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block/parallels: read up to cluster end in one go

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Teach parallels_read() to do reads in coarser granularity than just a
single sector: if requested, read up to the cluster end in one go.

Signed-off-by: Roman Kagan <rkagan@parallels.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1430207220-24458-5-git-send-email-den@openvz.org
CC: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Roman Kagan 2015-04-28 10:46:37 +03:00 committed by Stefan Hajnoczi
parent 2944256997
commit 9de9da17d8
1 changed files with 13 additions and 5 deletions
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18
block/parallels.c
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@ -159,6 +159,13 @@ static int64_t seek_to_sector(BDRVParallelsState *s, int64_t sector_num)
return (uint64_t)s->catalog_bitmap[index] * s->off_multiplier + offset;
}
static int cluster_remainder(BDRVParallelsState *s, int64_t sector_num,
int nb_sectors)
{
int ret = s->tracks - sector_num % s->tracks;
return MIN(nb_sectors, ret);
}
static int parallels_read(BlockDriverState *bs, int64_t sector_num,
uint8_t *buf, int nb_sectors)
{
@ -166,17 +173,18 @@ static int parallels_read(BlockDriverState *bs, int64_t sector_num,
while (nb_sectors > 0) {
int64_t position = seek_to_sector(s, sector_num);
int n = cluster_remainder(s, sector_num, nb_sectors);
if (position >= 0) {
int ret = bdrv_read(bs->file, position, buf, 1);
int ret = bdrv_read(bs->file, position, buf, n);
if (ret < 0) {
return ret;
}
} else {
memset(buf, 0, BDRV_SECTOR_SIZE);
memset(buf, 0, n << BDRV_SECTOR_BITS);
}
nb_sectors--;
sector_num++;
buf += BDRV_SECTOR_SIZE;
nb_sectors -= n;
sector_num += n;
buf += n << BDRV_SECTOR_BITS;
}
return 0;
}