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Btrfs: Fix snapshot deletion to release the alloc_mutex much more often.

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This lowers the impact of snapshot deletion on the rest of the FS.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2008-06-25 16:01:30 -04:00
parent 5cd57b2cbb
commit 333db94cdd
3 changed files with 23 additions and 9 deletions
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28
fs/btrfs/extent-tree.c
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@@ -1223,8 +1223,8 @@ printk("space info full %Lu\n", flags);
ret = btrfs_make_block_group(trans, extent_root, 0, flags,
BTRFS_FIRST_CHUNK_TREE_OBJECTID, start, num_bytes);
BUG_ON(ret);
mutex_unlock(&extent_root->fs_info->chunk_mutex);
out:
mutex_unlock(&extent_root->fs_info->chunk_mutex);
return 0;
}
@@ -2181,17 +2181,29 @@ static void noinline reada_walk_down(struct btrfs_root *root,
continue;
}
}
mutex_unlock(&root->fs_info->alloc_mutex);
ret = readahead_tree_block(root, bytenr, blocksize,
btrfs_node_ptr_generation(node, i));
last = bytenr + blocksize;
cond_resched();
mutex_lock(&root->fs_info->alloc_mutex);
if (ret)
break;
}
}
/*
* we want to avoid as much random IO as we can with the alloc mutex
* held, so drop the lock and do the lookup, then do it again with the
* lock held.
*/
int drop_snap_lookup_refcount(struct btrfs_root *root, u64 start, u64 len,
u32 *refs)
{
mutex_unlock(&root->fs_info->alloc_mutex);
lookup_extent_ref(NULL, root, start, len, refs);
mutex_lock(&root->fs_info->alloc_mutex);
return lookup_extent_ref(NULL, root, start, len, refs);
}
/*
* helper function for drop_snapshot, this walks down the tree dropping ref
* counts as it goes.
@@ -2215,8 +2227,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
WARN_ON(*level < 0);
WARN_ON(*level >= BTRFS_MAX_LEVEL);
ret = lookup_extent_ref(trans, root,
path->nodes[*level]->start,
ret = drop_snap_lookup_refcount(root, path->nodes[*level]->start,
path->nodes[*level]->len, &refs);
BUG_ON(ret);
if (refs > 1)
@@ -2245,7 +2256,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);
blocksize = btrfs_level_size(root, *level - 1);
ret = lookup_extent_ref(trans, root, bytenr, blocksize, &refs);
ret = drop_snap_lookup_refcount(root, bytenr, blocksize, &refs);
BUG_ON(ret);
if (refs != 1) {
parent = path->nodes[*level];
@@ -2261,15 +2272,16 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
next = btrfs_find_tree_block(root, bytenr, blocksize);
if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
free_extent_buffer(next);
mutex_unlock(&root->fs_info->alloc_mutex);
reada_walk_down(root, cur, path->slots[*level]);
mutex_unlock(&root->fs_info->alloc_mutex);
next = read_tree_block(root, bytenr, blocksize,
ptr_gen);
mutex_lock(&root->fs_info->alloc_mutex);
/* we've dropped the lock, double check */
ret = lookup_extent_ref(trans, root, bytenr,
ret = drop_snap_lookup_refcount(root, bytenr,
blocksize, &refs);
BUG_ON(ret);
if (refs != 1) {