Debian Bug report logs - #772744
btrfs-tools: btrfs dev scan called multiple times from udev rules

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Goffredo Baroncelli <kreijack@gmail.com>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: btrfs-tools: btrfs dev scan called multiple times from udev rules

Date: Wed, 10 Dec 2014 20:00:46 +0100

Package: btrfs-tools
Version: 3.17-1.1
Severity: important

Hi all,

currently btrfs-tools contains two udev rules: 
- 80-btrfs-lvm.rules
- 70-btrfs.rules

But also udev contains a btrfs rules

- 64-btrfs.rules

All rules do the same thing: invoke "btrfs device scan". Ok the
udev rules uses an internal builtin, but the results is the same
of the first two rules.

I am asking to remove the btrfs-tools rules (80-... and 70-...)
because the udev rule is sufficient and always present.

As confirmation I checked fedora, and there is only one
btrfs rule, the udev one.

BR
G.Baroncelli


-- System Information:
Debian Release: 8.0
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages btrfs-tools depends on:
ii  e2fslibs    1.42.12-1
ii  libblkid1   2.25.2-3
ii  libc6       2.19-13
ii  libcomerr2  1.42.12-1
ii  liblzo2-2   2.08-1
ii  libuuid1    2.25.2-3
ii  zlib1g      1:1.2.8.dfsg-2+b1

btrfs-tools recommends no packages.

btrfs-tools suggests no packages.

-- no debconf information

Message #10 received at 772744@bugs.debian.org (full text, mbox, reply):

From: Dimitri John Ledkov <xnox@debian.org>

To: Goffredo Baroncelli <kreijack@gmail.com>, 772744@bugs.debian.org

Subject: Re: Bug#772744: btrfs-tools: btrfs dev scan called multiple times from udev rules

Date: Thu, 11 Dec 2014 20:37:31 +0000

On 10 December 2014 at 19:00, Goffredo Baroncelli <kreijack@gmail.com> wrote:
> Package: btrfs-tools
> Version: 3.17-1.1
> Severity: important
>
> Hi all,
>
> currently btrfs-tools contains two udev rules:
> - 80-btrfs-lvm.rules
> - 70-btrfs.rules
>

These two are different due to different conditions. These could be
combined into a single file, but imho it's best to keep them
segregated.

> But also udev contains a btrfs rules
>
> - 64-btrfs.rules
>
> All rules do the same thing: invoke "btrfs device scan". Ok the
> udev rules uses an internal builtin, but the results is the same
> of the first two rules.
>

64-btrfs.rules does not call scan, it marks btrfs devices as ready
only. These are not equivalent.


> I am asking to remove the btrfs-tools rules (80-... and 70-...)
> because the udev rule is sufficient and always present.
>

All three do different things, under different conditions and are not
equivalent.

> As confirmation I checked fedora, and there is only one
> btrfs rule, the udev one.
>

Fedora does not use initramfs-tools, but dracut which incidentally
ships a udev rule to call btrfs device scan. Thus even fedora has an
extra udev rule to call btrfs scan.

Do you have a bug with current package? If yes, please describe it,
otherwise I will be closing this bug report as won't fix.

Regards,

Dimitri.


> BR
> G.Baroncelli
>
>
> -- System Information:
> Debian Release: 8.0
>   APT prefers unstable
>   APT policy: (500, 'unstable')
> Architecture: amd64 (x86_64)
>
> Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
> Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
> Shell: /bin/sh linked to /bin/dash
> Init: systemd (via /run/systemd/system)
>
> Versions of packages btrfs-tools depends on:
> ii  e2fslibs    1.42.12-1
> ii  libblkid1   2.25.2-3
> ii  libc6       2.19-13
> ii  libcomerr2  1.42.12-1
> ii  liblzo2-2   2.08-1
> ii  libuuid1    2.25.2-3
> ii  zlib1g      1:1.2.8.dfsg-2+b1
>
> btrfs-tools recommends no packages.
>
> btrfs-tools suggests no packages.
>
> -- no debconf information

-- 
Regards,

Dimitri.

