[PATCH AUTOSEL 6.12 12/31] btrfs: fix two misuses of folio_shift()

[Sasha Levin]

From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>

[ 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@xxxxxxxx>
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 42c9899d9241c..aa13a3bca715c 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