From ceda08642459e31673d24d7968d864390d2ce5fa Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Thu, 11 Apr 2013 10:30:16 +0000 Subject: [PATCH] Btrfs: use a lock to protect incompat/compat flag of the super block The following case will make the incompat/compat flag of the super block be recovered. Task1 |Task2 flags = btrfs_super_incompat_flags(); | |flags = btrfs_super_incompat_flags(); flags |= new_flag1; | |flags |= new_flag2; btrfs_set_super_incompat_flags(flags); | |btrfs_set_super_incompat_flags(flags); the new_flag1 is recovered. In order to avoid this problem, we introduce a lock named super_lock into the btrfs_fs_info structure. If we want to update incompat/compat flags of the super block, we must hold it. Signed-off-by: Miao Xie Signed-off-by: Josef Bacik --- fs/btrfs/ctree.h | 22 ++++++++++++++++++++-- fs/btrfs/disk-io.c | 5 +++++ fs/btrfs/volumes.c | 10 +--------- 3 files changed, 26 insertions(+), 11 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 1a85040..c3b15f8 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1362,6 +1362,17 @@ struct btrfs_fs_info { wait_queue_head_t transaction_blocked_wait; wait_queue_head_t async_submit_wait; + /* + * Used to protect the incompat_flags, compat_flags, compat_ro_flags + * when they are updated. + * + * Because we do not clear the flags for ever, so we needn't use + * the lock on the read side. + * + * We also needn't use the lock when we mount the fs, because + * there is no other task which will update the flag. + */ + spinlock_t super_lock; struct btrfs_super_block *super_copy; struct btrfs_super_block *super_for_commit; struct block_device *__bdev; @@ -3688,8 +3699,15 @@ static inline void __btrfs_set_fs_incompat(struct btrfs_fs_info *fs_info, disk_super = fs_info->super_copy; features = btrfs_super_incompat_flags(disk_super); if (!(features & flag)) { - features |= flag; - btrfs_set_super_incompat_flags(disk_super, features); + spin_lock(&fs_info->super_lock); + features = btrfs_super_incompat_flags(disk_super); + if (!(features & flag)) { + features |= flag; + btrfs_set_super_incompat_flags(disk_super, features); + printk(KERN_INFO "btrfs: setting %llu feature flag\n", + flag); + } + spin_unlock(&fs_info->super_lock); } } diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 9f83e5b..8a7a366 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2086,6 +2086,7 @@ int open_ctree(struct super_block *sb, spin_lock_init(&fs_info->defrag_inodes_lock); spin_lock_init(&fs_info->free_chunk_lock); spin_lock_init(&fs_info->tree_mod_seq_lock); + spin_lock_init(&fs_info->super_lock); rwlock_init(&fs_info->tree_mod_log_lock); mutex_init(&fs_info->reloc_mutex); seqlock_init(&fs_info->profiles_lock); @@ -2349,6 +2350,10 @@ int open_ctree(struct super_block *sb, goto fail_alloc; } + /* + * Needn't use the lock because there is no other task which will + * update the flag. + */ btrfs_set_super_incompat_flags(disk_super, features); features = btrfs_super_compat_ro_flags(disk_super) & diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 5aa52ee..76ded9e 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -3674,18 +3674,10 @@ static u32 find_raid56_stripe_len(u32 data_devices, u32 dev_stripe_target) static void check_raid56_incompat_flag(struct btrfs_fs_info *info, u64 type) { - u64 features; - if (!(type & (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6))) return; - features = btrfs_super_incompat_flags(info->super_copy); - if (features & BTRFS_FEATURE_INCOMPAT_RAID56) - return; - - features |= BTRFS_FEATURE_INCOMPAT_RAID56; - btrfs_set_super_incompat_flags(info->super_copy, features); - printk(KERN_INFO "btrfs: setting RAID5/6 feature flag\n"); + btrfs_set_fs_incompat(info, RAID56); } static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans, -- 2.7.4