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Btrfs: avoid taking the chunk_mutex in do_chunk_alloc
Everytime we try to allocate disk space we try and see if we can pre-emptively allocate a chunk, but in the common case we don't allocate anything, so there is no sense in taking the chunk_mutex at all. So instead if we are allocating a chunk, mark it in the space_info so we don't get two people trying to allocate at the same time. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> Reviewed-by: Liu Bo <liubo2009@cn.fujitsu.com>
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parent
0d399205ed
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6d74119f1a
2 changed files with 28 additions and 6 deletions
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@ -740,8 +740,10 @@ struct btrfs_space_info {
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*/
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unsigned long reservation_progress;
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int full; /* indicates that we cannot allocate any more
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int full:1; /* indicates that we cannot allocate any more
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chunks for this space */
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int chunk_alloc:1; /* set if we are allocating a chunk */
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int force_alloc; /* set if we need to force a chunk alloc for
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this space */
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@ -3039,6 +3039,7 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
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found->bytes_may_use = 0;
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found->full = 0;
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found->force_alloc = CHUNK_ALLOC_NO_FORCE;
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found->chunk_alloc = 0;
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*space_info = found;
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list_add_rcu(&found->list, &info->space_info);
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atomic_set(&found->caching_threads, 0);
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@ -3318,10 +3319,9 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
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{
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struct btrfs_space_info *space_info;
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struct btrfs_fs_info *fs_info = extent_root->fs_info;
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int wait_for_alloc = 0;
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int ret = 0;
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mutex_lock(&fs_info->chunk_mutex);
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flags = btrfs_reduce_alloc_profile(extent_root, flags);
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space_info = __find_space_info(extent_root->fs_info, flags);
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@ -3332,21 +3332,40 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
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}
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BUG_ON(!space_info);
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again:
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spin_lock(&space_info->lock);
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if (space_info->force_alloc)
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force = space_info->force_alloc;
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if (space_info->full) {
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spin_unlock(&space_info->lock);
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goto out;
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return 0;
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}
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if (!should_alloc_chunk(extent_root, space_info, alloc_bytes, force)) {
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spin_unlock(&space_info->lock);
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goto out;
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return 0;
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} else if (space_info->chunk_alloc) {
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wait_for_alloc = 1;
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} else {
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space_info->chunk_alloc = 1;
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}
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spin_unlock(&space_info->lock);
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mutex_lock(&fs_info->chunk_mutex);
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/*
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* The chunk_mutex is held throughout the entirety of a chunk
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* allocation, so once we've acquired the chunk_mutex we know that the
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* other guy is done and we need to recheck and see if we should
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* allocate.
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*/
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if (wait_for_alloc) {
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mutex_unlock(&fs_info->chunk_mutex);
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wait_for_alloc = 0;
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goto again;
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}
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/*
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* If we have mixed data/metadata chunks we want to make sure we keep
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* allocating mixed chunks instead of individual chunks.
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@ -3372,9 +3391,10 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
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space_info->full = 1;
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else
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ret = 1;
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space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
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space_info->chunk_alloc = 0;
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spin_unlock(&space_info->lock);
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out:
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mutex_unlock(&extent_root->fs_info->chunk_mutex);
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return ret;
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}
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