On Sun, Nov 24, 2024 at 07:38:44AM -0500, Sasha Levin wrote:
From: Qu Wenruo wqu@suse.com
[ Upstream commit f6ebedb09bb276256e084196e2322562dc4aac10 ]
Inside zlib_compress_folios(), each time we switch the input page cache, the @start is increased by PAGE_SIZE.
But for the incoming compression support for sector size < page size (previously we support compression only when the range is fully page aligned), this is not going to handle the following case:
0 32K 64K 96K | |///////////||///////////|@start has the initial value 32K, indicating the start filepos of the to-be-compressed range.
And when grabbing the first page as input, we always call "start += PAGE_SIZE;".
But since @start is starting at 32K, it will be increased by 64K, resulting it to be 96K for the next range, causing incorrect input range and corruption for the future subpage compression.
Fix it by only increase @start by the input size.
Signed-off-by: Qu Wenruo wqu@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org
Please drop this patch from stable, it's preparatory work and has otherwise no effect.