From: Tejun Heo <htejun@gmail.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Benjamin Thery <benjamin.thery@bull.net>,
Greg Kroah-Hartman <gregkh@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Daniel Lezcano <dlezcano@fr.ibm.com>,
Serge Hallyn <serue@us.ibm.com>,
linux-kernel@vger.kernel.org, Al Viro <viro@ftp.linux.org.uk>,
Linux Containers <containers@lists.osdl.org>
Subject: Re: [PATCH 06/11] sysfs: Implement sysfs tagged directory support.
Date: Tue, 01 Jul 2008 15:47:48 +0900 [thread overview]
Message-ID: <4869D314.5030403@gmail.com> (raw)
In-Reply-To: <m18wwmsqdv.fsf@frodo.ebiederm.org>
Hello, Eric.
Eric W. Biederman wrote:
>> It's still dynamic from sysfs's POV and I think that will make
>> maintenance more difficult.
>
> Potentially. I have no problem make it clear that things are more static.
Great. :-)
>> What you described is pretty much what I'm talking about. The only
>> difference is whether to use caller-provided pointer as tag or an
>> ida-allocated integer. The last sentence of the above paragraph is
>> basically sys_tag_enabled() function (maybe misnamed).
>
> So some concrete code examples here. In the current code in lookup
> what I am doing is:
>
> tag = sysfs_lookup_tag(parent_sd, parent->d_sb);
> sd = sysfs_find_dirent(parent_sd, tag, dentry->d_name.name);
>
> With the proposed change of adding tag types sysfs_lookup_tag becomes:
>
> const void *sysfs_lookup_tag(struct sysfs_dirent *dir_sd, struct super_block *sb)
> {
> const void *tag = NULL;
>
> if (dir_sd->s_flags & SYSFS_FLAG_TAGGED)
> tag = sysfs_info(sb)->tag[dir_sd->tag_type];
>
> return tag;
> }
>
> Which means that in practice I can lookup that tag that I am displaying
> once.
>
> Then in sysfs_find_dirent we do:
>
> for (sd = parent_sd->s_dir.children; sd; sd = sd->s_sibling) {
> if ((parent_sd->s_flags & SYSFS_FLAG_TAGGED) &&
> (sd->s_tag.tag != tag))
> continue;
> if (!strcmp(sd->s_name, name))
> return sd;
> }
>
> That should keep the implementation sufficiently inside of sysfs for there
> to be no guessing. In addition as a practical matter we can only allow
> one tag to be visible in a directory at once or else we can not check
> for duplicate names. Which is the problem I see with a bitmap based test
> too unnecessary many degrees of freedom.
Having enumed tag types limits that a sb can have map to only one tag
but it doesn't really prevent multiple possibly visible entries which is
the real unnecessary degrees of freedom. That said, I don't really
think it's an issue.
> The number of tag types will be low as it is the number of subsystems
> that use the feature. Simple enough that I expect statically allocating
> the tag types in an enumeration is a safe and sane way to operate.
> i.e.
>
> enum sysfs_tag_types {
> SYSFS_TAG_NETNS,
> SYSFS_TAG_USERNS,
> SYSFS_TAG_MAX
> };
I still would prefer something which is more generic. The abstraction
is clearer too. A sb shows untagged and a set of tags. A sd can either
be untagged or tagged (a single tag).
>> The main reason why I'm whining about this so much is because I think
>> tag should be something abstracted inside sysfs proper. It's something
>> which affects very internal operation of sysfs and I really want to keep
>> the implementation details inside sysfs. Spreading implementation over
>> kobject and sysfs didn't turn out too pretty after all.
>
> I agree. Most of the implementation is in sysfs already. We just have
> a few corner cases.
>
> Fundamentally it is the subsystems responsibility that creates the
> kobjects and the sysfs entries. The only case where I can see an
> ida generated number being a help is if we start having lifetime
> issues. Further the extra work to allocate and free tags ida based
> tags seems unnecessary.
>
> I don't doubt that there is a lot we can do better. My current goal
> is for something that is clean enough it won't get us into trouble
> later, and then merging the code. In tree where people can see
> the code and the interactions I expect it will be easier to talk
> about.
