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

John Garry
2024-06-07T14:41:07Z

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@oracle.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