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authorPeter Lieven <pl@kamp.de>2013-10-24 12:06:52 +0200
committerKevin Wolf <kwolf@redhat.com>2013-11-28 10:30:51 +0100
commitd32f35cbc5a87af5e1100dd55074a79fc2cb5307 (patch)
tree55fa60fcbf692789af57904cb5bc84be7b649df7
parentaa7bfbfff792538a9eeefe879fc4c629aa0b4203 (diff)
downloadqemu-arm-d32f35cbc5a87af5e1100dd55074a79fc2cb5307.tar.gz
block: introduce BDRV_REQ_MAY_UNMAP request flag
Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Peter Lieven <pl@kamp.de> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
-rw-r--r--block-migration.c3
-rw-r--r--block.c4
-rw-r--r--block/backup.c2
-rw-r--r--include/block/block.h7
4 files changed, 14 insertions, 2 deletions
diff --git a/block-migration.c b/block-migration.c
index 713a8e36e1..fc4ef93ea2 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -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);
diff --git a/block.c b/block.c
index e14ba48720..d34e974d07 100644
--- a/block.c
+++ b/block.c
@@ -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);
}
diff --git a/block/backup.c b/block/backup.c
index 830a179d6d..0198514043 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -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,
diff --git a/include/block/block.h b/include/block/block.h
index 8ba9f0c80f..1f30a56fb0 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -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