xfs: introduce xfs_bmapi_read()

xfs_bmapi() currently handles both extent map reading and
allocation. As a result, the code is littered with "if (wr)"
branches to conditionally do allocation operations if required.
This makes the code much harder to follow and causes significant
indent issues with the code.

Given that read mapping is much simpler than allocation, we can
split out read mapping from xfs_bmapi() and reuse the logic that
we have already factored out do do all the hard work of handling the
extent map manipulations. The results in a much simpler function for
the common extent read operations, and will allow the allocation
code to be simplified in another commit.

Once xfs_bmapi_read() is implemented, convert all the callers of
xfs_bmapi() that are only reading extents to use the new function.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/xfs/xfs_bmap.h b/fs/xfs/xfs_bmap.h
index c62234bde053..16257c6eba71 100644
--- a/fs/xfs/xfs_bmap.h
+++ b/fs/xfs/xfs_bmap.h
@@ -294,6 +294,10 @@ xfs_bmapi(
         int                     *nmap,          /* i/o: mval size/count */
         xfs_bmap_free_t         *flist);        /* i/o: list extents to free */
 
+int     xfs_bmapi_read(struct xfs_inode *ip, xfs_fileoff_t bno,
+                xfs_filblks_t len, struct xfs_bmbt_irec *mval,
+                int *nmap, int flags);
+
 /*
  * Map file blocks to filesystem blocks, simple version.
  * One block only, read-only.