>
> Currently the interface with the users is very small. Adding the
> tag_type enumeration should make it smaller and make things more
> obviously static.
Using ida (or idr if a pointer for private data is necessary) is really
easy. It'll probably take a few tens of lines of code. That said, I
don't think I have enough rationale to nack what you described. So, as
long as the tags are made static, I won't object.
Thanks.
--
tejun
next prev parent reply other threads:[~2008-07-01 6:48 UTC|newest]
Thread overview: 138+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-18 17:07 [PATCH 00/11] sysfs tagged directories V6 Benjamin Thery
2008-06-18 17:07 ` [PATCH 01/11] sysfs: Support for preventing unmounts Benjamin Thery
2008-06-18 17:44 ` Dave Hansen
2008-06-18 20:12 ` Eric W. Biederman
2008-06-19 8:54 ` Benjamin Thery
2008-06-19 16:32 ` Dave Hansen
2008-06-19 20:19 ` Benjamin Thery
2008-06-18 17:07 ` [PATCH 02/11] sysfs: sysfs_get_dentry add a sb parameter Benjamin Thery
2008-06-18 17:07 ` [PATCH 03/11] sysfs: Implement __sysfs_get_dentry Benjamin Thery
2008-06-18 17:08 ` [PATCH 04/11] sysfs: Rename Support multiple superblocks Benjamin Thery
2008-06-18 17:08 ` [PATCH 05/11] sysfs: sysfs_chmod_file handle " Benjamin Thery
2008-06-22 4:46 ` Tejun Heo
2008-06-23 21:42 ` Daniel Lezcano
2008-06-24 4:45 ` Tejun Heo
2008-06-24 10:39 ` Daniel Lezcano
2008-06-24 13:37 ` Daniel Lezcano
2008-06-25 12:31 ` Tejun Heo
2008-06-18 17:08 ` [PATCH 06/11] sysfs: Implement sysfs tagged directory support Benjamin Thery
2008-06-23 2:05 ` Tejun Heo
2008-06-26 20:21 ` Eric W. Biederman
2008-06-29 3:51 ` Tejun Heo
2008-06-30 18:56 ` Eric W. Biederman
2008-06-30 21:44 ` Serge E. Hallyn
2008-07-01 7:50 ` Eric W. Biederman
2008-07-01 6:47 ` Tejun Heo [this message]
2008-07-01 9:20 ` Eric W. Biederman
2008-07-01 10:30 ` Tejun Heo
2008-07-01 12:30 ` Eric W. Biederman
2008-07-02 3:24 ` Tejun Heo
2008-07-02 3:53 ` Eric W. Biederman
2008-07-02 4:37 ` Tejun Heo
2008-07-02 16:49 ` Eric W. Biederman
2008-07-03 0:15 ` Greg KH
2008-07-03 3:18 ` Tejun Heo
2008-07-03 5:11 ` Eric W. Biederman
2008-07-03 10:56 ` Daniel Lezcano
2008-07-03 12:27 ` Eric W. Biederman
2008-07-03 12:37 ` Benjamin Thery
2008-07-03 19:57 ` Eric W. Biederman
2008-07-03 12:55 ` Daniel Lezcano
2008-07-03 15:58 ` Tejun Heo
2008-07-03 18:29 ` Daniel Lezcano
2008-07-03 20:08 ` Eric W. Biederman
2008-07-04 0:48 ` [PATCH 00/15] sysfs support for namespaces Eric W. Biederman
2008-07-04 1:05 ` [PATCH 01/15] kobject: Cleanup kobject_rename and !CONFIG_SYSFS Eric W. Biederman
2008-07-04 1:07 ` [PATCH 02/15] sysfs: Support for preventing unmounts Eric W. Biederman
2008-07-04 1:08 ` [PATCH 03/15] sysfs: sysfs_get_dentry add a sb parameter Eric W. Biederman
2008-07-04 1:09 ` [PATCH 04/15] sysfs: Implement __sysfs_get_dentry Eric W. Biederman
