[RFC] usb: don't dput() in usbfs_rmdir()

[Sebastian Andrzej Siewior <bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>]

rmmod of every hcd results currently in somethig like

|uhci_hcd 0000:00:01.2: USB bus 1 deregistered
|------------[ cut here ]------------
|kernel BUG at /home/bigeasy/git/linux/fs/dcache.c:419!
|invalid opcode: 0000 [#1]
|Modules linked in: uhci_hcd(-) ehci_hcd usbcore
|
|Pid: 1736, comm: rmmod Not tainted 3.0.0-rc1-00001-geb7d864-dirty #148 Bochs Bochs
|EIP: 0060:[<810c3f6b>] EFLAGS: 00010246 CPU: 0
|EIP is at dput+0x12b/0x130
|EAX: 00000000 EBX: af3ca9a0 ECX: af3cbd00 EDX: 00000202
|ESI: af3c6000 EDI: af3cbca8 EBP: aeae7ddc ESP: aeae7dd4
| DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
|Process rmmod (pid: 1736, ti=aeae6000 task=ae815c00 task.ti=aeae6000)
|Stack:
| af3ca9a0 af3c6000 aeae7dfc b0a489b6 af3cb9d8 af3cbcc0 af3caa10 aefb2230
| 00000000 00000000 aeae7e28 b0a48de5 afa37140 af402300 ade0a038 aeae7e40
| 810ae9f5 81177295 b0a4dce0 00000000 00000000 aeae7e44 81049395 aefb2230
|Call Trace:
| [<b0a489b6>] fs_remove_file+0x76/0x120 [usbcore]
| [<b0a48de5>] usbfs_notify+0x35/0x2d0 [usbcore]
| [<810ae9f5>] ? kfree+0x105/0x130
| [<81177295>] ? kobject_release+0x45/0x80
| [<81049395>] notifier_call_chain+0x45/0x60
| [<81049793>] __blocking_notifier_call_chain+0x43/0x70
| [<810497df>] blocking_notifier_call_chain+0x1f/0x30
| [<b0a46a39>] usb_notify_remove_bus+0x19/0x20 [usbcore]
| [<b0a3af0b>] usb_deregister_bus+0x5b/0x70 [usbcore]
| [<b0a3b011>] usb_remove_hcd+0xf1/0x100 [usbcore]

a bisect turned up:

|commit 64252c75a2196a0cf1e0d3777143ecfe0e3ae650
|Author: Sage Weil <sage-BnTBU8nroG7k1uMJSBkQmQ@public.gmane.org>
|Date:   Tue May 24 13:06:05 2011 -0700
|
|    vfs: remove dget() from dentry_unhash()
|
|    This serves no useful purpose that I can discern.  All callers (rename,
|    rmdir) hold their own reference to the dentry.
|
|    A quick audit of all file systems showed no relevant checks on the value
|    of d_count in vfs_rmdir/vfs_rename_dir paths.
|
|    Signed-off-by: Sage Weil <sage-BnTBU8nroG7k1uMJSBkQmQ@public.gmane.org>
|    Signed-off-by: Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>

I removed the "inner" dput() which is called on emptry dir and sets error
to zero. This looks like the same change in 64252c7 for vfs_rmdir()
where dput() is removed from the path where we have dont_mount() and
S_DEAD.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
---
Could one of VFS ppl look at this an NACK/ACK it?

Jessi: I've seen your patch after I had mine done. If you send me a
sign-off-by for this, I will resend it with you as Author + SOB if you
like once the VFS are fine with this.

 drivers/usb/core/inode.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/drivers/usb/core/inode.c b/drivers/usb/core/inode.c
index 1b125c2..3ef9308 100644
--- a/drivers/usb/core/inode.c
+++ b/drivers/usb/core/inode.c
@@ -381,7 +381,6 @@ static int usbfs_rmdir(struct inode *dir, struct dentry *dentry)
 		dont_mount(dentry);
 		drop_nlink(dentry->d_inode);
 		drop_nlink(dentry->d_inode);
-		dput(dentry);
 		inode->i_flags |= S_DEAD;
 		drop_nlink(dir);
 		error = 0;
-- 
1.7.4.4

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