1 files changed, 103 insertions, 71 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 94dfda24c06e..8bed0557d88c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -216,8 +216,6 @@ EXPORT_SYMBOL(fsync_bdev);
  * freeze_bdev  --  lock a filesystem and force it into a consistent state
  * @bdev:       blockdevice to lock
  *
- * This takes the block device bd_mount_sem to make sure no new mounts
- * happen on bdev until thaw_bdev() is called.
  * If a superblock is found on this device, we take the s_umount semaphore
  * on it to make sure nobody unmounts until the snapshot creation is done.
  * The reference counter (bd_fsfreeze_count) guarantees that only the last
@@ -232,46 +230,55 @@ struct super_block *freeze_bdev(struct block_device *bdev)
         int error = 0;
 
         mutex_lock(&bdev->bd_fsfreeze_mutex);
-        if (bdev->bd_fsfreeze_count > 0) {
-                bdev->bd_fsfreeze_count++;
+        if (++bdev->bd_fsfreeze_count > 1) {
+                /*
+                 * We don't even need to grab a reference - the first call
+                 * to freeze_bdev grab an active reference and only the last
+                 * thaw_bdev drops it.
+                 */
                 sb = get_super(bdev);
+                drop_super(sb);
                 mutex_unlock(&bdev->bd_fsfreeze_mutex);
                 return sb;
         }
-        bdev->bd_fsfreeze_count++;
-
-        down(&bdev->bd_mount_sem);
-        sb = get_super(bdev);
-        if (sb && !(sb->s_flags & MS_RDONLY)) {
-                sb->s_frozen = SB_FREEZE_WRITE;
-                smp_wmb();
-
-                sync_filesystem(sb);
-
-                sb->s_frozen = SB_FREEZE_TRANS;
-                smp_wmb();
-
-                sync_blockdev(sb->s_bdev);
-
-                if (sb->s_op->freeze_fs) {
-                        error = sb->s_op->freeze_fs(sb);
-                        if (error) {
-                                printk(KERN_ERR
-                                        "VFS:Filesystem freeze failed\n");
-                                sb->s_frozen = SB_UNFROZEN;
-                                drop_super(sb);
-                                up(&bdev->bd_mount_sem);
-                                bdev->bd_fsfreeze_count--;
-                                mutex_unlock(&bdev->bd_fsfreeze_mutex);
-                                return ERR_PTR(error);
-                        }
+
+        sb = get_active_super(bdev);
+        if (!sb)
+                goto out;
+        if (sb->s_flags & MS_RDONLY) {
+                deactivate_locked_super(sb);
+                mutex_unlock(&bdev->bd_fsfreeze_mutex);
+                return sb;
+        }
+
+        sb->s_frozen = SB_FREEZE_WRITE;
+        smp_wmb();
+
+        sync_filesystem(sb);
+
+        sb->s_frozen = SB_FREEZE_TRANS;
+        smp_wmb();
+
+        sync_blockdev(sb->s_bdev);
+
+        if (sb->s_op->freeze_fs) {
+                error = sb->s_op->freeze_fs(sb);
+                if (error) {
+                        printk(KERN_ERR
+                                "VFS:Filesystem freeze failed\n");
+                        sb->s_frozen = SB_UNFROZEN;
+                        deactivate_locked_super(sb);
+                        bdev->bd_fsfreeze_count--;
+                        mutex_unlock(&bdev->bd_fsfreeze_mutex);
+                        return ERR_PTR(error);
                 }
         }
+        up_write(&sb->s_umount);
 
+ out:
         sync_blockdev(bdev);
         mutex_unlock(&bdev->bd_fsfreeze_mutex);
-
-        return sb;      /* thaw_bdev releases s->s_umount and bd_mount_sem */
+        return sb;      /* thaw_bdev releases s->s_umount */
 }
 EXPORT_SYMBOL(freeze_bdev);
 
@@ -284,44 +291,44 @@ EXPORT_SYMBOL(freeze_bdev);
  */
 int thaw_bdev(struct block_device *bdev, struct super_block *sb)
 {
-        int error = 0;
+        int error = -EINVAL;
 
