diff mbox series

[14/20] block: remove the nr_sects field in struct hd_struct

Message ID 20201118084800.2339180-15-hch@lst.de (mailing list archive)
State New
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 the hd_struct always has a block device attached to it, there is
no need for having two size field that just get out of sync.

Additional the field in hd_struct did not use proper serializiation,
possibly allowing for torn writes.  By only using the block_device field
this problem also gets fixed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/bio.c                        |  2 +-
 block/blk-core.c                   |  2 +-
 block/blk.h                        | 53 ----------------------
 block/genhd.c                      | 34 +++++++-------
 block/partitions/core.c            | 17 ++++---
 drivers/block/loop.c               |  1 -
 drivers/block/nbd.c                |  2 +-
 drivers/block/xen-blkback/common.h |  4 +-
 drivers/md/bcache/super.c          |  2 +-
 drivers/s390/block/dasd_ioctl.c    |  4 +-
 drivers/target/target_core_pscsi.c |  7 +--
 fs/block_dev.c                     | 73 +-----------------------------
 fs/f2fs/super.c                    |  2 +-
 fs/pstore/blk.c                    |  2 +-
 include/linux/genhd.h              | 29 +++---------
 kernel/trace/blktrace.c            |  2 +-
 16 files changed, 47 insertions(+), 189 deletions(-)

Comments

Jan Kara Nov. 19, 2020, 12:05 p.m. UTC | #1
On Wed 18-11-20 09:47:54, Christoph Hellwig wrote:
> Now that the hd_struct always has a block device attached to it, there is
> no need for having two size field that just get out of sync.
> 
> Additional the field in hd_struct did not use proper serializiation,
> possibly allowing for torn writes.  By only using the block_device field
> this problem also gets fixed.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Overall the patch looks good but I have a couple of comments below.

> diff --git a/block/bio.c b/block/bio.c
> index fa01bef35bb1fe..0c5269997434d6 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -613,7 +613,7 @@ void guard_bio_eod(struct bio *bio)
>  	rcu_read_lock();
>  	part = __disk_get_part(bio->bi_disk, bio->bi_partno);
>  	if (part)
> -		maxsector = part_nr_sects_read(part);
> +		maxsector = bdev_nr_sectors(part->bdev);
>  	else
>  		maxsector = get_capacity(bio->bi_disk);

I have to say that after these changes I find it a bit confusing that we
have get/set_capacity() and bdev_nr_sectors() / bdev_set_nr_sectors() and
they are all the same thing (i_size of the bdev). Is there a reason for the
distinction?

> diff --git a/block/genhd.c b/block/genhd.c
> index 94de95287a6370..e101b6843f7437 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -38,6 +38,16 @@ static void disk_add_events(struct gendisk *disk);
>  static void disk_del_events(struct gendisk *disk);
>  static void disk_release_events(struct gendisk *disk);
>  
> +void set_capacity(struct gendisk *disk, sector_t sectors)
> +{
> +	struct block_device *bdev = disk->part0.bdev;
> +
> +	spin_lock(&bdev->bd_size_lock);
> +	i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
> +	spin_unlock(&bdev->bd_size_lock);

AFAICT bd_size_lock is pointless after these changes so we can just remove
it?

> +}
> +EXPORT_SYMBOL(set_capacity);
> +
>  /*
>   * Set disk capacity and notify if the size is not currently zero and will not
>   * be set to zero.  Returns true if a uevent was sent, otherwise false.
> @@ -47,11 +57,12 @@ bool set_capacity_and_notify(struct gendisk *disk, sector_t size)
>  	sector_t capacity = get_capacity(disk);
>  
>  	set_capacity(disk, size);
> -	revalidate_disk_size(disk, true);
>  
>  	if (capacity != size && capacity != 0 && size != 0) {
>  		char *envp[] = { "RESIZE=1", NULL };
>  
> +		pr_info("%s: detected capacity change from %lld to %lld\n",
> +		       disk->disk_name, size, capacity);

So we are now missing above message for transitions from / to 0 capacity?
Is there any other notification in the kernel log when e.g. media is
inserted into a CD-ROM drive? I remember using these messages for detecting
that...

Also what about GENHD_FL_HIDDEN devices? Are we sure we never set capacity
for them?

>  		kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
>  		return true;
>  	}

...

