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.ga...@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



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