iomap: iomap that extends beyond EOF should be marked dirty

When doing a direct IO that spans the current EOF, and there are
written blocks beyond EOF that extend beyond the current write, the
only metadata update that needs to be done is a file size extension.

However, we don't mark such iomaps as IOMAP_F_DIRTY to indicate that
there is IO completion metadata updates required, and hence we may
fail to correctly sync file size extensions made in IO completion
when O_DSYNC writes are being used and the hardware supports FUA.

Hence when setting IOMAP_F_DIRTY, we need to also take into account
whether the iomap spans the current EOF. If it does, then we need to
mark it dirty so that IO completion will call generic_write_sync()
to flush the inode size update to stable storage correctly.

Fixes: 3460cac1ca76 ("iomap: Use FUA for pure data O_DSYNC DIO writes")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
[darrick: removed the ext4 part; they'll handle it separately]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index f780e223b11852cca45aa6b1093facc4734a9b79..32993c2acbd9e4566a19ed2d27ab74570f344aa5 100644 (file)
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1049,6 +1049,13 @@ xfs_file_iomap_begin(
        trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
 
 out_finish:
+       /*
+        * Writes that span EOF might trigger an IO size update on completion,
+        * so consider them to be dirty for the purposes of O_DSYNC even if
+        * there is no other metadata changes pending or have been made here.
+        */
+       if ((flags & IOMAP_WRITE) && offset + length > i_size_read(inode))
+               iomap->flags |= IOMAP_F_DIRTY;
        return xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
 
 out_found:

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 76b14cb729dc918b3de300de7aa969bdc1b93459..4b25ad6b5edd025419e90783c1a1eeca784ed845 100644 (file)
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -32,6 +32,8 @@ struct vm_fault;
  *
  * IOMAP_F_DIRTY indicates the inode has uncommitted metadata needed to access
  * written data and requires fdatasync to commit them to persistent storage.
+ * This needs to take into account metadata changes that *may* be made at IO
+ * completion, such as file size updates from direct IO.
  */
 #define IOMAP_F_NEW            0x01    /* blocks have been newly allocated */
 #define IOMAP_F_DIRTY          0x02    /* uncommitted metadata */