> @@ -983,7 +994,7 @@ void __init printk_all_partitions(void)
>  
>  			printk("%s%s %10llu %s %s", is_part0 ? "" : "  ",
>  			       bdevt_str(part_devt(part), devt_buf),
> -			       (unsigned long long)part_nr_sects_read(part) >> 1
> +			       bdev_nr_sectors(part->bdev) >> 1
>  			       , disk_name(disk, part->partno, name_buf),
>  			       part->info ? part->info->uuid : "");
>  			if (is_part0) {
> @@ -1076,7 +1087,7 @@ static int show_partition(struct seq_file *seqf, void *v)
>  	while ((part = disk_part_iter_next(&piter)))
>  		seq_printf(seqf, "%4d  %7d %10llu %s\n",
>  			   MAJOR(part_devt(part)), MINOR(part_devt(part)),
> -			   (unsigned long long)part_nr_sects_read(part) >> 1,
> +			   bdev_nr_sectors(part->bdev) >> 1,
>  			   disk_name(sgp, part->partno, buf));
>  	disk_part_iter_exit(&piter);
>  
> @@ -1158,8 +1169,7 @@ ssize_t part_size_show(struct device *dev,
>  {
>  	struct hd_struct *p = dev_to_part(dev);
>  
> -	return sprintf(buf, "%llu\n",
> -		(unsigned long long)part_nr_sects_read(p));
> +	return sprintf(buf, "%llu\n", bdev_nr_sectors(p->bdev));

Is sector_t really guaranteed to be unsigned long long?

								Honza
Christoph Hellwig Nov. 20, 2020, 9:08 a.m. UTC | #2
On Thu, Nov 19, 2020 at 01:05:25PM +0100, Jan Kara wrote:
> > @@ -613,7 +613,7 @@ void guard_bio_eod(struct bio *bio)
> >  	rcu_read_lock();
> >  	part = __disk_get_part(bio->bi_disk, bio->bi_partno);
> >  	if (part)
> > -		maxsector = part_nr_sects_read(part);
> > +		maxsector = bdev_nr_sectors(part->bdev);
> >  	else
> >  		maxsector = get_capacity(bio->bi_disk);
> 
> I have to say that after these changes I find it a bit confusing that we
> have get/set_capacity() and bdev_nr_sectors() / bdev_set_nr_sectors() and
> they are all the same thing (i_size of the bdev). Is there a reason for the
> distinction?

get_capacity/set_capacity are the existing unchanged interfaces that
work on struct gendisk, and unchanged from what we had before.  They also
have lots of users which makes them kinda awkward to touch.

bdev_nr_sectors is the public interface to query the size for any
kind of struct block device, to be used by consumers of the block
device interface.

bdev_set_nr_sectors is a private helper for the partitions core that
avoids duplicating a bit of code, and works on partitions.



> > @@ -38,6 +38,16 @@ static void disk_add_events(struct gendisk *disk);
> >  static void disk_del_events(struct gendisk *disk);
> >  static void disk_release_events(struct gendisk *disk);
> >  
> > +void set_capacity(struct gendisk *disk, sector_t sectors)
> > +{
> > +	struct block_device *bdev = disk->part0.bdev;
> > +
> > +	spin_lock(&bdev->bd_size_lock);
> > +	i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
> > +	spin_unlock(&bdev->bd_size_lock);
> 
> AFAICT bd_size_lock is pointless after these changes so we can just remove
> it?

I don't think it is, as reuqiring bd_mutex for size updates leads to
rather awkward lock ordering problems.

> >  	if (capacity != size && capacity != 0 && size != 0) {
> >  		char *envp[] = { "RESIZE=1", NULL };
> >  
> > +		pr_info("%s: detected capacity change from %lld to %lld\n",
> > +		       disk->disk_name, size, capacity);
> 
> So we are now missing above message for transitions from / to 0 capacity?
> Is there any other notification in the kernel log when e.g. media is
> inserted into a CD-ROM drive? I remember using these messages for detecting
> that...

True, I guess we should keep the messages for that case at least under
some circumstances.  Let me take a closer look at what could make sense.

> Also what about GENHD_FL_HIDDEN devices? Are we sure we never set capacity
> for them?

We absolutely set the capacity for them, as we have to.  And even use
this interface.  But yes, I think we should skip sending the uevent for
them.

> > @@ -1158,8 +1169,7 @@ ssize_t part_size_show(struct device *dev,
> >  {
> >  	struct hd_struct *p = dev_to_part(dev);
> >  
> > -	return sprintf(buf, "%llu\n",
> > -		(unsigned long long)part_nr_sects_read(p));
> > +	return sprintf(buf, "%llu\n", bdev_nr_sectors(p->bdev));
> 
> Is sector_t really guaranteed to be unsigned long long?

Yes, it is these days, ever since I removed the option to have a 32-bit
one on 32-bit platforms a while ago.
Jan Kara Nov. 20, 2020, 11:21 a.m. UTC | #3
On Fri 20-11-20 10:08:20, Christoph Hellwig wrote:
> On Thu, Nov 19, 2020 at 01:05:25PM +0100, Jan Kara wrote:
> > > @@ -613,7 +613,7 @@ void guard_bio_eod(struct bio *bio)
> > >  	rcu_read_lock();
> > >  	part = __disk_get_part(bio->bi_disk, bio->bi_partno);
> > >  	if (part)
> > > -		maxsector = part_nr_sects_read(part);
> > > +		maxsector = bdev_nr_sectors(part->bdev);
> > >  	else
> > >  		maxsector = get_capacity(bio->bi_disk);
> > 
> > I have to say that after these changes I find it a bit confusing that we
> > have get/set_capacity() and bdev_nr_sectors() / bdev_set_nr_sectors() and
> > they are all the same thing (i_size of the bdev). Is there a reason for the
> > distinction?
> 
> get_capacity/set_capacity are the existing unchanged interfaces that
> work on struct gendisk, and unchanged from what we had before.  They also
> have lots of users which makes them kinda awkward to touch.
> 
> bdev_nr_sectors is the public interface to query the size for any
> kind of struct block device, to be used by consumers of the block
> device interface.
> 
> bdev_set_nr_sectors is a private helper for the partitions core that
> avoids duplicating a bit of code, and works on partitions.

OK, I guess I'll get used to this...

> > > @@ -38,6 +38,16 @@ static void disk_add_events(struct gendisk *disk);
> > >  static void disk_del_events(struct gendisk *disk);
> > >  static void disk_release_events(struct gendisk *disk);
> > >  
> > > +void set_capacity(struct gendisk *disk, sector_t sectors)
> > > +{
> > > +	struct block_device *bdev = disk->part0.bdev;
> > > +
> > > +	spin_lock(&bdev->bd_size_lock);
> > > +	i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
> > > +	spin_unlock(&bdev->bd_size_lock);
> > 
> > AFAICT bd_size_lock is pointless after these changes so we can just remove
> > it?
> 
> I don't think it is, as reuqiring bd_mutex for size updates leads to
> rather awkward lock ordering problems.

OK, let me ask differently: What is bd_size_lock protecting now? Ah, I see,
on 32-bit it is needed to prevent torn writes to i_size, right?

> > >  	if (capacity != size && capacity != 0 && size != 0) {
> > >  		char *envp[] = { "RESIZE=1", NULL };
> > >  
> > > +		pr_info("%s: detected capacity change from %lld to %lld\n",
> > > +		       disk->disk_name, size, capacity);
> > 
> > So we are now missing above message for transitions from / to 0 capacity?
> > Is there any other notification in the kernel log when e.g. media is
> > inserted into a CD-ROM drive? I remember using these messages for detecting
> > that...
> 
> True, I guess we should keep the messages for that case at least under
> some circumstances.  Let me take a closer look at what could make sense.
> 
> > Also what about GENHD_FL_HIDDEN devices? Are we sure we never set capacity
> > for them?
> 
> We absolutely set the capacity for them, as we have to.  And even use
> this interface.  But yes, I think we should skip sending the uevent for
> them.

Also previously we were not printing any messages for hidden devices and
now we do. I'm not sure whether that's intended or not.

								Honza
Christoph Hellwig Nov. 20, 2020, 3:32 p.m. UTC | #4
On Fri, Nov 20, 2020 at 12:21:21PM +0100, Jan Kara wrote:
> > > AFAICT bd_size_lock is pointless after these changes so we can just remove
> > > it?
> > 
> > I don't think it is, as reuqiring bd_mutex for size updates leads to
> > rather awkward lock ordering problems.
> 
> OK, let me ask differently: What is bd_size_lock protecting now? Ah, I see,
> on 32-bit it is needed to prevent torn writes to i_size, right?

