From ddffcf6fb5ac54ffcd7e90b10554d89dbd10b47b Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Wed, 27 Jan 2021 10:34:54 +0000 Subject: [PATCH] btrfs: remove unnecessary directory inode item update when deleting dir entry When we remove a directory entry, as part of an unlink operation, if the directory was logged before we must remove the directory index items from the log. We are also updating the inode item of the directory to update its i_size, but that is not necessary because during log replay we do not need it and we correctly adjust the i_size in the inode item of the subvolume as we process directory index items and replay deletes. This is not needed since commit d555438b6e1dad ("Btrfs: drop dir i_size when adding new names on replay"), where we explicitly ignore the i_size of directory inode items on log replay. Before that we used it but it was buggy as mentioned in that commit's change log (i_size got a larger value then it should have). So stop updating the i_size of the directory inode item in the log, as that is a waste of time, adds more log contention to the log tree and often results in COWing more extent buffers for the log tree. This code path is triggered often during dbench workloads for example. This patch is part of a patchset comprised of the following patches: btrfs: remove unnecessary directory inode item update when deleting dir entry btrfs: stop setting nbytes when filling inode item for logging btrfs: avoid logging new ancestor inodes when logging new inode btrfs: skip logging directories already logged when logging all parents btrfs: skip logging inodes already logged when logging new entries btrfs: remove unnecessary check_parent_dirs_for_sync() btrfs: make concurrent fsyncs wait less when waiting for a transaction commit Performance results, after applying all patches, are mentioned in the change log of the last patch. Reviewed-by: Josef Bacik Signed-off-by: Filipe Manana Signed-off-by: David Sterba --- fs/btrfs/tree-log.c | 39 ++++----------------------------------- 1 file changed, 4 insertions(+), 35 deletions(-) diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 8ee0700a980f..5d87afc6058a 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -3379,7 +3379,6 @@ int btrfs_del_dir_entries_in_log(struct btrfs_trans_handle *trans, struct btrfs_path *path; int ret; int err = 0; - int bytes_del = 0; u64 dir_ino = btrfs_ino(dir); if (!inode_logged(trans, dir)) @@ -3406,7 +3405,6 @@ int btrfs_del_dir_entries_in_log(struct btrfs_trans_handle *trans, } if (di) { ret = btrfs_delete_one_dir_name(trans, log, path, di); - bytes_del += name_len; if (ret) { err = ret; goto fail; @@ -3421,46 +3419,17 @@ int btrfs_del_dir_entries_in_log(struct btrfs_trans_handle *trans, } if (di) { ret = btrfs_delete_one_dir_name(trans, log, path, di); - bytes_del += name_len; if (ret) { err = ret; goto fail; } } - /* update the directory size in the log to reflect the names - * we have removed + /* + * We do not need to update the size field of the directory's inode item + * because on log replay we update the field to reflect all existing + * entries in the directory (see overwrite_item()). */ - if (bytes_del) { - struct btrfs_key key; - - key.objectid = dir_ino; - key.offset = 0; - key.type = BTRFS_INODE_ITEM_KEY; - btrfs_release_path(path); - - ret = btrfs_search_slot(trans, log, &key, path, 0, 1); - if (ret < 0) { - err = ret; - goto fail; - } - if (ret == 0) { - struct btrfs_inode_item *item; - u64 i_size; - - item = btrfs_item_ptr(path->nodes[0], path->slots[0], - struct btrfs_inode_item); - i_size = btrfs_inode_size(path->nodes[0], item); - if (i_size > bytes_del) - i_size -= bytes_del; - else - i_size = 0; - btrfs_set_inode_size(path->nodes[0], item, i_size); - btrfs_mark_buffer_dirty(path->nodes[0]); - } else - ret = 0; - btrfs_release_path(path); - } fail: btrfs_free_path(path); out_unlock: