1 files changed, 146 insertions, 0 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index b3c1efff5e1d..8c3c6899ccf3 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -18,6 +18,7 @@
 #include <linux/module.h>
 #include <linux/blkpg.h>
 #include <linux/buffer_head.h>
+#include <linux/pagevec.h>
 #include <linux/writeback.h>
 #include <linux/mpage.h>
 #include <linux/mount.h>
@@ -174,6 +175,151 @@ blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
                                 iov, offset, nr_segs, blkdev_get_blocks, NULL);
 }
 
+/*
+ * Write out and wait upon all the dirty data associated with a block
+ * device via its mapping.  Does not take the superblock lock.
+ */
+int sync_blockdev(struct block_device *bdev)
+{
+        int ret = 0;
+
+        if (bdev)
+                ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
+        return ret;
+}
+EXPORT_SYMBOL(sync_blockdev);
+
+/*
+ * Write out and wait upon all dirty data associated with this
+ * device.   Filesystem data as well as the underlying block
+ * device.  Takes the superblock lock.
+ */
+int fsync_bdev(struct block_device *bdev)
+{
+        struct super_block *sb = get_super(bdev);
+        if (sb) {
+                int res = fsync_super(sb);
+                drop_super(sb);
+                return res;
+        }
+        return sync_blockdev(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
+ * unfreeze process can unfreeze the frozen filesystem actually when multiple
+ * freeze requests arrive simultaneously. It counts up in freeze_bdev() and
+ * count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze
+ * actually.
+ */
+struct super_block *freeze_bdev(struct block_device *bdev)
+{
+        struct super_block *sb;
+        int error = 0;
+
+        mutex_lock(&bdev->bd_fsfreeze_mutex);
+        if (bdev->bd_fsfreeze_count > 0) {
+                bdev->bd_fsfreeze_count++;
+                sb = get_super(bdev);
+                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();
+
+                __fsync_super(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);
+                        }
+                }
+        }
+
+        sync_blockdev(bdev);
+        mutex_unlock(&bdev->bd_fsfreeze_mutex);
+
+        return sb;      /* thaw_bdev releases s->s_umount and bd_mount_sem */
+}
+EXPORT_SYMBOL(freeze_bdev);
+
+/**
+ * thaw_bdev  -- unlock filesystem
+ * @bdev:       blockdevice to unlock
+ * @sb:         associated superblock
+ *
+ * Unlocks the filesystem and marks it writeable again after freeze_bdev().
+ */
+int thaw_bdev(struct block_device *bdev, struct super_block *sb)
+{
+        int error = 0;
+
+        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);
+                }
+                drop_super(sb);
+        }
+
+        up(&bdev->bd_mount_sem);
+        mutex_unlock(&bdev->bd_fsfreeze_mutex);
+        return 0;
+}
+EXPORT_SYMBOL(thaw_bdev);
+
 static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
 {
         return block_write_full_page(page, blkdev_get_block, wbc);