Exactly.  In theory we could skip it for 64-bit, but as updating the
size isn't a fast path, and struct block_device isn't super size critical
I'd rather keep the same code for 32 vs 64-bit builds.
Matthew Wilcox Nov. 20, 2020, 3:59 p.m. UTC | #5
On Fri, Nov 20, 2020 at 04:32:53PM +0100, Christoph Hellwig wrote:
> On Fri, Nov 20, 2020 at 12:21:21PM +0100, Jan Kara wrote:
> > > > AFAICT bd_size_lock is pointless after these changes so we can just remove
> > > > it?
> > > 
> > > I don't think it is, as reuqiring bd_mutex for size updates leads to
> > > rather awkward lock ordering problems.
> > 
> > OK, let me ask differently: What is bd_size_lock protecting now? Ah, I see,
> > on 32-bit it is needed to prevent torn writes to i_size, right?
> 
> Exactly.  In theory we could skip it for 64-bit, but as updating the
> size isn't a fast path, and struct block_device isn't super size critical
> I'd rather keep the same code for 32 vs 64-bit builds.

Is it better to switch to i_size_write() / i_size_read()?
Christoph Hellwig Nov. 20, 2020, 4:01 p.m. UTC | #6
On Fri, Nov 20, 2020 at 03:59:56PM +0000, Matthew Wilcox wrote:
> > Exactly.  In theory we could skip it for 64-bit, but as updating the
> > size isn't a fast path, and struct block_device isn't super size critical
> > I'd rather keep the same code for 32 vs 64-bit builds.
> 
> Is it better to switch to i_size_write() / i_size_read()?

I think we've stopped updating the size from contexts that can't block,
so it is worth pursuing. I'd rather do it after this series is done
and merged, though.
Jan Kara Nov. 20, 2020, 8:05 p.m. UTC | #7
On Fri 20-11-20 15:59:56, Matthew Wilcox wrote:
> On Fri, Nov 20, 2020 at 04:32:53PM +0100, Christoph Hellwig wrote:
> > On Fri, Nov 20, 2020 at 12:21:21PM +0100, Jan Kara wrote:
> > > > > AFAICT bd_size_lock is pointless after these changes so we can just remove
> > > > > it?
> > > > 
> > > > I don't think it is, as reuqiring bd_mutex for size updates leads to
> > > > rather awkward lock ordering problems.
> > > 
> > > OK, let me ask differently: What is bd_size_lock protecting now? Ah, I see,
> > > on 32-bit it is needed to prevent torn writes to i_size, right?
> > 
> > Exactly.  In theory we could skip it for 64-bit, but as updating the
> > size isn't a fast path, and struct block_device isn't super size critical
> > I'd rather keep the same code for 32 vs 64-bit builds.
> 
> Is it better to switch to i_size_write() / i_size_read()?

The code is already switched to it AFAICT (the lock is really only used in
the two places that write i_size). But the problem is that in theory two
i_size_write() calls can race in a way that the resulting stored i_size is a
mix of two stored sizes. Now I have hard time imagining how this could
happen for a block device and if two reconfigurations of a block device
could race like that we'd have a large problems anyway...

								Honza
Christoph Hellwig Nov. 21, 2020, 4:24 p.m. UTC | #8
On Fri, Nov 20, 2020 at 09:05:48PM +0100, Jan Kara wrote:
> The code is already switched to it AFAICT (the lock is really only used in
> the two places that write i_size). But the problem is that in theory two
> i_size_write() calls can race in a way that the resulting stored i_size is a
> mix of two stored sizes. Now I have hard time imagining how this could
> happen for a block device and if two reconfigurations of a block device
> could race like that we'd have a large problems anyway...

Now that you mention it, yes - i_size_write needs to be under i_rwsem
or an equivalent lock.  We could look into using i_rwsem also for block
device, but for now the spinlock seems to be doing fine.  Note that
in current mainline we only have such a lock protecting i_size of the
block_device inode, but none for the size in hd_struct.
diff mbox series

