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block: add .bdrv_co_is_allocated()

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This patch adds the .bdrv_co_is_allocated() interface which is identical
to .bdrv_is_allocated() but runs in coroutine context.  Running in
coroutine context implies that other coroutines might be performing I/O
at the same time.   Therefore it must be safe to run while the following
BlockDriver functions are in-flight:

    .bdrv_co_readv()
    .bdrv_co_writev()
    .bdrv_co_flush()
    .bdrv_co_is_allocated()

The new .bdrv_co_is_allocated() interface is useful because it can be
used when a VM is running, whereas .bdrv_is_allocated() is a synchronous
interface that does not cope with parallel requests.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2011-11-14 12:44:19 +00:00 committed by Kevin Wolf
parent 05c4af54c6
commit 376ae3f1cb
2 changed files with 39 additions and 0 deletions
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37
block.c
View File

@ -1887,6 +1887,26 @@ int bdrv_has_zero_init(BlockDriverState *bs)
return 1;
}
typedef struct BdrvCoIsAllocatedData {
BlockDriverState *bs;
int64_t sector_num;
int nb_sectors;
int *pnum;
int ret;
bool done;
} BdrvCoIsAllocatedData;
/* Coroutine wrapper for bdrv_is_allocated() */
static void coroutine_fn bdrv_is_allocated_co_entry(void *opaque)
{
BdrvCoIsAllocatedData *data = opaque;
BlockDriverState *bs = data->bs;
data->ret = bs->drv->bdrv_co_is_allocated(bs, data->sector_num,
data->nb_sectors, data->pnum);
data->done = true;
}
/*
* Returns true iff the specified sector is present in the disk image. Drivers
* not implementing the functionality are assumed to not support backing files,
@ -1902,6 +1922,23 @@ int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
int *pnum)
{
int64_t n;
if (bs->drv->bdrv_co_is_allocated) {
Coroutine *co;
BdrvCoIsAllocatedData data = {
.bs = bs,
.sector_num = sector_num,
.nb_sectors = nb_sectors,
.pnum = pnum,
.done = false,
};
co = qemu_coroutine_create(bdrv_is_allocated_co_entry);
qemu_coroutine_enter(co, &data);
while (!data.done) {
qemu_aio_wait();
}
return data.ret;
}
if (!bs->drv->bdrv_is_allocated) {
if (sector_num >= bs->total_sectors) {
*pnum = 0;

2
block_int.h
View File

@ -103,6 +103,8 @@ struct BlockDriver {
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
int coroutine_fn (*bdrv_co_discard)(BlockDriverState *bs,
int64_t sector_num, int nb_sectors);
int coroutine_fn (*bdrv_co_is_allocated)(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, int *pnum);
/*
* Invalidate any cached meta-data.