Message #15 received at 772744@bugs.debian.org (full text, mbox, reply):

From: Goffredo Baroncelli <kreijack@gmail.com>

To: Dimitri John Ledkov <xnox@debian.org>, 772744@bugs.debian.org

Subject: Re: Bug#772744: btrfs-tools: btrfs dev scan called multiple times from udev rules

Date: Thu, 11 Dec 2014 23:10:53 +0100

On 12/11/2014 09:37 PM, Dimitri John Ledkov wrote:
> On 10 December 2014 at 19:00, Goffredo Baroncelli <kreijack@gmail.com> wrote:
[...]
>> But also udev contains a btrfs rules
>>
>> - 64-btrfs.rules
>>
>> All rules do the same thing: invoke "btrfs device scan". Ok the
>> udev rules uses an internal builtin, but the results is the same
>> of the first two rules.
>>
> 
> 64-btrfs.rules does not call scan, it marks btrfs devices as ready
> only. These are not equivalent.

It does a "BTRFS_IOC_DEVICES_READY" ioctl (see udev-builtin-btrfs.c), 
which, despite its name, *registers* the passed device *and checks* if 
the number of registered device is sufficient. From fs/btrfs/super.c

[...]
/*
 * used by btrfsctl to scan devices when no FS is mounted
 */
static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
                                unsigned long arg)
{
[...]
	switch (cmd) {
        case BTRFS_IOC_SCAN_DEV:
                ret = btrfs_scan_one_device(vol->name, FMODE_READ,
                                            &btrfs_fs_type, &fs_devices);
                break;
        case BTRFS_IOC_DEVICES_READY:
                ret = btrfs_scan_one_device(vol->name, FMODE_READ,
                                            &btrfs_fs_type, &fs_devices);
                if (ret)
                        break;
                ret = !(fs_devices->num_devices == fs_devices->total_devices);
                break;
        }


As you can see BTRFS_IOC_DEVICES_READY acts ALSO as BTRFS_IOC_SCAN_DEV.
(Yes, the name is very confusing, so only looking at the code this thing 
is clear)


> 
>> I am asking to remove the btrfs-tools rules (80-... and 70-...)
>> because the udev rule is sufficient and always present.
>>
> 
> All three do different things, under different conditions and are not
> equivalent.

The 64-btrfs.rules is able to superseed the two btrfs-tools package rules (80-...
and 70-...). So it is not true that these rules do different thing.


The 80-btrfs-lvm.rules and 70-btrfs.rules appeared before the 64-btrfs.rules (March 2012 vs September 2012). This explain the redundancy.

BTW, ironically I was one of the first to suggest to put "btrfs device scan" in a btrfs rule (http://permalink.gmane.org/gmane.comp.file-systems.btrfs/5374)

> 
>> As confirmation I checked fedora, and there is only one
>> btrfs rule, the udev one.
>>
> 
> Fedora does not use initramfs-tools, but dracut which incidentally
> ships a udev rule to call btrfs device scan. 

I checked a fedora initramfs and I was unable to find this rule (except
the 64-btrfs.rules)

I am referring the Fedora case to support my request to leave
only 64-btrfs.rules: it is sufficient to cover all the cases. Otherwise
we could drop the 64-btrfs.rules and leave the 70-... and 80-... But
because these are less generic and Debian specific I don't see a valid reason
for that.
64-btrfs.rules is also more efficient because it calls a built-in command and
not an external one.

> Thus even fedora has an
> extra udev rule to call btrfs scan.

No, it has only the 64-btrfs.rules. I re-checked now a fedora-20 initramfs (
initramfs-3.17.4-200.fc20.x86_64.img) and:

- I was able to find the btrfs tools
- I found /lib/udev/rules/64-btrfs.rules (which is the same shipped by
the debian udev package)
- I didn't find any "btrfs dev scan" invocation.

