Messages in this thread Patch in this message | | | Date | Tue, 7 Nov 2006 18:34:59 +0000 | From | Alasdair G Kergon <> | Subject | [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex |
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From: Srinivasa Ds <srinivasa@in.ibm.com>
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.
Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Eric Sandeen <sandeen@sandeen.net> Cc: dm-devel@redhat.com
Index: linux-2.6.19-rc4/fs/block_dev.c =================================================================== --- linux-2.6.19-rc4.orig/fs/block_dev.c 2006-11-07 17:06:20.000000000 +0000 +++ linux-2.6.19-rc4/fs/block_dev.c 2006-11-07 17:26:04.000000000 +0000 @@ -263,7 +263,7 @@ 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 Index: linux-2.6.19-rc4/fs/buffer.c =================================================================== --- linux-2.6.19-rc4.orig/fs/buffer.c 2006-11-07 17:06:20.000000000 +0000 +++ linux-2.6.19-rc4/fs/buffer.c 2006-11-07 17:26:04.000000000 +0000 @@ -188,7 +188,9 @@ struct super_block *freeze_bdev(struct b { struct super_block *sb; - mutex_lock(&bdev->bd_mount_mutex); + if (down_trylock(&bdev->bd_mount_sem)) + return -EBUSY; + sb = get_super(bdev); if (sb && !(sb->s_flags & MS_RDONLY)) { sb->s_frozen = SB_FREEZE_WRITE; @@ -230,7 +232,7 @@ 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); Index: linux-2.6.19-rc4/fs/super.c =================================================================== --- linux-2.6.19-rc4.orig/fs/super.c 2006-11-07 17:06:20.000000000 +0000 +++ linux-2.6.19-rc4/fs/super.c 2006-11-07 17:26:04.000000000 +0000 @@ -735,9 +735,9 @@ 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; Index: linux-2.6.19-rc4/include/linux/fs.h =================================================================== --- linux-2.6.19-rc4.orig/include/linux/fs.h 2006-11-07 17:06:20.000000000 +0000 +++ linux-2.6.19-rc4/include/linux/fs.h 2006-11-07 17:26:04.000000000 +0000 @@ -456,7 +456,7 @@ 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; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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