From 7fae9688dcbf254cd260c67c82dd1c76b21c8253 Mon Sep 17 00:00:00 2001 From: Ritesh Harjani Date: Tue, 22 Sep 2020 10:18:39 +0800 Subject: [PATCH] ext4: fix ext4_dax_read/write inode locking sequence for IOCB_NOWAIT stable inclusion from linux-4.19.106 commit 428bb08aed38d08bd78a0b8a69afa97094b46b53 -------------------------------- [ Upstream commit f629afe3369e9885fd6e9cc7a4f514b6a65cf9e9 ] Apparently our current rwsem code doesn't like doing the trylock, then lock for real scheme. So change our dax read/write methods to just do the trylock for the RWF_NOWAIT case. This seems to fix AIM7 regression in some scalable filesystems upto ~25% in some cases. Claimed in commit 942491c9e6d6 ("xfs: fix AIM7 regression") Reviewed-by: Jan Kara Reviewed-by: Matthew Bobrowski Tested-by: Joseph Qi Signed-off-by: Ritesh Harjani Link: https://lore.kernel.org/r/20191212055557.11151-2-riteshh@linux.ibm.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin Signed-off-by: Yang Yingliang --- fs/ext4/file.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index f4a24a46245e..52d155b4e733 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -40,9 +40,10 @@ static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to) struct inode *inode = file_inode(iocb->ki_filp); ssize_t ret; - if (!inode_trylock_shared(inode)) { - if (iocb->ki_flags & IOCB_NOWAIT) + if (iocb->ki_flags & IOCB_NOWAIT) { + if (!inode_trylock_shared(inode)) return -EAGAIN; + } else { inode_lock_shared(inode); } /* @@ -190,9 +191,10 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from) struct inode *inode = file_inode(iocb->ki_filp); ssize_t ret; - if (!inode_trylock(inode)) { - if (iocb->ki_flags & IOCB_NOWAIT) + if (iocb->ki_flags & IOCB_NOWAIT) { + if (!inode_trylock(inode)) return -EAGAIN; + } else { inode_lock(inode); } ret = ext4_write_checks(iocb, from); -- GitLab