[PATCH AUTOSEL 6.13 12/31] btrfs: fix two misuses of folio_shift()

Sasha Levin
2025-02-18T20:25:23Z

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

[ Upstream commit 01af106a076352182b2916b143fc50272600bd81 ]

It is meaningless to shift a byte count by folio_shift(). The folio index
is in units of PAGE_SIZE, not folio_size(). We can use folio_contains()
to make this work for arbitrary-order folios, so remove the assertion
that the folios are of order 0.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/extent_io.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index b923d0cec61c7..a8e0076d44c72 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -526,8 +526,6 @@ static void end_bbio_data_read(struct btrfs_bio *bbio)
u64 end;
u32 len;

- /* For now only order 0 folios are supported for data. */
- ASSERT(folio_order(folio) == 0);
btrfs_debug(fs_info,
"%s: bi_sector=%llu, err=%d, mirror=%u",
__func__, bio->bi_iter.bi_sector, bio->bi_status,
@@ -555,7 +553,6 @@ static void end_bbio_data_read(struct btrfs_bio *bbio)

if (likely(uptodate)) {
loff_t i_size = i_size_read(inode);
- pgoff_t end_index = i_size >> folio_shift(folio);

/*
* Zero out the remaining part if this range straddles
@@ -564,9 +561,11 @@ static void end_bbio_data_read(struct btrfs_bio *bbio)
* Here we should only zero the range inside the folio,
* not touch anything else.
*
- * NOTE: i_size is exclusive while end is inclusive.
+ * NOTE: i_size is exclusive while end is inclusive and
+ * folio_contains() takes PAGE_SIZE units.
*/
- if (folio_index(folio) == end_index && i_size <= end) {
+ if (folio_contains(folio, i_size >> PAGE_SHIFT) &&
+ i_size <= end) {
u32 zero_start = max(offset_in_folio(folio, i_size),
offset_in_folio(folio, start));
u32 zero_len = offset_in_folio(folio, end) + 1 -
@@ -963,7 +962,7 @@ static int btrfs_do_readpage(struct folio *folio, struct extent_map **em_cached,
return ret;
}

- if (folio->index == last_byte >> folio_shift(folio)) {
+ if (folio_contains(folio, last_byte >> PAGE_SHIFT)) {
size_t zero_offset = offset_in_folio(folio, last_byte);

if (zero_offset) {
--
2.39.5