Patch

diff --git a/block/bio.c b/block/bio.c
index fa01bef35bb1fe..0c5269997434d6 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -613,7 +613,7 @@  void guard_bio_eod(struct bio *bio)
 	rcu_read_lock();
 	part = __disk_get_part(bio->bi_disk, bio->bi_partno);
 	if (part)
-		maxsector = part_nr_sects_read(part);
+		maxsector = bdev_nr_sectors(part->bdev);
 	else
 		maxsector = get_capacity(bio->bi_disk);
 	rcu_read_unlock();
diff --git a/block/blk-core.c b/block/blk-core.c
index 2db8bda43b6e6d..988f45094a387b 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -755,7 +755,7 @@  static inline int blk_partition_remap(struct bio *bio)
 		goto out;
 
 	if (bio_sectors(bio)) {
-		if (bio_check_eod(bio, part_nr_sects_read(p)))
+		if (bio_check_eod(bio, bdev_nr_sectors(p->bdev)))
 			goto out;
 		bio->bi_iter.bi_sector += p->start_sect;
 		trace_block_bio_remap(bio->bi_disk->queue, bio, part_devt(p),
diff --git a/block/blk.h b/block/blk.h
index c4839abcfa27eb..09cee7024fb43e 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -387,59 +387,6 @@  static inline void hd_free_part(struct hd_struct *part)
 	percpu_ref_exit(&part->ref);
 }
 
-/*
- * Any access of part->nr_sects which is not protected by partition
- * bd_mutex or gendisk bdev bd_mutex, should be done using this
- * accessor function.
- *
- * Code written along the lines of i_size_read() and i_size_write().
- * CONFIG_PREEMPTION case optimizes the case of UP kernel with preemption
- * on.
- */
-static inline sector_t part_nr_sects_read(struct hd_struct *part)
-{
-#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
-	sector_t nr_sects;
-	unsigned seq;
-	do {
-		seq = read_seqcount_begin(&part->nr_sects_seq);
-		nr_sects = part->nr_sects;
-	} while (read_seqcount_retry(&part->nr_sects_seq, seq));
-	return nr_sects;
-#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
-	sector_t nr_sects;
-
-	preempt_disable();
-	nr_sects = part->nr_sects;
-	preempt_enable();
-	return nr_sects;
-#else
-	return part->nr_sects;
-#endif
-}
-
-/*
- * Should be called with mutex lock held (typically bd_mutex) of partition
- * to provide mutual exlusion among writers otherwise seqcount might be
- * left in wrong state leaving the readers spinning infinitely.
- */
-static inline void part_nr_sects_write(struct hd_struct *part, sector_t size)
-{
-#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
-	preempt_disable();
-	write_seqcount_begin(&part->nr_sects_seq);
-	part->nr_sects = size;
-	write_seqcount_end(&part->nr_sects_seq);
-	preempt_enable();
-#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPTION)
-	preempt_disable();
-	part->nr_sects = size;
-	preempt_enable();
-#else
-	part->nr_sects = size;
-#endif
-}
-
 int bio_add_hw_page(struct request_queue *q, struct bio *bio,
 		struct page *page, unsigned int len, unsigned int offset,
 		unsigned int max_sectors, bool *same_page);
diff --git a/block/genhd.c b/block/genhd.c
index 94de95287a6370..e101b6843f7437 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -38,6 +38,16 @@  static void disk_add_events(struct gendisk *disk);
 static void disk_del_events(struct gendisk *disk);
 static void disk_release_events(struct gendisk *disk);
 
+void set_capacity(struct gendisk *disk, sector_t sectors)
+{
+	struct block_device *bdev = disk->part0.bdev;
+
+	spin_lock(&bdev->bd_size_lock);
+	i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
+	spin_unlock(&bdev->bd_size_lock);
+}
+EXPORT_SYMBOL(set_capacity);
+
 /*
  * Set disk capacity and notify if the size is not currently zero and will not
  * be set to zero.  Returns true if a uevent was sent, otherwise false.
@@ -47,11 +57,12 @@  bool set_capacity_and_notify(struct gendisk *disk, sector_t size)
 	sector_t capacity = get_capacity(disk);
 
 	set_capacity(disk, size);
-	revalidate_disk_size(disk, true);
 
 	if (capacity != size && capacity != 0 && size != 0) {
 		char *envp[] = { "RESIZE=1", NULL };
 
+		pr_info("%s: detected capacity change from %lld to %lld\n",
+		       disk->disk_name, size, capacity);
 		kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
 		return true;
 	}
@@ -245,7 +256,7 @@  struct hd_struct *disk_part_iter_next(struct disk_part_iter *piter)
 		part = rcu_dereference(ptbl->part[piter->idx]);
 		if (!part)
 			continue;
-		if (!part_nr_sects_read(part) &&
+		if (!bdev_nr_sectors(part->bdev) &&
 		    !(piter->flags & DISK_PITER_INCL_EMPTY) &&
 		    !(piter->flags & DISK_PITER_INCL_EMPTY_PART0 &&
 		      piter->idx == 0))
@@ -282,7 +293,7 @@  EXPORT_SYMBOL_GPL(disk_part_iter_exit);
 static inline int sector_in_part(struct hd_struct *part, sector_t sector)
 {
 	return part->start_sect <= sector &&
-		sector < part->start_sect + part_nr_sects_read(part);
+		sector < part->start_sect + bdev_nr_sectors(part->bdev);
 }
 
 /**
@@ -983,7 +994,7 @@  void __init printk_all_partitions(void)
 
 			printk("%s%s %10llu %s %s", is_part0 ? "" : "  ",
 			       bdevt_str(part_devt(part), devt_buf),
-			       (unsigned long long)part_nr_sects_read(part) >> 1
+			       bdev_nr_sectors(part->bdev) >> 1
 			       , disk_name(disk, part->partno, name_buf),
 			       part->info ? part->info->uuid : "");
 			if (is_part0) {
@@ -1076,7 +1087,7 @@  static int show_partition(struct seq_file *seqf, void *v)
 	while ((part = disk_part_iter_next(&piter)))
 		seq_printf(seqf, "%4d  %7d %10llu %s\n",
 			   MAJOR(part_devt(part)), MINOR(part_devt(part)),
-			   (unsigned long long)part_nr_sects_read(part) >> 1,
+			   bdev_nr_sectors(part->bdev) >> 1,
 			   disk_name(sgp, part->partno, buf));
 	disk_part_iter_exit(&piter);
 
@@ -1158,8 +1169,7 @@  ssize_t part_size_show(struct device *dev,
 {
 	struct hd_struct *p = dev_to_part(dev);
 
-	return sprintf(buf, "%llu\n",
-		(unsigned long long)part_nr_sects_read(p));
+	return sprintf(buf, "%llu\n", bdev_nr_sectors(p->bdev));
 }
 
 ssize_t part_stat_show(struct device *dev,
@@ -1616,16 +1626,6 @@  struct gendisk *__alloc_disk_node(int minors, int node_id)
 	ptbl = rcu_dereference_protected(disk->part_tbl, 1);
 	rcu_assign_pointer(ptbl->part[0], &disk->part0);
 
-	/*
-	 * set_capacity() and get_capacity() currently don't use
-	 * seqcounter to read/update the part0->nr_sects. Still init
-	 * the counter as we can read the sectors in IO submission
-	 * patch using seqence counters.
-	 *
-	 * TODO: Ideally set_capacity() and get_capacity() should be
-	 * converted to make use of bd_mutex and sequence counters.
-	 */
-	hd_sects_seq_init(&disk->part0);
 	if (hd_ref_init(&disk->part0)) {
 		hd_free_part(&disk->part0);
 		return NULL;
diff --git a/block/partitions/core.c b/block/partitions/core.c
index 0ba0bf44b88af3..aae857c22af05d 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -85,6 +85,13 @@  static int (*check_part[])(struct parsed_partitions *) = {
 	NULL
 };
 
+static void bdev_set_nr_sectors(struct block_device *bdev, sector_t sectors)
+{
+	spin_lock(&bdev->bd_size_lock);
+	i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
+	spin_unlock(&bdev->bd_size_lock);
+}
+
 static struct parsed_partitions *allocate_partitions(struct gendisk *hd)
 {
 	struct parsed_partitions *state;
@@ -295,7 +302,7 @@  static void hd_struct_free_work(struct work_struct *work)
 	put_device(disk_to_dev(disk));
 
 	part->start_sect = 0;
-	part->nr_sects = 0;
+	bdev_set_nr_sectors(part->bdev, 0);
 	part_stat_set_all(part, 0);
 	put_device(part_to_dev(part));
 }
@@ -410,11 +417,10 @@  static struct hd_struct *add_partition(struct gendisk *disk, int partno,
 	if (!p->bdev)
 		goto out_free_stats;
 
-	hd_sects_seq_init(p);
 	pdev = part_to_dev(p);
 
 	p->start_sect = start;
-	p->nr_sects = len;
+	bdev_set_nr_sectors(p->bdev, len);
 	p->partno = partno;
 	p->policy = get_disk_ro(disk);
 
