From: Qu Wenruo wqu@suse.com
[ Upstream commit 951c80f83d61bd4b21794c8aba829c3c1a45c2d0 ]
Commit dbfdb6d1b369 ("Btrfs: Search for all ordered extents that could span across a page") make btrfs_invalidapage() to search all ordered extents.
The offending code looks like this:
again: start = page_start; ordered = btrfs_lookup_ordered_range(inode, start, page_end - start + 1); if (ordred) { end = min(page_end, ordered->file_offset + ordered->num_bytes - 1);
/* Do the cleanup */
start = end + 1; if (start < page_end) goto again; }
The behavior is indeed necessary for the incoming subpage support, but when it iterates through all the ordered extents, it also resets the search range @start.
This means, for the following cases, we can double account the ordered extents, causing its bytes_left underflow:
Page offset 0 16K 32K |<--- OE 1 --->|<--- OE 2 ---->|
As the first iteration will find ordered extent (OE) 1, which doesn't cover the full page, thus after cleanup code, we need to retry again. But again label will reset start to page_start, and we got OE 1 again, which causes double accounting on OE 1, and cause OE 1's byte_left to underflow.
This problem can only happen for subpage case, as for regular sectorsize == PAGE_SIZE case, we will always find a OE ends at or after page end, thus no way to trigger the problem.
Move the again label after start = page_start. There will be more comprehensive rework to convert the open coded loop to a proper while loop for subpage support.
Fixes: dbfdb6d1b369 ("Btrfs: Search for all ordered extents that could span across a page") Reviewed-by: Filipe Manana fdmanana@suse.com Signed-off-by: Qu Wenruo wqu@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/inode.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index b536d21541a9f..4d85f3a6695d1 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8207,8 +8207,9 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset,
if (!inode_evicting) lock_extent_bits(tree, page_start, page_end, &cached_state); -again: + start = page_start; +again: ordered = btrfs_lookup_ordered_range(inode, start, page_end - start + 1); if (ordered) { end = min(page_end,