Btrfs: introduce mount option no_space_cache

Some users have requested this and I've found I needed a way to disable cache
loading without actually clearing the cache, so introduce the no_space_cache
option.  Before we check the super blocks cache generation field and if it was
populated we always turned space caching on.  Now we check this and set the
space cache option on, and then parse the mount options so that if we want it
off it get's turned off.  Then we check the mount option all the places we do
the caching work instead of checking the super's cache generation.  This makes
things more consistent and lets us turn space caching off.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 25b69d0f9135..f9711a82fc54 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -481,7 +481,8 @@ static int cache_block_group(struct btrfs_block_group_cache *cache,
          * we likely hold important locks.
          */
         if (trans && (!trans->transaction->in_commit) &&
-            (root && root != root->fs_info->tree_root)) {
+            (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);
@@ -4223,7 +4224,7 @@ static int update_block_group(struct btrfs_trans_handle *trans,
                 spin_lock(&cache->space_info->lock);
                 spin_lock(&cache->lock);
 
-                if (btrfs_super_cache_generation(&info->super_copy) != 0 &&
+                if (btrfs_test_opt(root, SPACE_CACHE) &&
                     cache->disk_cache_state < BTRFS_DC_CLEAR)
                         cache->disk_cache_state = BTRFS_DC_CLEAR;
 
@@ -7038,13 +7039,11 @@ int btrfs_read_block_groups(struct btrfs_root *root)
         path->reada = 1;
 
         cache_gen = btrfs_super_cache_generation(&root->fs_info->super_copy);
-        if (cache_gen != 0 &&
+        if (btrfs_test_opt(root, SPACE_CACHE) &&
             btrfs_super_generation(&root->fs_info->super_copy) != cache_gen)
                 need_clear = 1;
         if (btrfs_test_opt(root, CLEAR_CACHE))
                 need_clear = 1;
-        if (!btrfs_test_opt(root, SPACE_CACHE) && cache_gen)
-                printk(KERN_INFO "btrfs: disk space caching is enabled\n");
 
         while (1) {
                 ret = find_first_block_group(root, path, &key);