linux-kernel - Re: [RFC][PATCHSET] sorting out RCU-delayed stuff in ->destroy

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Date:   Wed, 17 Apr 2019 17:55:20 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCHSET] sorting out RCU-delayed stuff in
 ->destroy_inode()

On Tue, Apr 16, 2019 at 06:49:00PM +0100, Al Viro wrote:
> 	We have a lot of boilerplate in ->destroy_inode()
> instances, and several filesystems got the things wrong
> in that area.  The patchset below attempts to deal with that.
> 
> 	New method (void ->free_inode(inode)) is introduced,
> and RCU-delayed parts of ->destroy_inode() are moved there.
> The change is backwards-compatible - unmodified filesystem
> will behave as it used to.  Rules:
> 	->destroy_inode		->free_inode
> 	f			g		f(), rcu-delayed g()
> 	f			NULL		f()
> 	NULL			g		rcu-delayed g()
> 	NULL			NULL		rcu-delayed free_inode_nonrcu()
> IOW, NULL/NULL acts as NULL/free_inode_nonrcu.
> 
> 	For a lot of filesystems ->destroy_inode() used to consist
> only of call_rcu(foo_i_callback, &inode->i_rcu).  Those simply get
> rid of ->destroy_inode() and have the callback (with saner prototype)
> become their ->free_inode().

The simplified API looks good to me. For btrfs and affs bits:

Acked-by: David Sterba <dsterba@...e.com>