Mark inodes without acls with cache_no_acl() in __ext4_iget() so that path lookup can run in RCU mode from the start. This is interesting in particular for the case where the file owner does the lookup because in that case end up constantly hitting the slow path otherwise. We drop out from the fast path (because ACL state is unknown) but never end up calling check_acl() to cache ACL state. The problem was originally analyzed by Linus and fix tested by Matheusz, I'm just putting it into mergeable form :). Link: https://lore.kernel.org/all/CAHk-=whSzc75TLLPWskV0xuaHR4tpWBr=LduqhcCFr4kCmme_w@mail.gmail.com Reported-by: Mateusz Guzik Reported-by: Linus Torvalds Signed-off-by: Jan Kara --- fs/ext4/inode.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index e99306a8f47c..2b68d0651652 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5521,7 +5521,9 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino, if (ret) goto bad_inode; brelse(iloc.bh); - + /* Initialize the "no ACL's" state for the simple cases */ + if (!ext4_test_inode_state(inode, EXT4_STATE_XATTR) && !ei->i_file_acl) + cache_no_acl(inode); unlock_new_inode(inode); return inode; -- 2.51.0