linux-ext4 - [PATCHv2 1/2] iomap: Fix iomap_adjust_read

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Message-ID: <a32e5f9a4fcfdb99077300c4020ed7ae61d6e0f9.1715067055.git.ritesh.list@gmail.com>
Date: Tue,  7 May 2024 14:25:42 +0530
From: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To: linux-xfs@...r.kernel.org
Cc: linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Matthew Wilcox <willy@...radead.org>,
	"Darrick J . Wong" <djwong@...nel.org>,
	Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
	Ritesh Harjani <ritesh.list@...il.com>,
	Jan Kara <jack@...e.cz>,
	Christoph Hellwig <hch@....de>
Subject: [PATCHv2 1/2] iomap: Fix iomap_adjust_read_range for plen calculation

If the extent spans the block that contains i_size, we need to handle
both halves separately so that we properly zero data in the page cache
for blocks that are entirely outside of i_size. But this is needed only
when i_size is within the current folio under processing.
"orig_pos + length > isize" can be true for all folios if the mapped
extent length is greater than the folio size. That is making plen to
break for every folio instead of only the last folio.

So use orig_plen for checking if "orig_pos + orig_plen > isize".

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
cc: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Darrick J. Wong <djwong@...nel.org>
---
 fs/iomap/buffered-io.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 4e8e41c8b3c0..9f79c82d1f73 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -241,6 +241,7 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
 	unsigned block_size = (1 << block_bits);
 	size_t poff = offset_in_folio(folio, *pos);
 	size_t plen = min_t(loff_t, folio_size(folio) - poff, length);
+	size_t orig_plen = plen;
 	unsigned first = poff >> block_bits;
 	unsigned last = (poff + plen - 1) >> block_bits;

@@ -277,7 +278,7 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
 	 * handle both halves separately so that we properly zero data in the
 	 * page cache for blocks that are entirely outside of i_size.
 	 */
-	if (orig_pos <= isize && orig_pos + length > isize) {
+	if (orig_pos <= isize && orig_pos + orig_plen > isize) {
 		unsigned end = offset_in_folio(folio, isize - 1) >> block_bits;

 		if (first <= end && last > end)
--
2.44.0