[PATCH] USB: Remove BKL from remount() function in usbfs

[PATCH] USB: Remove BKL from remount() function in usbfs

[Alessio Igor Bogani]

The BKL was used into remount_fs pointed function for serialized access to
super_block from the others super_operations functions.

The function update_sb(), invoked by remount(), seems already well serialized
with &root->d_inode->i_mutex. Moreover don't seems there are others
super_operations functions in USB core for usbfs that should access to
super_block in a way which require BKL.

Signed-off-by: Alessio Igor Bogani <abogani@texware.it>
---
 drivers/usb/core/inode.c |    5 -----
 1 files changed, 0 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/core/inode.c b/drivers/usb/core/inode.c
index 97b40ce..54972d6 100644
--- a/drivers/usb/core/inode.c
+++ b/drivers/usb/core/inode.c
@@ -39,7 +39,6 @@
 #include <linux/parser.h>
 #include <linux/notifier.h>
 #include <linux/seq_file.h>
-#include <linux/smp_lock.h>
 #include <asm/byteorder.h>
 #include "usb.h"
 #include "hcd.h"
@@ -265,13 +264,9 @@ static int remount(struct super_block *sb, int *flags, char *data)
 		return -EINVAL;
 	}
 
-	lock_kernel();
-
 	if (usbfs_mount && usbfs_mount->mnt_sb)
 		update_sb(usbfs_mount->mnt_sb);
 
-	unlock_kernel();
-
 	return 0;
 }
 
-- 
1.6.3.3

Re: [PATCH] USB: Remove BKL from remount() function in usbfs

[Arnd Bergmann]

On Wednesday 31 March 2010, Alessio Igor Bogani wrote:
> 
> The BKL was used into remount_fs pointed function for serialized access to
> super_block from the others super_operations functions.
> 
> The function update_sb(), invoked by remount(), seems already well serialized
> with &root->d_inode->i_mutex. Moreover don't seems there are others
> super_operations functions in USB core for usbfs that should access to
> super_block in a way which require BKL.

There is a patch from Jan Blunck pending in the bkl-removal tree that pushes
down the BKL into usbfs_fill_super. Can you confirm that this BKL usage does
not interfere with the one you just removed, and that it can go the same way?

	Arnd

Re: [PATCH] USB: Remove BKL from remount() function in usbfs

[Alessio Igor Bogani]

Mr Bergmann,

2010/3/31 Arnd Bergmann <arnd@arndb.de>:
[...]
>> The function update_sb(), invoked by remount(), seems already well serialized
>> with &root->d_inode->i_mutex. Moreover don't seems there are others
>> super_operations functions in USB core for usbfs that should access to
>> super_block in a way which require BKL.
>
> There is a patch from Jan Blunck pending in the bkl-removal tree that pushes
> down the BKL into usbfs_fill_super. Can you confirm that this BKL usage does
> not interfere with the one you just removed, and that it can go the same way?

I can confirm that this certainly interfere: So please ignore my patch.

I'll elaborate a new patch when Blunck's works is merged.

Thanks!

Ciao,
Alessio