diff options
| author | Filipe Manana <fdmanana@suse.com> | 2026-02-18 18:07:09 +0300 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2026-04-07 19:55:58 +0300 |
| commit | 1fce8eec9f89e3aaa13ced7c7ca625ab427b1bcc (patch) | |
| tree | 222ca7089207e54bbc63d0c9e45cbd72ace13603 | |
| parent | 13816fd5aa3ca2842be5dba1dcff3b86b174c9c0 (diff) | |
| download | linux-1fce8eec9f89e3aaa13ced7c7ca625ab427b1bcc.tar.xz | |
btrfs: avoid unnecessary root node COW during snapshotting
There's no need to COW the root node of the subvolume we are snapshotting
because we then call btrfs_copy_root(), which creates a copy of the root
node and sets its generation to the current transaction. So remove this
redundant COW right before calling btrfs_copy_root(), saving one extent
allocation, memory allocation, copying things, etc, and making the code
less confusing. Also rename the extent buffer variable from "old" to
"root_eb" since that name no longer makes any sense after removing the
unnecessary COW operation.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/transaction.c | 20 |
1 files changed, 5 insertions, 15 deletions
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index ca780e332a5b..36d0f05b06e0 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -1669,7 +1669,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, BTRFS_PATH_AUTO_FREE(path); struct btrfs_dir_item *dir_item; struct extent_buffer *tmp; - struct extent_buffer *old; + struct extent_buffer *root_eb; struct timespec64 cur_time; int ret = 0; u64 to_reserve = 0; @@ -1807,20 +1807,10 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, btrfs_set_stack_timespec_nsec(&new_root_item->otime, cur_time.tv_nsec); btrfs_set_root_otransid(new_root_item, trans->transid); - old = btrfs_lock_root_node(root); - ret = btrfs_cow_block(trans, root, old, NULL, 0, &old, - BTRFS_NESTING_COW); - if (unlikely(ret)) { - btrfs_tree_unlock(old); - free_extent_buffer(old); - btrfs_abort_transaction(trans, ret); - goto fail; - } - - ret = btrfs_copy_root(trans, root, old, &tmp, objectid); - /* clean up in any case */ - btrfs_tree_unlock(old); - free_extent_buffer(old); + root_eb = btrfs_lock_root_node(root); + ret = btrfs_copy_root(trans, root, root_eb, &tmp, objectid); + btrfs_tree_unlock(root_eb); + free_extent_buffer(root_eb); if (unlikely(ret)) { btrfs_abort_transaction(trans, ret); goto fail; |