PM / Hibernate: Replace bdget call with simple atomic_inc of i_count

Create bdgrab(). This function copies an existing reference to a block_device. It is safe to call from any context. Hibernation code wishes to copy a reference to the active swap device. Right now it calls bdget() under a spinlock, but this is wrong because bdget() can sleep. It doesn't need a full bdget() because we already hold a reference to active swap devices (and the spinlock protects against swapoff). Fixes http://bugzilla.kernel.org/show_bug.cgi?id=13827 Signed-off-by: Alan Jenkins <[email protected]> Signed-off-by: Rafael J. Wysocki <[email protected]>
diverger · Jul 29, 2009 · dddac6a · dddac6a
1 parent ec79be2
commit dddac6a
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Showing 3 changed files with 13 additions and 2 deletions.
diff --git a/fs/block_dev.c b/fs/block_dev.c
@@ -564,6 +564,16 @@ struct block_device *bdget(dev_t dev)
 
 EXPORT_SYMBOL(bdget);
 
+/**
+ * bdgrab -- Grab a reference to an already referenced block device
+ * @bdev:	Block device to grab a reference to.
+ */
+struct block_device *bdgrab(struct block_device *bdev)
+{
+	atomic_inc(&bdev->bd_inode->i_count);
+	return bdev;
+}
+
 long nr_blockdev_pages(void)
 {
 	struct block_device *bdev;

diff --git a/include/linux/fs.h b/include/linux/fs.h
@@ -1946,6 +1946,7 @@ extern void putname(const char *name);
 extern int register_blkdev(unsigned int, const char *);
 extern void unregister_blkdev(unsigned int, const char *);
 extern struct block_device *bdget(dev_t);
+extern struct block_device *bdgrab(struct block_device *bdev);
 extern void bd_set_size(struct block_device *, loff_t size);
 extern void bd_forget(struct inode *inode);
 extern void bdput(struct block_device *);

diff --git a/mm/swapfile.c b/mm/swapfile.c
@@ -753,7 +753,7 @@ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
 
 		if (!bdev) {
 			if (bdev_p)
-				*bdev_p = bdget(sis->bdev->bd_dev);
+				*bdev_p = bdgrab(sis->bdev);
 
 			spin_unlock(&swap_lock);
 			return i;
@@ -765,7 +765,7 @@ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
 					struct swap_extent, list);
 			if (se->start_block == offset) {
 				if (bdev_p)
-					*bdev_p = bdget(sis->bdev->bd_dev);
+					*bdev_p = bdgrab(sis->bdev);
 
 				spin_unlock(&swap_lock);
 				bdput(bdev);