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throttle: acquire the ThrottleGroup lock in bdrv_swap()
bdrv_swap() touches the fields of a BlockDriverState that are protected by the ThrottleGroup lock. Although those fields end up in their original place, they are temporarily swapped in the process, so there's a chance that an operation on a member of the same group happening on a different thread can try to use them. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: d92dc40d7c4f1fc5cda5cbbf4ffb7a4670b79d17.1433779731.git.berto@igalia.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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76f4afb40f
commit
db6283385c
16
block.c
16
block.c
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@ -36,6 +36,7 @@
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#include "qmp-commands.h"
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#include "qemu/timer.h"
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#include "qapi-event.h"
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#include "block/throttle-groups.h"
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#ifdef CONFIG_BSD
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#include <sys/types.h>
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@ -1887,11 +1888,20 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
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QTAILQ_REMOVE(&graph_bdrv_states, bs_old, node_list);
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}
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/* If the BlockDriverState is part of a throttling group acquire
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* its lock since we're going to mess with the protected fields.
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* Otherwise there's no need to worry since no one else can touch
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* them. */
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if (bs_old->throttle_state) {
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throttle_group_lock(bs_old);
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}
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/* bs_new must be unattached and shouldn't have anything fancy enabled */
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assert(!bs_new->blk);
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assert(QLIST_EMPTY(&bs_new->dirty_bitmaps));
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assert(bs_new->job == NULL);
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assert(bs_new->io_limits_enabled == false);
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assert(bs_new->throttle_state == NULL);
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assert(!throttle_timers_are_initialized(&bs_new->throttle_timers));
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tmp = *bs_new;
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@ -1909,8 +1919,14 @@ void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
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/* Check a few fields that should remain attached to the device */
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assert(bs_new->job == NULL);
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assert(bs_new->io_limits_enabled == false);
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assert(bs_new->throttle_state == NULL);
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assert(!throttle_timers_are_initialized(&bs_new->throttle_timers));
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/* Release the ThrottleGroup lock */
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if (bs_old->throttle_state) {
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throttle_group_unlock(bs_old);
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}
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/* insert the nodes back into the graph node list if needed */
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if (bs_new->node_name[0] != '\0') {
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QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs_new, node_list);
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@ -33,7 +33,8 @@
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* its own locking.
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*
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* This locking is however handled internally in this file, so it's
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* transparent to outside users.
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* mostly transparent to outside users (but see the documentation in
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* throttle_groups_lock()).
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*
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* The whole ThrottleGroup structure is private and invisible to
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* outside users, that only use it through its ThrottleState.
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@ -459,6 +460,34 @@ void throttle_group_unregister_bs(BlockDriverState *bs)
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bs->throttle_state = NULL;
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}
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/* Acquire the lock of this throttling group.
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*
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* You won't normally need to use this. None of the functions from the
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* ThrottleGroup API require you to acquire the lock since all of them
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* deal with it internally.
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*
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* This should only be used in exceptional cases when you want to
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* access the protected fields of a BlockDriverState directly
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* (e.g. bdrv_swap()).
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*
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* @bs: a BlockDriverState that is member of the group
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*/
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void throttle_group_lock(BlockDriverState *bs)
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{
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ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
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qemu_mutex_lock(&tg->lock);
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}
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/* Release the lock of this throttling group.
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*
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* See the comments in throttle_group_lock().
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*/
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void throttle_group_unlock(BlockDriverState *bs)
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{
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ThrottleGroup *tg = container_of(bs->throttle_state, ThrottleGroup, ts);
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qemu_mutex_unlock(&tg->lock);
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}
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static void throttle_groups_init(void)
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{
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qemu_mutex_init(&throttle_groups_lock);
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@ -40,4 +40,7 @@ void coroutine_fn throttle_group_co_io_limits_intercept(BlockDriverState *bs,
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unsigned int bytes,
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bool is_write);
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void throttle_group_lock(BlockDriverState *bs);
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void throttle_group_unlock(BlockDriverState *bs);
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#endif
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