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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>
This commit is contained in:
Josef Bacik 2011-04-11 20:20:11 -04:00 committed by Chris Mason
parent 0d399205ed
commit 6d74119f1a
2 changed files with 28 additions and 6 deletions
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4
fs/btrfs/ctree.h
View File

@ -740,8 +740,10 @@ struct btrfs_space_info {
*/
unsigned long reservation_progress;
int full; /* indicates that we cannot allocate any more
int full:1; /* indicates that we cannot allocate any more
chunks for this space */
int chunk_alloc:1; /* set if we are allocating a chunk */
int force_alloc; /* set if we need to force a chunk alloc for
this space */

30
fs/btrfs/extent-tree.c
View File

@ -3039,6 +3039,7 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
found->bytes_may_use = 0;
found->full = 0;
found->force_alloc = CHUNK_ALLOC_NO_FORCE;
found->chunk_alloc = 0;
*space_info = found;
list_add_rcu(&found->list, &info->space_info);
atomic_set(&found->caching_threads, 0);
@ -3318,10 +3319,9 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
{
struct btrfs_space_info *space_info;
struct btrfs_fs_info *fs_info = extent_root->fs_info;
int wait_for_alloc = 0;
int ret = 0;
mutex_lock(&fs_info->chunk_mutex);
flags = btrfs_reduce_alloc_profile(extent_root, flags);
space_info = __find_space_info(extent_root->fs_info, flags);
@ -3332,21 +3332,40 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
}
BUG_ON(!space_info);
again:
spin_lock(&space_info->lock);
if (space_info->force_alloc)
force = space_info->force_alloc;
if (space_info->full) {
spin_unlock(&space_info->lock);
goto out;
return 0;
}
if (!should_alloc_chunk(extent_root, space_info, alloc_bytes, force)) {
spin_unlock(&space_info->lock);
goto out;
return 0;
} else if (space_info->chunk_alloc) {
wait_for_alloc = 1;
} else {
space_info->chunk_alloc = 1;
}
spin_unlock(&space_info->lock);
mutex_lock(&fs_info->chunk_mutex);
/*
* The chunk_mutex is held throughout the entirety of a chunk
* allocation, so once we've acquired the chunk_mutex we know that the
* other guy is done and we need to recheck and see if we should
* allocate.
*/
if (wait_for_alloc) {
mutex_unlock(&fs_info->chunk_mutex);
wait_for_alloc = 0;
goto again;
}
/*
* If we have mixed data/metadata chunks we want to make sure we keep
* allocating mixed chunks instead of individual chunks.
@ -3372,9 +3391,10 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
space_info->full = 1;
else
ret = 1;
space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
space_info->chunk_alloc = 0;
spin_unlock(&space_info->lock);
out:
mutex_unlock(&extent_root->fs_info->chunk_mutex);
return ret;
}