Merge branch 'linus' into cont_syslog

[safe/jmp/linux-2.6] / fs / block_dev.c

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7346c96..99d6af8 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -706,8 +706,13 @@ retry:
  * @bdev is about to be opened exclusively.  Check @bdev can be opened
  * exclusively and mark that an exclusive open is in progress.  Each
  * successful call to this function must be matched with a call to
- * either bd_claim() or bd_abort_claiming().  If this function
- * succeeds, the matching bd_claim() is guaranteed to succeed.
+ * either bd_finish_claiming() or bd_abort_claiming() (which do not
+ * fail).
+ *
+ * This function is used to gain exclusive access to the block device
+ * without actually causing other exclusive open attempts to fail. It
+ * should be used when the open sequence itself requires exclusive
+ * access but may subsequently fail.
  *
  * CONTEXT:
  * Might sleep.
@@ -734,6 +739,7 @@ static struct block_device *bd_start_claiming(struct block_device *bdev,
                return ERR_PTR(-ENXIO);
 
        whole = bdget_disk(disk, 0);
+       module_put(disk->fops->owner);
        put_disk(disk);
        if (!whole)
                return ERR_PTR(-ENOMEM);
@@ -782,15 +788,46 @@ static void bd_abort_claiming(struct block_device *whole, void *holder)
        __bd_abort_claiming(whole, holder);             /* releases bdev_lock */
 }
 
+/* increment holders when we have a legitimate claim. requires bdev_lock */
+static void __bd_claim(struct block_device *bdev, struct block_device *whole,
+                                       void *holder)
+{
+       /* note that for a whole device bd_holders
+        * will be incremented twice, and bd_holder will
+        * be set to bd_claim before being set to holder
+        */
+       whole->bd_holders++;
+       whole->bd_holder = bd_claim;
+       bdev->bd_holders++;
+       bdev->bd_holder = holder;
+}
+
+/**
+ * bd_finish_claiming - finish claiming a block device
+ * @bdev: block device of interest (passed to bd_start_claiming())
+ * @whole: whole block device returned by bd_start_claiming()
+ * @holder: holder trying to claim @bdev
+ *
+ * Finish a claiming block started by bd_start_claiming().
+ *
+ * CONTEXT:
+ * Grabs and releases bdev_lock.
+ */
+static void bd_finish_claiming(struct block_device *bdev,
+                               struct block_device *whole, void *holder)
+{
+       spin_lock(&bdev_lock);
+       BUG_ON(!bd_may_claim(bdev, whole, holder));
+       __bd_claim(bdev, whole, holder);
+       __bd_abort_claiming(whole, holder); /* not actually an abort */
+}
+
 /**
  * bd_claim - claim a block device
  * @bdev: block device to claim
  * @holder: holder trying to claim @bdev
  *
- * Try to claim @bdev which must have been opened successfully.  This
- * function may be called with or without preceding
- * blk_start_claiming().  In the former case, this function is always
- * successful and terminates the claiming block.
+ * Try to claim @bdev which must have been opened successfully.
  *
  * CONTEXT:
  * Might sleep.
@@ -806,23 +843,10 @@ int bd_claim(struct block_device *bdev, void *holder)
        might_sleep();
 
        spin_lock(&bdev_lock);
-
        res = bd_prepare_to_claim(bdev, whole, holder);
-       if (res == 0) {
-               /* note that for a whole device bd_holders
-                * will be incremented twice, and bd_holder will
-                * be set to bd_claim before being set to holder
-                */
-               whole->bd_holders++;
-               whole->bd_holder = bd_claim;
-               bdev->bd_holders++;
-               bdev->bd_holder = holder;
-       }
-
-       if (whole->bd_claiming)
-               __bd_abort_claiming(whole, holder);     /* releases bdev_lock */
-       else
-               spin_unlock(&bdev_lock);
+       if (res == 0)
+               __bd_claim(bdev, whole, holder);
+       spin_unlock(&bdev_lock);
 
        return res;
 }
@@ -1476,7 +1500,7 @@ static int blkdev_open(struct inode * inode, struct file * filp)
 
        if (whole) {
                if (res == 0)
-                       BUG_ON(bd_claim(bdev, filp) != 0);
+                       bd_finish_claiming(bdev, whole, filp);
                else
                        bd_abort_claiming(whole, filp);
        }
@@ -1712,7 +1736,7 @@ struct block_device *open_bdev_exclusive(const char *path, fmode_t mode, void *h
        if ((mode & FMODE_WRITE) && bdev_read_only(bdev))
                goto out_blkdev_put;
 
-       BUG_ON(bd_claim(bdev, holder) != 0);
+       bd_finish_claiming(bdev, whole, holder);
        return bdev;
 
 out_blkdev_put: