xfs: refine atomic write size check in xfs_file_write_iter()

Currently the size of atomic write allowed is fixed at the blocksize.

To start to lift this restriction, partly refactor
xfs_report_atomic_write() to into helpers -
xfs_get_atomic_write_{min, max}() - and use those helpers to find the
per-inode atomic write limits and check according to that.

Also add xfs_get_atomic_write_max_opt() to return the optimal limit, and
just return 0 since large atomics aren't supported yet.

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

1 files changed, 31 insertions, 5 deletions

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 22432c300fd7..77a0606e9dc9 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -601,16 +601,42 @@ xfs_report_dioalign(
 		stat->dio_offset_align = stat->dio_read_offset_align;
 }
 
+unsigned int
+xfs_get_atomic_write_min(
+	struct xfs_inode	*ip)
+{
+	if (!xfs_inode_can_hw_atomic_write(ip))
+		return 0;
+
+	return ip->i_mount->m_sb.sb_blocksize;
+}
+
+unsigned int
+xfs_get_atomic_write_max(
+	struct xfs_inode	*ip)
+{
+	if (!xfs_inode_can_hw_atomic_write(ip))
+		return 0;
+
+	return ip->i_mount->m_sb.sb_blocksize;
+}
+
+unsigned int
+xfs_get_atomic_write_max_opt(
+	struct xfs_inode	*ip)
+{
+	return 0;
+}
+
 static void
 xfs_report_atomic_write(
 	struct xfs_inode	*ip,
 	struct kstat		*stat)
 {
-	unsigned int		unit_min = 0, unit_max = 0;
-
-	if (xfs_inode_can_hw_atomic_write(ip))
-		unit_min = unit_max = ip->i_mount->m_sb.sb_blocksize;
-	generic_fill_statx_atomic_writes(stat, unit_min, unit_max, 0);
+	generic_fill_statx_atomic_writes(stat,
+			xfs_get_atomic_write_min(ip),
+			xfs_get_atomic_write_max(ip),
+			xfs_get_atomic_write_max_opt(ip));
 }
 
 STATIC int