linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Miklos Szeredi <miklos@szeredi.hu>
To: Miklos Szeredi <mszeredi@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	overlayfs <linux-unionfs@vger.kernel.org>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	garyhuang <zjh.20052005@163.com>
Subject: Re: [PATCH] vfs: allow stacked ->get_acl() in RCU lookup
Date: Mon, 12 Apr 2021 11:27:33 +0200	[thread overview]
Message-ID: <CAJfpegv4ttfCZY0DPm+SSc85eL5m3jqhdOS_avu1+WMZhdg7iA@mail.gmail.com> (raw)
In-Reply-To: <20210323160629.228597-1-mszeredi@redhat.com>

On Tue, Mar 23, 2021 at 5:07 PM Miklos Szeredi <mszeredi@redhat.com> wrote:
>
> Overlayfs does not cache ACL's to avoid double caching with all its
> problems.  Instead it just calls the underlying filesystem's
> i_op->get_acl(), which will return the cached value, if possible.
>
> In rcu path walk, however, get_cached_acl_rcu() is employed to get the
> value from the cache, which will fail on overlayfs resulting in dropping
> out of rcu walk mode.  This can result in a big performance hit in certain
> situations.
>
> Add a flags argument to the ->get_acl() callback, and allow
> get_cached_acl_rcu() to call the ->get_acl() method with LOOKUP_RCU.
>
> Don't do this for the generic case of a cache miss, only in case of
> ACL_DONT_CACHE.
>
> Reported-by: garyhuang <zjh.20052005@163.com>
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Hi Al,

Could you please apply this patch?

It's fairly trivial, but unfortunately adds a fair bit of API churn.

Thanks,
Miklos

      reply	other threads:[~2021-04-12  9:31 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-23 16:06 [PATCH] vfs: allow stacked ->get_acl() in RCU lookup Miklos Szeredi
2021-04-12  9:27 ` Miklos Szeredi [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAJfpegv4ttfCZY0DPm+SSc85eL5m3jqhdOS_avu1+WMZhdg7iA@mail.gmail.com \
    --to=miklos@szeredi.hu \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-unionfs@vger.kernel.org \
    --cc=mszeredi@redhat.com \
    --cc=viro@zeniv.linux.org.uk \
    --cc=zjh.20052005@163.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).