From: Tony Breeds <tony@bakeyournoodle.com>
Date: Fri, 26 Sep 2014 09:14:12 +1000
Subject: [PATCH] block/raw-posix: use seek_hole ahead of fiemap
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try_fiemap() uses FIEMAP_FLAG_SYNC which has a significant performance
impact.

Prefer seek_hole() over fiemap() to avoid this impact where possible.
seek_hole is more widely used and, arguably, has potential to be
optimised in the kernel.

Reported-By: Michael Steffens <michael_steffens@posteo.de>
Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: Pádraig Brady <pbrady@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 7c15903789953ead14a417882657d52dc0c19a24)
---
 block/raw-posix.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index 8f6c923..50d29e7 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -1509,9 +1509,9 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
 
     start = sector_num * BDRV_SECTOR_SIZE;
 
-    ret = try_fiemap(bs, start, &data, &hole, nb_sectors, pnum);
+    ret = try_seek_hole(bs, start, &data, &hole, pnum);
     if (ret < 0) {
-        ret = try_seek_hole(bs, start, &data, &hole, pnum);
+        ret = try_fiemap(bs, start, &data, &hole, nb_sectors, pnum);
         if (ret < 0) {
             /* Assume everything is allocated. */
             data = 0;