linux-kernel - Re: Bug in mount options handling in EXT4?

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Date:	Wed, 04 Feb 2015 21:57:24 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Enrico Mioso <mrkiko.rs@...il.com>, linux-kernel@...r.kernel.org
CC:	linux-ext4@...r.kernel.org
Subject: Re: Bug in mount options handling in EXT4?

On 2/4/15 9:22 PM, Enrico Mioso wrote:
> Hello guys.
> I noticed from some time, that I can make mount options accumulate simply continously repeating them.
> By typing:
> sudo mount -t ext4 -o rw,noatime,nobarrier,nobarrier,nobarrier, ...
> I can get:
> $ dmesg | tail
> [  216.075581] EXT4-fs (sdb): mounted filesystem without journal. Opts: nobarrier
> [  472.851105] snd_hda_intel 0000:00:1b.0: IRQ timing workaround is activated for card #0. Suggest a bigger bdl_pos_adj.
> [41950.250515] EXT4-fs (sdc1): re-mounted. Opts: nobarrier,nobarrier
> [42093.049879] EXT4-fs (sdc1): re-mounted. Opts: nobarrier,nobarrier
> [42095.673967] EXT4-fs (sdc1): re-mounted. Opts: nobarrier,nobarrier
> [42095.954595] EXT4-fs (sdc1): re-mounted. Opts: nobarrier,nobarrier
> [42096.220220] EXT4-fs (sdc1): re-mounted. Opts: nobarrier,nobarrier
> [42103.212371] EXT4-fs (sdc1): re-mounted. Opts: nobarrier,nobarrier,nobarrier
> [42128.137609] EXT4-fs (sdc1): re-mounted. Opts: nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier
> [42144.960612] EXT4-fs (sdc1): re-mounted. Opts: nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier,nobarrier

Hm, yes, it's really only cosmetic in that printk.

> But the problem seems limited to the filesystem messages / something like that:
> $ cat /proc/mounts

...

> /dev/sdc1 /mnt/trekstor ext4 rw,noatime,nobarrier 0 0

Yep, because when this is printed, it simply looks at the set option flags,
and essentially prints the option name once for each (non-default) flag
that is set.

What we probably would want is something similar to that code (in
_ext4_show_options) which is more generic, and could generate a string
for use in the remount case as well.

-Eric

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