[PATCH] lockdep: annotate blkdev nesting

Teach special (recursive) locking code to the lock validator.

Effects on non-lockdep kernels:

- the introduction of the following function variants:

  extern struct block_device *open_partition_by_devnum(dev_t, unsigned);

  extern int blkdev_put_partition(struct block_device *);

  static int
  blkdev_get_whole(struct block_device *bdev, mode_t mode, unsigned flags);

 which on non-lockdep are the same as open_by_devnum(), blkdev_put()
 and blkdev_get().

- a subclass parameter to do_open(). [unused on non-lockdep]

- a subclass parameter to __blkdev_put(), which is a new internal
  function for the main blkdev_put*() functions. [parameter unused
  on non-lockdep kernels, except for two sanity check WARN_ON()s]

these functions carry no semantical difference - they only express
object dependencies towards the lockdep subsystem.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 107 insertions, 18 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 2fe32c261922..e4e161372a3e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1404,7 +1404,7 @@ static int lock_rdev(mdk_rdev_t *rdev, dev_t dev)
         struct block_device *bdev;
         char b[BDEVNAME_SIZE];
 
-        bdev = open_by_devnum(dev, FMODE_READ|FMODE_WRITE);
+        bdev = open_partition_by_devnum(dev, FMODE_READ|FMODE_WRITE);
         if (IS_ERR(bdev)) {
                 printk(KERN_ERR "md: could not open %s.\n",
                         __bdevname(dev, b));
@@ -1414,7 +1414,7 @@ static int lock_rdev(mdk_rdev_t *rdev, dev_t dev)
         if (err) {
                 printk(KERN_ERR "md: could not bd_claim %s.\n",
                         bdevname(bdev, b));
-                blkdev_put(bdev);
+                blkdev_put_partition(bdev);
                 return err;
         }
         rdev->bdev = bdev;
@@ -1428,7 +1428,7 @@ static void unlock_rdev(mdk_rdev_t *rdev)
         if (!bdev)
                 MD_BUG();
         bd_release(bdev);
-        blkdev_put(bdev);
+        blkdev_put_partition(bdev);
 }
 
 void md_autodetect_dev(dev_t dev);
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 9633a490dab0..37534573960b 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -739,7 +739,7 @@ static int bd_claim_by_kobject(struct block_device *bdev, void *holder,
         if (!bo)
                 return -ENOMEM;
 
-        mutex_lock(&bdev->bd_mutex);
+        mutex_lock_nested(&bdev->bd_mutex, BD_MUTEX_PARTITION);
         res = bd_claim(bdev, holder);
         if (res || !add_bd_holder(bdev, bo))
                 free_bd_holder(bo);
@@ -764,7 +764,7 @@ static void bd_release_from_kobject(struct block_device *bdev,
         if (!kobj)
                 return;
 
-        mutex_lock(&bdev->bd_mutex);
+        mutex_lock_nested(&bdev->bd_mutex, BD_MUTEX_PARTITION);
         bd_release(bdev);
         if ((bo = del_bd_holder(bdev, kobj)))
                 free_bd_holder(bo);
@@ -822,6 +822,22 @@ struct block_device *open_by_devnum(dev_t dev, unsigned mode)
 
 EXPORT_SYMBOL(open_by_devnum);
 
+static int
+blkdev_get_partition(struct block_device *bdev, mode_t mode, unsigned flags);
+
+struct block_device *open_partition_by_devnum(dev_t dev, unsigned mode)
+{
+        struct block_device *bdev = bdget(dev);
+        int err = -ENOMEM;
+        int flags = mode & FMODE_WRITE ? O_RDWR : O_RDONLY;
+        if (bdev)
+                err = blkdev_get_partition(bdev, mode, flags);
+        return err ? ERR_PTR(err) : bdev;
+}
+
+EXPORT_SYMBOL(open_partition_by_devnum);
+
+
 /*
  * This routine checks whether a removable media has been changed,
  * and invalidates all buffer-cache-entries in that case. This
@@ -868,7 +884,11 @@ void bd_set_size(struct block_device *bdev, loff_t size)
 }
 EXPORT_SYMBOL(bd_set_size);
 
