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block: introduce BDRV_REQ_MAY_UNMAP request flag

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Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Peter Lieven 2013-10-24 12:06:52 +02:00 committed by Kevin Wolf
parent aa7bfbfff7
commit d32f35cbc5
4 changed files with 14 additions and 2 deletions
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3
block-migration.c
View file

@ -780,7 +780,8 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
}
if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
ret = bdrv_write_zeroes(bs, addr, nr_sectors, 0);
ret = bdrv_write_zeroes(bs, addr, nr_sectors,
BDRV_REQ_MAY_UNMAP);
} else {
buf = g_malloc(BLOCK_SIZE);
qemu_get_buffer(f, buf, BLOCK_SIZE);

4
block.c
View file

@ -2818,6 +2818,10 @@ int coroutine_fn bdrv_co_write_zeroes(BlockDriverState *bs,
{
trace_bdrv_co_write_zeroes(bs, sector_num, nb_sectors);
if (!(bs->open_flags & BDRV_O_UNMAP)) {
flags &= ~BDRV_REQ_MAY_UNMAP;
}
return bdrv_co_do_writev(bs, sector_num, nb_sectors, NULL,
BDRV_REQ_ZERO_WRITE | flags);
}

2
block/backup.c
View file

@ -139,7 +139,7 @@ static int coroutine_fn backup_do_cow(BlockDriverState *bs,
if (buffer_is_zero(iov.iov_base, iov.iov_len)) {
ret = bdrv_co_write_zeroes(job->target,
start * BACKUP_SECTORS_PER_CLUSTER,
n, 0);
n, BDRV_REQ_MAY_UNMAP);
} else {
ret = bdrv_co_writev(job->target,
start * BACKUP_SECTORS_PER_CLUSTER, n,

7
include/block/block.h
View file

@ -65,6 +65,13 @@ typedef struct BlockDevOps {
typedef enum {
BDRV_REQ_COPY_ON_READ = 0x1,
BDRV_REQ_ZERO_WRITE = 0x2,
/* The BDRV_REQ_MAY_UNMAP flag is used to indicate that the block driver
* is allowed to optimize a write zeroes request by unmapping (discarding)
* blocks if it is guaranteed that the result will read back as
* zeroes. The flag is only passed to the driver if the block device is
* opened with BDRV_O_UNMAP.
*/
BDRV_REQ_MAY_UNMAP = 0x4,
} BdrvRequestFlags;
#define BDRV_O_RDWR 0x0002