xfs: don't bother looking at the refcount tree for reads

There is no need to trim an extent into a shared or non-shared one, or
report any flags for plain old reads.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index d907eb9f8ef3..1dabf2eb136a 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -996,11 +996,14 @@ xfs_file_iomap_begin(
                 return error;
         }
 
-        /* Trim the mapping to the nearest shared extent boundary. */
-        error = xfs_reflink_trim_around_shared(ip, &imap, &shared, &trimmed);
-        if (error) {
-                xfs_iunlock(ip, lockmode);
-                return error;
+        if (flags & (IOMAP_WRITE | IOMAP_ZERO | IOMAP_REPORT)) {
+                /* Trim the mapping to the nearest shared extent boundary. */
+                error = xfs_reflink_trim_around_shared(ip, &imap, &shared,
+                                &trimmed);
+                if (error) {
+                        xfs_iunlock(ip, lockmode);
+                        return error;
+                }
         }
 
         if ((flags & IOMAP_WRITE) && imap_needs_alloc(inode, &imap, nimaps)) {