On Tuesday 21 July 2009, Christoph Hellwig wrote:
> On Tue, Jul 21, 2009 at 11:50:29AM +0100, Alan Jenkins wrote:
> > +struct block_device *bdcopy(struct block_device *bdev)
> > +{
> > + atomic_inc(&bdev->bd_inode->i_count);
> > + return bdev;
> > +}
> > +
> > +EXPORT_SYMBOL(bdcopy);
>
> The function name doesn't make any sense. You don't copy anything
> here, but you grab a reference to it. A better name would be bdgrab,
> mirroing the names of functions like igrab. A kerneldoc comment
> documenting it would also be very helpful.
>
> Why do you export it? The swapfile code is not actually modular.
Thanks for the comments. Does the one below look better?
Rafael
---
From: Alan Jenkins <alan-jenkins@xxxxxxxxxxxxxx>
Subject: 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).
Signed-off-by: Alan Jenkins <alan-jenkins@xxxxxxxxxxxxxx>
CC: linux-fsdevel@xxxxxxxxxxxxxxx
Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
fs/block_dev.c | 10 ++++++++++
include/linux/fs.h | 1 +
mm/swapfile.c | 4 ++--
3 files changed, 13 insertions(+), 2 deletions(-)
Index: linux-2.6/fs/block_dev.c
===================================================================
--- linux-2.6.orig/fs/block_dev.c
+++ linux-2.6/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;
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h
+++ linux-2.6/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 *);
Index: linux-2.6/mm/swapfile.c
===================================================================
--- linux-2.6.orig/mm/swapfile.c
+++ linux-2.6/mm/swapfile.c
@@ -753,7 +753,7 @@ int swap_type_of(dev_t device, sector_t
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
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);
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