From: Tejun Heo <firstname.lastname@example.org> To: Minchan Kim <email@example.com> Cc: Greg Kroah-Hartman <firstname.lastname@example.org>, LKML <email@example.com> Subject: Re: [RFC PATCH] kernfs: release kernfs_mutex before the inode allocation Date: Wed, 17 Nov 2021 12:23:55 -1000 [thread overview] Message-ID: <YZWA+8B1xQOKCMnS@slm.duckdns.org> (raw) In-Reply-To: <YZV+j5LivK+9Dt50@google.com> Hello, On Wed, Nov 17, 2021 at 02:13:35PM -0800, Minchan Kim wrote: > > So, one really low hanging fruit here would be using a separate rwsem per > > superblock. Nothing needs synchronization across different users of kernfs > > and the locking is shared just because nobody bothered to separate them out > > while generalizing it from sysfs. > > That's really what I wanted but had a question whether we can access > superblock from the kernfs_node all the time since there are some > functions to access the kernfs_rwsem without ionde, sb context. > > Is it doable to get the superblock from the kernfs_node all the time? Ah, right, kernfs_node doesn't point back to kernfs_root. I guess it can go one of three ways: a. Follow parent until root kernfs_node and make that guy point to kernfs_root through its parent field. This isn't great but the hotter paths all have sb / inode already, I think, so if we do this only in the really cold paths, it likely isn't too bad. b. Change the interface so that the callers have to provide kernfs_root. I don't think this is gonna be a huge problem. There are a few users of kernfs and they always know their roots. c. Add a field to kernfs_node so that we can always find kernfs_root. I think b is likely the cheapest && cleanest. Thanks. -- tejun
next prev parent reply other threads:[~2021-11-17 22:24 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-11-16 19:43 Minchan Kim 2021-11-16 19:49 ` Greg Kroah-Hartman 2021-11-16 21:36 ` Minchan Kim 2021-11-17 6:44 ` Greg Kroah-Hartman 2021-11-17 7:27 ` Minchan Kim 2021-11-17 7:39 ` Greg Kroah-Hartman 2021-11-17 21:43 ` Minchan Kim 2021-11-17 21:45 ` Tejun Heo 2021-11-17 22:13 ` Minchan Kim 2021-11-17 22:23 ` Tejun Heo [this message] 2021-11-18 1:55 ` Minchan Kim 2021-11-18 16:35 ` Tejun Heo
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