diff mbox series

[13/20] block: remove ->bd_contains

Message ID 20201118084800.2339180-14-hch@lst.de (mailing list archive)
State New, archived
Headers show
Series [01/20] blk-cgroup: fix a hd_struct leak in blkcg_fill_root_iostats | expand

Commit Message

Christoph Hellwig Nov. 18, 2020, 8:47 a.m. UTC 
Now that each hd_struct has a reference to the corresponding
block_device, there is no need for the bd_contains pointer.  Add
a bdev_whole() helper to look up the whole device block_device
struture instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/scsi/scsicam.c    |  2 +-
 fs/block_dev.c            | 46 ++++++++++++---------------------------
 include/linux/blk_types.h |  4 +++-
 3 files changed, 18 insertions(+), 34 deletions(-)

Comments

Jan Kara Nov. 19, 2020, 10:32 a.m. UTC | #1 
On Wed 18-11-20 09:47:53, Christoph Hellwig wrote:
> Now that each hd_struct has a reference to the corresponding
> block_device, there is no need for the bd_contains pointer.  Add
> a bdev_whole() helper to look up the whole device block_device
> struture instead.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Just two nits below. Otherwise feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

> @@ -1521,7 +1510,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
>  		if (bdev->bd_bdi == &noop_backing_dev_info)
>  			bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info);
>  	} else {
> -		if (bdev->bd_contains == bdev) {
> +		if (!bdev->bd_partno) {

This should be !bdev_is_partition(bdev) for consistency, right?

>  			ret = 0;
>  			if (bdev->bd_disk->fops->open)
>  				ret = bdev->bd_disk->fops->open(bdev, mode);
...
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 0069bee992063e..453b940b87d8e9 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -32,7 +32,6 @@ struct block_device {
>  #ifdef CONFIG_SYSFS
>  	struct list_head	bd_holder_disks;
>  #endif
> -	struct block_device *	bd_contains;
>  	u8			bd_partno;
>  	struct hd_struct *	bd_part;
>  	/* number of times partitions within this device have been opened. */
> @@ -48,6 +47,9 @@ struct block_device {
>  	struct mutex		bd_fsfreeze_mutex;
>  } __randomize_layout;
>  
> +#define bdev_whole(_bdev) \
> +	((_bdev)->bd_disk->part0.bdev)
> +
>  #define bdev_kobj(_bdev) \
>  	(&part_to_dev((_bdev)->bd_part)->kobj)

I'd somewhat prefer if these helpers could actually be inline functions and
not macros. I guess they are macros because hd_struct isn't in blk_types.h.
But if we moved helpers to blkdev.h, we'd have all definitions we need...
Is that a problem for some users?

								Honza
Christoph Hellwig Nov. 20, 2020, 9:01 a.m. UTC | #2 
On Thu, Nov 19, 2020 at 11:32:53AM +0100, Jan Kara wrote:
> > @@ -1521,7 +1510,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
> >  		if (bdev->bd_bdi == &noop_backing_dev_info)
> >  			bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info);
> >  	} else {
> > -		if (bdev->bd_contains == bdev) {
> > +		if (!bdev->bd_partno) {
> 
> This should be !bdev_is_partition(bdev) for consistency, right?

Yes.  Same for the same check further up for the !bdev->bd_openers
case.

> > +#define bdev_whole(_bdev) \
> > +	((_bdev)->bd_disk->part0.bdev)
> > +
> >  #define bdev_kobj(_bdev) \
> >  	(&part_to_dev((_bdev)->bd_part)->kobj)
> 
> I'd somewhat prefer if these helpers could actually be inline functions and
> not macros. I guess they are macros because hd_struct isn't in blk_types.h.
> But if we moved helpers to blkdev.h, we'd have all definitions we need...
> Is that a problem for some users?

