Re: [PATCH] ide-tape: fix proc warning

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Sunday 07 June 2009 11:20:54 Borislav Petkov wrote:
> Hi,
> 
> this is yet another ide-tape fix against ide-2.6.git/for-next.
> 
> --
> From: Borislav Petkov <petkovbb@gmail.com>
> Date: Sun, 7 Jun 2009 11:05:53 +0200
> Subject: [PATCH] ide-tape: fix proc warning
> 
> When accessing ide-tape over the chrdev interface, I get
> 
> [  278.147906] ------------[ cut here ]------------
> [  278.152685] WARNING: at fs/proc/generic.c:847 remove_proc_entry+0x199/0x1b8()
> [  278.160070] Hardware name: P4I45PE    1.00
> [  278.160076] remove_proc_entry: removing non-empty directory 'ide0/hdb', leaking at least 'name'
> [  278.160080] Modules linked in: rtc intel_agp pcspkr thermal processor thermal_sys parport_pc parport agpgart button
> [  278.160100] Pid: 2312, comm: mt Not tainted 2.6.30-rc2 #3
> [  278.160105] Call Trace:
> [  278.160117]  [<c012141d>] warn_slowpath+0x71/0xa0
> [  278.160126]  [<c035f219>] ? _spin_unlock_irqrestore+0x29/0x2c
> [  278.160132]  [<c011c686>] ? try_to_wake_up+0x1b6/0x1c0
> [  278.160141]  [<c011c69b>] ? default_wake_function+0xb/0xd
> [  278.160149]  [<c0177ead>] ? pollwake+0x4a/0x55
> [  278.160156]  [<c035f240>] ? _spin_unlock+0x24/0x26
> [  278.160163]  [<c0165d38>] ? add_partial+0x44/0x49
> [  278.160169]  [<c01669e8>] ? __slab_free+0xba/0x29c
> [  278.160177]  [<c01a13d8>] ? sysfs_delete_inode+0x0/0x3c
> [  278.160184]  [<c019ca92>] remove_proc_entry+0x199/0x1b8
> [  278.160191]  [<c01a297e>] ? remove_dir+0x27/0x2e
> [  278.160199]  [<c025f3ab>] ide_proc_unregister_device+0x40/0x4c
> [  278.160207]  [<c02599cd>] drive_release_dev+0x14/0x47
> [  278.160214]  [<c0250538>] device_release+0x35/0x5a
> [  278.160221]  [<c01f8bed>] kobject_release+0x40/0x50
> [  278.160226]  [<c01f8bad>] ? kobject_release+0x0/0x50
> [  278.160232]  [<c01f96ac>] kref_put+0x3c/0x4a
> [  278.160238]  [<c01f8b29>] kobject_put+0x37/0x3c
> [  278.160243]  [<c025020c>] put_device+0xf/0x11
> [  278.160249]  [<c025789f>] ide_device_put+0x2d/0x30
> [  278.160255]  [<c02658da>] ide_tape_put+0x24/0x32
> [  278.160261]  [<c0266e0c>] idetape_chrdev_release+0x17f/0x18e
> [  278.160269]  [<c016c4f5>] __fput+0xca/0x175
> [  278.160275]  [<c016c5b9>] fput+0x19/0x1b
> [  278.160280]  [<c0169d19>] filp_close+0x51/0x5b
> [  278.160286]  [<c0169d96>] sys_close+0x73/0xad
> [  278.160293]  [<c0102a61>] syscall_call+0x7/0xb
> [  278.160298] ---[ end trace f16d907ea1f89336 ]---
> 
> because it tries to free its proc entry in drive_release_dev()
> in the call chain resulting from ide_tape_put() but it chokes on
> /proc/ide/ide[01]/hd?/name which is added during driver registration and
> should go only at driver removal time.
> 
> Add/remove those proc entries everytime the device is accessed.

This looks more like broken ide-tape refcounting for chrdev interface
than mismatch of /proc entries registration time (especially since other
device drivers are not having the above problem)..

Please see ide_tape_chrdev_get() -- it misses ide_device_get() call
[present in ide_tape_get()] which can result in premature release of
IDE device during ide_tape_put() call.