Commit 51288d79 authored by Fam Zheng's avatar Fam Zheng Committed by Kevin Wolf
Browse files

block: Introduce "drained begin/end" API 



The semantics is that after bdrv_drained_begin(bs), bs will not get new external
requests until the matching bdrv_drained_end(bs).

Signed-off-by: default avatarFam Zheng <famz@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent c1e1e5fa

block/io.c

+17 −0
Original line number Diff line number Diff line
@@ -2624,3 +2624,20 @@ void bdrv_flush_io_queue(BlockDriverState *bs) 
    }

    bdrv_start_throttled_reqs(bs);

}



void bdrv_drained_begin(BlockDriverState *bs)

{

    if (!bs->quiesce_counter++) {

        aio_disable_external(bdrv_get_aio_context(bs));

    }

    bdrv_drain(bs);

}



void bdrv_drained_end(BlockDriverState *bs)

{

    assert(bs->quiesce_counter > 0);

    if (--bs->quiesce_counter > 0) {

        return;

    }

    aio_enable_external(bdrv_get_aio_context(bs));

}

include/block/block.h

+19 −0
Original line number Diff line number Diff line
@@ -610,4 +610,23 @@ void bdrv_io_plug(BlockDriverState *bs); 
void bdrv_io_unplug(BlockDriverState *bs);

void bdrv_flush_io_queue(BlockDriverState *bs);



/**

 * bdrv_drained_begin:

 *

 * Begin a quiesced section for exclusive access to the BDS, by disabling

 * external request sources including NBD server and device model. Note that

 * this doesn't block timers or coroutines from submitting more requests, which

 * means block_job_pause is still necessary.

 *

 * This function can be recursive.

 */

void bdrv_drained_begin(BlockDriverState *bs);



/**

 * bdrv_drained_end:

 *

 * End a quiescent section started by bdrv_drained_begin().

 */

void bdrv_drained_end(BlockDriverState *bs);



#endif

include/block/block_int.h

+2 −0
Original line number Diff line number Diff line
@@ -448,6 +448,8 @@ struct BlockDriverState { 
    /* threshold limit for writes, in bytes. "High water mark". */

    uint64_t write_threshold_offset;

    NotifierWithReturn write_threshold_notifier;



    int quiesce_counter;

};



struct BlockBackendRootState {