Hi all
When I was executing "dmsetup resume <device-name>" command,I got the
error shown below. Which basically tells that, "bd_mount_mutex" in
thaw_bdev() is not locked by "dmsetup resume" command and hence it is
not allowing it to unlock also.
=========================================================
Badness in debug_mutex_unlock at kernel/mutex-debug.c:80
Call Trace:
[C0000000634DB260] [C000000000010948] .show_stack+0x68/0x1b0 (unreliable)
[C0000000634DB300] [C0000000003376C4] .program_check_exception+0x1cc/0x5b0
[C0000000634DB3D0] [C0000000000047EC] program_check_common+0xec/0x100
--- Exception: 700 at .debug_mutex_unlock+0x3c/0xc4
LR = .debug_mutex_unlock+0x30/0xc4
[C0000000634DB6C0] [C0000000634DB750] 0xc0000000634db750 (unreliable)
[C0000000634DB740] [C000000000335950] .__mutex_unlock_slowpath+0xd8/0x144
[C0000000634DB7E0] [C0000000000E2370] .thaw_bdev+0x9c/0xb8
[C0000000634DB870] [D000000000480830] .unlock_fs+0x34/0x70 [dm_mod]
[C0000000634DB900] [D000000000481720] .dm_resume+0x110/0x1ac [dm_mod]
[C0000000634DB9A0] [D000000000485C54] .dev_suspend+0x1b0/0x204 [dm_mod]
[C0000000634DBA40] [D000000000486728] .ctl_ioctl+0x29c/0x318 [dm_mod]
[C0000000634DBC30] [C0000000000F8310] .do_ioctl+0xbc/0xf0
[C0000000634DBCD0] [C0000000000F879C] .vfs_ioctl+0x458/0x498
[C0000000634DBD80] [C0000000000F8874] .sys_ioctl+0x98/0xe0
[C0000000634DBE30] [C00000000000871C] syscall_exit+0x0/0x40
======================================================================
On debugging I found out that,"dmsetup suspend <device name>" calls
"freeze_bdev()",which locks "bd_mount_mutex" to make sure that no new
mounts happen on bdev until thaw_bdev() is called.
This "thaw_bdev()" is getting called when we resume the device through
"dmsetup resume <device-name>".
Hence we have 2 processes,one of which locks "bd_mount_mutex"(dmsetup
suspend) and Another(dmsetup resume) unlocks it.
Since this is not allowed in mutex,I reverted back to
bd_mount_sem(semaphore),It worked for me.
So need your comments for changing "bd_mount_mutex" to "bd_mount_sem".
This is the patch,which I have used.
Thanks
Srinivasa Ds
LTC-IBM
Bangalore
diff -Naurp linux-2.6.18-rc6-orig/fs/block_dev.c linux-2.6.18-rc6-mod/fs/block_dev.c
--- linux-2.6.18-rc6-orig/fs/block_dev.c 2006-09-27 04:47:25.000000000 -0700
+++ linux-2.6.18-rc6-mod/fs/block_dev.c 2006-09-27 04:53:29.000000000 -0700
@@ -261,7 +261,7 @@ static void init_once(void * foo, kmem_c
{
memset(bdev, 0, sizeof(*bdev));
mutex_init(&bdev->bd_mutex);
- mutex_init(&bdev->bd_mount_mutex);
+ sema_init(&bdev->bd_mount_sem, 1);
INIT_LIST_HEAD(&bdev->bd_inodes);
INIT_LIST_HEAD(&bdev->bd_list);
#ifdef CONFIG_SYSFS
diff -Naurp linux-2.6.18-rc6-orig/fs/buffer.c linux-2.6.18-rc6-mod/fs/buffer.c
--- linux-2.6.18-rc6-orig/fs/buffer.c 2006-09-27 04:46:14.000000000 -0700
+++ linux-2.6.18-rc6-mod/fs/buffer.c 2006-09-27 04:49:55.000000000 -0700
@@ -213,7 +213,7 @@ struct super_block *freeze_bdev(struct b
{
struct super_block *sb;
- mutex_lock(&bdev->bd_mount_mutex);
+ down(&bdev->bd_mount_sem);
sb = get_super(bdev);
if (sb && !(sb->s_flags & MS_RDONLY)) {
sb->s_frozen = SB_FREEZE_WRITE;
@@ -255,7 +255,7 @@ void thaw_bdev(struct block_device *bdev
drop_super(sb);
}
- mutex_unlock(&bdev->bd_mount_mutex);
+ up(&bdev->bd_mount_sem);
}
EXPORT_SYMBOL(thaw_bdev);
diff -Naurp linux-2.6.18-rc6-orig/fs/super.c linux-2.6.18-rc6-mod/fs/super.c
--- linux-2.6.18-rc6-orig/fs/super.c 2006-09-27 04:46:51.000000000 -0700
+++ linux-2.6.18-rc6-mod/fs/super.c 2006-09-27 04:50:56.000000000 -0700
@@ -700,9 +700,9 @@ int get_sb_bdev(struct file_system_type
* will protect the lockfs code from trying to start a snapshot
* while we are mounting
*/
- mutex_lock(&bdev->bd_mount_mutex);
+ down(&bdev->bd_mount_sem);
s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
- mutex_unlock(&bdev->bd_mount_mutex);
+ up(&bdev->bd_mount_sem);
if (IS_ERR(s))
goto error_s;
diff -Naurp linux-2.6.18-rc6-orig/include/linux/fs.h linux-2.6.18-rc6-mod/include/linux/fs.h
--- linux-2.6.18-rc6-orig/include/linux/fs.h 2006-09-27 04:45:31.000000000 -0700
+++ linux-2.6.18-rc6-mod/include/linux/fs.h 2006-09-27 04:52:30.000000000 -0700
@@ -414,7 +414,7 @@ struct block_device {
struct inode * bd_inode; /* will die */
int bd_openers;
struct mutex bd_mutex; /* open/close mutex */
- struct mutex bd_mount_mutex; /* mount mutex */
+ struct semaphore bd_mount_sem;
struct list_head bd_inodes;
void * bd_holder;
int bd_holders;
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