Commit d03654ea authored by Stefan Hajnoczi's avatar Stefan Hajnoczi Committed by Eric Blake
Browse files

block: let blk_add/remove_aio_context_notifier() tolerate BDS changes 



Commit 2019ba0a ("block: Add AioContextNotifier functions to BB")
added blk_add/remove_aio_context_notifier() and implemented them by
passing through the bdrv_*() equivalent.

This doesn't work across bdrv_append(), which detaches child->bs and
re-attaches it to a new BlockDriverState.  When
blk_remove_aio_context_notifier() is called we will access the new BDS
instead of the one where the notifier was added!

>From the point of view of the blk_*() API user, changes to the root BDS
should be transparent.

This patch maintains a list of AioContext notifiers in BlockBackend and
adds/removes them from the BlockDriverState as needed.

Reported-by: default avatarStefano Panella <spanella@gmail.com>
Cc: Max Reitz <mreitz@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20180306204819.11266-2-stefanha@redhat.com>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
parent 65529782

block/block-backend.c

+63 −0
Original line number Diff line number Diff line
@@ -31,6 +31,13 @@ 


static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb);



typedef struct BlockBackendAioNotifier {

    void (*attached_aio_context)(AioContext *new_context, void *opaque);

    void (*detach_aio_context)(void *opaque);

    void *opaque;

    QLIST_ENTRY(BlockBackendAioNotifier) list;

} BlockBackendAioNotifier;



struct BlockBackend {

    char *name;

    int refcnt;
@@ -69,6 +76,7 @@ struct BlockBackend { 
    bool allow_write_beyond_eof;



    NotifierList remove_bs_notifiers, insert_bs_notifiers;

    QLIST_HEAD(, BlockBackendAioNotifier) aio_notifiers;



    int quiesce_counter;

    VMChangeStateEntry *vmsh;
@@ -247,6 +255,36 @@ static int blk_root_inactivate(BdrvChild *child) 
    return 0;

}



static void blk_root_attach(BdrvChild *child)

{

    BlockBackend *blk = child->opaque;

    BlockBackendAioNotifier *notifier;



    trace_blk_root_attach(child, blk, child->bs);



    QLIST_FOREACH(notifier, &blk->aio_notifiers, list) {

        bdrv_add_aio_context_notifier(child->bs,

                notifier->attached_aio_context,

                notifier->detach_aio_context,

                notifier->opaque);

    }

}



static void blk_root_detach(BdrvChild *child)

{

    BlockBackend *blk = child->opaque;

    BlockBackendAioNotifier *notifier;



    trace_blk_root_detach(child, blk, child->bs);



    QLIST_FOREACH(notifier, &blk->aio_notifiers, list) {

        bdrv_remove_aio_context_notifier(child->bs,

                notifier->attached_aio_context,

                notifier->detach_aio_context,

                notifier->opaque);

    }

}



static const BdrvChildRole child_root = {

    .inherit_options    = blk_root_inherit_options,
@@ -260,6 +298,9 @@ static const BdrvChildRole child_root = { 


    .activate           = blk_root_activate,

    .inactivate         = blk_root_inactivate,



    .attach             = blk_root_attach,

    .detach             = blk_root_detach,

};



/*
@@ -287,6 +328,7 @@ BlockBackend *blk_new(uint64_t perm, uint64_t shared_perm) 


    notifier_list_init(&blk->remove_bs_notifiers);

    notifier_list_init(&blk->insert_bs_notifiers);

    QLIST_INIT(&blk->aio_notifiers);



    QTAILQ_INSERT_TAIL(&block_backends, blk, link);

    return blk;
@@ -364,6 +406,7 @@ static void blk_delete(BlockBackend *blk) 
    }

    assert(QLIST_EMPTY(&blk->remove_bs_notifiers.notifiers));

    assert(QLIST_EMPTY(&blk->insert_bs_notifiers.notifiers));

    assert(QLIST_EMPTY(&blk->aio_notifiers));

    QTAILQ_REMOVE(&block_backends, blk, link);

    drive_info_del(blk->legacy_dinfo);

    block_acct_cleanup(&blk->stats);
@@ -1857,8 +1900,15 @@ void blk_add_aio_context_notifier(BlockBackend *blk, 
        void (*attached_aio_context)(AioContext *new_context, void *opaque),

        void (*detach_aio_context)(void *opaque), void *opaque)

{

    BlockBackendAioNotifier *notifier;

    BlockDriverState *bs = blk_bs(blk);



    notifier = g_new(BlockBackendAioNotifier, 1);

    notifier->attached_aio_context = attached_aio_context;

    notifier->detach_aio_context = detach_aio_context;

    notifier->opaque = opaque;

    QLIST_INSERT_HEAD(&blk->aio_notifiers, notifier, list);



    if (bs) {

        bdrv_add_aio_context_notifier(bs, attached_aio_context,

                                      detach_aio_context, opaque);
@@ -1871,12 +1921,25 @@ void blk_remove_aio_context_notifier(BlockBackend *blk, 
                                     void (*detach_aio_context)(void *),

                                     void *opaque)

{

    BlockBackendAioNotifier *notifier;

    BlockDriverState *bs = blk_bs(blk);



    if (bs) {

        bdrv_remove_aio_context_notifier(bs, attached_aio_context,

                                         detach_aio_context, opaque);

    }



    QLIST_FOREACH(notifier, &blk->aio_notifiers, list) {

        if (notifier->attached_aio_context == attached_aio_context &&

            notifier->detach_aio_context == detach_aio_context &&

            notifier->opaque == opaque) {

            QLIST_REMOVE(notifier, list);

            g_free(notifier);

            return;

        }

    }



    abort();

}



void blk_add_remove_bs_notifier(BlockBackend *blk, Notifier *notify)

block/trace-events

+2 −0
Original line number Diff line number Diff line
@@ -7,6 +7,8 @@ bdrv_lock_medium(void *bs, bool locked) "bs %p locked %d" 
# block/block-backend.c

blk_co_preadv(void *blk, void *bs, int64_t offset, unsigned int bytes, int flags) "blk %p bs %p offset %"PRId64" bytes %u flags 0x%x"

blk_co_pwritev(void *blk, void *bs, int64_t offset, unsigned int bytes, int flags) "blk %p bs %p offset %"PRId64" bytes %u flags 0x%x"

blk_root_attach(void *child, void *blk, void *bs) "child %p blk %p bs %p"

blk_root_detach(void *child, void *blk, void *bs) "child %p blk %p bs %p"



# block/io.c

bdrv_co_preadv(void *bs, int64_t offset, int64_t nbytes, unsigned int flags) "bs %p offset %"PRId64" nbytes %"PRId64" flags 0x%x"