diff options
| -rw-r--r-- | fs/super.c | 111 | ||||
| -rw-r--r-- | include/linux/fs.h | 19 |
2 files changed, 36 insertions, 94 deletions
diff --git a/fs/super.c b/fs/super.c index c937bd7b4d33..767b1e10f6ad 100644 --- a/fs/super.c +++ b/fs/super.c @@ -142,7 +142,7 @@ static void destroy_super_work(struct work_struct *work) int i; for (i = 0; i < SB_FREEZE_LEVELS; i++) - percpu_counter_destroy(&s->s_writers.counter[i]); + percpu_free_rwsem(&s->s_writers.rw_sem[i]); kfree(s); } @@ -193,13 +193,11 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags) goto fail; for (i = 0; i < SB_FREEZE_LEVELS; i++) { - if (percpu_counter_init(&s->s_writers.counter[i], 0, - GFP_KERNEL) < 0) + if (__percpu_init_rwsem(&s->s_writers.rw_sem[i], + sb_writers_name[i], + &type->s_writers_key[i])) goto fail; - lockdep_init_map(&s->s_writers.lock_map[i], sb_writers_name[i], - &type->s_writers_key[i], 0); } - init_waitqueue_head(&s->s_writers.wait); init_waitqueue_head(&s->s_writers.wait_unfrozen); s->s_bdi = &noop_backing_dev_info; s->s_flags = flags; @@ -1161,47 +1159,10 @@ out: */ void __sb_end_write(struct super_block *sb, int level) { - percpu_counter_dec(&sb->s_writers.counter[level-1]); - /* - * Make sure s_writers are updated before we wake up waiters in - * freeze_super(). - */ - smp_mb(); - if (waitqueue_active(&sb->s_writers.wait)) - wake_up(&sb->s_writers.wait); - rwsem_release(&sb->s_writers.lock_map[level-1], 1, _RET_IP_); + percpu_up_read(sb->s_writers.rw_sem + level-1); } EXPORT_SYMBOL(__sb_end_write); -static int do_sb_start_write(struct super_block *sb, int level, bool wait, - unsigned long ip) -{ - if (wait) - rwsem_acquire_read(&sb->s_writers.lock_map[level-1], 0, 0, ip); -retry: - if (unlikely(sb->s_writers.frozen >= level)) { - if (!wait) - return 0; - wait_event(sb->s_writers.wait_unfrozen, - sb->s_writers.frozen < level); - } - - percpu_counter_inc(&sb->s_writers.counter[level-1]); - /* - * Make sure counter is updated before we check for frozen. - * freeze_super() first sets frozen and then checks the counter. - */ - smp_mb(); - if (unlikely(sb->s_writers.frozen >= level)) { - __sb_end_write(sb, level); - goto retry; - } - - if (!wait) - rwsem_acquire_read(&sb->s_writers.lock_map[level-1], 0, 1, ip); - return 1; -} - /* * This is an internal function, please use sb_start_{write,pagefault,intwrite} * instead. @@ -1209,7 +1170,7 @@ retry: int __sb_start_write(struct super_block *sb, int level, bool wait) { bool force_trylock = false; - int ret; + int ret = 1; #ifdef CONFIG_LOCKDEP /* @@ -1225,13 +1186,17 @@ int __sb_start_write(struct super_block *sb, int level, bool wait) int i; for (i = 0; i < level - 1; i++) - if (lock_is_held(&sb->s_writers.lock_map[i])) { + if (percpu_rwsem_is_held(sb->s_writers.rw_sem + i)) { force_trylock = true; break; } } #endif - ret = do_sb_start_write(sb, level, wait && !force_trylock, _RET_IP_); + if (wait && !force_trylock) + percpu_down_read(sb->s_writers.rw_sem + level-1); + else + ret = percpu_down_read_trylock(sb->s_writers.rw_sem + level-1); + WARN_ON(force_trylock & !ret); return ret; } @@ -1243,15 +1208,11 @@ EXPORT_SYMBOL(__sb_start_write); * @level: type of writers we wait for (normal vs page fault) * * This function waits until there are no writers of given type to given file - * system. Caller of this function should make sure there can be no new writers - * of type @level before calling this function. Otherwise this function can - * livelock. + * system. */ static void sb_wait_write(struct super_block *sb, int level) { - s64 writers; - - rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_); + percpu_down_write(sb->s_writers.rw_sem + level-1); /* * We are going to return to userspace and forget about this lock, the * ownership goes to the caller of thaw_super() which does unlock. @@ -1262,24 +1223,18 @@ static void sb_wait_write(struct super_block *sb, int level) * this leads to lockdep false-positives, so currently we do the early * release right after acquire. */ - rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_); - - do { - DEFINE_WAIT(wait); + percpu_rwsem_release(sb->s_writers.rw_sem + level-1, 0, _THIS_IP_); +} - /* - * We use a barrier in prepare_to_wait() to separate setting - * of frozen and checking of the counter - */ - prepare_to_wait(&sb->s_writers.wait, &wait, - TASK_UNINTERRUPTIBLE); +static void sb_freeze_unlock(struct super_block *sb) +{ + int level; - writers = percpu_counter_sum(&sb->s_writers.counter[level-1]); - if (writers) - schedule(); + for (level = 0; level < SB_FREEZE_LEVELS; ++level) + percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_); - finish_wait(&sb->s_writers.wait, &wait); - } while (writers); + for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--) + percpu_up_write(sb->s_writers.rw_sem + level); } /** @@ -1338,20 +1293,14 @@ int freeze_super(struct super_block *sb) return 0; } - /* From now on, no new normal writers can start */ sb->s_writers.frozen = SB_FREEZE_WRITE; - smp_wmb(); - /* Release s_umount to preserve sb_start_write -> s_umount ordering */ up_write(&sb->s_umount); - sb_wait_write(sb, SB_FREEZE_WRITE); + down_write(&sb->s_umount); /* Now we go and block page faults... */ - down_write(&sb->s_umount); sb->s_writers.frozen = SB_FREEZE_PAGEFAULT; - smp_wmb(); - sb_wait_write(sb, SB_FREEZE_PAGEFAULT); /* All writers are done so after syncing there won't be dirty data */ @@ -1359,7 +1308,6 @@ int freeze_super(struct super_block *sb) /* Now wait for internal filesystem counter */ sb->s_writers.frozen = SB_FREEZE_FS; - smp_wmb(); sb_wait_write(sb, SB_FREEZE_FS); if (sb->s_op->freeze_fs) { @@ -1368,7 +1316,7 @@ int freeze_super(struct super_block *sb) printk(KERN_ERR "VFS:Filesystem freeze failed\n"); sb->s_writers.frozen = SB_UNFROZEN; - smp_wmb(); + sb_freeze_unlock(sb); wake_up(&sb->s_writers.wait_unfrozen); deactivate_locked_super(sb); return ret; @@ -1400,8 +1348,10 @@ int thaw_super(struct super_block *sb) return -EINVAL; } - if (sb->s_flags & MS_RDONLY) + if (sb->s_flags & MS_RDONLY) { + sb->s_writers.frozen = SB_UNFROZEN; goto out; + } if (sb->s_op->unfreeze_fs) { error = sb->s_op->unfreeze_fs(sb); @@ -1413,12 +1363,11 @@ int thaw_super(struct super_block *sb) } } -out: sb->s_writers.frozen = SB_UNFROZEN; - smp_wmb(); + sb_freeze_unlock(sb); +out: wake_up(&sb->s_writers.wait_unfrozen); deactivate_locked_super(sb); - return 0; } EXPORT_SYMBOL(thaw_super); diff --git a/include/linux/fs.h b/include/linux/fs.h index 4bed78966c6b..ce356f66cc2a 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1,7 +1,6 @@ #ifndef _LINUX_FS_H #define _LINUX_FS_H - #include <linux/linkage.h> #include <linux/wait.h> #include <linux/kdev_t.h> @@ -31,6 +30,7 @@ #include <linux/percpu-rwsem.h> #include <linux/blk_types.h> #include <linux/workqueue.h> +#include <linux/percpu-rwsem.h> #include <asm/byteorder.h> #include <uapi/linux/fs.h> @@ -1275,16 +1275,9 @@ enum { #define SB_FREEZE_LEVELS (SB_FREEZE_COMPLETE - 1) struct sb_writers { - /* Counters for counting writers at each level */ - struct percpu_counter counter[SB_FREEZE_LEVELS]; - wait_queue_head_t wait; /* queue for waiting for - writers / faults to finish */ - int frozen; /* Is sb frozen? */ - wait_queue_head_t wait_unfrozen; /* queue for waiting for - sb to be thawed */ -#ifdef CONFIG_DEBUG_LOCK_ALLOC - struct lockdep_map lock_map[SB_FREEZE_LEVELS]; -#endif + int frozen; /* Is sb frozen? */ + wait_queue_head_t wait_unfrozen; /* for get_super_thawed() */ + struct percpu_rw_semaphore rw_sem[SB_FREEZE_LEVELS]; }; struct super_block { @@ -1393,9 +1386,9 @@ void __sb_end_write(struct super_block *sb, int level); int __sb_start_write(struct super_block *sb, int level, bool wait); #define __sb_writers_acquired(sb, lev) \ - rwsem_acquire_read(&(sb)->s_writers.lock_map[(lev)-1], 0, 1, _THIS_IP_) + percpu_rwsem_acquire(&(sb)->s_writers.rw_sem[(lev)-1], 1, _THIS_IP_) #define __sb_writers_release(sb, lev) \ - rwsem_release(&(sb)->s_writers.lock_map[(lev)-1], 1, _THIS_IP_) + percpu_rwsem_release(&(sb)->s_writers.rw_sem[(lev)-1], 1, _THIS_IP_) /** * sb_end_write - drop write access to a superblock |