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block: introduce BDRV_REQ_NO_WAIT flag

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Add flag to make serialising request no wait: if there are conflicting
requests, just return error immediately. It's will be used in upcoming
preallocate filter.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20201021145859.11201-7-vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2020-10-21 17:58:44 +03:00 committed by Max Reitz
parent 8ac5aab255
commit d1a764d126
2 changed files with 18 additions and 2 deletions
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11
block/io.c
View File

@ -1858,9 +1858,18 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, uint64_t bytes,
assert(!(bs->open_flags & BDRV_O_INACTIVE));
assert((bs->open_flags & BDRV_O_NO_IO) == 0);
assert(!(flags & ~BDRV_REQ_MASK));
assert(!((flags & BDRV_REQ_NO_WAIT) && !(flags & BDRV_REQ_SERIALISING)));
if (flags & BDRV_REQ_SERIALISING) {
bdrv_make_request_serialising(req, bdrv_get_cluster_size(bs));
QEMU_LOCK_GUARD(&bs->reqs_lock);
tracked_request_set_serialising(req, bdrv_get_cluster_size(bs));
if ((flags & BDRV_REQ_NO_WAIT) && bdrv_find_conflicting_request(req)) {
return -EBUSY;
}
bdrv_wait_serialising_requests_locked(req);
} else {
bdrv_wait_serialising_requests(req);
}

9
include/block/block.h
View File

@ -77,8 +77,15 @@ typedef enum {
* written to qiov parameter which may be NULL.
*/
BDRV_REQ_PREFETCH = 0x200,
/*
* If we need to wait for other requests, just fail immediately. Used
* only together with BDRV_REQ_SERIALISING.
*/
BDRV_REQ_NO_WAIT = 0x400,
/* Mask of valid flags */
BDRV_REQ_MASK = 0x3ff,
BDRV_REQ_MASK = 0x7ff,
} BdrvRequestFlags;
typedef struct BlockSizes {