@@ -508,7 +514,7 @@  static bool partition_overlaps(struct gendisk *disk, sector_t start,
 	disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
 	while ((part = disk_part_iter_next(&piter))) {
 		if (part->partno == skip_partno ||
-		    start >= part->start_sect + part->nr_sects ||
+		    start >= part->start_sect + bdev_nr_sectors(part->bdev) ||
 		    start + length <= part->start_sect)
 			continue;
 		overlap = true;
@@ -599,8 +605,7 @@  int bdev_resize_partition(struct block_device *bdev, int partno,
 	if (partition_overlaps(bdev->bd_disk, start, length, partno))
 		goto out_unlock;
 
-	part_nr_sects_write(part, length);
-	bd_set_nr_sectors(bdevp, length);
+	bdev_set_nr_sectors(bdevp, length);
 
 	ret = 0;
 out_unlock:
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 599e94a7e69259..9d2587f6167cd8 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1243,7 +1243,6 @@  static int __loop_clr_fd(struct loop_device *lo, bool release)
 	set_capacity(lo->lo_disk, 0);
 	loop_sysfs_exit(lo);
 	if (bdev) {
-		bd_set_nr_sectors(bdev, 0);
 		/* let user-space know about this change */
 		kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
 	}
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 45b0423ef2c53d..014683968ce174 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1132,7 +1132,7 @@  static void nbd_bdev_reset(struct block_device *bdev)
 {
 	if (bdev->bd_openers > 1)
 		return;
-	bd_set_nr_sectors(bdev, 0);
+	set_capacity(bdev->bd_disk, 0);
 }
 
 static void nbd_parse_flags(struct nbd_device *nbd)
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index c6ea5d38c509a6..0762db247b41b3 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -358,9 +358,7 @@  struct pending_req {
 };
 
 
-#define vbd_sz(_v)	((_v)->bdev->bd_part ? \
-			 (_v)->bdev->bd_part->nr_sects : \
-			  get_capacity((_v)->bdev->bd_disk))
+#define vbd_sz(_v)	bdev_nr_sectors((_v)->bdev)
 
 #define xen_blkif_get(_b) (atomic_inc(&(_b)->refcnt))
 #define xen_blkif_put(_b)				\
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index a6a5e21e4fd136..e5db2cdd114112 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1408,7 +1408,7 @@  static int cached_dev_init(struct cached_dev *dc, unsigned int block_size)
 			q->limits.raid_partial_stripes_expensive;
 
 	ret = bcache_device_init(&dc->disk, block_size,
-			 dc->bdev->bd_part->nr_sects - dc->sb.data_offset,
+			 bdev_nr_sectors(dc->bdev) - dc->sb.data_offset,
 			 dc->bdev, &bcache_cached_ops);
 	if (ret)
 		return ret;
diff --git a/drivers/s390/block/dasd_ioctl.c b/drivers/s390/block/dasd_ioctl.c
index 3359559517bfcf..304eba1acf163c 100644
--- a/drivers/s390/block/dasd_ioctl.c
+++ b/drivers/s390/block/dasd_ioctl.c
@@ -54,8 +54,6 @@  dasd_ioctl_enable(struct block_device *bdev)
 		return -ENODEV;
 
 	dasd_enable_device(base);
-	/* Formatting the dasd device can change the capacity. */
-	bd_set_nr_sectors(bdev, get_capacity(base->block->gdp));
 	dasd_put_device(base);
 	return 0;
 }
@@ -88,7 +86,7 @@  dasd_ioctl_disable(struct block_device *bdev)
 	 * Set i_size to zero, since read, write, etc. check against this
 	 * value.
 	 */
-	bd_set_nr_sectors(bdev, 0);
+	set_capacity(bdev->bd_disk, 0);
 	dasd_put_device(base);
 	return 0;
 }
diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index 4e37fa9b409d52..a70c33c49f0960 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -1027,12 +1027,7 @@  static u32 pscsi_get_device_type(struct se_device *dev)
 
 static sector_t pscsi_get_blocks(struct se_device *dev)
 {
-	struct pscsi_dev_virt *pdv = PSCSI_DEV(dev);
-
-	if (pdv->pdv_bd && pdv->pdv_bd->bd_part)
-		return pdv->pdv_bd->bd_part->nr_sects;
-
-	return 0;
+	return bdev_nr_sectors(PSCSI_DEV(dev)->pdv_bd);
 }
 
 static void pscsi_req_done(struct request *req, blk_status_t status)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 258a1ced924483..a5a2ac4ca1ce9c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1278,70 +1278,6 @@  void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
 EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
 #endif
 
