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

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Message-ID: <CAH2r5muV-vC6twZbNQQ3DHoXJTdaUwhzZi7YH+rhxr0BiMseJQ@mail.gmail.com>
Date:   Tue, 2 Oct 2018 16:25:46 -0500
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>
Subject: Re: [PATCH v2] CIFS: Print message when attempting a mount

It is an interesting question - my gut reaction is that messages that
need more immediate attention should be logged as KERN_ERR (similar to
cifs_dbg(VFS ...) but given how easy it is now to use dynamic tracing
and better to read, if a developer would need it ... probably best to
use ftrace (trace-cmd).  Note that xfs has more than 570 (!) dynamic
trace point callouts now vs. fewer than 30 for xfs_notice
On Tue, Oct 2, 2018 at 4:20 PM Rodrigo Freire <rfreire@...hat.com> wrote:
>
> Hi Steve o/
>
> I personally like more a pr_info() instead of a cifs_dbg (which wraps to a
> pr_warn). But in order to keep in line with the general CIFS coding style
> I stuck to cifs_dbg
>
> But I would happily rewrite the cifs_dbg to pr_info a v3: That would be
> good enough too.
>
> Ah for what is worth my test/target systems are CentOS/Red Hat Enterprise
> Linux.
>
> Thoughts?
>
> Thanks!
>
> - RF.
>
> ----- 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 5:35:49 PM
> > Subject: Re: [PATCH v2] CIFS: Print message when attempting a mount
>
> > I noticed that on at least the first system I looked at (Ubuntu 18.04)
> > it defaults to KERN_WARNING (ie 4) so wouldn't have shown a KERN_INFO
> > which is level 6 (as the mount example from ext4) by default
> > or the xfs_notice (which is level 5)
>
> > https://elinux.org/Debugging_by_printing
>
> > On Tue, Oct 2, 2018 at 2:28 PM Rodrigo Freire <rfreire@...hat.com> wrote:
> > >
> > > 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/
>
> > --
> > Thanks,
>
> > Steve



-- 
Thanks,

Steve