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

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Date:   Tue,  2 Oct 2018 08:57:01 -0300
From:   Rodrigo Freire <rfreire@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     sfrench@...ba.org, linux-cifs@...r.kernel.org, piastryyy@...il.com
Subject: [PATCH v2] CIFS: Print message when attempting a mount

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.

A terse log message is printed only if cifsFYI is not enabled.

Sample mount operations:

[root@...inthians ~]# mount -o user=administrator //172.25.250.18/c$ /mnt
(non-existent system)

[root@...inthians ~]# mount -o user=administrator //172.25.250.19/c$ /mnt
(Valid system)

Kernel message log for the mount operations:

[  450.464543] CIFS VFS: Attempting to mount //172.25.250.18/c$
[  456.478186] CIFS VFS: Error connecting to socket. Aborting operation.
[  456.478381] CIFS VFS: cifs_mount failed w/return code = -113
[  467.688866] CIFS VFS: Attempting to mount //172.25.250.19/c$

v2: Created a loop to select the right cifs_dbg message to be printed,
    considering the current system's scenario, in order to avoid a
    duplicate message or stripping out important information in
    debug.

Signed-off-by: Rodrigo Freire <rfreire@...hat.com>
---
 fs/cifs/cifsfs.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 7065426..7fde6bc 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -707,7 +707,11 @@ static int cifs_set_super(struct super_block *sb, void *data)
 	struct cifs_mnt_data mnt_data;
 	struct dentry *root;
 
-	cifs_dbg(FYI, "Devname: %s flags: %d\n", dev_name, flags);
+	/* Prints in Kernel / CIFS log the attempted mount operation */
+	if (cifsFYI)
+		cifs_dbg(FYI, "Devname: %s flags: %d\n", dev_name, flags);
+	else
+		cifs_dbg(VFS, "Attempting to mount %s\n", dev_name);
 
 	volume_info = cifs_get_volume_info((char *)data, dev_name, is_smb3);
 	if (IS_ERR(volume_info))
-- 
1.8.3.1