linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Tobin C. Harding" <me@tobin.cc>
To: linux-fsdevel@vger.kernel.org
Subject: Re: dcache locking question
Date: Fri, 15 Mar 2019 10:19:39 +1100	[thread overview]
Message-ID: <20190314231939.GA17269@eros.localdomain> (raw)
In-Reply-To: <20190314225632.GB15813@eros.localdomain>

On Fri, Mar 15, 2019 at 09:56:32AM +1100, Tobin C. Harding wrote:
> Hi,
> 
> I'm not able to understand the locking order in dcache.  dcache has been
> around for a while so clearly its right and I'm wrong.
> 
> Could someone please explain to me how the locking order commented at
> the top of the file is not violated in the following:

> 
> From top of fs/dcache.c
> 
>  * If there is an ancestor relationship:
>  * dentry->d_parent->...->d_parent->d_lock
>  *   ...
>  *     dentry->d_parent->d_lock
>  *       dentry->d_lock
> 

This is a more simple example

static struct dentry *dentry_kill(struct dentry *dentry)
	__releases(dentry->d_lock)
{
        ...

slow_positive:
	spin_unlock(&dentry->d_lock);
	spin_lock(&inode->i_lock);
	spin_lock(&dentry->d_lock);
	parent = lock_parent(dentry);

        ...

thanks,
Tobin.


  parent reply	other threads:[~2019-03-14 23:20 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-14 22:56 dcache locking question Tobin C. Harding
2019-03-14 23:09 ` Matthew Wilcox
2019-03-15  1:38   ` Tobin C. Harding
2019-03-14 23:19 ` Tobin C. Harding [this message]
2019-03-15  1:50   ` Al Viro
2019-03-15 17:38     ` Eric Biggers
2019-03-15 18:54       ` Al Viro
2019-03-16 22:31         ` Paul E. McKenney
2019-03-17  0:18           ` Al Viro
2019-03-17  0:50             ` Paul E. McKenney
2019-03-17  2:20               ` James Bottomley
2019-03-17  3:06                 ` Al Viro
2019-03-17  4:23                   ` James Bottomley
2019-03-18  0:35                     ` Paul E. McKenney
2019-03-18 16:26                       ` James Bottomley
2019-03-18 17:11                         ` Paul E. McKenney
2019-03-19 15:45                           ` Paul E. McKenney

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=20190314231939.GA17269@eros.localdomain \
    --to=me@tobin.cc \
    --cc=linux-fsdevel@vger.kernel.org \
    /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).