linux-ext4 - [RFC PATCH 6/8] xfs: Report atomic write min and max for buf io as well

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Message-ID: <9d0ec1039dd3fb40419cef56470ca508f36b8f51.1762945505.git.ojaswin@linux.ibm.com>
Date: Wed, 12 Nov 2025 16:36:09 +0530
From: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To: Christian Brauner <brauner@...nel.org>, djwong@...nel.org,
        ritesh.list@...il.com, john.g.garry@...cle.com, tytso@....edu,
        willy@...radead.org, dchinner@...hat.com, hch@....de
Cc: linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, jack@...e.cz, nilay@...ux.ibm.com,
        martin.petersen@...cle.com, rostedt@...dmis.org, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: [RFC PATCH 6/8] xfs: Report atomic write min and max for buf io as well

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@...ux.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