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163 lines
4.5 KiB
163 lines
4.5 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Copyright (c) 2016 Trond Myklebust |
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* Copyright (c) 2019 Jeff Layton |
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* |
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* I/O and data path helper functionality. |
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* |
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* Heavily borrowed from equivalent code in fs/nfs/io.c |
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*/ |
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#include <linux/ceph/ceph_debug.h> |
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#include <linux/types.h> |
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#include <linux/kernel.h> |
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#include <linux/rwsem.h> |
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#include <linux/fs.h> |
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#include "super.h" |
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#include "io.h" |
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/* Call with exclusively locked inode->i_rwsem */ |
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static void ceph_block_o_direct(struct ceph_inode_info *ci, struct inode *inode) |
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{ |
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lockdep_assert_held_write(&inode->i_rwsem); |
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if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT) { |
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spin_lock(&ci->i_ceph_lock); |
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ci->i_ceph_flags &= ~CEPH_I_ODIRECT; |
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spin_unlock(&ci->i_ceph_lock); |
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inode_dio_wait(inode); |
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} |
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} |
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/** |
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* ceph_start_io_read - declare the file is being used for buffered reads |
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* @inode: file inode |
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* |
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* Declare that a buffered read operation is about to start, and ensure |
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* that we block all direct I/O. |
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* On exit, the function ensures that the CEPH_I_ODIRECT flag is unset, |
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* and holds a shared lock on inode->i_rwsem to ensure that the flag |
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* cannot be changed. |
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* In practice, this means that buffered read operations are allowed to |
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* execute in parallel, thanks to the shared lock, whereas direct I/O |
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* operations need to wait to grab an exclusive lock in order to set |
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* CEPH_I_ODIRECT. |
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* Note that buffered writes and truncates both take a write lock on |
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* inode->i_rwsem, meaning that those are serialised w.r.t. the reads. |
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*/ |
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void |
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ceph_start_io_read(struct inode *inode) |
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{ |
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struct ceph_inode_info *ci = ceph_inode(inode); |
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/* Be an optimist! */ |
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down_read(&inode->i_rwsem); |
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if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)) |
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return; |
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up_read(&inode->i_rwsem); |
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/* Slow path.... */ |
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down_write(&inode->i_rwsem); |
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ceph_block_o_direct(ci, inode); |
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downgrade_write(&inode->i_rwsem); |
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} |
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/** |
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* ceph_end_io_read - declare that the buffered read operation is done |
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* @inode: file inode |
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* |
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* Declare that a buffered read operation is done, and release the shared |
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* lock on inode->i_rwsem. |
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*/ |
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void |
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ceph_end_io_read(struct inode *inode) |
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{ |
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up_read(&inode->i_rwsem); |
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} |
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/** |
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* ceph_start_io_write - declare the file is being used for buffered writes |
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* @inode: file inode |
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* |
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* Declare that a buffered write operation is about to start, and ensure |
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* that we block all direct I/O. |
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*/ |
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void |
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ceph_start_io_write(struct inode *inode) |
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{ |
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down_write(&inode->i_rwsem); |
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ceph_block_o_direct(ceph_inode(inode), inode); |
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} |
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/** |
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* ceph_end_io_write - declare that the buffered write operation is done |
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* @inode: file inode |
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* |
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* Declare that a buffered write operation is done, and release the |
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* lock on inode->i_rwsem. |
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*/ |
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void |
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ceph_end_io_write(struct inode *inode) |
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{ |
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up_write(&inode->i_rwsem); |
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} |
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/* Call with exclusively locked inode->i_rwsem */ |
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static void ceph_block_buffered(struct ceph_inode_info *ci, struct inode *inode) |
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{ |
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lockdep_assert_held_write(&inode->i_rwsem); |
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if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)) { |
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spin_lock(&ci->i_ceph_lock); |
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ci->i_ceph_flags |= CEPH_I_ODIRECT; |
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spin_unlock(&ci->i_ceph_lock); |
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/* FIXME: unmap_mapping_range? */ |
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filemap_write_and_wait(inode->i_mapping); |
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} |
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} |
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/** |
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* ceph_start_io_direct - declare the file is being used for direct i/o |
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* @inode: file inode |
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* |
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* Declare that a direct I/O operation is about to start, and ensure |
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* that we block all buffered I/O. |
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* On exit, the function ensures that the CEPH_I_ODIRECT flag is set, |
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* and holds a shared lock on inode->i_rwsem to ensure that the flag |
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* cannot be changed. |
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* In practice, this means that direct I/O operations are allowed to |
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* execute in parallel, thanks to the shared lock, whereas buffered I/O |
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* operations need to wait to grab an exclusive lock in order to clear |
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* CEPH_I_ODIRECT. |
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* Note that buffered writes and truncates both take a write lock on |
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* inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT. |
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*/ |
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void |
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ceph_start_io_direct(struct inode *inode) |
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{ |
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struct ceph_inode_info *ci = ceph_inode(inode); |
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/* Be an optimist! */ |
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down_read(&inode->i_rwsem); |
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if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT) |
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return; |
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up_read(&inode->i_rwsem); |
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/* Slow path.... */ |
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down_write(&inode->i_rwsem); |
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ceph_block_buffered(ci, inode); |
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downgrade_write(&inode->i_rwsem); |
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} |
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/** |
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* ceph_end_io_direct - declare that the direct i/o operation is done |
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* @inode: file inode |
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* |
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* Declare that a direct I/O operation is done, and release the shared |
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* lock on inode->i_rwsem. |
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*/ |
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void |
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ceph_end_io_direct(struct inode *inode) |
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{ |
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up_read(&inode->i_rwsem); |
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}
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