-static int do_open(struct block_device *bdev, struct file *file)
+static int
+blkdev_get_whole(struct block_device *bdev, mode_t mode, unsigned flags);
+
+static int
+do_open(struct block_device *bdev, struct file *file, unsigned int subclass)
 {
         struct module *owner = NULL;
         struct gendisk *disk;
@@ -885,7 +905,8 @@ static int do_open(struct block_device *bdev, struct file *file)
         }
         owner = disk->fops->owner;
 
-        mutex_lock(&bdev->bd_mutex);
+        mutex_lock_nested(&bdev->bd_mutex, subclass);
+
         if (!bdev->bd_openers) {
                 bdev->bd_disk = disk;
                 bdev->bd_contains = bdev;
@@ -912,11 +933,11 @@ static int do_open(struct block_device *bdev, struct file *file)
                         ret = -ENOMEM;
                         if (!whole)
                                 goto out_first;
-                        ret = blkdev_get(whole, file->f_mode, file->f_flags);
+                        ret = blkdev_get_whole(whole, file->f_mode, file->f_flags);
                         if (ret)
                                 goto out_first;
                         bdev->bd_contains = whole;
-                        mutex_lock(&whole->bd_mutex);
+                        mutex_lock_nested(&whole->bd_mutex, BD_MUTEX_WHOLE);
                         whole->bd_part_count++;
                         p = disk->part[part - 1];
                         bdev->bd_inode->i_data.backing_dev_info =
@@ -944,7 +965,8 @@ static int do_open(struct block_device *bdev, struct file *file)
                         if (bdev->bd_invalidated)
                                 rescan_partitions(bdev->bd_disk, bdev);
                 } else {
-                        mutex_lock(&bdev->bd_contains->bd_mutex);
+                        mutex_lock_nested(&bdev->bd_contains->bd_mutex,
+                                          BD_MUTEX_PARTITION);
                         bdev->bd_contains->bd_part_count++;
                         mutex_unlock(&bdev->bd_contains->bd_mutex);
                 }
@@ -985,11 +1007,49 @@ int blkdev_get(struct block_device *bdev, mode_t mode, unsigned flags)
         fake_file.f_dentry = &fake_dentry;
         fake_dentry.d_inode = bdev->bd_inode;
 
-        return do_open(bdev, &fake_file);
+        return do_open(bdev, &fake_file, BD_MUTEX_NORMAL);
 }
 
 EXPORT_SYMBOL(blkdev_get);
 
+static int
+blkdev_get_whole(struct block_device *bdev, mode_t mode, unsigned flags)
+{
+        /*
+         * This crockload is due to bad choice of ->open() type.
+         * It will go away.
+         * For now, block device ->open() routine must _not_
+         * examine anything in 'inode' argument except ->i_rdev.
+         */
+        struct file fake_file = {};
+        struct dentry fake_dentry = {};
+        fake_file.f_mode = mode;
+        fake_file.f_flags = flags;
+        fake_file.f_dentry = &fake_dentry;
+        fake_dentry.d_inode = bdev->bd_inode;
+
+        return do_open(bdev, &fake_file, BD_MUTEX_WHOLE);
+}
+
+static int
+blkdev_get_partition(struct block_device *bdev, mode_t mode, unsigned flags)
+{
+        /*
+         * This crockload is due to bad choice of ->open() type.
+         * It will go away.
+         * For now, block device ->open() routine must _not_
+         * examine anything in 'inode' argument except ->i_rdev.
+         */
+        struct file fake_file = {};
+        struct dentry fake_dentry = {};
+        fake_file.f_mode = mode;
+        fake_file.f_flags = flags;
+        fake_file.f_dentry = &fake_dentry;
+        fake_dentry.d_inode = bdev->bd_inode;
+
+        return do_open(bdev, &fake_file, BD_MUTEX_PARTITION);
+}
+
 static int blkdev_open(struct inode * inode, struct file * filp)
 {
         struct block_device *bdev;
@@ -1005,7 +1065,7 @@ static int blkdev_open(struct inode * inode, struct file * filp)
 
         bdev = bd_acquire(inode);
 
