From: Filipe Manana fdmanana@suse.com
[ Upstream commit 1cab1375ba6d5337a25acb346996106c12bb2dd0 ]
During fiemap we may have to visit multiple leaves of the subvolume's inode tree, and each time we are freeing and allocating an extent buffer to use as a clone of each visited leaf. Optimize this by reusing cloned extent buffers, to avoid the freeing and re-allocation both of the extent buffer structure itself and more importantly of the pages attached to the extent buffer.
CC: stable@vger.kernel.org # 6.1 Reviewed-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com [cherry picked from upstream commit] Signed-off-by: Andrey Kalachev kalachev@swemel.ru --- fs/btrfs/extent_io.c | 32 ++++++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 8 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index b65cd7adb7e3..da90e5a5f855 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3800,7 +3800,7 @@ static int emit_last_fiemap_cache(struct fiemap_extent_info *fieinfo,
static int fiemap_next_leaf_item(struct btrfs_inode *inode, struct btrfs_path *path) { - struct extent_buffer *clone; + struct extent_buffer *clone = path->nodes[0]; struct btrfs_key key; int slot; int ret; @@ -3809,29 +3809,45 @@ static int fiemap_next_leaf_item(struct btrfs_inode *inode, struct btrfs_path *p if (path->slots[0] < btrfs_header_nritems(path->nodes[0])) return 0;
+ /* + * Add a temporary extra ref to an already cloned extent buffer to + * prevent btrfs_next_leaf() freeing it, we want to reuse it to avoid + * the cost of allocating a new one. + */ + ASSERT(test_bit(EXTENT_BUFFER_UNMAPPED, &clone->bflags)); + atomic_inc(&clone->refs); + ret = btrfs_next_leaf(inode->root, path); if (ret != 0) - return ret; + goto out;
/* * Don't bother with cloning if there are no more file extent items for * our inode. */ btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); - if (key.objectid != btrfs_ino(inode) || key.type != BTRFS_EXTENT_DATA_KEY) - return 1; + if (key.objectid != btrfs_ino(inode) || key.type != BTRFS_EXTENT_DATA_KEY) { + ret = 1; + goto out; + }
/* See the comment at fiemap_search_slot() about why we clone. */ - clone = btrfs_clone_extent_buffer(path->nodes[0]); - if (!clone) - return -ENOMEM; + copy_extent_buffer_full(clone, path->nodes[0]); + /* + * Important to preserve the start field, for the optimizations when + * checking if extents are shared (see extent_fiemap()). + */ + clone->start = path->nodes[0]->start;
slot = path->slots[0]; btrfs_release_path(path); path->nodes[0] = clone; path->slots[0] = slot; +out: + if (ret) + free_extent_buffer(clone);
- return 0; + return ret; }
/*