linux-kernel - [PATCH v6 6/7] xfs: Validate atomic writes

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Message-Id: <20240930125438.2501050-7-john.g.garry@oracle.com>
Date: Mon, 30 Sep 2024 12:54:37 +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 v6 6/7] 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_dio_write(),
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.

Signed-off-by: John Garry <john.g.garry@...cle.com>
---
 fs/xfs/xfs_file.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 412b1d71b52b..fa6a44b88ecc 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -688,6 +688,13 @@ xfs_file_dio_write(
 	struct xfs_buftarg      *target = xfs_inode_buftarg(ip);
 	size_t			count = iov_iter_count(from);
 
+	if (iocb->ki_flags & IOCB_ATOMIC) {
+		if (count != ip->i_mount->m_sb.sb_blocksize)
+			return -EINVAL;
+		if (!generic_atomic_write_valid(iocb, from))
+			return -EINVAL;
+	}
+
 	/* direct I/O must be aligned to device logical sector size */
 	if ((iocb->ki_pos | count) & target->bt_logical_sectormask)
 		return -EINVAL;
-- 
2.31.1