PM/hibernate: fix "swap breaks after hibernation failures"

http://bugzilla.kernel.org/show_bug.cgi?id=12239

The image writing code dropped a reference to the current swap device.
This doesn't show up if the hibernation succeeds - because it doesn't
affect the image which gets resumed.  But it means multiple _failed_
hibernations end up freeing the swap device while it is still use!

swsusp_write() finds the block device for the swap file using swap_type_of().
It then uses blkdev_get() / blkdev_put() to open and close the block device.

Unfortunately, blkdev_get() assumes ownership of the inode of the block_device
passed to it.  So blkdev_put() calls iput() on the inode.  This is by design
and other callers expect this behaviour.  The fix is for swap_type_of() to take
a reference on the inode using bdget().

Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Len Brown <lenb@kernel.org>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 7e6304d..312fafe 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -635,7 +635,7 @@ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
 
                if (!bdev) {
                        if (bdev_p)
-                               *bdev_p = sis->bdev;
+                               *bdev_p = bdget(sis->bdev->bd_dev);
 
                        spin_unlock(&swap_lock);
                        return i;
@@ -647,7 +647,7 @@ 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 = sis->bdev;
+                                       *bdev_p = bdget(sis->bdev->bd_dev);
 
                                spin_unlock(&swap_lock);
                                bdput(bdev);