From 291c7d2f577428f896daa5002e784959328a80aa Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Mon, 14 Nov 2011 13:52:14 -0500 Subject: Btrfs: wait on caching if we're loading the free space cache We've been hitting panics when running xfstest 13 in a loop for long periods of time. And actually this problem has always existed so we've been hitting these things randomly for a while. Basically what happens is we get a thread coming into the allocator and reading the space cache off of disk and adding the entries to the free space cache as we go. Then we get another thread that comes in and tries to allocate from that block group. Since block_group->cached != BTRFS_CACHE_NO it goes ahead and tries to do the allocation. We do this because if we're doing the old slow way of caching we don't want to hold people up and wait for everything to finish. The problem with this is we could end up discarding the space cache at some arbitrary point in the future, which means we could very well end up allocating space that is either bad, or when the real caching happens it could end up thinking the space isn't in use when it really is and cause all sorts of other problems. The solution is to add a new flag to indicate we are loading the free space cache from disk, and always try to cache the block group if cache->cached != BTRFS_CACHE_FINISHED. That way if we are loading the space cache anybody else who tries to allocate from the block group will have to wait until it's finished to make sure it completes successfully. Thanks, Signed-off-by: Josef Bacik --- fs/btrfs/extent-tree.c | 119 ++++++++++++++++++++++++++++++++----------------- 1 file changed, 79 insertions(+), 40 deletions(-) (limited to 'fs/btrfs/extent-tree.c') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 0f47b3e..5d86877 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -467,13 +467,59 @@ static int cache_block_group(struct btrfs_block_group_cache *cache, struct btrfs_root *root, int load_cache_only) { + DEFINE_WAIT(wait); struct btrfs_fs_info *fs_info = cache->fs_info; struct btrfs_caching_control *caching_ctl; int ret = 0; - smp_mb(); - if (cache->cached != BTRFS_CACHE_NO) + caching_ctl = kzalloc(sizeof(*caching_ctl), GFP_NOFS); + BUG_ON(!caching_ctl); + + INIT_LIST_HEAD(&caching_ctl->list); + mutex_init(&caching_ctl->mutex); + init_waitqueue_head(&caching_ctl->wait); + caching_ctl->block_group = cache; + caching_ctl->progress = cache->key.objectid; + atomic_set(&caching_ctl->count, 1); + caching_ctl->work.func = caching_thread; + + spin_lock(&cache->lock); + /* + * This should be a rare occasion, but this could happen I think in the + * case where one thread starts to load the space cache info, and then + * some other thread starts a transaction commit which tries to do an + * allocation while the other thread is still loading the space cache + * info. The previous loop should have kept us from choosing this block + * group, but if we've moved to the state where we will wait on caching + * block groups we need to first check if we're doing a fast load here, + * so we can wait for it to finish, otherwise we could end up allocating + * from a block group who's cache gets evicted for one reason or + * another. + */ + while (cache->cached == BTRFS_CACHE_FAST) { + struct btrfs_caching_control *ctl; + + ctl = cache->caching_ctl; + atomic_inc(&ctl->count); + prepare_to_wait(&ctl->wait, &wait, TASK_UNINTERRUPTIBLE); + spin_unlock(&cache->lock); + + schedule(); + + finish_wait(&ctl->wait, &wait); + put_caching_control(ctl); + spin_lock(&cache->lock); + } + + if (cache->cached != BTRFS_CACHE_NO) { + spin_unlock(&cache->lock); + kfree(caching_ctl); return 0; + } + WARN_ON(cache->caching_ctl); + cache->caching_ctl = caching_ctl; + cache->cached = BTRFS_CACHE_FAST; + spin_unlock(&cache->lock); /* * We can't do the read from on-disk cache during a commit since we need @@ -484,56 +530,51 @@ static int cache_block_group(struct btrfs_block_group_cache *cache, if (trans && (!trans->transaction->in_commit) && (root && root != root->fs_info->tree_root) && btrfs_test_opt(root, SPACE_CACHE)) { - spin_lock(&cache->lock); - if (cache->cached != BTRFS_CACHE_NO) { - spin_unlock(&cache->lock); - return 0; - } - cache->cached = BTRFS_CACHE_STARTED; - spin_unlock(&cache->lock); - ret = load_free_space_cache(fs_info, cache); spin_lock(&cache->lock); if (ret == 1) { + cache->caching_ctl = NULL; cache->cached = BTRFS_CACHE_FINISHED; cache->last_byte_to_unpin = (u64)-1; } else { - cache->cached = BTRFS_CACHE_NO; + if (load_cache_only) { + cache->caching_ctl = NULL; + cache->cached = BTRFS_CACHE_NO; + } else { + cache->cached = BTRFS_CACHE_STARTED; + } } spin_unlock(&cache->lock); + wake_up(&caching_ctl->wait); if (ret == 1) { + put_caching_control(caching_ctl); free_excluded_extents(fs_info->extent_root, cache); return 0; } + } else { + /* + * We are not going to do the fast caching, set cached to the + * appropriate value and wakeup any waiters. + */ + spin_lock(&cache->lock); + if (load_cache_only) { + cache->caching_ctl = NULL; + cache->cached = BTRFS_CACHE_NO; + } else { + cache->cached = BTRFS_CACHE_STARTED; + } + spin_unlock(&cache->lock); + wake_up(&caching_ctl->wait); } - if (load_cache_only) - return 0; - - caching_ctl = kzalloc(sizeof(*caching_ctl), GFP_NOFS); - BUG_ON(!caching_ctl); - - INIT_LIST_HEAD(&caching_ctl->list); - mutex_init(&caching_ctl->mutex); - init_waitqueue_head(&caching_ctl->wait); - caching_ctl->block_group = cache; - caching_ctl->progress = cache->key.objectid; - /* one for caching kthread, one for caching block group list */ - atomic_set(&caching_ctl->count, 2); - caching_ctl->work.func = caching_thread; - - spin_lock(&cache->lock); - if (cache->cached != BTRFS_CACHE_NO) { - spin_unlock(&cache->lock); - kfree(caching_ctl); + if (load_cache_only) { + put_caching_control(caching_ctl); return 0; } - cache->caching_ctl = caching_ctl; - cache->cached = BTRFS_CACHE_STARTED; - spin_unlock(&cache->lock); down_write(&fs_info->extent_commit_sem); + atomic_inc(&caching_ctl->count); list_add_tail(&caching_ctl->list, &fs_info->caching_block_groups); up_write(&fs_info->extent_commit_sem); @@ -5177,13 +5218,15 @@ search: } have_block_group: - if (unlikely(block_group->cached == BTRFS_CACHE_NO)) { + cached = block_group_cache_done(block_group); + if (unlikely(!cached)) { u64 free_percent; + found_uncached_bg = true; ret = cache_block_group(block_group, trans, orig_root, 1); if (block_group->cached == BTRFS_CACHE_FINISHED) - goto have_block_group; + goto alloc; free_percent = btrfs_block_group_used(&block_group->item); free_percent *= 100; @@ -5205,7 +5248,6 @@ have_block_group: orig_root, 0); BUG_ON(ret); } - found_uncached_bg = true; /* * If loop is set for cached only, try the next block @@ -5215,10 +5257,7 @@ have_block_group: goto loop; } - cached = block_group_cache_done(block_group); - if (unlikely(!cached)) - found_uncached_bg = true; - +alloc: if (unlikely(block_group->ro)) goto loop; -- cgit v1.1 From aa38a711a893accf5b5192f3d705a120deaa81e0 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Fri, 18 Nov 2011 17:43:00 +0800 Subject: Btrfs: fix deadlock on metadata reservation when evicting a inode When I ran the xfstests, I found the test tasks was blocked on meta-data reservation. By debugging, I found the reason of this bug: start transaction | v reserve meta-data space | v flush delay allocation -> iput inode -> evict inode ^ | | v wait for delay allocation flush <- reserve meta-data space And besides that, the flush on evicting inode will block the thread, which is reclaiming the memory, and make oom happen easily. Fix this bug by skipping the flush step when evicting inode. Signed-off-by: Miao Xie --- fs/btrfs/extent-tree.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) (limited to 'fs/btrfs/extent-tree.c') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 5d86877..b7e5f68 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3887,9 +3887,9 @@ int btrfs_block_rsv_check(struct btrfs_root *root, return ret; } -int btrfs_block_rsv_refill(struct btrfs_root *root, - struct btrfs_block_rsv *block_rsv, - u64 min_reserved) +static inline int __btrfs_block_rsv_refill(struct btrfs_root *root, + struct btrfs_block_rsv *block_rsv, + u64 min_reserved, int flush) { u64 num_bytes = 0; int ret = -ENOSPC; @@ -3908,7 +3908,7 @@ int btrfs_block_rsv_refill(struct