 
> Do you have a bug with current package? If yes, please describe it,
> otherwise I will be closing this bug report as won't fix.

the problem tha I found was that we have three udev rules, when only one 
is sufficient; I am suggesting to adopt the rule shipped with udev.
If you think that this is not a bug, please consider it as wishlist

BTW, I noticed that the debian rules do the insmod the btrfs module. But this 
should be not necessary anymore. Udev is in charge to create the /dev/btrfs-control
device. Any access to this device name starts the insmod of the btrfs module.
(see https://lkml.org/lkml/2010/5/21/134)

> 
> Regards,
> 
> Dimitri.
> 
BR
Goffredo

> 
>> BR
>> G.Baroncelli
>>
>>
>> -- System Information:
>> Debian Release: 8.0
>>   APT prefers unstable
>>   APT policy: (500, 'unstable')
>> Architecture: amd64 (x86_64)
>>
>> Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
>> Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
>> Shell: /bin/sh linked to /bin/dash
>> Init: systemd (via /run/systemd/system)
>>
>> Versions of packages btrfs-tools depends on:
>> ii  e2fslibs    1.42.12-1
>> ii  libblkid1   2.25.2-3
>> ii  libc6       2.19-13
>> ii  libcomerr2  1.42.12-1
>> ii  liblzo2-2   2.08-1
>> ii  libuuid1    2.25.2-3
>> ii  zlib1g      1:1.2.8.dfsg-2+b1
>>
>> btrfs-tools recommends no packages.
>>
>> btrfs-tools suggests no packages.
>>
>> -- no debconf information
> 


-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

Message #20 received at 772744-close@bugs.debian.org (full text, mbox, reply):

From: Dimitri John Ledkov <dimitri.j.ledkov@linux.intel.com>

To: 772744-close@bugs.debian.org

Subject: Bug#772744: fixed in btrfs-tools 4.0-1

Date: Sun, 03 May 2015 23:04:01 +0000

Source: btrfs-tools
Source-Version: 4.0-1

We believe that the bug you reported is fixed in the latest version of
btrfs-tools, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 772744@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Dimitri John Ledkov <dimitri.j.ledkov@linux.intel.com> (supplier of updated btrfs-tools package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Format: 1.8
Date: Sun, 18 Jan 2015 00:14:20 +0000
Source: btrfs-tools
Binary: btrfs-tools btrfs-tools-udeb btrfs-tools-dbg
Architecture: amd64 source
Version: 4.0-1
Distribution: unstable
Urgency: medium
Maintainer: Dimitri John Ledkov <xnox@debian.org>
Changed-By: Dimitri John Ledkov <dimitri.j.ledkov@linux.intel.com>
Closes: 770806 772744
Description: 
 btrfs-tools - Checksumming Copy on Write Filesystem utilities
 btrfs-tools-dbg - Checksumming Copy on Write Filesystem utilities (debug)
 btrfs-tools-udeb - Checksumming Copy on Write Filesystem utilities (udeb) (udeb)
Changes: 
 btrfs-tools (4.0-1) unstable; urgency=medium
 .
   * New upstream release.
   * Drop all patches.
   * Experiment with dropping udev rules, in favour of systemd-udev builtin
     integration. (Closes: #772744)
   * Move all binaries to /bin (Closes: #770806)
   * Switch to autoconf based build system.
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 6774e3086176f972abf210b6aa1397dec10f7576 476136 btrfs-tools_4.0-1_amd64.deb
 55945fd0e1c1c5a179e953442ad4847ab2ee7b79 231100 btrfs-tools-udeb_4.0-1_amd64.udeb
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Files: 
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 38e79509adc689ca7a88860b91954a02 1102500 admin optional btrfs-tools_4.0.orig.tar.xz
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