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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id x21sm8654744wmc.14.2021.10.07.05.07.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Oct 2021 05:07:01 -0700 (PDT) Message-ID: <05c35f57-ad34-563e-d850-9652735cb23a@redhat.com> Date: Thu, 7 Oct 2021 14:06:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [RFC PATCH v2 15/25] include/block/snapshot: global state API + assertions To: Emanuele Giuseppe Esposito , qemu-block@nongnu.org References: <20211005143215.29500-1-eesposit@redhat.com> <20211005143215.29500-16-eesposit@redhat.com> From: Paolo Bonzini In-Reply-To: <20211005143215.29500-16-eesposit@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -47 X-Spam_score: -4.8 X-Spam_bar: ---- X-Spam_report: (-4.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.05, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-1.964, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Fam Zheng , Vladimir Sementsov-Ogievskiy , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Eduardo Habkost , Juan Quintela , Eric Blake , Richard Henderson , qemu-devel@nongnu.org, Markus Armbruster , Hanna Reitz , Stefan Hajnoczi , John Snow , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 05/10/21 16:32, Emanuele Giuseppe Esposito wrote: > Snapshots run also under the BQL lock, so they all are > in the global state API. The aiocontext lock that they hold > is currently an overkill and in future could be removed. > > Signed-off-by: Emanuele Giuseppe Esposito > --- > block/snapshot.c | 28 ++++++++++++++++++++++++++++ > include/block/snapshot.h | 21 +++++++++++++++++++++ > migration/savevm.c | 2 ++ > 3 files changed, 51 insertions(+) > > diff --git a/block/snapshot.c b/block/snapshot.c > index ccacda8bd5..e8756f7f90 100644 > --- a/block/snapshot.c > +++ b/block/snapshot.c > @@ -57,6 +57,8 @@ int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info, > QEMUSnapshotInfo *sn_tab, *sn; > int nb_sns, i, ret; > > + g_assert(qemu_in_main_thread()); > + > ret = -ENOENT; > nb_sns = bdrv_snapshot_list(bs, &sn_tab); > if (nb_sns < 0) { > @@ -105,6 +107,7 @@ bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs, > bool ret = false; > > assert(id || name); > + g_assert(qemu_in_main_thread()); > > nb_sns = bdrv_snapshot_list(bs, &sn_tab); > if (nb_sns < 0) { > @@ -200,6 +203,7 @@ static BlockDriverState *bdrv_snapshot_fallback(BlockDriverState *bs) > int bdrv_can_snapshot(BlockDriverState *bs) > { > BlockDriver *drv = bs->drv; > + g_assert(qemu_in_main_thread()); > if (!drv || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) { > return 0; > } > @@ -220,6 +224,9 @@ int bdrv_snapshot_create(BlockDriverState *bs, > { > BlockDriver *drv = bs->drv; > BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs); > + > + g_assert(qemu_in_main_thread()); > + > if (!drv) { > return -ENOMEDIUM; > } > @@ -240,6 +247,8 @@ int bdrv_snapshot_goto(BlockDriverState *bs, > BdrvChild **fallback_ptr; > int ret, open_ret; > > + g_assert(qemu_in_main_thread()); > + > if (!drv) { > error_setg(errp, "Block driver is closed"); > return -ENOMEDIUM; > @@ -348,6 +357,8 @@ int bdrv_snapshot_delete(BlockDriverState *bs, > BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs); > int ret; > > + g_assert(qemu_in_main_thread()); > + > if (!drv) { > error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs)); > return -ENOMEDIUM; > @@ -380,6 +391,8 @@ int bdrv_snapshot_list(BlockDriverState *bs, > { > BlockDriver *drv = bs->drv; > BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs); > + > + g_assert(qemu_in_main_thread()); > if (!drv) { > return -ENOMEDIUM; > } > @@ -419,6 +432,8 @@ int bdrv_snapshot_load_tmp(BlockDriverState *bs, > { > BlockDriver *drv = bs->drv; > > + g_assert(qemu_in_main_thread()); > + > if (!drv) { > error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs)); > return -ENOMEDIUM; > @@ -447,6 +462,8 @@ int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs, > int ret; > Error *local_err = NULL; > > + g_assert(qemu_in_main_thread()); > + > ret = bdrv_snapshot_load_tmp(bs, id_or_name, NULL, &local_err); > if (ret == -ENOENT || ret == -EINVAL) { > error_free(local_err); > @@ -515,6 +532,8 @@ bool bdrv_all_can_snapshot(bool has_devices, strList *devices, > g_autoptr(GList) bdrvs = NULL; > GList *iterbdrvs; > > + g_assert(qemu_in_main_thread()); > + > if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) { > return false; > } > @@ -549,6 +568,8 @@ int bdrv_all_delete_snapshot(const char *name, > g_autoptr(GList) bdrvs = NULL; > GList *iterbdrvs; > > + g_assert(qemu_in_main_thread()); > + > if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) { > return -1; > } > @@ -588,6 +609,8 @@ int bdrv_all_goto_snapshot(const char *name, > g_autoptr(GList) bdrvs = NULL; > GList *iterbdrvs; > > + g_assert(qemu_in_main_thread()); > + > if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) { > return -1; > } > @@ -622,6 +645,8 @@ int bdrv_all_has_snapshot(const char *name, > g_autoptr(GList) bdrvs = NULL; > GList *iterbdrvs; > > + g_assert(qemu_in_main_thread()); > + > if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) { > return -1; > } > @@ -663,6 +688,7 @@ int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn, > { > g_autoptr(GList) bdrvs = NULL; > GList *iterbdrvs; > + g_assert(qemu_in_main_thread()); > > if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) { > return -1; > @@ -703,6 +729,8 @@ BlockDriverState *bdrv_all_find_vmstate_bs(const char *vmstate_bs, > g_autoptr(GList) bdrvs = NULL; > GList *iterbdrvs; > > + g_assert(qemu_in_main_thread()); > + > if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) { > return NULL; > } > diff --git a/include/block/snapshot.h b/include/block/snapshot.h > index 940345692f..3a84849388 100644 > --- a/include/block/snapshot.h > +++ b/include/block/snapshot.h > @@ -45,6 +45,27 @@ typedef struct QEMUSnapshotInfo { > uint64_t icount; /* record/replay step */ > } QEMUSnapshotInfo; > > +/* > + * Global state (GS) API. These functions run under the BQL lock. > + * > + * If a function modifies the graph, it also uses drain and/or > + * aio_context_acquire/release to be sure it has unique access. > + * aio_context locking is needed together with BQL because of > + * the thread-safe I/O API that concurrently runs and accesses > + * the graph without the BQL. > + * > + * It is important to note that not all of these functions are > + * necessarily limited to running under the BQL, but they would > + * require additional auditing and may small thread-safety changes Apart from the usual comment about s/may/many/, Reviewed-by: Paolo Bonzini > + * to move them into the I/O API. Often it's not worth doing that > + * work since the APIs are only used with the BQL held at the > + * moment, so they have been placed in the GS API (for now). > + * > + * All functions in this header must use this assertion: > + * g_assert(qemu_in_main_thread()); > + * to catch when they are accidentally called without the BQL. > + */ > + > int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info, > const char *name); > bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs, > diff --git a/migration/savevm.c b/migration/savevm.c > index 7b7b64bd13..439f736ad5 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -2785,6 +2785,8 @@ bool save_snapshot(const char *name, bool overwrite, const char *vmstate, > g_autoptr(GDateTime) now = g_date_time_new_now_local(); > AioContext *aio_context; > > + g_assert(qemu_in_main_thread()); > + > if (migration_is_blocked(errp)) { > return false; > } >