linux-kernel - [PATCH v4 21/22] xfs: Validate atomic writes

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Date: Fri,  7 Jun 2024 14:39:18 +0000
From: John Garry <john.g.garry@...cle.com>
To: axboe@...nel.dk, tytso@....edu, dchinner@...hat.com,
        viro@...iv.linux.org.uk, brauner@...nel.org, djwong@...nel.org,
        jack@...e.com, chandan.babu@...cle.com, hch@....de
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-erofs@...ts.ozlabs.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, gfs2@...ts.linux.dev,
        linux-xfs@...r.kernel.org, catherine.hoang@...cle.com,
        ritesh.list@...il.com, mcgrof@...nel.org,
        mikulas@...ax.karlin.mff.cuni.cz, agruenba@...hat.com,
        miklos@...redi.hu, martin.petersen@...cle.com,
        John Garry <john.g.garry@...cle.com>
Subject: [PATCH v4 21/22] xfs: Validate atomic writes

Validate that an atomic write adheres to length/offset rules. Since we
require extent alignment for atomic writes, this effectively also enforces
that the BIO which iomap produces is aligned.

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,
FORCEALIGN and also 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 | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 24fe3c2e03da..eeb267ae2bf2 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -695,12 +695,21 @@ xfs_file_dio_write(
 	struct kiocb		*iocb,
 	struct iov_iter		*from)
 {
-	struct xfs_inode	*ip = XFS_I(file_inode(iocb->ki_filp));
+	struct inode		*inode = file_inode(iocb->ki_filp);
+	struct xfs_inode	*ip = XFS_I(inode);
 	struct xfs_buftarg      *target = xfs_inode_buftarg(ip);
 	size_t			count = iov_iter_count(from);
+	struct xfs_mount	*mp = ip->i_mount;
 	bool			unaligned;
 	u64			unitsize;
 
+	if (iocb->ki_flags & IOCB_ATOMIC) {
+		if (!generic_atomic_write_valid_size(iocb->ki_pos, from,
+			i_blocksize(inode), XFS_FSB_TO_B(mp, ip->i_extsize))) {
+			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