linux-kernel - [PATCH v10 7/8] xfs: Validate atomic writes

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Message-Id: <20241019125113.369994-8-john.g.garry@oracle.com>
Date: Sat, 19 Oct 2024 12:51:12 +0000
From: John Garry <john.g.garry@...cle.com>
To: axboe@...nel.dk, brauner@...nel.org, djwong@...nel.org,
        viro@...iv.linux.org.uk, jack@...e.cz, dchinner@...hat.com, hch@....de,
        cem@...nel.org
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, hare@...e.de,
        martin.petersen@...cle.com, catherine.hoang@...cle.com,
        mcgrof@...nel.org, ritesh.list@...il.com, ojaswin@...ux.ibm.com,
        John Garry <john.g.garry@...cle.com>
Subject: [PATCH v10 7/8] xfs: Validate atomic writes

Validate that an atomic write adheres to length/offset rules. Currently
we can only write a single FS block.

For an IOCB with IOCB_ATOMIC set to get as far as xfs_file_write_iter(),
FMODE_CAN_ATOMIC_WRITE will need to be set for the file; for this,
ATOMICWRITES flags would also need to be set for the inode.

Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: "Darrick J. Wong" <djwong@...nel.org>
Signed-off-by: John Garry <john.g.garry@...cle.com>
---
 fs/xfs/xfs_file.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index b19916b11fd5..1ccbc1eb75c9 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -852,6 +852,20 @@ xfs_file_write_iter(
 	if (IS_DAX(inode))
 		return xfs_file_dax_write(iocb, from);
 
+	if (iocb->ki_flags & IOCB_ATOMIC) {
+		/*
+		 * Currently only atomic writing of a single FS block is
+		 * supported. It would be possible to atomic write smaller than
+		 * a FS block, but there is no requirement to support this.
+		 * Note that iomap also does not support this yet.
+		 */
+		if (ocount != ip->i_mount->m_sb.sb_blocksize)
+			return -EINVAL;
+		ret = generic_atomic_write_valid(iocb, from);
+		if (ret)
+			return ret;
+	}
+
 	if (iocb->ki_flags & IOCB_DIRECT) {
 		/*
 		 * Allow a directio write to fall back to a buffered
-- 
2.31.1