Btrfs: switch extent_map to a rw lock
There are two main users of the extent_map tree. The
first is regular file inodes, where it is evenly spread
between readers and writers.
The second is the chunk allocation tree, which maps blocks from
logical addresses to phyiscal ones, and it is 99.99% reads.
The mapping tree is a point of lock contention during heavy IO
workloads, so this commit switches things to a rw lock.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index a7e5377..d2358c0 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1749,9 +1749,9 @@
* step two, delete the device extents and the
* chunk tree entries
*/
- spin_lock(&em_tree->lock);
+ read_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, chunk_offset, 1);
- spin_unlock(&em_tree->lock);
+ read_unlock(&em_tree->lock);
BUG_ON(em->start > chunk_offset ||
em->start + em->len < chunk_offset);
@@ -1780,9 +1780,9 @@
ret = btrfs_remove_block_group(trans, extent_root, chunk_offset);
BUG_ON(ret);
- spin_lock(&em_tree->lock);
+ write_lock(&em_tree->lock);
remove_extent_mapping(em_tree, em);
- spin_unlock(&em_tree->lock);
+ write_unlock(&em_tree->lock);
kfree(map);
em->bdev = NULL;
@@ -2294,9 +2294,9 @@
em->block_len = em->len;
em_tree = &extent_root->fs_info->mapping_tree.map_tree;
- spin_lock(&em_tree->lock);
+ write_lock(&em_tree->lock);
ret = add_extent_mapping(em_tree, em);
- spin_unlock(&em_tree->lock);
+ write_unlock(&em_tree->lock);
BUG_ON(ret);
free_extent_map(em);
@@ -2491,9 +2491,9 @@
int readonly = 0;
int i;
- spin_lock(&map_tree->map_tree.lock);
+ read_lock(&map_tree->map_tree.lock);
em = lookup_extent_mapping(&map_tree->map_tree, chunk_offset, 1);
- spin_unlock(&map_tree->map_tree.lock);
+ read_unlock(&map_tree->map_tree.lock);
if (!em)
return 1;
@@ -2518,11 +2518,11 @@
struct extent_map *em;
while (1) {
- spin_lock(&tree->map_tree.lock);
+ write_lock(&tree->map_tree.lock);
em = lookup_extent_mapping(&tree->map_tree, 0, (u64)-1);
if (em)
remove_extent_mapping(&tree->map_tree, em);
- spin_unlock(&tree->map_tree.lock);
+ write_unlock(&tree->map_tree.lock);
if (!em)
break;
kfree(em->bdev);
@@ -2540,9 +2540,9 @@
struct extent_map_tree *em_tree = &map_tree->map_tree;
int ret;
- spin_lock(&em_tree->lock);
+ read_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, logical, len);
- spin_unlock(&em_tree->lock);
+ read_unlock(&em_tree->lock);
BUG_ON(!em);
BUG_ON(em->start > logical || em->start + em->len < logical);
@@ -2604,9 +2604,9 @@
atomic_set(&multi->error, 0);
}
- spin_lock(&em_tree->lock);
+ read_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, logical, *length);
- spin_unlock(&em_tree->lock);
+ read_unlock(&em_tree->lock);
if (!em && unplug_page)
return 0;
@@ -2763,9 +2763,9 @@
u64 stripe_nr;
int i, j, nr = 0;
- spin_lock(&em_tree->lock);
+ read_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, chunk_start, 1);
- spin_unlock(&em_tree->lock);
+ read_unlock(&em_tree->lock);
BUG_ON(!em || em->start != chunk_start);
map = (struct map_lookup *)em->bdev;
@@ -3053,9 +3053,9 @@
logical = key->offset;
length = btrfs_chunk_length(leaf, chunk);
- spin_lock(&map_tree->map_tree.lock);
+ read_lock(&map_tree->map_tree.lock);
em = lookup_extent_mapping(&map_tree->map_tree, logical, 1);
- spin_unlock(&map_tree->map_tree.lock);
+ read_unlock(&map_tree->map_tree.lock);
/* already mapped? */
if (em && em->start <= logical && em->start + em->len > logical) {
@@ -3114,9 +3114,9 @@
map->stripes[i].dev->in_fs_metadata = 1;
}
- spin_lock(&map_tree->map_tree.lock);
+ write_lock(&map_tree->map_tree.lock);
ret = add_extent_mapping(&map_tree->map_tree, em);
- spin_unlock(&map_tree->map_tree.lock);
+ write_unlock(&map_tree->map_tree.lock);
BUG_ON(ret);
free_extent_map(em);