From: Christoph Hellwig <hch@lst.de>
Date: Thu, 20 Oct 2016 04:53:32 +0000 (+1100)
Subject: xfs: don't bother looking at the refcount tree for reads
X-Git-Tag: v4.9-rc3~32^2~8
X-Git-Url: http://git.cascardo.info/?p=cascardo%2Flinux.git;a=commitdiff_plain;h=5f9268ca53aca992106d74edde3e7cf6c1be60a0

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>
---

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)) {