linux-kernel - Re: [git pull] vfs pile 1.5

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Message-ID: <CA+55aFzxmLvLcEagYqE5iOTRv724ecW3va+Pv_RPsPLKeYHTCA@mail.gmail.com>
Date:	Tue, 26 Jul 2011 09:10:02 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Markus Trippelsdorf <markus@...ppelsdorf.de>
Cc:	Steven Liu <lingjiujianke@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [git pull] vfs pile 1.5

On Tue, Jul 26, 2011 at 8:59 AM, Markus Trippelsdorf
<markus@...ppelsdorf.de> wrote:
>
> Yes, that was my first idea, too. But unfortunately it doesn't work:
>
>  CC      fs/xfs/linux-2.6/xfs_iops.o
> fs/xfs/linux-2.6/xfs_iops.c: In function ‘xfs_vn_mknod’:
> fs/xfs/linux-2.6/xfs_iops.c:184:28: error: called object ‘0u’ is not a function
> make[2]: *** [fs/xfs/linux-2.6/xfs_iops.o] Error 1

Ahh, we use that elsewhere too.

However, if we *do* have POSIX ACL's enabled, but we just have the XFS
ACL's disabled, then just returning NULL from xfs_get_acl() is
actually a horrible idea, because then the VFS code will always call
that function and it never gets cached as "I have no ACL's". Which is
why I didn't like the inline function approach. Well, at least not the
one that only returns NULL - we also want to fill in the cache.

I'm actually getting more and more convinced that we should just do
that "set_acl_cache()" in generic code for the "get_acl()" case. Even
without any locking it's no worse than all the current filesystems,
since they *also* do it with no locking. And then this kind of issue
wouldn't come up.

Christoph, Al, comments?

                           Linus
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