btrfs: move comments to btrfs_loop_type definition

Some of these loop types aren't described, and they should be with the
definitions to make it easier to tell what each of them do.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d674e42..6dfe086 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3329,11 +3329,38 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_ref *ref)
 }
 
 enum btrfs_loop_type {
+       /*
+        * Start caching block groups but do not wait for progress or for them
+        * to be done.
+        */
        LOOP_CACHING_NOWAIT,
+
+       /*
+        * Wait for the block group free_space >= the space we're waiting for if
+        * the block group isn't cached.
+        */
        LOOP_CACHING_WAIT,
+
+       /*
+        * Allow allocations to happen from block groups that do not yet have a
+        * size classification.
+        */
        LOOP_UNSET_SIZE_CLASS,
+
+       /*
+        * Allocate a chunk and then retry the allocation.
+        */
        LOOP_ALLOC_CHUNK,
+
+       /*
+        * Ignore the size class restrictions for this allocation.
+        */
        LOOP_WRONG_SIZE_CLASS,
+
+       /*
+        * Ignore the empty size, only try to allocate the number of bytes
+        * needed for this allocation.
+        */
        LOOP_NO_EMPTY_SIZE,
 };
 
@@ -3927,15 +3954,7 @@ static int find_free_extent_update_loop(struct btrfs_fs_info *fs_info,
        if (ffe_ctl->index < BTRFS_NR_RAID_TYPES)
                return 1;
 
-       /*
-        * LOOP_CACHING_NOWAIT, search partially cached block groups, kicking
-        *                      caching kthreads as we move along
-        * LOOP_CACHING_WAIT, search everything, and wait if our bg is caching
-        * LOOP_UNSET_SIZE_CLASS, allow unset size class
-        * LOOP_ALLOC_CHUNK, force a chunk allocation and try again
-        * LOOP_NO_EMPTY_SIZE, set empty_size and empty_cluster to 0 and try
-        *                     again
-        */
+       /* See the comments for btrfs_loop_type for an explanation of the phases. */
        if (ffe_ctl->loop < LOOP_NO_EMPTY_SIZE) {
                ffe_ctl->index = 0;
                /*