iomap: Fix iomap_adjust_read_range for plen calculation

[ Upstream commit f5ceb1bbc98c69536d4673a97315e8427e67de1b ]

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@gmail.com>
Link: https://lore.kernel.org/r/a32e5f9a4fcfdb99077300c4020ed7ae61d6e0f9.1715067055.git.ritesh.list@gmail.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
cc: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 4ac6c8c403c2653180852ebd92c56670c5b73891..248e615270ff77d9d00ce3eb1f2f71dfc388e4a5 100644 (file)
--- 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)