Linux-Fsdevel Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Miklos Szeredi <miklos@szeredi.hu>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Jeff Layton <jlayton@poochiereds.net>,
	"J . Bruce Fields" <bfields@fieldses.org>,
	overlayfs <linux-unionfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v2 04/17] ovl: decode connected upper dir file handles
Date: Mon, 15 Jan 2018 12:41:25 +0100	[thread overview]
Message-ID: <CAJfpegsZTQ6Gn1Y6Ddjo47H7MrJsT5xWaDCZP4MswGt2vBt4jg@mail.gmail.com> (raw)
In-Reply-To: <CAOQ4uxhpNCUzcuFSvntAN_JDB=L5NDqZP4m9TxytyO-P6t3F0Q@mail.gmail.com>

On Fri, Jan 5, 2018 at 1:33 PM, Amir Goldstein <amir73il@gmail.com> wrote:
> On Thu, Jan 4, 2018 at 7:20 PM, Amir Goldstein <amir73il@gmail.com> wrote:
>> Until this change, we decoded upper file handles by instantiating an
>> overlay dentry from the real upper dentry. This is sufficient to handle
>> pure upper files, but insufficient to handle merge/impure dirs.
>>
>> To that end, if decoded real upper dir is connected and hashed, we
>> lookup an overlay dentry with the same path as the real upper dir.
>> If decoded real upper is non-dir, we instantiate a disconnected overlay
>> dentry as before this change.
>>
>> Because ovl_fh_to_dentry() returns connected overlay dir dentries,
>> exportfs never need to call get_parent() and get_name() to reconnect an
>> upper overlay dir. Because connectable non-dir file handles are not
>> supported, exportfs will not be able to use fh_to_parent() and get_name()
>> methods to reconnect a disconnected non-dir to its parent. Therefore, the
>> methods get_parent() and get_name() are implemented just to print out a
>> sanity warning and the method fh_to_parent() is implemented to warn the
>> user that using the 'subtree_check' exportfs option is not supported.
>>
>
> Reviewers who will get this far, should have their eyebrows slightly raised
> after reading this commit message and should be asking themselves:
>
> "Why not return a disconnected overlay dentry like any other fs and implement
> ovl_get_parent()/ovl_get_name() by looking at parent/name of upper dir?"
>
> I have had this debate with myself for a while and experimented a bit with
> both approaches and in the end, I liked the "return connected dentry" result
> better. I did not want to write this entire story in commit message, because
> in the end, there is nothing incorrect about the choice of either implementation
> there are only pros and cons to each choice.
>
> At the moment, the only argument I can think of to counter the chosen approach
> is that it adds ~100 lines on code in ovl_lookup_real() and
> ovl_lookup_real_one()
> helpers that could have been avoided by using the common reconnect_path()
> code in fs/exportfs/expfs.c.

And also not having to deal with rename races would be good.  And the
way to do it is the same way as ovl_get_redirect(), except now we are
walking the upper layer instead of the overlay layer.

Not sure which approach is better.

Thanks,
Miklos

  parent reply	other threads:[~2018-01-15 11:41 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-04 17:20 [PATCH v2 00/17] Overlayfs NFS export support Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 01/17] ovl: document NFS export Amir Goldstein
2018-01-11 16:06   ` Miklos Szeredi
2018-01-11 16:26     ` Amir Goldstein
2018-01-12 15:43       ` Miklos Szeredi
2018-01-12 15:49         ` Miklos Szeredi
2018-01-12 18:50           ` Amir Goldstein
2018-01-13  8:54           ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 02/17] ovl: encode pure upper file handles Amir Goldstein
2018-01-18 10:31   ` Miklos Szeredi
2018-01-04 17:20 ` [PATCH v2 03/17] ovl: decode " Amir Goldstein
2018-01-18 14:09   ` Miklos Szeredi
2018-01-18 14:34     ` Amir Goldstein
2018-01-18 14:39       ` Miklos Szeredi
2018-01-18 19:49         ` Amir Goldstein
2018-01-18 20:10           ` Miklos Szeredi
2018-01-18 20:35             ` Amir Goldstein
2018-01-18 22:57               ` Amir Goldstein
2018-01-19  0:23                 ` Amir Goldstein
2018-01-19 10:39                   ` Miklos Szeredi
2018-01-19 11:07                     ` Amir Goldstein
2018-01-19 20:10                       ` Amir Goldstein
2018-01-24 10:34                         ` Miklos Szeredi
2018-01-24 11:04                           ` Amir Goldstein
2018-01-24 11:18                             ` Amir Goldstein
2018-01-24 11:55                               ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 04/17] ovl: decode connected upper dir " Amir Goldstein
2018-01-05 12:33   ` Amir Goldstein
2018-01-05 15:18     ` J . Bruce Fields
2018-01-05 15:34       ` Amir Goldstein
2018-01-15 11:41     ` Miklos Szeredi [this message]
2018-01-15 11:33   ` Miklos Szeredi
2018-01-15 12:20     ` Amir Goldstein
2018-01-15 14:56       ` Miklos Szeredi
2018-01-17 11:18         ` Amir Goldstein
2018-01-17 12:20           ` Amir Goldstein
2018-01-17 13:29             ` Amir Goldstein
2018-01-17 15:42           ` Miklos Szeredi
2018-01-17 16:34             ` Amir Goldstein
2018-01-17 21:36               ` Amir Goldstein
2018-01-18  8:22               ` Miklos Szeredi
2018-01-18  8:47                 ` Amir Goldstein
2018-01-18  9:12                   ` Miklos Szeredi
2018-01-18 10:28                     ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 05/17] ovl: encode non-indexed upper " Amir Goldstein
2018-01-15 11:58   ` Miklos Szeredi
2018-01-15 12:07     ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 06/17] ovl: copy up before encoding dir file handle when ofs->numlower > 1 Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 07/17] ovl: encode lower file handles Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 08/17] ovl: decode lower non-dir " Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 09/17] ovl: decode indexed " Amir Goldstein
2018-01-18 13:11   ` Miklos Szeredi
2018-01-04 17:20 ` [PATCH v2 10/17] ovl: decode lower file handles of unlinked but open files Amir Goldstein
2018-01-16  9:16   ` Miklos Szeredi
2018-01-16  9:37     ` Amir Goldstein
2018-01-16 10:10       ` Miklos Szeredi
2018-01-16 10:40         ` Amir Goldstein
2018-01-16 11:07           ` Miklos Szeredi
2018-01-17 21:05         ` Amir Goldstein
2018-01-18 14:18   ` Amir Goldstein
2018-02-27 11:35     ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 11/17] ovl: decode indexed dir file handles Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 12/17] ovl: decode pure lower " Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 13/17] ovl: hash directory inodes for NFS export Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 14/17] ovl: lookup connected ancestor of dir in inode cache Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 15/17] ovl: lookup indexed ancestor of lower dir Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 16/17] ovl: wire up NFS export support Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 17/17] nfsd: encode stat->mtime for getattr instead of inode->i_mtime Amir Goldstein

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=CAJfpegsZTQ6Gn1Y6Ddjo47H7MrJsT5xWaDCZP4MswGt2vBt4jg@mail.gmail.com \
    --to=miklos@szeredi.hu \
    --cc=amir73il@gmail.com \
    --cc=bfields@fieldses.org \
    --cc=jlayton@poochiereds.net \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-unionfs@vger.kernel.org \
    --subject='Re: [PATCH v2 04/17] ovl: decode connected upper dir file handles' \
    /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

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).