linux-ext4 - [PATCH v12 07/17] xfs: ignore HW which cannot atomic write a single block

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Message-Id: <20250506090427.2549456-8-john.g.garry@oracle.com>
Date: Tue,  6 May 2025 09:04:17 +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 v12 07/17] xfs: ignore HW which cannot atomic write a single block

From: "Darrick J. Wong" <djwong@...nel.org>

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@...nel.org>
Signed-off-by: John Garry <john.g.garry@...cle.com>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 fs/xfs/xfs_buf.c   | 12 ++++++++++++
 fs/xfs/xfs_buf.h   |  2 +-
 fs/xfs/xfs_inode.h | 10 +---------
 3 files changed, 14 insertions(+), 10 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;
 }
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index a7026fb255c4..9d2ab567cf81 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -112,7 +112,7 @@ struct xfs_buftarg {
 	struct percpu_counter	bt_readahead_count;
 	struct ratelimit_state	bt_ioerror_rl;
 
-	/* Atomic write unit values */
+	/* Atomic write unit values, bytes */
 	unsigned int		bt_bdev_awu_min;
 	unsigned int		bt_bdev_awu_max;
 
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index d3471a7418b9..d7e2b902ef5c 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -358,15 +358,7 @@ static inline bool xfs_inode_has_bigrtalloc(const struct xfs_inode *ip)
 
 static inline bool xfs_inode_can_hw_atomic_write(const 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_buftarg(ip)->bt_bdev_awu_max > 0;
 }
 
 /*
-- 
2.31.1