As you pointed out the reason these are macros is that the obvious
placement doesn't work.  My plan was to look into cleaning up the block
headers, which are a complete mess between blk_types.h, bio.h, blkdev.h
and genhd.h after I'm done making sense of the data structures, so for
now I didn't want to move too much around.  Hopefully we'll be able to
convert these helpers to inlines once I'm done.
diff mbox series

Patch

diff --git a/drivers/scsi/scsicam.c b/drivers/scsi/scsicam.c
index 682cf08ab04153..f1553a453616fd 100644
--- a/drivers/scsi/scsicam.c
+++ b/drivers/scsi/scsicam.c
@@ -32,7 +32,7 @@ 
  */
 unsigned char *scsi_bios_ptable(struct block_device *dev)
 {
-	struct address_space *mapping = dev->bd_contains->bd_inode->i_mapping;
+	struct address_space *mapping = bdev_whole(dev)->bd_inode->i_mapping;
 	unsigned char *res = NULL;
 	struct page *page;
 
diff --git a/fs/block_dev.c b/fs/block_dev.c
index dd52dbd266cde7..258a1ced924483 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -879,7 +879,6 @@  struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
 	spin_lock_init(&bdev->bd_size_lock);
 	bdev->bd_disk = disk;
 	bdev->bd_partno = partno;
-	bdev->bd_contains = NULL;
 	bdev->bd_super = NULL;
 	bdev->bd_inode = inode;
 	bdev->bd_part_count = 0;
@@ -1054,7 +1053,7 @@  static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
  */
 int bd_prepare_to_claim(struct block_device *bdev, void *holder)
 {
-	struct block_device *whole = bdev->bd_contains;
+	struct block_device *whole = bdev_whole(bdev);
 
 retry:
 	spin_lock(&bdev_lock);
@@ -1102,7 +1101,7 @@  static void bd_clear_claiming(struct block_device *whole, void *holder)
  */
 static void bd_finish_claiming(struct block_device *bdev, void *holder)
 {
-	struct block_device *whole = bdev->bd_contains;
+	struct block_device *whole = bdev_whole(bdev);
 
 	spin_lock(&bdev_lock);
 	BUG_ON(!bd_may_claim(bdev, whole, holder));
@@ -1131,7 +1130,7 @@  static void bd_finish_claiming(struct block_device *bdev, void *holder)
 void bd_abort_claiming(struct block_device *bdev, void *holder)
 {
 	spin_lock(&bdev_lock);
-	bd_clear_claiming(bdev->bd_contains, holder);
+	bd_clear_claiming(bdev_whole(bdev), holder);
 	spin_unlock(&bdev_lock);
 }
 EXPORT_SYMBOL(bd_abort_claiming);
@@ -1429,7 +1428,6 @@  static void put_disk_and_module(struct gendisk *disk)
 static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
 		int for_part)
 {
-	struct block_device *whole = NULL;
 	struct gendisk *disk = bdev->bd_disk;
 	int ret;
 	bool first_open = false, unblock_events = true, need_restart;
@@ -1447,26 +1445,17 @@  static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
 	}
 	up_read(&disk->lookup_sem);
 
-	if (bdev->bd_partno) {
-		whole = bdget_disk(disk, 0);
-		if (!whole) {
-			ret = -ENOMEM;
-			goto out_put_disk;
-		}
-	}
-
 	if (!for_part && (mode & FMODE_EXCL)) {
 		WARN_ON_ONCE(!holder);
 		ret = bd_prepare_to_claim(bdev, holder);
 		if (ret)
-			goto out_put_whole;
+			goto out_put_disk;
 	}
 
 	disk_block_events(disk);
 	mutex_lock_nested(&bdev->bd_mutex, for_part);
 	if (!bdev->bd_openers) {
 		first_open = true;
-		bdev->bd_contains = bdev;
 