btrfs_root *root, if (!ret) return 0; - ret = reserve_metadata_bytes(root, block_rsv, num_bytes, 1); + ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush); if (!ret) { block_rsv_add_bytes(block_rsv, num_bytes, 0); return 0; @@ -3917,6 +3917,20 @@ int btrfs_block_rsv_refill(struct btrfs_root *root, return ret; } +int btrfs_block_rsv_refill(struct btrfs_root *root, + struct btrfs_block_rsv *block_rsv, + u64 min_reserved) +{ + return __btrfs_block_rsv_refill(root, block_rsv, min_reserved, 1); +} + +int btrfs_block_rsv_refill_noflush(struct btrfs_root *root, + struct btrfs_block_rsv *block_rsv, + u64 min_reserved) +{ + return __btrfs_block_rsv_refill(root, block_rsv, min_reserved, 0); +} + int btrfs_block_rsv_migrate(struct btrfs_block_rsv *src_rsv, struct btrfs_block_rsv *dst_rsv, u64 num_bytes) -- cgit v1.1 From 1b22bad779be7fe07242be04749ec969164528b8 Mon Sep 17 00:00:00 2001 From: Alexandre Oliva Date: Wed, 30 Nov 2011 13:43:00 -0500 Subject: Btrfs: start search for new cluster at the beginning Instead of starting at zero (offset is always zero), request a cluster starting at search_start, that denotes the beginning of the current block group. Signed-off-by: Alexandre Oliva Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'fs/btrfs/extent-tree.c') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index b7e5f68..97c1206 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -5301,10 +5301,8 @@ alloc: spin_lock(&last_ptr->refill_lock); if (last_ptr->block_group && (last_ptr->block_group->ro || - !block_group_bits(last_ptr->block_group, data))) { - offset = 0; + !block_group_bits(last_ptr->block_group, data))) goto refill_cluster; - } offset = btrfs_alloc_from_cluster(block_group, last_ptr, num_bytes, search_start); @@ -5355,7 +5353,7 @@ refill_cluster: /* allocate a cluster in this block group */ ret = btrfs_find_space_cluster(trans, root, block_group, last_ptr, - offset, num_bytes, + search_start, num_bytes, empty_cluster + empty_size); if (ret == 0) { /* -- cgit v1.1 From 425d83156ca27f74e2cc3f370138038c3c8947f8 Mon Sep 17 00:00:00 2001 From: Alexandre Oliva Date: Wed, 30 Nov 2011 13:43:00 -0500 Subject: Btrfs: skip block groups without enough space for a cluster We test whether a block group has enough free space to hold the requested block, but when we're doing clustered allocation, we can save some cycles by testing whether it has enough room for the cluster upfront, otherwise we end up attempting to set up a cluster and failing. Only in the NO_EMPTY_SIZE loop do we attempt an unclustered allocation, and by then we'll have zeroed the cluster size, so this patch won't stop us from using the block group as a last resort. Signed-off-by: Alexandre Oliva Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/btrfs/extent-tree.c') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 97c1206..71c8e70 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -5278,7 +5278,7 @@ alloc: spin_lock(&block_group->free_space_ctl->tree_lock); if (cached && block_group->free_space_ctl->free_space < - num_bytes + empty_size) { + num_bytes + empty_cluster + empty_size) { spin_unlock(&block_group->free_space_ctl->tree_lock); goto loop; } -- cgit v1.1 From be064d113906f04ea13088a8260e1e68ae0a4050 Mon Sep 17 00:00:00 2001 From: Alexandre Oliva Date: Wed, 30 Nov 2011 13:43:00 -0500 Subject: Btrfs: skip allocation attempt from empty cluster If we don't have a cluster, don't bother trying to allocate from it, jumping right away to the attempt to allocate a new cluster. Signed-off-by: Alexandre Oliva Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs/btrfs/extent-tree.c') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 71c8e70..813c6bb 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -5299,9 +5299,9 @@ alloc: * people trying to start a new cluster */ spin_lock(&last_ptr->refill_lock); - if (last_ptr->block_group && - (last_ptr->block_group->ro || - !block_group_bits(last_ptr->block_group, data))) + if (!last_ptr->block_group || + last_ptr->block_group->ro || + !block_group_bits(last_ptr->block_group, data)) goto refill_cluster; offset = btrfs_alloc_from_cluster(block_group, last_ptr, -- cgit v1.1