range_start = 0, |
|
.range_end = LLONG_MAX, |
|
}; |
|
|
|
if (!mapping_can_writeback(inode->i_mapping)) |
|
wbc.nr_to_write = 0; |
|
|
|
might_sleep(); |
|
return writeback_single_inode(inode, &wbc); |
|
} |
|
EXPORT_SYMBOL(write_inode_now); |
|
|
|
/** |
|
* sync_inode_metadata - write an inode to disk |
|
* @inode: the inode to sync |
|
* @wait: wait for I/O to complete. |
|
* |
|
* Write an inode to disk and adjust its dirty state after completion. |
|
* |
|
* Note: only writes the actual inode, no associated data or other metadata. |
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*/ |
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int sync_inode_metadata(struct inode *inode, int wait) |
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{ |
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struct writeback_control wbc = { |
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.sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE, |
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.nr_to_write = 0, /* metadata-only */ |
|
}; |
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|
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return writeback_single_inode(inode, &wbc); |
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} |
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EXPORT_SYMBOL(sync_inode_metadata);
|
|
|