[PATCH 12/43] xfs: refine the unaligned check for always COW inodes in xfs_file_dio_write

Christoph Hellwig
2024-12-11T08:57:10Z

For always COW inodes we also must check the alignment of each individual
iovec segment, as they could end up with different I/Os due to the way
bio_iov_iter_get_pages works, and we'd then overwrite an already written
block.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/xfs_file.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 2b6d4c71994d..6bcfd4c34a37 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -721,7 +721,16 @@ xfs_file_dio_write(
/* direct I/O must be aligned to device logical sector size */
if ((iocb->ki_pos | count) & target->bt_logical_sectormask)
return -EINVAL;
- if ((iocb->ki_pos | count) & ip->i_mount->m_blockmask)
+
+ /*
+ * For always COW inodes we also must check the alignment of each
+ * individual iovec segment, as they could end up with different
+ * I/Os due to the way bio_iov_iter_get_pages works, and we'd
+ * then overwrite an already written block.
+ */
+ if (((iocb->ki_pos | count) & ip->i_mount->m_blockmask) ||
+ (xfs_is_always_cow_inode(ip) &&
+ (iov_iter_alignment(from) & ip->i_mount->m_blockmask)))
return xfs_file_dio_write_unaligned(ip, iocb, from);
return xfs_file_dio_write_aligned(ip, iocb, from);
}
--
2.45.2