From: Jeff Layton <jlayton@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Ilya Dryomov <idryomov@gmail.com>
Cc: ceph-devel@vger.kernel.org,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [GIT PULL] Ceph fixes for 5.1-rc7
Date: Thu, 25 Apr 2019 14:23:59 -0400 [thread overview]
Message-ID: <342ef35feb1110197108068d10e518742823a210.camel@kernel.org> (raw)
In-Reply-To: <CAHk-=wgPBx9xPWY7obK60=RTnOF3Ln0j9XkhYbekML=Fi3bFXg@mail.gmail.com>
On Thu, 2019-04-25 at 11:02 -0700, Linus Torvalds wrote:
> On Thu, Apr 25, 2019 at 10:48 AM Ilya Dryomov <idryomov@gmail.com> wrote:
> > dentry name handling fixes from Jeff and a memory leak fix from Zheng.
> > Both are old issues, marked for stable.
>
> Hmm. You probably should have talked to Al about the dentry name
> issue, because he'd most likely have pointed you towards our helper
> function for exactly this thing:
>
> struct name_snapshot stable;
>
> take_dentry_name_snapshot(&stable, dentry);
> ... use stable.name ..
> release_dentry_name_snapshot(&stable);
>
> which doesn't need any extra memory allocation outside of some fairly
> limited stack allocation for the 'name_snapshot' itself, because it
> knows about the dentry name rules, and
>
> - for inline names, it copies it under the d_lock into the fixed
> DNAME_INLINE_LEN-sized buffer
>
> - for out-of-line names, it knows that the name allocation is stable
> and ref-counted, and just increments the refcount and uses the
> existing name pointer.
>
> now, maybe you need to always do that name allocation anyway (looking
> at the diff it looks like you often do that for other cases), so maybe
> the name snapshot capability isn't all that useful for you and the
> above wouldn't have helped, but I suspect you might not even have
> realized that there was an option like this.
>
> I've pulled this, but maybe Jeff wants to look at whether that
> snapshotting model could have helped.
>
> Linus
Thanks for the info! I think it would have.
I took a quick look at the dcache code to see if we had something like
that before I did this, but I guess I didn't look closely enough. Those
routines do look nicer than my hand-rolled version.
I'll look at spinning up a patch to switch that over in the near future.
Thanks,
--
Jeff Layton <jlayton@kernel.org>
next prev parent reply other threads:[~2019-04-25 18:24 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-25 17:47 [GIT PULL] Ceph fixes for 5.1-rc7 Ilya Dryomov
2019-04-25 18:02 ` Linus Torvalds
2019-04-25 18:21 ` Al Viro
2019-04-25 18:24 ` Linus Torvalds
2019-04-25 18:31 ` Al Viro
2019-04-25 18:36 ` Jeff Layton
2019-04-25 18:23 ` Jeff Layton [this message]
2019-04-25 20:09 ` Al Viro
2019-04-26 16:25 ` Jeff Layton
2019-04-26 16:36 ` Linus Torvalds
2019-04-26 16:43 ` Linus Torvalds
2019-04-26 17:01 ` Al Viro
2019-04-26 17:08 ` Linus Torvalds
2019-04-26 17:11 ` Al Viro
2019-04-26 20:49 ` Jeff Layton
2019-04-26 21:28 ` Al Viro
2019-04-26 16:50 ` Al Viro
2019-04-26 17:30 ` Jeff Layton
2019-04-28 4:38 ` Al Viro
2019-04-28 13:27 ` Jeff Layton
2019-04-28 14:48 ` Al Viro
2019-04-28 15:47 ` Jeff Layton
2019-04-28 15:52 ` Al Viro
2019-04-28 16:18 ` Jeff Layton
2019-04-28 16:40 ` Al Viro
2019-04-25 18:35 ` pr-tracker-bot
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