btrfs: fiemap: preallocate ulists for btrfs_check_shared

btrfs_check_shared looks up parents of a given extent and uses ulists
for that. These are allocated and freed repeatedly. Preallocation in the
caller will avoid the overhead and also allow us to use the GFP_KERNEL
as it is happens before the extent locks are taken.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 6 insertions, 11 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 982152d3f920..89116afda7a2 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -1465,12 +1465,11 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
  *
  * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
  */
-int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr)
+int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr,
+		struct ulist *roots, struct ulist *tmp)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_trans_handle *trans;
-	struct ulist *tmp = NULL;
-	struct ulist *roots = NULL;
 	struct ulist_iterator uiter;
 	struct ulist_node *node;
 	struct seq_list elem = SEQ_LIST_INIT(elem);
@@ -1481,12 +1480,8 @@ int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr)
 		.share_count = 0,
 	};
 
-	tmp = ulist_alloc(GFP_NOFS);
-	roots = ulist_alloc(GFP_NOFS);
-	if (!tmp || !roots) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	ulist_init(roots);
+	ulist_init(tmp);
 
 	trans = btrfs_attach_transaction(root);
 	if (IS_ERR(trans)) {
@@ -1527,8 +1522,8 @@ int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr)
 		up_read(&fs_info->commit_root_sem);
 	}
 out:
-	ulist_free(tmp);
-	ulist_free(roots);
+	ulist_release(roots);
+	ulist_release(tmp);
 	return ret;
 }