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btrfs: zstd: make the compression path to handle sector size < page size

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Inside zstd_compress_folios(), after exhausted one input page, we need
to switch to the next page as input.

However when counting the total input bytes (@tot_in), we always increase
it by PAGE_SIZE.

For the following case, it can cause incorrect value:

        0          32K         64K          96K
        |          |///////////||///////////|

After compressing range [32K, 64K), we switch to the next page, and
increasing @tot_in by 64K, while we only read 32K.

This will cause the @total_in to return a value larger than the input
length.

Fix it by only increase @tot_in by the input size.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2024-09-06 13:40:30 +09:30 committed by David Sterba
parent f6ebedb09b
commit 90275a7762
1 changed files with 1 additions and 1 deletions
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2
fs/btrfs/zstd.c
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@ -495,7 +495,7 @@ int zstd_compress_folios(struct list_head *ws, struct address_space *mapping,
/* Check if we need more input */
if (workspace->in_buf.pos == workspace->in_buf.size) {
tot_in += PAGE_SIZE;
tot_in += workspace->in_buf.size;
kunmap_local(workspace->in_buf.src);
workspace->in_buf.src = NULL;
folio_put(in_folio);