         mutex_lock(&bdev->bd_fsfreeze_mutex);
-        if (!bdev->bd_fsfreeze_count) {
-                mutex_unlock(&bdev->bd_fsfreeze_mutex);
-                return -EINVAL;
-        }
-
-        bdev->bd_fsfreeze_count--;
-        if (bdev->bd_fsfreeze_count > 0) {
-                if (sb)
-                        drop_super(sb);
-                mutex_unlock(&bdev->bd_fsfreeze_mutex);
-                return 0;
-        }
-
-        if (sb) {
-                BUG_ON(sb->s_bdev != bdev);
-                if (!(sb->s_flags & MS_RDONLY)) {
-                        if (sb->s_op->unfreeze_fs) {
-                                error = sb->s_op->unfreeze_fs(sb);
-                                if (error) {
-                                        printk(KERN_ERR
-                                                "VFS:Filesystem thaw failed\n");
-                                        sb->s_frozen = SB_FREEZE_TRANS;
-                                        bdev->bd_fsfreeze_count++;
-                                        mutex_unlock(&bdev->bd_fsfreeze_mutex);
-                                        return error;
-                                }
-                        }
-                        sb->s_frozen = SB_UNFROZEN;
-                        smp_wmb();
-                        wake_up(&sb->s_wait_unfrozen);
+        if (!bdev->bd_fsfreeze_count)
+                goto out_unlock;
+
+        error = 0;
+        if (--bdev->bd_fsfreeze_count > 0)
+                goto out_unlock;
+
+        if (!sb)
+                goto out_unlock;
+
+        BUG_ON(sb->s_bdev != bdev);
+        down_write(&sb->s_umount);
+        if (sb->s_flags & MS_RDONLY)
+                goto out_deactivate;
+
+        if (sb->s_op->unfreeze_fs) {
+                error = sb->s_op->unfreeze_fs(sb);
+                if (error) {
+                        printk(KERN_ERR
+                                "VFS:Filesystem thaw failed\n");
+                        sb->s_frozen = SB_FREEZE_TRANS;
+                        bdev->bd_fsfreeze_count++;
+                        mutex_unlock(&bdev->bd_fsfreeze_mutex);
+                        return error;
                 }
-                drop_super(sb);
         }
 
-        up(&bdev->bd_mount_sem);
+        sb->s_frozen = SB_UNFROZEN;
+        smp_wmb();
+        wake_up(&sb->s_wait_unfrozen);
+
+out_deactivate:
+        if (sb)
+                deactivate_locked_super(sb);
+out_unlock:
         mutex_unlock(&bdev->bd_fsfreeze_mutex);
         return 0;
 }
@@ -420,7 +427,6 @@ static void bdev_destroy_inode(struct inode *inode)
 {
         struct bdev_inode *bdi = BDEV_I(inode);
 
-        bdi->bdev.bd_inode_backing_dev_info = NULL;
         kmem_cache_free(bdev_cachep, bdi);
 }
 
@@ -431,7 +437,6 @@ static void init_once(void *foo)
 
         memset(bdev, 0, sizeof(*bdev));
         mutex_init(&bdev->bd_mutex);
-        sema_init(&bdev->bd_mount_sem, 1);
         INIT_LIST_HEAD(&bdev->bd_inodes);
         INIT_LIST_HEAD(&bdev->bd_list);
 #ifdef CONFIG_SYSFS
@@ -1115,7 +1120,7 @@ EXPORT_SYMBOL(revalidate_disk);
 int check_disk_change(struct block_device *bdev)
 {
         struct gendisk *disk = bdev->bd_disk;
-        struct block_device_operations * bdops = disk->fops;
+        const struct block_device_operations *bdops = disk->fops;
 
         if (!bdops->media_changed)
                 return 0;
@@ -1243,8 +1248,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                         bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
                 }
         } else {
-                put_disk(disk);
                 module_put(disk->fops->owner);
+                put_disk(disk);
                 disk = NULL;
                 if (bdev->bd_contains == bdev) {
                         if (bdev->bd_disk->fops->open) {
@@ -1405,6 +1410,33 @@ static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 }
 
 /*
+ * Write data to the block device.  Only intended for the block device itself
+ * and the raw driver which basically is a fake block device.
+ *
+ * Does not take i_mutex for the write and thus is not for general purpose
+ * use.
+ */
+ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov,
+                         unsigned long nr_segs, loff_t pos)
+{
+        struct file *file = iocb->ki_filp;
+        ssize_t ret;
+
+        BUG_ON(iocb->ki_pos != pos);
+
+        ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
+        if (ret > 0 || ret == -EIOCBQUEUED) {
+                ssize_t err;
+
+                err = generic_write_sync(file, pos, ret);
+                if (err < 0 && ret > 0)
+                        ret = err;
+        }
+        return ret;
+}
+EXPORT_SYMBOL_GPL(blkdev_aio_write);
+
+/*
  * Try to release a page associated with block device when the system
  * is under memory pressure.
  */
@@ -1436,7 +1468,7 @@ const struct file_operations def_blk_fops = {
         .read           = do_sync_read,
         .write          = do_sync_write,
         .aio_read       = generic_file_aio_read,
-        .aio_write      = generic_file_aio_write_nolock,
+        .aio_write      = blkdev_aio_write,
         .mmap           = generic_file_mmap,
         .fsync          = block_fsync,
         .unlocked_ioctl = block_ioctl,