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block: add bdrv_add_before_write_notifier()

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The bdrv_add_before_write_notifier() function installs a callback that
is invoked before a write request is processed.  This will be used to
implement copy-on-write point-in-time snapshots where we need to copy
out old data before overwriting it.

Note that BdrvTrackedRequest is moved to block_int.h since it is passed
to .notify() functions.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2013-06-24 17:13:10 +02:00 • committed by Kevin Wolf
parent 5dae8e5fb8
commit d616b22474
2 changed files with 34 additions and 12 deletions
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23
include/block/block_int.h
View file

@ -59,7 +59,16 @@
#define BLOCK_OPT_LAZY_REFCOUNTS "lazy_refcounts"
#define BLOCK_OPT_ADAPTER_TYPE "adapter_type"
typedef struct BdrvTrackedRequest BdrvTrackedRequest;
typedef struct BdrvTrackedRequest {
BlockDriverState *bs;
int64_t sector_num;
int nb_sectors;
bool is_write;
QLIST_ENTRY(BdrvTrackedRequest) list;
Coroutine *co; /* owner, used for deadlock detection */
CoQueue wait_queue; /* coroutines blocked on this request */
} BdrvTrackedRequest;
typedef struct BlockIOLimit {
int64_t bps[3];
@ -248,6 +257,9 @@ struct BlockDriverState {
NotifierList close_notifiers;
/* Callback before write request is processed */
NotifierWithReturnList before_write_notifiers;
/* number of in-flight copy-on-read requests */
unsigned int copy_on_read_in_flight;
@ -298,6 +310,15 @@ int get_tmp_filename(char *filename, int size);
void bdrv_set_io_limits(BlockDriverState *bs,
BlockIOLimit *io_limits);
/**
* bdrv_add_before_write_notifier:
*
* Register a callback that is invoked before write requests are processed but
* after any throttling or waiting for overlapping requests.
*/
void bdrv_add_before_write_notifier(BlockDriverState *bs,
NotifierWithReturn *notifier);
/**
* bdrv_get_aio_context:
*