ext4: add fs-verity read support
Make ext4_mpage_readpages() verify data as it is read from fs-verity files, using the helper functions from fs/verity/. To support both encryption and verity simultaneously, this required refactoring the decryption workflow into a generic "post-read processing" workflow which can do decryption, verification, or both. The case where the ext4 block size is not equal to the PAGE_SIZE is not supported yet, since in that case ext4_mpage_readpages() sometimes falls back to block_read_full_page(), which does not support fs-verity yet. Co-developed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers
parent
c93d8f8858
commit
22cfe4b48c
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@ -3191,6 +3191,8 @@ static inline void ext4_set_de_type(struct super_block *sb,
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extern int ext4_mpage_readpages(struct address_space *mapping,
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struct list_head *pages, struct page *page,
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unsigned nr_pages, bool is_readahead);
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extern int __init ext4_init_post_read_processing(void);
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extern void ext4_exit_post_read_processing(void);
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/* symlink.c */
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extern const struct inode_operations ext4_encrypted_symlink_inode_operations;
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@ -3912,6 +3912,8 @@ static ssize_t ext4_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
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if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
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return 0;
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#endif
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if (fsverity_active(inode))
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return 0;
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/*
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* If we are doing data journalling we don't support O_DIRECT
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@ -47,13 +47,103 @@
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#include "ext4.h"
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static inline bool ext4_bio_encrypted(struct bio *bio)
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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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};
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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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#ifdef CONFIG_FS_ENCRYPTION
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return unlikely(bio->bi_private != NULL);
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#else
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return false;
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#endif
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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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fsverity_verify_bio(ctx->bio);
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bio_post_read_processing(ctx);
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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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/* fall-through */
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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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/* fall-through */
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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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@ -70,30 +160,53 @@ static inline bool ext4_bio_encrypted(struct bio *bio)
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*/
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static void mpage_end_io(struct bio *bio)
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{
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struct bio_vec *bv;
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struct bvec_iter_all iter_all;
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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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if (ext4_bio_encrypted(bio)) {
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if (bio->bi_status) {
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fscrypt_release_ctx(bio->bi_private);
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} else {
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fscrypt_enqueue_decrypt_bio(bio->bi_private, bio);
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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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}
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bio_for_each_segment_all(bv, bio, iter_all) {
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struct page *page = bv->bv_page;
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if (!bio->bi_status) {
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SetPageUptodate(page);
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} else {
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ClearPageUptodate(page);
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SetPageError(page);
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}
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unlock_page(page);
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__read_end_io(bio);
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}
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bio_put(bio);
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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 struct bio_post_read_ctx *get_bio_post_read_ctx(struct inode *inode,
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struct bio *bio,
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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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struct bio_post_read_ctx *ctx = NULL;
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if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
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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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ctx = mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
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if (!ctx)
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return ERR_PTR(-ENOMEM);
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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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return ctx;
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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 address_space *mapping,
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@ -141,7 +254,8 @@ int ext4_mpage_readpages(struct address_space *mapping,
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block_in_file = (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 = (i_size_read(inode) + blocksize - 1) >> blkbits;
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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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@ -218,6 +332,9 @@ int ext4_mpage_readpages(struct address_space *mapping,
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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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@ -241,18 +358,16 @@ int ext4_mpage_readpages(struct address_space *mapping,
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bio = NULL;
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}
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if (bio == NULL) {
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struct fscrypt_ctx *ctx = NULL;
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struct bio_post_read_ctx *ctx;
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if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode)) {
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ctx = fscrypt_get_ctx(GFP_NOFS);
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if (IS_ERR(ctx))
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goto set_error_page;
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}
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bio = bio_alloc(GFP_KERNEL,
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min_t(int, nr_pages, BIO_MAX_PAGES));
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if (!bio) {
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if (ctx)
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fscrypt_release_ctx(ctx);
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if (!bio)
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goto set_error_page;
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ctx = get_bio_post_read_ctx(inode, bio, page->index);
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if (IS_ERR(ctx)) {
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bio_put(bio);
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bio = NULL;
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goto set_error_page;
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}
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bio_set_dev(bio, bdev);
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@ -293,3 +408,29 @@ int ext4_mpage_readpages(struct address_space *mapping,
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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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@ -6103,6 +6103,10 @@ static int __init ext4_init_fs(void)
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return err;
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err = ext4_init_pending();
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if (err)
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goto out7;
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err = ext4_init_post_read_processing();
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if (err)
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goto out6;
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@ -6144,8 +6148,10 @@ out3:
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out4:
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ext4_exit_pageio();
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out5:
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ext4_exit_pending();
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ext4_exit_post_read_processing();
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out6:
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ext4_exit_pending();
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out7:
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ext4_exit_es();
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return err;
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@ -6162,6 +6168,7 @@ static void __exit ext4_exit_fs(void)
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ext4_exit_sysfs();
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ext4_exit_system_zone();
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ext4_exit_pageio();
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ext4_exit_post_read_processing();
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ext4_exit_es();
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ext4_exit_pending();
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}
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