linux-kernel - [RFC v3 0/1] fs/namespace: defer RCU sync for MNT

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Date: Wed, 26 Jun 2024 16:07:48 -0400
From: Lucas Karpinski <lkarpins@...hat.com>
To: viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz
Cc: raven@...maw.net,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Lucas Karpinski <lkarpins@...hat.com>
Subject: [RFC v3 0/1] fs/namespace: defer RCU sync for MNT_DETACH umount 

Hi all,                                            

Attached is v3 of the umount optimization. Please take a look at v1 for
the original introduction to the problem. Al made it clear in the
RFC v1 that if a filesystem is shut down by umount(2), that the
shut down needs to be completed before the return from the syscall. In 
the RFC v2, it was pointed out that call_rcu can block within an 
interrupt context. This RFC v3 addresses both that and removes 
unneccesary code by taking advantage of mntput for the cleanup of lazy 
umounts.                                           

Lucas                                              

v3:                                                
- Removed unneeded code for lazy umount case.      
- Don't block within interrupt context.            
v2:                                                
- Only defer releasing umount'ed filesystems for lazy umounts
v1:                                                
https://lore.kernel.org/all/20230119205521.497401-1-echanude@redhat.com/

Lucas Karpinski (1):
  fs/namespace: remove RCU sync for MNT_DETACH umount

 fs/namespace.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

-- 
2.45.2