xfs: ignore HW which cannot atomic write a single block

Currently only HW which can write at least 1x block is supported.

For supporting atomic writes > 1x block, a CoW-based method will also be
used and this will not be resticted to using HW which can write >= 1x
block.

However for deciding if HW-based atomic writes can be used, we need to
start adding checks for write length < HW min, which complicates the
code.  Indeed, a statx field similar to unit_max_opt should also be
added for this minimum, which is undesirable.

HW which can only write > 1x blocks would be uncommon and quite weird,
so let's just not support it.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 12 insertions, 0 deletions

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index e2374c503e79..d52d9587b42c 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1722,11 +1722,23 @@ static inline void
 xfs_configure_buftarg_atomic_writes(
 	struct xfs_buftarg	*btp)
 {
+	struct xfs_mount	*mp = btp->bt_mount;
 	unsigned int		min_bytes, max_bytes;
 
 	min_bytes = bdev_atomic_write_unit_min_bytes(btp->bt_bdev);
 	max_bytes = bdev_atomic_write_unit_max_bytes(btp->bt_bdev);
 
+	/*
+	 * Ignore atomic write geometry that is nonsense or doesn't even cover
+	 * a single fsblock.
+	 */
+	if (min_bytes > max_bytes ||
+	    min_bytes > mp->m_sb.sb_blocksize ||
+	    max_bytes < mp->m_sb.sb_blocksize) {
+		min_bytes = 0;
+		max_bytes = 0;
+	}
+
 	btp->bt_bdev_awu_min = min_bytes;
 	btp->bt_bdev_awu_max = max_bytes;
 }