 		if (!bdev->bd_partno) {
 			ret = -ENXIO;
@@ -1504,10 +1493,10 @@  static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
 				goto out_clear;
 		} else {
 			BUG_ON(for_part);
-			ret = __blkdev_get(whole, mode, NULL, 1);
+			ret = __blkdev_get(bdev_whole(bdev), mode, NULL, 1);
 			if (ret)
 				goto out_clear;
-			bdev->bd_contains = bdgrab(whole);
+			bdgrab(bdev_whole(bdev));
 			bdev->bd_part = disk_get_part(disk, bdev->bd_partno);
 			if (!(disk->flags & GENHD_FL_UP) ||
 			    !bdev->bd_part || !bdev->bd_part->nr_sects) {
@@ -1521,7 +1510,7 @@  static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
 		if (bdev->bd_bdi == &noop_backing_dev_info)
 			bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info);
 	} else {
-		if (bdev->bd_contains == bdev) {
+		if (!bdev->bd_partno) {
 			ret = 0;
 			if (bdev->bd_disk->fops->open)
 				ret = bdev->bd_disk->fops->open(bdev, mode);
@@ -1560,24 +1549,18 @@  static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
 	/* only one opener holds refs to the module and disk */
 	if (!first_open)
 		put_disk_and_module(disk);
-	if (whole)
-		bdput(whole);
 	return 0;
 
  out_clear:
 	disk_put_part(bdev->bd_part);
 	bdev->bd_part = NULL;
-	if (bdev != bdev->bd_contains)
-		__blkdev_put(bdev->bd_contains, mode, 1);
-	bdev->bd_contains = NULL;
+	if (bdev_is_partition(bdev))
+		__blkdev_put(bdev_whole(bdev), mode, 1);
  out_unlock_bdev:
 	if (!for_part && (mode & FMODE_EXCL))
 		bd_abort_claiming(bdev, holder);
 	mutex_unlock(&bdev->bd_mutex);
 	disk_unblock_events(disk);
- out_put_whole:
- 	if (whole)
-		bdput(whole);
  out_put_disk:
 	put_disk_and_module(disk);
 	if (need_restart)
@@ -1768,8 +1751,7 @@  static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
 		disk_put_part(bdev->bd_part);
 		bdev->bd_part = NULL;
 		if (bdev_is_partition(bdev))
-			victim = bdev->bd_contains;
-		bdev->bd_contains = NULL;
+			victim = bdev_whole(bdev);
 
 		put_disk_and_module(disk);
 	} else {
@@ -1787,6 +1769,7 @@  void blkdev_put(struct block_device *bdev, fmode_t mode)
 	mutex_lock(&bdev->bd_mutex);
 
 	if (mode & FMODE_EXCL) {
+		struct block_device *whole = bdev_whole(bdev);
 		bool bdev_free;
 
 		/*
@@ -1797,13 +1780,12 @@  void blkdev_put(struct block_device *bdev, fmode_t mode)
 		spin_lock(&bdev_lock);
 
 		WARN_ON_ONCE(--bdev->bd_holders < 0);
-		WARN_ON_ONCE(--bdev->bd_contains->bd_holders < 0);
+		WARN_ON_ONCE(--whole->bd_holders < 0);
 
-		/* bd_contains might point to self, check in a separate step */
 		if ((bdev_free = !bdev->bd_holders))
 			bdev->bd_holder = NULL;
-		if (!bdev->bd_contains->bd_holders)
-			bdev->bd_contains->bd_holder = NULL;
+		if (!whole->bd_holders)
+			whole->bd_holder = NULL;
 
 		spin_unlock(&bdev_lock);
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 0069bee992063e..453b940b87d8e9 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -32,7 +32,6 @@  struct block_device {
 #ifdef CONFIG_SYSFS
 	struct list_head	bd_holder_disks;
 #endif
-	struct block_device *	bd_contains;
 	u8			bd_partno;
 	struct hd_struct *	bd_part;
 	/* number of times partitions within this device have been opened. */
@@ -48,6 +47,9 @@  struct block_device {
 	struct mutex		bd_fsfreeze_mutex;
 } __randomize_layout;
 
+#define bdev_whole(_bdev) \
+	((_bdev)->bd_disk->part0.bdev)
+
 #define bdev_kobj(_bdev) \
 	(&part_to_dev((_bdev)->bd_part)->kobj)