2008-07-04 1:10 ` [PATCH 05/15] sysfs: Rename Support multiple superblocks Eric W. Biederman
2008-07-04 1:11 ` [PATCH 06/15] Introduce sysfs_sd_setattr and fix sysfs_chmod Eric W. Biederman
2008-07-04 1:13 ` [PATCH 07/15] sysfs: sysfs_chmod_file handle multiple superblocks Eric W. Biederman
2008-07-04 1:14 ` [PATCH 08/15] sysfs: Make sysfs_mount static once again Eric W. Biederman
2008-07-04 1:16 ` [PATCH 09/15] sysfs: Implement sysfs tagged directory support Eric W. Biederman
2008-07-04 1:17 ` [PATCH 10/15] sysfs: Merge sysfs_rename_dir and sysfs_move_dir Eric W. Biederman
2008-07-04 1:18 ` [PATCH 11/15] sysfs: Implement sysfs_delete_link and sysfs_rename_link Eric W. Biederman
2008-07-04 1:20 ` [PATCH 12/15] driver core: Implement tagged directory support for device classes Eric W. Biederman
2008-07-04 1:21 ` [PATCH 13/15] Revert "netns: Fix device renaming for sysfs" Eric W. Biederman
2008-07-04 1:22 ` [PATCH 14/15] netns: Enable tagging for net_class directories in sysfs Eric W. Biederman
2008-07-04 1:23 ` [PATCH 15/15] sysfs: user namespaces: fix bug with clone(CLONE_NEWUSER) with fairsched Eric W. Biederman
2008-07-04 7:50 ` [PATCH 12/15] driver core: Implement tagged directory support for device classes Tejun Heo
2008-07-04 13:31 ` Eric W. Biederman
2008-07-04 13:57 ` Tejun Heo
2008-07-04 16:12 ` Greg KH
2008-07-04 21:49 ` Eric W. Biederman
2008-07-14 1:54 ` Eric W. Biederman
2008-07-16 3:25 ` Tejun Heo
2008-07-16 5:41 ` Eric W. Biederman
2008-07-16 5:50 ` Tejun Heo
2008-07-16 6:32 ` Eric W. Biederman
2008-07-16 6:48 ` Tejun Heo
2008-07-16 7:02 ` Tejun Heo
2008-07-16 19:07 ` Eric W. Biederman
2008-07-16 21:09 ` Eric W. Biederman
2008-07-17 23:08 ` Greg KH
2008-07-18 12:41 ` Tejun Heo
2008-07-18 18:49 ` Greg KH
2008-07-18 20:19 ` Eric W. Biederman
2008-07-19 1:07 ` Tejun Heo
2008-08-03 6:59 ` Eric W. Biederman
2008-09-11 12:45 ` Jiri Slaby
2008-09-11 13:05 ` Benjamin Thery
2008-09-12 6:32 ` Jiri Slaby
2008-07-04 22:00 ` Eric W. Biederman
2008-08-20 2:17 ` [PATCH 09/15] sysfs: Implement sysfs tagged directory support Greg KH
2008-08-20 6:58 ` Eric W. Biederman
2008-08-21 6:31 ` [PATCH 0/8] sysfs namespace support Eric W. Biederman
2008-08-21 6:33 ` [PATCH 1/8] sysfs: Implement sysfs tagged directory support Eric W. Biederman
2008-08-21 6:34 ` [PATCH 2/8] sysfs: Merge sysfs_rename_dir and sysfs_move_dir Eric W. Biederman
2008-08-21 6:35 ` [PATCH 3/8] sysfs: Implement sysfs_delete_link and sysfs_rename_link Eric W. Biederman
2008-08-21 6:36 ` [PATCH 5/8] sysfs: Remove sysfs_create_link_nowarn Eric W. Biederman
2008-08-21 6:38 ` [PATCH 6/8] Revert "netns: Fix device renaming for sysfs" Eric W. Biederman
2008-08-21 6:39 ` [PATCH 7/8] netns: Enable tagging for net_class directories in sysfs Eric W. Biederman
2008-08-21 6:40 ` [PATCH 8/8] sysfs: user namespaces: fix bug with clone(CLONE_NEWUSER) with fairsched Eric W. Biederman
