On Thu, Apr 26, 2018 at 09:27:43AM +0800, Liu Bo wrote: > path->keep_lock may force to lock tree root and higher nodes, and make > lock contention worse, thus it needs to be avoided as much as > possible. > > In btrfs_degrag_leaves, path->keep_lock is set but @path immediatley > gets released, which is not necessary at all.
So what is the effect of this? The locks are held throughout btrfs_search_forward and released after that. Thi > Signed-off-by: Liu Bo <bo....@linux.alibaba.com> > --- > v2: update commit log with more details. > > fs/btrfs/tree-defrag.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/fs/btrfs/tree-defrag.c b/fs/btrfs/tree-defrag.c > index 3c0987ab587d..c12747904d4c 100644 > --- a/fs/btrfs/tree-defrag.c > +++ b/fs/btrfs/tree-defrag.c > @@ -65,8 +65,6 @@ int btrfs_defrag_leaves(struct btrfs_trans_handle *trans, > memcpy(&key, &root->defrag_progress, sizeof(key)); > } > > - path->keep_locks = 1; > - > ret = btrfs_search_forward(root, &key, path, BTRFS_OLDEST_GENERATION); What does btrfs_search_forward do as the first statement: 5115 int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key, 5116 struct btrfs_path *path, 5117 u64 min_trans) 5118 { .... declarations 5128 5129 path->keep_locks = 1; So even if removed from above, there will be no change. The value of keep_locks is preserved after btrfs_path_release. > if (ret < 0) > goto out; > @@ -81,6 +79,7 @@ int btrfs_defrag_leaves(struct btrfs_trans_handle *trans, > * a deadlock (attempting to write lock an already write locked leaf). > */ > path->lowest_level = 1; > + path->keep_locks = 1; > wret = btrfs_search_slot(trans, root, &key, path, 0, 1); > > if (wret < 0) { > -- > 1.8.3.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html