From: Nikolay Borisov Date: Wed, 15 Aug 2018 15:26:51 +0000 (+0300) Subject: btrfs: Remove needless tree locking in iterate_inode_refs X-Git-Tag: 4.21-smb3-small-fixes~79^2~101 X-Git-Url: http://git.samba.org/samba.git/?p=sfrench%2Fcifs-2.6.git;a=commitdiff_plain;h=e5bba0b0f843e047ca025b53f1dcfa7e6bd05d86;ds=sidebyside btrfs: Remove needless tree locking in iterate_inode_refs In iterate_inode_refs the eb is cloned via btrfs_clone_extent_buffer which creates a private extent buffer with the dummy flag set and ref count of 1. Then this buffer is locked for reading and its ref count is incremented by 1. Finally it's fed to the passed iterate_irefs_t function. The actual iterate call back is inode_to_path (coming from paths_from_inode) which feeds the eb to btrfs_ref_to_path. In this final function the passed eb is only read by first assigning it to the local eb variable. This variable is only modified in the case another eb was referenced from the passed path that is eb != eb_in check triggers. Considering this there is no point in locking the cloned eb in iterate_inode_refs since it's never being modified and is not published anywhere. Furthermore the cloned eb is completely fine having its ref count be 1. Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba Signed-off-by: David Sterba --- diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c index 68ebe188446a..65f327b34cfb 100644 --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -2020,9 +2020,6 @@ static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root, ret = -ENOMEM; break; } - extent_buffer_get(eb); - btrfs_tree_read_lock(eb); - btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK); btrfs_release_path(path); item = btrfs_item_nr(slot); @@ -2042,7 +2039,6 @@ static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root, len = sizeof(*iref) + name_len; iref = (struct btrfs_inode_ref *)((char *)iref + len); } - btrfs_tree_read_unlock_blocking(eb); free_extent_buffer(eb); }