Subject: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex To: Andrew Morton Cc: linux-kernel@vger.kernel.org, dm-devel@redhat.com, Ingo Molnar , Eric Sandeen , Srinivasa DS From: Srinivasa Ds On debugging I found out that,"dmsetup suspend " 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 ". 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 Signed-off-by: Alasdair G Kergon Cc: Ingo Molnar Cc: Eric Sandeen Cc: dm-devel@redhat.com fs/block_dev.c | 2 +- fs/buffer.c | 6 ++++-- fs/super.c | 4 ++-- include/linux/fs.h | 2 +- 4 files changed, 8 insertions(+), 6 deletions(-) Index: linux-2.6.19/fs/block_dev.c =================================================================== --- linux-2.6.19.orig/fs/block_dev.c 2006-12-06 20:49:18.000000000 +0000 +++ linux-2.6.19/fs/block_dev.c 2006-12-06 20:49:35.000000000 +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/fs/buffer.c =================================================================== --- linux-2.6.19.orig/fs/buffer.c 2006-12-06 20:48:29.000000000 +0000 +++ linux-2.6.19/fs/buffer.c 2006-12-06 20:49:35.000000000 +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/fs/super.c =================================================================== --- linux-2.6.19.orig/fs/super.c 2006-12-06 20:48:29.000000000 +0000 +++ linux-2.6.19/fs/super.c 2006-12-06 20:49:35.000000000 +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/include/linux/fs.h =================================================================== --- linux-2.6.19.orig/include/linux/fs.h 2006-12-06 20:48:29.000000000 +0000 +++ linux-2.6.19/include/linux/fs.h 2006-12-06 20:49:35.000000000 +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;