linux-kernel - Re: [PATCH v2] CIFS: Print message when attempting a mount

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Message-ID: <194690850.32402710.1538508513975.JavaMail.zimbra@redhat.com>
Date:   Tue, 2 Oct 2018 15:28:33 -0400 (EDT)
From:   Rodrigo Freire <rfreire@...hat.com>
To:     Steve French <smfrench@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Steve French <sfrench@...ba.org>,
        CIFS <linux-cifs@...r.kernel.org>,
        Pavel Shilovsky <piastryyy@...il.com>
Subject: Re: [PATCH v2] CIFS: Print message when attempting a mount

Hi Steve,

----- Original Message ----- 
> From: "Steve French" <smfrench@...il.com>
> To: rfreire@...hat.com
> Cc: "LKML" <linux-kernel@...r.kernel.org>, "Steve French"
> <sfrench@...ba.org>, "CIFS" <linux-cifs@...r.kernel.org>, "Pavel Shilovsky"
> <piastryyy@...il.com>
> Sent: Tuesday, October 2, 2018 4:17:02 PM
> Subject: Re: [PATCH v2] CIFS: Print message when attempting a mount
>
> Are you sure that these aren't logged by the automounter (for ext4,
> xfs etc.). When I looked in my dmesg logs I didn't find matching log
> entries in the file systems themselves. Do you have an example?

I'm positive about it. Check it out:

[rfreire@rf ~]$ cd git/upstream/fs/ext4/
[rfreire@rf ext4]$ 
[rfreire@rf ext4]$ 
[rfreire@rf ext4]$ grep -r "mounted filesystem with"
super.c:		ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "

[rfreire@rf ext4]$ dmesg | grep mount
[   21.550897] EXT4-fs (dm-1): mounted filesystem with ordered data mode. Opts: (null)
[   22.216213] EXT4-fs (dm-1): re-mounted. Opts: discard
[   22.598267] EXT4-fs (sda1): mounted filesystem with ordered data mode. Opts: (null)
[   22.605225] EXT4-fs (sdc): mounted filesystem without journal. Opts: discard
[   24.029161] EXT4-fs (dm-2): mounted filesystem with ordered data mode. Opts: (null)
[   24.047777] EXT4-fs (dm-4): mounted filesystem without journal. Opts: (null)

XFS sample dmesg (from https://www.reddit.com/r/archlinux/comments/40b9r9/xfs_partition_is_mounted_during_boot_and_then/):

[ 2.764491] XFS (sdb1): Mounting V5 Filesystem
[ 3.200886] XFS (sdb1): Ending clean mount
[ 5.384218] XFS (sdb1): Unmounting Filesystem

Relevant code:

[rfreire@rf ~]$ cd ../xfs

[rfreire@rf xfs]$ grep "Mounting V" *.c
xfs_log.c:		xfs_notice(mp, "Mounting V%d Filesystem",

> On the idea of adding cifsFYI logging here - I slightly prefer using
> ftrace (trace-cmd, ie dynamic tracing) so there is less overhead and
> easier to turn on/off following the example of xfs, f2fs, nfs, nfsd
> etc.

Remember that cifsFYI already exists; I just moved it inside a if clause
to print it only when running under debug. (they way it is originally).

> On Tue, Oct 2, 2018 at 6:57 AM Rodrigo Freire <rfreire@...hat.com> wrote:
> >
> > Currently, no messages are printed when mounting a CIFS filesystem and
> > no debug configuration is enabled.
> >
> > However, a CIFS mount information is valuable when troubleshooting
> > and/or forensic analyzing a system and finding out if was a CIFS
> > endpoint mount attempted.
> >
> > Other filesystems such as XFS, EXT* does issue a printk() when mounting
> > their filesystems.

> --
> Thanks,

Thank You! o/