From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH] vfs: move ACL cache lookup into generic code
Date: Fri, 22 Jul 2011 20:42:35 -0700 [thread overview]
Message-ID: <CA+55aFx90c2HaBJ+SA7zEVrnQJkiQRrfK6XUqJvLVA1CsR1Okw@mail.gmail.com> (raw)
In-Reply-To: <20110723032944.GA24703@ZenIV.linux.org.uk>
On Fri, Jul 22, 2011 at 8:29 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
>> + * Under RCU walk, we cannot even do a "get_cached_acl()",
>> + * because that involves locking and getting a refcount on
>> + * a cached ACL.
>
> ... why is that a problem? Locking there is mere ->i_lock and getting
> a refcount is atomic_inc(). Grabbing a reference might be Not Nice from
> the cacheline bouncing POV, but...
I agree in theory, but it's not something we've done before. Some of
the posix-acl code is pretty disgusting, I didn't even want to go
there.
And the case that tends to really *matter* is the "no acls" case
anyway, and that's the case that is guaranteed to have no nasty races
or odd issues with having to allocate/de-allocate any acl structures.
But yes, this could be looked at.
Linus
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next prev parent reply other threads:[~2011-07-23 3:42 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-22 17:37 VFS pathname walking cleanups (i_op and ACL access) Linus Torvalds
2011-07-22 17:37 ` [PATCH 1/2] VFS: Cut down inode->i_op->xyz accesses in path walking Linus Torvalds
2011-07-22 17:47 ` Christoph Hellwig
2011-07-22 23:40 ` Al Viro
2011-07-22 23:54 ` Linus Torvalds
2011-07-23 3:55 ` [PATCH] " Linus Torvalds
2011-07-23 13:35 ` Christoph Hellwig
2011-07-23 14:46 ` Al Viro
2011-07-23 14:51 ` Christoph Hellwig
2011-07-23 15:45 ` Linus Torvalds
[not found] ` <alpine.LFD.2.02.1107251852220.13796@i5.linux-foundation.org>
2011-07-26 3:05 ` Al Viro
2011-07-26 3:23 ` Linus Torvalds
2011-07-26 18:41 ` Al Viro
2011-07-26 18:45 ` Linus Torvalds
2011-08-07 6:06 ` Linus Torvalds
2011-08-07 6:51 ` Al Viro
2011-08-07 23:43 ` Linus Torvalds
2011-07-22 17:40 ` VFS pathname walking cleanups (i_op and ACL access) Christoph Hellwig
2011-07-22 17:45 ` [PATCH 2/2] vfs: move ACL cache lookup into generic code Linus Torvalds
2011-07-22 17:50 ` Christoph Hellwig
2011-07-22 17:54 ` Linus Torvalds
2011-07-23 2:34 ` [PATCH] " Linus Torvalds
2011-07-23 3:29 ` Al Viro
2011-07-23 3:42 ` Linus Torvalds [this message]
2011-07-23 4:31 ` Al Viro
2011-07-23 6:06 ` Al Viro
2011-07-25 8:15 ` Aneesh Kumar K.V
2011-07-25 8:16 ` Aneesh Kumar K.V
2011-07-23 7:47 ` Al Viro
2011-07-23 14:50 ` Christoph Hellwig
2011-07-23 15:32 ` Al Viro
2011-07-23 17:02 ` Al Viro
2011-07-23 17:31 ` Linus Torvalds
2011-07-23 18:20 ` Al Viro
2011-07-23 18:29 ` Linus Torvalds
2011-07-23 21:53 ` Al Viro
2011-07-23 22:38 ` Al Viro
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