From 68a505bb87f948f72e5d230dfd7b40debdb195ed Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Thu, 25 Jul 2024 11:48:10 +0100 Subject: [PATCH] btrfs: more efficient chunk map iteration when device replace finishes When iterating the chunk maps when a device replace finishes we are doing a full rbtree search for each chunk map, which is not the most efficient thing to do, wasting CPU time. As we are holding a write lock on the tree during the whole iteration, we can simply start from the first node in the tree and then move to the next chunk map by doing a rb_next() call - the only exception is when we need to reschedule, in which case we have to do a full rbtree search since we dropped the write lock and the tree may have changed (chunk maps may have been removed and the tree got rebalanced). So just do that. Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/dev-replace.c | 36 +++++++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 11 deletions(-) diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 20cf5e95f2bc..83d5cdd77f29 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -824,8 +824,7 @@ static void btrfs_dev_replace_update_device_in_mapping_tree( struct btrfs_device *srcdev, struct btrfs_device *tgtdev) { - u64 start = 0; - int i; + struct rb_node *node; /* * The chunk mutex must be held so that no new chunks can be created @@ -836,19 +835,34 @@ static void btrfs_dev_replace_update_device_in_mapping_tree( lockdep_assert_held(&fs_info->chunk_mutex); write_lock(&fs_info->mapping_tree_lock); - do { + node = rb_first_cached(&fs_info->mapping_tree); + while (node) { + struct rb_node *next = rb_next(node); struct btrfs_chunk_map *map; + u64 next_start; - map = btrfs_find_chunk_map_nolock(fs_info, start, U64_MAX); - if (!map) - break; - for (i = 0; i < map->num_stripes; i++) + map = rb_entry(node, struct btrfs_chunk_map, rb_node); + next_start = map->start + map->chunk_len; + + for (int i = 0; i < map->num_stripes; i++) if (srcdev == map->stripes[i].dev) map->stripes[i].dev = tgtdev; - start = map->start + map->chunk_len; - btrfs_free_chunk_map(map); - cond_resched_rwlock_write(&fs_info->mapping_tree_lock); - } while (start); + + if (cond_resched_rwlock_write(&fs_info->mapping_tree_lock)) { + map = btrfs_find_chunk_map_nolock(fs_info, next_start, U64_MAX); + if (!map) + break; + node = &map->rb_node; + /* + * Drop the lookup reference since we are holding the + * lock in write mode and no one can remove the chunk + * map from the tree and drop its tree reference. + */ + btrfs_free_chunk_map(map); + } else { + node = next; + } + } write_unlock(&fs_info->mapping_tree_lock); }