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Date: Tue, 30 Dec 2025 19:33:57 +0800 Message-ID: <20251230113357.1299759-1-wale.zhang.ftd@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" bcache: make bcache_is_reboot atomic. The smp_mb is mainly used to ensure the dependency relationship between variables, but there is only one variable bcache_is_reboot. Therefore, using smp_mb is not very appropriate. When bcache_reboot and register_bcache occur concurrently, register_bcache cannot immediately detect that bcache_is_reboot has been set to true. cpu0 cpu1 bcache_reboot bcache_is_reboot =3D true; smp_mb(); register_bcache smp_mb(); if (bcache_is_reboot) // bcache_is_reboot may still be false. Signed-off-by: Wale Zhang --- drivers/md/bcache/super.c | 19 ++++++------------- drivers/md/bcache/sysfs.c | 14 +++++++------- 2 files changed, 13 insertions(+), 20 deletions(-) diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index c17d4517af22..0b2098aa7234 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -41,7 +41,7 @@ static const char invalid_uuid[] =3D { =20 static struct kobject *bcache_kobj; struct mutex bch_register_lock; -bool bcache_is_reboot; +atomic_t bcache_is_reboot =3D ATOMIC_INIT(0); LIST_HEAD(bch_cache_sets); static LIST_HEAD(uncached_devices); =20 @@ -2561,10 +2561,8 @@ static ssize_t register_bcache(struct kobject *k, st= ruct kobj_attribute *attr, if (!try_module_get(THIS_MODULE)) goto out; =20 - /* For latest state of bcache_is_reboot */ - smp_mb(); err =3D "bcache is in reboot"; - if (bcache_is_reboot) + if (atomic_read(&bcache_is_reboot)) goto out_module_put; =20 ret =3D -ENOMEM; @@ -2735,7 +2733,7 @@ static ssize_t bch_pending_bdevs_cleanup(struct kobje= ct *k, =20 static int bcache_reboot(struct notifier_block *n, unsigned long code, voi= d *x) { - if (bcache_is_reboot) + if (atomic_read(&bcache_is_reboot)) return NOTIFY_DONE; =20 if (code =3D=3D SYS_DOWN || @@ -2750,16 +2748,11 @@ static int bcache_reboot(struct notifier_block *n, = unsigned long code, void *x) =20 mutex_lock(&bch_register_lock); =20 - if (bcache_is_reboot) + if (atomic_read(&bcache_is_reboot)) goto out; =20 /* New registration is rejected since now */ - bcache_is_reboot =3D true; - /* - * Make registering caller (if there is) on other CPU - * core know bcache_is_reboot set to true earlier - */ - smp_mb(); + atomic_set(&bcache_is_reboot, 1); =20 if (list_empty(&bch_cache_sets) && list_empty(&uncached_devices)) @@ -2935,7 +2928,7 @@ static int __init bcache_init(void) =20 bch_debug_init(); =20 - bcache_is_reboot =3D false; + atomic_set(&bcache_is_reboot, 0); =20 return 0; err: diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c index 72f38e5b6f5c..5384653c5bbb 100644 --- a/drivers/md/bcache/sysfs.c +++ b/drivers/md/bcache/sysfs.c @@ -17,7 +17,7 @@ #include #include =20 -extern bool bcache_is_reboot; +extern atomic_t bcache_is_reboot; =20 /* Default is 0 ("writethrough") */ static const char * const bch_cache_modes[] =3D { @@ -296,7 +296,7 @@ STORE(__cached_dev) struct kobj_uevent_env *env; =20 /* no user space access if system is rebooting */ - if (bcache_is_reboot) + if (atomic_read(&bcache_is_reboot)) return -EBUSY; =20 #define d_strtoul(var) sysfs_strtoul(var, dc->var) @@ -459,7 +459,7 @@ STORE(bch_cached_dev) disk.kobj); =20 /* no user space access if system is rebooting */ - if (bcache_is_reboot) + if (atomic_read(&bcache_is_reboot)) return -EBUSY; =20 mutex_lock(&bch_register_lock); @@ -571,7 +571,7 @@ STORE(__bch_flash_dev) struct uuid_entry *u =3D &d->c->uuids[d->id]; =20 /* no user space access if system is rebooting */ - if (bcache_is_reboot) + if (atomic_read(&bcache_is_reboot)) return -EBUSY; =20 sysfs_strtoul(data_csum, d->data_csum); @@ -814,7 +814,7 @@ STORE(__bch_cache_set) ssize_t v; =20 /* no user space access if system is rebooting */ - if (bcache_is_reboot) + if (atomic_read(&bcache_is_reboot)) return -EBUSY; =20 if (attr =3D=3D &sysfs_unregister) @@ -941,7 +941,7 @@ STORE(bch_cache_set_internal) struct cache_set *c =3D container_of(kobj, struct cache_set, internal); =20 /* no user space access if system is rebooting */ - if (bcache_is_reboot) + if (atomic_read(&bcache_is_reboot)) return -EBUSY; =20 return bch_cache_set_store(&c->kobj, attr, buf, size); @@ -1137,7 +1137,7 @@ STORE(__bch_cache) ssize_t v; =20 /* no user space access if system is rebooting */ - if (bcache_is_reboot) + if (atomic_read(&bcache_is_reboot)) return -EBUSY; =20 if (attr =3D=3D &sysfs_cache_replacement_policy) { --=20 2.43.0