[PATCH 7/7] xfs: (re-)implement FIEMAP_FLAG_XATTR

[Christoph Hellwig <hch@xxxxxx>]

Use a special read-only iomap_ops implementation to support fiemap on
the attr fork.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/xfs/xfs_iomap.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_iomap.h |  1 +
 fs/xfs/xfs_iops.c  |  9 ++++++++-
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 1cce760..697c8fd 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1106,3 +1106,48 @@ struct iomap_ops xfs_iomap_ops = {
        .iomap_begin            = xfs_file_iomap_begin,
        .iomap_end              = xfs_file_iomap_end,
 };
+
+static int
+xfs_xattr_iomap_begin(
+       struct inode            *inode,
+       loff_t                  offset,
+       loff_t                  length,
+       unsigned                flags,
+       struct iomap            *iomap)
+{
+       struct xfs_inode        *ip = XFS_I(inode);
+       struct xfs_mount        *mp = ip->i_mount;
+       xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
+       xfs_fileoff_t           end_fsb = XFS_B_TO_FSB(mp, offset + length);
+       struct xfs_bmbt_irec    imap;
+       int                     nimaps = 1, error = 0;
+       unsigned                lockmode;
+
+       if (XFS_FORCED_SHUTDOWN(mp))
+               return -EIO;
+
+       lockmode = xfs_ilock_data_map_shared(ip);
+
+       /* if there are no attribute fork or extents, return ENOENT */
+       if (XFS_IFORK_Q(ip) || !ip->i_d.di_anextents) {
+               error = -ENOENT;
+               goto out_unlock;
+       }
+
+       ASSERT(ip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL);
+       error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
+                              &nimaps, XFS_BMAPI_ENTIRE | XFS_BMAPI_ATTRFORK);
+out_unlock:
+       xfs_iunlock(ip, lockmode);
+
+       if (!error) {
+               ASSERT(nimaps);
+               xfs_bmbt_to_iomap(ip, iomap, &imap);
+       }
+
+       return error;
+}
+
+struct iomap_ops xfs_xattr_iomap_ops = {
+       .iomap_begin            = xfs_xattr_iomap_begin,
+};
diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index e066d04..fb8aca3 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -35,5 +35,6 @@ void xfs_bmbt_to_iomap(struct xfs_inode *, struct iomap *,
                struct xfs_bmbt_irec *);
 
 extern struct iomap_ops xfs_iomap_ops;
+extern struct iomap_ops xfs_xattr_iomap_ops;
 
 #endif /* __XFS_IOMAP_H__*/
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index ab820f8..b24c310 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1009,7 +1009,14 @@ xfs_vn_fiemap(
        int                     error;
 
        xfs_ilock(XFS_I(inode), XFS_IOLOCK_SHARED);
-       error = iomap_fiemap(inode, fieinfo, start, length, &xfs_iomap_ops);
+       if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR) {
+               fieinfo->fi_flags &= ~FIEMAP_FLAG_XATTR;
+               error = iomap_fiemap(inode, fieinfo, start, length,
+                               &xfs_xattr_iomap_ops);
+       } else {
+               error = iomap_fiemap(inode, fieinfo, start, length,
+                               &xfs_iomap_ops);
+       }
        xfs_iunlock(XFS_I(inode), XFS_IOLOCK_SHARED);
 
        return error;
-- 
2.1.4