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439 lines
11 KiB
439 lines
11 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* linux/fs/ext4/readpage.c |
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* |
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* Copyright (C) 2002, Linus Torvalds. |
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* Copyright (C) 2015, Google, Inc. |
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* |
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* This was originally taken from fs/mpage.c |
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* |
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* The ext4_mpage_readpages() function here is intended to |
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* replace mpage_readahead() in the general case, not just for |
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* encrypted files. It has some limitations (see below), where it |
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* will fall back to read_block_full_page(), but these limitations |
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* should only be hit when page_size != block_size. |
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* |
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* This will allow us to attach a callback function to support ext4 |
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* encryption. |
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* |
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* If anything unusual happens, such as: |
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* |
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* - encountering a page which has buffers |
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* - encountering a page which has a non-hole after a hole |
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* - encountering a page with non-contiguous blocks |
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* |
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* then this code just gives up and calls the buffer_head-based read function. |
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* It does handle a page which has holes at the end - that is a common case: |
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* the end-of-file on blocksize < PAGE_SIZE setups. |
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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/mm.h> |
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#include <linux/kdev_t.h> |
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#include <linux/gfp.h> |
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#include <linux/bio.h> |
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#include <linux/fs.h> |
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#include <linux/buffer_head.h> |
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#include <linux/blkdev.h> |
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#include <linux/highmem.h> |
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#include <linux/prefetch.h> |
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#include <linux/mpage.h> |
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#include <linux/writeback.h> |
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#include <linux/backing-dev.h> |
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#include <linux/pagevec.h> |
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#include <linux/cleancache.h> |
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#include "ext4.h" |
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#define NUM_PREALLOC_POST_READ_CTXS 128 |
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static struct kmem_cache *bio_post_read_ctx_cache; |
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static mempool_t *bio_post_read_ctx_pool; |
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/* postprocessing steps for read bios */ |
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enum bio_post_read_step { |
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STEP_INITIAL = 0, |
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STEP_DECRYPT, |
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STEP_VERITY, |
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STEP_MAX, |
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}; |
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struct bio_post_read_ctx { |
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struct bio *bio; |
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struct work_struct work; |
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unsigned int cur_step; |
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unsigned int enabled_steps; |
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}; |
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static void __read_end_io(struct bio *bio) |
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{ |
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struct page *page; |
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struct bio_vec *bv; |
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struct bvec_iter_all iter_all; |
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bio_for_each_segment_all(bv, bio, iter_all) { |
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page = bv->bv_page; |
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/* PG_error was set if any post_read step failed */ |
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if (bio->bi_status || PageError(page)) { |
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ClearPageUptodate(page); |
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/* will re-read again later */ |
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ClearPageError(page); |
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} else { |
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SetPageUptodate(page); |
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} |
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unlock_page(page); |
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} |
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if (bio->bi_private) |
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mempool_free(bio->bi_private, bio_post_read_ctx_pool); |
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bio_put(bio); |
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} |
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static void bio_post_read_processing(struct bio_post_read_ctx *ctx); |
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static void decrypt_work(struct work_struct *work) |
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{ |
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struct bio_post_read_ctx *ctx = |
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container_of(work, struct bio_post_read_ctx, work); |
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fscrypt_decrypt_bio(ctx->bio); |
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bio_post_read_processing(ctx); |
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} |
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static void verity_work(struct work_struct *work) |
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{ |
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struct bio_post_read_ctx *ctx = |
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container_of(work, struct bio_post_read_ctx, work); |
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struct bio *bio = ctx->bio; |
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/* |
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* fsverity_verify_bio() may call readpages() again, and although verity |
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* will be disabled for that, decryption may still be needed, causing |
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* another bio_post_read_ctx to be allocated. So to guarantee that |
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* mempool_alloc() never deadlocks we must free the current ctx first. |
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* This is safe because verity is the last post-read step. |
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*/ |
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BUILD_BUG_ON(STEP_VERITY + 1 != STEP_MAX); |
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mempool_free(ctx, bio_post_read_ctx_pool); |
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bio->bi_private = NULL; |
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fsverity_verify_bio(bio); |
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__read_end_io(bio); |
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} |
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static void bio_post_read_processing(struct bio_post_read_ctx *ctx) |
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{ |
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/* |
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* We use different work queues for decryption and for verity because |
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* verity may require reading metadata pages that need decryption, and |
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* we shouldn't recurse to the same workqueue. |
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*/ |
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switch (++ctx->cur_step) { |
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case STEP_DECRYPT: |
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if (ctx->enabled_steps & (1 << STEP_DECRYPT)) { |
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INIT_WORK(&ctx->work, decrypt_work); |
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fscrypt_enqueue_decrypt_work(&ctx->work); |
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return; |
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} |
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ctx->cur_step++; |
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fallthrough; |
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case STEP_VERITY: |
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if (ctx->enabled_steps & (1 << STEP_VERITY)) { |
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INIT_WORK(&ctx->work, verity_work); |
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fsverity_enqueue_verify_work(&ctx->work); |
