linux-kernel - [PATCH v8 05/15] xfs: ignore HW which cannot atomic write a single block

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Message-Id: <20250422122739.2230121-6-john.g.garry@oracle.com>
Date: Tue, 22 Apr 2025 12:27:29 +0000
From: John Garry <john.g.garry@...cle.com>
To: brauner@...nel.org, djwong@...nel.org, hch@....de, viro@...iv.linux.org.uk,
        jack@...e.cz, cem@...nel.org
Cc: linux-fsdevel@...r.kernel.org, dchinner@...hat.com,
        linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        ojaswin@...ux.ibm.com, ritesh.list@...il.com,
        martin.petersen@...cle.com, linux-ext4@...r.kernel.org,
        linux-block@...r.kernel.org, catherine.hoang@...cle.com,
        linux-api@...r.kernel.org, John Garry <john.g.garry@...cle.com>
Subject: [PATCH v8 05/15] 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: John Garry <john.g.garry@...cle.com>
---
 fs/xfs/xfs_inode.h | 17 ++++++++---------
 fs/xfs/xfs_mount.c | 14 ++++++++++++++
 fs/xfs/xfs_mount.h |  4 ++++
 3 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index cff643cd03fc..725cd7c16a6e 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -355,20 +355,19 @@ static inline bool xfs_inode_has_bigrtalloc(const struct xfs_inode *ip)
 #define xfs_inode_buftarg(ip) \
 	(XFS_IS_REALTIME_INODE(ip) ? \
 		(ip)->i_mount->m_rtdev_targp : (ip)->i_mount->m_ddev_targp)
+/*
+ * Return max atomic write unit for a given inode.
+ */
+#define xfs_inode_hw_atomicwrite_max(ip) \
+	(XFS_IS_REALTIME_INODE(ip) ? \
+		(ip)->i_mount->m_rt_awu_hw_max : \
+		(ip)->i_mount->m_dd_awu_hw_max)
 
 static inline bool
 xfs_inode_can_hw_atomicwrite(
 	struct xfs_inode	*ip)
 {
-	struct xfs_mount	*mp = ip->i_mount;
-	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
-
-	if (mp->m_sb.sb_blocksize < target->bt_bdev_awu_min)
-		return false;
-	if (mp->m_sb.sb_blocksize > target->bt_bdev_awu_max)
-		return false;
-
-	return true;
+	return xfs_inode_hw_atomicwrite_max(ip);
 }
 
 /*
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 00b53f479ece..ee68c026e6cd 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1082,6 +1082,20 @@ xfs_mountfs(
 		xfs_zone_gc_start(mp);
 	}
 
+	/*
+	 * Set atomic write unit max for mp. Ignore devices which cannot atomic
+	 * a single block, as they would be uncommon and more difficult to
+	 * support.
+	 */
+	if (mp->m_ddev_targp->bt_bdev_awu_min <= mp->m_sb.sb_blocksize &&
+	    mp->m_ddev_targp->bt_bdev_awu_max >= mp->m_sb.sb_blocksize)
+		mp->m_dd_awu_hw_max = mp->m_ddev_targp->bt_bdev_awu_max;
+
+	if (mp->m_rtdev_targp &&
+	    mp->m_rtdev_targp->bt_bdev_awu_min <= mp->m_sb.sb_blocksize &&
+	    mp->m_rtdev_targp->bt_bdev_awu_max >= mp->m_sb.sb_blocksize)
+		mp->m_rt_awu_hw_max = mp->m_rtdev_targp->bt_bdev_awu_max;
+
 	return 0;
 
  out_agresv:
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index e5192c12e7ac..2819e160f0e9 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -231,6 +231,10 @@ typedef struct xfs_mount {
 	unsigned int		m_max_open_zones;
 	unsigned int		m_zonegc_low_space;
 
+	/* ddev and rtdev HW max atomic write size */
+	unsigned int		m_dd_awu_hw_max;
+	unsigned int		m_rt_awu_hw_max;
+
 	/*
 	 * Bitsets of per-fs metadata that have been checked and/or are sick.
 	 * Callers must hold m_sb_lock to access these two fields.
-- 
2.31.1