-        res = do_open(bdev, filp);
+        res = do_open(bdev, filp, BD_MUTEX_NORMAL);
         if (res)
                 return res;
 
@@ -1019,13 +1079,13 @@ static int blkdev_open(struct inode * inode, struct file * filp)
         return res;
 }
 
-int blkdev_put(struct block_device *bdev)
+static int __blkdev_put(struct block_device *bdev, unsigned int subclass)
 {
         int ret = 0;
         struct inode *bd_inode = bdev->bd_inode;
         struct gendisk *disk = bdev->bd_disk;
 
-        mutex_lock(&bdev->bd_mutex);
+        mutex_lock_nested(&bdev->bd_mutex, subclass);
         lock_kernel();
         if (!--bdev->bd_openers) {
                 sync_blockdev(bdev);
@@ -1035,7 +1095,8 @@ int blkdev_put(struct block_device *bdev)
                 if (disk->fops->release)
                         ret = disk->fops->release(bd_inode, NULL);
         } else {
-                mutex_lock(&bdev->bd_contains->bd_mutex);
+                mutex_lock_nested(&bdev->bd_contains->bd_mutex,
+                                  subclass + 1);
                 bdev->bd_contains->bd_part_count--;
                 mutex_unlock(&bdev->bd_contains->bd_mutex);
         }
@@ -1051,9 +1112,8 @@ int blkdev_put(struct block_device *bdev)
                 }
                 bdev->bd_disk = NULL;
                 bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info;
-                if (bdev != bdev->bd_contains) {
-                        blkdev_put(bdev->bd_contains);
-                }
+                if (bdev != bdev->bd_contains)
+                        __blkdev_put(bdev->bd_contains, subclass + 1);
                 bdev->bd_contains = NULL;
         }
         unlock_kernel();
@@ -1062,8 +1122,20 @@ int blkdev_put(struct block_device *bdev)
         return ret;
 }
 
+int blkdev_put(struct block_device *bdev)
+{
+        return __blkdev_put(bdev, BD_MUTEX_NORMAL);
+}
+
 EXPORT_SYMBOL(blkdev_put);
 
+int blkdev_put_partition(struct block_device *bdev)
+{
+        return __blkdev_put(bdev, BD_MUTEX_PARTITION);
+}
+
+EXPORT_SYMBOL(blkdev_put_partition);
+
 static int blkdev_close(struct inode * inode, struct file * filp)
 {
         struct block_device *bdev = I_BDEV(filp->f_mapping->host);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e26de68059af..134b32068246 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -436,6 +436,21 @@ struct block_device {
 };
 
 /*
+ * bdev->bd_mutex nesting subclasses for the lock validator:
+ *
+ * 0: normal
+ * 1: 'whole'
+ * 2: 'partition'
+ */
+enum bdev_bd_mutex_lock_class
+{
+        BD_MUTEX_NORMAL,
+        BD_MUTEX_WHOLE,
+        BD_MUTEX_PARTITION
+};
+
+
+/*
  * Radix-tree tags, for tagging dirty and writeback pages within the pagecache
  * radix trees
  */
@@ -1425,6 +1440,7 @@ extern void bd_set_size(struct block_device *, loff_t size);
 extern void bd_forget(struct inode *inode);
 extern void bdput(struct block_device *);
 extern struct block_device *open_by_devnum(dev_t, unsigned);
+extern struct block_device *open_partition_by_devnum(dev_t, unsigned);
 extern const struct file_operations def_blk_fops;
 extern const struct address_space_operations def_blk_aops;
 extern const struct file_operations def_chr_fops;
@@ -1435,6 +1451,7 @@ extern int blkdev_ioctl(struct inode *, struct file *, unsigned, unsigned long);
 extern long compat_blkdev_ioctl(struct file *, unsigned, unsigned long);
 extern int blkdev_get(struct block_device *, mode_t, unsigned);
 extern int blkdev_put(struct block_device *);
+extern int blkdev_put_partition(struct block_device *);
 extern int bd_claim(struct block_device *, void *);
 extern void bd_release(struct block_device *);
 #ifdef CONFIG_SYSFS