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

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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>
This commit is contained in:
Alan Jenkins 2009-07-29 21:07:55 +02:00 committed by Rafael J. Wysocki
parent ec79be2687
commit dddac6a7b4
3 changed files with 13 additions and 2 deletions
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10
fs/block_dev.c
View file

@ -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;

1
include/linux/fs.h
View file

@ -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 *);

4
mm/swapfile.c
View file

@ -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);