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return; |
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} |
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ctx->cur_step++; |
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fallthrough; |
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default: |
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__read_end_io(ctx->bio); |
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} |
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} |
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static bool bio_post_read_required(struct bio *bio) |
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{ |
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return bio->bi_private && !bio->bi_status; |
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} |
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/* |
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* I/O completion handler for multipage BIOs. |
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* |
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* The mpage code never puts partial pages into a BIO (except for end-of-file). |
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* If a page does not map to a contiguous run of blocks then it simply falls |
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* back to block_read_full_page(). |
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* |
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* Why is this? If a page's completion depends on a number of different BIOs |
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* which can complete in any order (or at the same time) then determining the |
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* status of that page is hard. See end_buffer_async_read() for the details. |
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* There is no point in duplicating all that complexity. |
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*/ |
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static void mpage_end_io(struct bio *bio) |
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{ |
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if (bio_post_read_required(bio)) { |
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struct bio_post_read_ctx *ctx = bio->bi_private; |
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ctx->cur_step = STEP_INITIAL; |
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bio_post_read_processing(ctx); |
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return; |
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} |
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__read_end_io(bio); |
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} |
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static inline bool ext4_need_verity(const struct inode *inode, pgoff_t idx) |
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{ |
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return fsverity_active(inode) && |
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idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE); |
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} |
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static void ext4_set_bio_post_read_ctx(struct bio *bio, |
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const struct inode *inode, |
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pgoff_t first_idx) |
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{ |
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unsigned int post_read_steps = 0; |
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if (fscrypt_inode_uses_fs_layer_crypto(inode)) |
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post_read_steps |= 1 << STEP_DECRYPT; |
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if (ext4_need_verity(inode, first_idx)) |
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post_read_steps |= 1 << STEP_VERITY; |
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if (post_read_steps) { |
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/* Due to the mempool, this never fails. */ |
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struct bio_post_read_ctx *ctx = |
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mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS); |
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ctx->bio = bio; |
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ctx->enabled_steps = post_read_steps; |
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bio->bi_private = ctx; |
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} |
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} |
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static inline loff_t ext4_readpage_limit(struct inode *inode) |
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{ |
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if (IS_ENABLED(CONFIG_FS_VERITY) && |
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(IS_VERITY(inode) || ext4_verity_in_progress(inode))) |
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return inode->i_sb->s_maxbytes; |
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return i_size_read(inode); |
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} |
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int ext4_mpage_readpages(struct inode *inode, |
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struct readahead_control *rac, struct page *page) |
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{ |
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struct bio *bio = NULL; |
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sector_t last_block_in_bio = 0; |
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const unsigned blkbits = inode->i_blkbits; |
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const unsigned blocks_per_page = PAGE_SIZE >> blkbits; |
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const unsigned blocksize = 1 << blkbits; |
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sector_t next_block; |
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sector_t block_in_file; |
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sector_t last_block; |
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sector_t last_block_in_file; |
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sector_t blocks[MAX_BUF_PER_PAGE]; |
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unsigned page_block; |
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struct block_device *bdev = inode->i_sb->s_bdev; |
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int length; |
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unsigned relative_block = 0; |
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struct ext4_map_blocks map; |
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unsigned int nr_pages = rac ? readahead_count(rac) : 1; |
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map.m_pblk = 0; |
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map.m_lblk = 0; |
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map.m_len = 0; |
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map.m_flags = 0; |
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for (; nr_pages; nr_pages--) { |
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int fully_mapped = 1; |
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unsigned first_hole = blocks_per_page; |
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if (rac) { |
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page = readahead_page(rac); |
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prefetchw(&page->flags); |
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} |
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if (page_has_buffers(page)) |
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goto confused; |
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block_in_file = next_block = |
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(sector_t)page->index << (PAGE_SHIFT - blkbits); |
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last_block = block_in_file + nr_pages * blocks_per_page; |
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last_block_in_file = (ext4_readpage_limit(inode) + |
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blocksize - 1) >> blkbits; |
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if (last_block > last_block_in_file) |
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last_block = last_block_in_file; |
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page_block = 0; |
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/* |
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* Map blocks using the previous result first. |
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*/ |
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if ((map.m_flags & EXT4_MAP_MAPPED) && |
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block_in_file > map.m_lblk && |
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block_in_file < (map.m_lblk + map.m_len)) { |
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unsigned map_offset = block_in_file - map.m_lblk; |
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unsigned last = map.m_len - map_offset; |
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for (relative_block = 0; ; relative_block++) { |
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if (relative_block == last) { |
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/* needed? */ |
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map.m_flags &= ~EXT4_MAP_MAPPED; |
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break; |
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} |
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if (page_block == blocks_per_page) |
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break; |
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blocks[page_block] = map.m_pblk + map_offset + |
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relative_block; |
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page_block++; |
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block_in_file++; |
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} |
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} |
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/* |
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* Then do more ext4_map_blocks() calls until we are |
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* done with this page. |
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*/ |
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while (page_block < blocks_per_page) { |
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if (block_in_file < last_block) { |
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map.m_lblk = block_in_file; |
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map.m_len = last_block - block_in_file; |
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if (ext4_map_blocks(NULL, inode, &map, 0) < 0) { |
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set_error_page: |
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SetPageError(page); |
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zero_user_segment(page, 0, |
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PAGE_SIZE); |
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unlock_page(page); |
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goto next_page; |
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} |
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} |
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if ((map.m_flags & EXT4_MAP_MAPPED) == 0) { |
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fully_mapped = 0; |
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if (first_hole == blocks_per_page) |
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first_hole = page_block; |
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page_block++; |
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block_in_file++; |
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continue; |
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} |
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if (first_hole != blocks_per_page) |
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goto confused; /* hole -> non-hole */ |
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/* Contiguous blocks? */ |
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if (page_block && blocks[page_block-1] != map.m_pblk-1) |
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goto confused; |
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for (relative_block = 0; ; relative_block++) { |
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if (relative_block == map.m_len) { |
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/* needed? */ |
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map.m_flags &= ~EXT4_MAP_MAPPED; |
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break; |
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} else if (page_block == blocks_per_page) |
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break; |
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blocks[page_block] = map.m_pblk+relative_block; |
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page_block++; |
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block_in_file++; |
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} |
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} |
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if (first_hole != blocks_per_page) { |
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zero_user_segment(page, first_hole << blkbits, |
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PAGE_SIZE); |
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if (first_hole == 0) { |
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if (ext4_need_verity(inode, page->index) && |
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!fsverity_verify_page(page)) |
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goto set_error_page; |
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SetPageUptodate(page); |
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unlock_page(page); |
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goto next_page; |
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} |
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} else if (fully_mapped) { |
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SetPageMappedToDisk(page); |
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} |
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if (fully_mapped && blocks_per_page == 1 && |
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!PageUptodate(page) && cleancache_get_page(page) == 0) { |
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SetPageUptodate(page); |
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goto confused; |
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} |
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/* |
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* This page will go to BIO. Do we need to send this |
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* BIO off first? |
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*/ |
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if (bio && (last_block_in_bio != blocks[0] - 1 || |
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!fscrypt_mergeable_bio(bio, inode, next_block))) { |
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submit_and_realloc: |
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submit_bio(bio); |
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bio = NULL; |
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} |
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if (bio == NULL) { |
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/* |
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* bio_alloc will _always_ be able to allocate a bio if |
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* __GFP_DIRECT_RECLAIM is set, see bio_alloc_bioset(). |
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*/ |
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bio = bio_alloc(GFP_KERNEL, bio_max_segs(nr_pages)); |
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fscrypt_set_bio_crypt_ctx(bio, inode, next_block, |
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GFP_KERNEL); |
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ext4_set_bio_post_read_ctx(bio, inode, page->index); |
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bio_set_dev(bio, bdev); |
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bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9); |
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bio->bi_end_io = mpage_end_io; |
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bio_set_op_attrs(bio, REQ_OP_READ, |
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rac ? REQ_RAHEAD : 0); |
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} |
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length = first_hole << blkbits; |
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if (bio_add_page(bio, page, length, 0) < length) |
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goto submit_and_realloc; |
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if (((map.m_flags & EXT4_MAP_BOUNDARY) && |
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(relative_block == map.m_len)) || |
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(first_hole != blocks_per_page)) { |
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submit_bio(bio); |
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bio = NULL; |
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} else |
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last_block_in_bio = blocks[blocks_per_page - 1]; |
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goto next_page; |
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confused: |
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if (bio) { |
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submit_bio(bio); |
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bio = NULL; |
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} |
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if (!PageUptodate(page)) |
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block_read_full_page(page, ext4_get_block); |
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else |
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unlock_page(page); |
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next_page: |
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if (rac) |
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put_page(page); |
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} |
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if (bio) |
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submit_bio(bio); |
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return 0; |
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} |
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int __init ext4_init_post_read_processing(void) |
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{ |
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bio_post_read_ctx_cache = |
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kmem_cache_create("ext4_bio_post_read_ctx", |
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sizeof(struct bio_post_read_ctx), 0, 0, NULL); |
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if (!bio_post_read_ctx_cache) |
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goto fail; |
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bio_post_read_ctx_pool = |
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mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS, |
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bio_post_read_ctx_cache); |
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if (!bio_post_read_ctx_pool) |
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goto fail_free_cache; |
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return 0; |
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fail_free_cache: |
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kmem_cache_destroy(bio_post_read_ctx_cache); |
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fail: |
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return -ENOMEM; |
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} |
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void ext4_exit_post_read_processing(void) |
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{ |
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mempool_destroy(bio_post_read_ctx_pool); |
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kmem_cache_destroy(bio_post_read_ctx_cache); |
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}
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