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btrfs: compression: don't try to compress if we don't have enough pages

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commit f216562731 upstream.

The early check if we should attempt compression does not take into
account the number of input pages. It can happen that there's only one
page, eg. a tail page after some ranges of the BTRFS_MAX_UNCOMPRESSED
have been processed, or an isolated page that won't be converted to an
inline extent.

The single page would be compressed but a later check would drop it
again because the result size must be at least one block shorter than
the input. That can never work with just one page.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
David Sterba
2021-06-14 12:45:18 +02:00
committed by Greg Kroah-Hartman
parent 34172f601a
commit 6b00b1717f
1 changed files with 1 additions and 1 deletions
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2
fs/btrfs/inode.c
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@@ -547,7 +547,7 @@ again:
* inode has not been flagged as nocompress. This flag can
* change at any time if we discover bad compression ratios.
*/
if (inode_need_compress(BTRFS_I(inode), start, end)) {
if (nr_pages > 1 && inode_need_compress(BTRFS_I(inode), start, end)) {
WARN_ON(pages);
pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
if (!pages) {