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 <alan-jenkins@tuffmail.co.uk>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 2 insertions, 2 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index d1ade1a48ee7..8ffdc0d23c53 100644
--- 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);