From: Jaegeuk Kim jaegeuk@kernel.org
[ Upstream commit 2eeb0dce728a7eac3e4dfe355d98af40d61f7a26 ]
This tries to fix priority inversion in the below condition resulting in long checkpoint delay.
f2fs_get_node_info() - nat_tree_lock -> sleep to grab journal_rwsem by contention
checkpoint - waiting for nat_tree_lock
In order to let checkpoint go, let's release nat_tree_lock, if there's a journal_rwsem contention.
Signed-off-by: Daeho Jeong daehojeong@google.com Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/f2fs/node.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c index e67ce5f13b98..b731d7ff455c 100644 --- a/fs/f2fs/node.c +++ b/fs/f2fs/node.c @@ -538,7 +538,7 @@ int f2fs_get_node_info(struct f2fs_sb_info *sbi, nid_t nid, int i;
ni->nid = nid; - +retry: /* Check nat cache */ down_read(&nm_i->nat_tree_lock); e = __lookup_nat_cache(nm_i, nid); @@ -550,10 +550,19 @@ int f2fs_get_node_info(struct f2fs_sb_info *sbi, nid_t nid, return 0; }
- memset(&ne, 0, sizeof(struct f2fs_nat_entry)); + /* + * Check current segment summary by trying to grab journal_rwsem first. + * This sem is on the critical path on the checkpoint requiring the above + * nat_tree_lock. Therefore, we should retry, if we failed to grab here + * while not bothering checkpoint. + */ + if (!rwsem_is_locked(&sbi->cp_global_sem)) { + down_read(&curseg->journal_rwsem); + } else if (!down_read_trylock(&curseg->journal_rwsem)) { + up_read(&nm_i->nat_tree_lock); + goto retry; + }
- /* Check current segment summary */ - down_read(&curseg->journal_rwsem); i = f2fs_lookup_journal_in_cursum(journal, NAT_JOURNAL, nid, 0); if (i >= 0) { ne = nat_in_journal(journal, i);