2008-08-21 6:47 ` [PATCH 7/8] netns: Enable tagging for net_class directories in sysfs David Miller
2008-08-21 6:47 ` [PATCH 6/8] Revert "netns: Fix device renaming for sysfs" David Miller
2008-08-21 6:37 ` [PATCH 4/8] driver core: Implement tagged directory support for device classes Eric W. Biederman
2008-08-27 15:18 ` [PATCH 1/8] sysfs: Implement sysfs tagged directory support Benjamin Thery
2008-09-02 13:54 ` Mark Ryden
2008-09-02 14:03 ` Benjamin Thery
2008-09-02 17:01 ` Greg KH
2008-09-04 5:33 ` David Shwatrz
2008-09-04 6:44 ` Benjamin Thery
2008-09-08 18:39 ` Mark Ryden
2008-10-07 16:39 ` Mark Ryden
2008-10-07 16:48 ` Greg KH
2008-10-07 20:31 ` Eric W. Biederman
2008-10-07 21:09 ` Greg KH
2008-10-07 22:27 ` Eric W. Biederman
2008-10-08 13:00 ` Christoph Hellwig
2008-10-14 3:20 ` Eric W. Biederman
2008-10-07 16:52 ` Daniel Lezcano
2008-08-21 6:37 ` [PATCH 0/8] sysfs namespace support David Miller
2008-07-04 6:44 ` [PATCH 08/15] sysfs: Make sysfs_mount static once again Tejun Heo
2008-07-04 6:44 ` [PATCH 07/15] sysfs: sysfs_chmod_file handle multiple superblocks Tejun Heo
2008-07-04 6:40 ` [PATCH 06/15] Introduce sysfs_sd_setattr and fix sysfs_chmod Tejun Heo
2008-07-04 6:33 ` [PATCH 01/15] kobject: Cleanup kobject_rename and !CONFIG_SYSFS Tejun Heo
2008-07-04 1:27 ` [PATCH 00/15] sysfs support for namespaces Eric W. Biederman
2008-07-06 4:42 ` Eric W. Biederman
2008-07-07 11:41 ` Cornelia Huck
2008-07-07 12:22 ` Eric W. Biederman
2008-06-18 17:08 ` [PATCH 07/11] sysfs: Implement sysfs_delete_link and sysfs_rename_link Benjamin Thery
2008-06-23 2:13 ` Tejun Heo
2008-06-26 20:24 ` Eric W. Biederman
2008-06-29 3:35 ` Tejun Heo
2008-06-30 3:02 ` Eric W. Biederman
2008-06-18 17:08 ` [PATCH 08/11] driver core: Implement tagged directory support for device classes Benjamin Thery
2008-06-18 17:08 ` [PATCH 09/11] sysfs: add sysfs_ns_exit routine Benjamin Thery
2008-06-18 20:19 ` Eric W. Biederman
2008-06-23 2:16 ` Tejun Heo
2008-06-18 17:09 ` [PATCH 10/11] netns: Enable tagging for net_class directories in sysfs Benjamin Thery
2008-06-23 2:18 ` Tejun Heo
2008-06-18 17:09 ` [PATCH 11/11] sysfs: user namespaces: fix bug with clone(CLONE_NEWUSER) with fairsched Benjamin Thery
2008-06-23 2:18 ` Tejun Heo
2008-06-25 18:44 ` Serge E. Hallyn
2008-06-25 21:11 ` Eric W. Biederman
2008-06-26 13:07 ` Serge E. Hallyn
-- strict thread matches above, loose matches on Subject: below --
2008-06-06 15:46 [PATCH 00/11] sysfs tagged directories V5 Benjamin Thery
2008-06-06 15:47 ` [PATCH 06/11] sysfs: Implement sysfs tagged directory support Benjamin Thery
2008-05-06 17:30 [RESEND][PATCH 00/11] sysfs tagged directories Benjamin Thery
2008-05-06 17:31 ` [PATCH 06/11] sysfs: Implement sysfs tagged directory support Benjamin Thery
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