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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>
This commit is contained in:
Tony Breeds 2014-09-26 09:14:12 +10:00 committed by Kevin Wolf
parent 38c4d0aea3
commit 7c15903789
1 changed files with 2 additions and 2 deletions
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4
block/raw-posix.c
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@ -1571,9 +1571,9 @@ 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;