[RFC PATCH 6/8] xfs: Report atomic write min and max for buf io as well

Ojaswin Mujoo
2025-11-12T11:07:39Z

Now that we can reliably perform a HW based single block buffered atomic
write for page size == blocksize, start advertising it in XFS.

Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
---
fs/xfs/xfs_iops.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index f036c46b19c5..67d370947d95 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -604,9 +604,10 @@ xfs_get_atomic_write_min(
struct xfs_inode *ip,
bool is_dio)
{
- if (is_dio) {
- struct xfs_mount *mp = ip->i_mount;
+ struct xfs_mount *mp = ip->i_mount;
+ uint32_t bs = mp->m_sb.sb_blocksize;

+ if (is_dio) {
/*
* If we can complete an atomic write via atomic out of place writes,
* then advertise a minimum size of one fsblock. Without this
@@ -618,10 +619,15 @@ xfs_get_atomic_write_min(
*/
if (xfs_inode_can_hw_atomic_write(ip) ||
xfs_inode_can_sw_atomic_write(ip))
- return mp->m_sb.sb_blocksize;
+ return bs;
}
+ /*
+ * Buffered IO only supports hw single block atomic writes and bs == ps
+ * configurations.
+ */
+ if (xfs_inode_can_hw_atomic_write(ip) && bs == PAGE_SIZE)
+ return bs;

- /* buffered IO not supported yet so return 0 right away */
return 0;
}

@@ -630,7 +636,8 @@ xfs_get_atomic_write_max(
struct xfs_inode *ip,
bool is_dio)
{
- struct xfs_mount *mp = ip->i_mount;
+ struct xfs_mount *mp = ip->i_mount;
+ uint32_t bs = mp->m_sb.sb_blocksize;

if (is_dio) {
/*
@@ -640,7 +647,7 @@ xfs_get_atomic_write_max(
*/
if (!xfs_inode_can_sw_atomic_write(ip)) {
if (xfs_inode_can_hw_atomic_write(ip))
- return mp->m_sb.sb_blocksize;
+ return bs;
return 0;
}

@@ -653,8 +660,13 @@ xfs_get_atomic_write_max(
return XFS_FSB_TO_B(mp, mp->m_groups[XG_TYPE_RTG].awu_max);
return XFS_FSB_TO_B(mp, mp->m_groups[XG_TYPE_AG].awu_max);
}
+ /*
+ * Buffered IO only supports hw single block atomic writes and bs == ps
+ * configurations.
+ */
+ if (xfs_inode_can_hw_atomic_write(ip) && bs == PAGE_SIZE)
+ return bs;

- /* buffered IO not supported yet so return 0 right away */
return 0;
}

@@ -679,7 +691,7 @@ xfs_get_atomic_write_max_opt(
return min(awu_max, xfs_inode_buftarg(ip)->bt_awu_max);
}

- /* buffered IO not supported yet so return 0 right away */
+ /* buffered IO for now only supports 1 filesyste block so max_opt is 0 */
return 0;
}

--
2.51.0