Add a min size parameter to btrfs_alloc_extent

On huge machines, delayed allocation may try to allocate massive extents.
This change allows btrfs_alloc_extent to return something smaller than
the caller asked for, and the data allocation routines will loop over
the allocations until it fills the whole delayed alloc.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index a056a2df689a..e49147e767df 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1694,7 +1694,8 @@ error:
  */
 int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root,
-                       u64 num_bytes, u64 root_objectid, u64 ref_generation,
+                       u64 num_bytes, u64 min_alloc_size,
+                       u64 root_objectid, u64 ref_generation,
                        u64 owner, u64 owner_offset,
                        u64 empty_size, u64 hint_byte,
                        u64 search_end, struct btrfs_key *ins, int data)
@@ -1727,7 +1728,7 @@ int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
                                 info->metadata_alloc_profile;
                 data = BTRFS_BLOCK_GROUP_METADATA | alloc_profile;
         }
-
+again:
         if (root->ref_cows) {
                 if (!(data & BTRFS_BLOCK_GROUP_METADATA)) {
                         ret = do_chunk_alloc(trans, root->fs_info->extent_root,
@@ -1751,6 +1752,11 @@ int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
                                search_start, search_end, hint_byte, ins,
                                trans->alloc_exclude_start,
                                trans->alloc_exclude_nr, data);
+        if (ret == -ENOSPC && num_bytes > min_alloc_size) {
+                num_bytes = num_bytes >> 1;
+                num_bytes = max(num_bytes, min_alloc_size);
+                goto again;
+        }
         BUG_ON(ret);
         if (ret)
                 return ret;
@@ -1869,7 +1875,7 @@ struct extent_buffer *__btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
         int ret;
         struct extent_buffer *buf;
 
-        ret = btrfs_alloc_extent(trans, root, blocksize,
+        ret = btrfs_alloc_extent(trans, root, blocksize, blocksize,
                                  root_objectid, ref_generation,
                                  level, first_objectid, empty_size, hint,
                                  (u64)-1, &ins, 0);