On Sun, Nov 24, 2024 at 07:38:45AM -0500, Sasha Levin wrote: > From: Qu Wenruo <wqu@xxxxxxxx> > > [ Upstream commit a4ef54dbb576032ba31a646a5ffc8a26a83cb92c ] > > For btrfs with sector size < page size (e.g. 4K sector size, 64K page > size), and enable the sector perfect compression support, then the > following dirty range can lead to problems: > > 0 32K 64K 96K 128K > | |///////||//////| |/| > 124K > > In above case, if we start writeback for that inode, the last dirty > range [124K, 128K) will not be submitted and cause reserved space > leakage: > > - Start writeback for page 0 > We find the range [32K, 96K) is suitable for compression, and queue it > into a workqueue to do the delayed compression and submission. > > - Compression happens for range [32K, 96K) > Function extent_range_clear_dirty_for_io() is called, however it is > only doing full page handling, not considering any the extra bitmaps > for subpage cases. > > That function will clear page dirty for both page 0 and page 64K. > > - Writeback for the inode is done > Because page 64K has its dirty flag cleared, it will not be considered > as a writeback target. > > This means the range [124K, 128K) will not be submitted, and reserved > space for it will be leaked. > > Fix this problem by using the subpage helper to clear the dirty flag. > > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> > Signed-off-by: David Sterba <dsterba@xxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> Please drop this patch from stable, it's preparatory work and has otherwise no effect.