-/**
- * check_disk_size_change - checks for disk size change and adjusts bdev size.
- * @disk: struct gendisk to check
- * @bdev: struct bdev to adjust.
- * @verbose: if %true log a message about a size change if there is any
- *
- * This routine checks to see if the bdev size does not match the disk size
- * and adjusts it if it differs. When shrinking the bdev size, its all caches
- * are freed.
- */
-static void check_disk_size_change(struct gendisk *disk,
-		struct block_device *bdev, bool verbose)
-{
-	loff_t disk_size, bdev_size;
-
-	spin_lock(&bdev->bd_size_lock);
-	disk_size = (loff_t)get_capacity(disk) << 9;
-	bdev_size = i_size_read(bdev->bd_inode);
-	if (disk_size != bdev_size) {
-		if (verbose) {
-			printk(KERN_INFO
-			       "%s: detected capacity change from %lld to %lld\n",
-			       disk->disk_name, bdev_size, disk_size);
-		}
-		i_size_write(bdev->bd_inode, disk_size);
-	}
-	spin_unlock(&bdev->bd_size_lock);
-}
-
-/**
- * revalidate_disk_size - checks for disk size change and adjusts bdev size.
- * @disk: struct gendisk to check
- * @verbose: if %true log a message about a size change if there is any
- *
- * This routine checks to see if the bdev size does not match the disk size
- * and adjusts it if it differs. When shrinking the bdev size, its all caches
- * are freed.
- */
-void revalidate_disk_size(struct gendisk *disk, bool verbose)
-{
-	struct block_device *bdev;
-
-	/*
-	 * Hidden disks don't have associated bdev so there's no point in
-	 * revalidating them.
-	 */
-	if (disk->flags & GENHD_FL_HIDDEN)
-		return;
-
-	bdev = bdget_disk(disk, 0);
-	if (bdev) {
-		check_disk_size_change(disk, bdev, verbose);
-		bdput(bdev);
-	}
-}
-
-void bd_set_nr_sectors(struct block_device *bdev, sector_t sectors)
-{
-	spin_lock(&bdev->bd_size_lock);
-	i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
-	spin_unlock(&bdev->bd_size_lock);
-}
-EXPORT_SYMBOL(bd_set_nr_sectors);
-
 static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
 
 int bdev_disk_changed(struct block_device *bdev, bool invalidate)
@@ -1375,8 +1311,6 @@  int bdev_disk_changed(struct block_device *bdev, bool invalidate)
 			disk->fops->revalidate_disk(disk);
 	}
 
-	check_disk_size_change(disk, bdev, !invalidate);
-
 	if (get_capacity(disk)) {
 		ret = blk_add_partitions(disk, bdev);
 		if (ret == -EAGAIN)
@@ -1474,10 +1408,8 @@  static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
 					need_restart = true;
 			}
 
-			if (!ret) {
-				bd_set_nr_sectors(bdev, get_capacity(disk));
+			if (!ret)
 				set_init_blocksize(bdev);
-			}
 
 			/*
 			 * If the device is invalidated, rescan partition
@@ -1499,11 +1431,10 @@  static int __blkdev_get(struct block_device *bdev, fmode_t mode, void *holder,
 			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) {
+			    !bdev->bd_part || !bdev_nr_sectors(bdev)) {
 				ret = -ENXIO;
 				goto out_clear;
 			}
-			bd_set_nr_sectors(bdev, bdev->bd_part->nr_sects);
 			set_init_blocksize(bdev);
 		}
 
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 00eff2f5180790..d4e7fab352bacb 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3151,7 +3151,7 @@  static int f2fs_report_zone_cb(struct blk_zone *zone, unsigned int idx,
 static int init_blkz_info(struct f2fs_sb_info *sbi, int devi)
 {
 	struct block_device *bdev = FDEV(devi).bdev;
-	sector_t nr_sectors = bdev->bd_part->nr_sects;
+	sector_t nr_sectors = bdev_nr_sectors(bdev);
 	struct f2fs_report_zones_args rep_zone_arg;
 	int ret;
 
diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
index fcd5563dde063c..777a26f7bbe2aa 100644
--- a/fs/pstore/blk.c
+++ b/fs/pstore/blk.c
@@ -245,7 +245,7 @@  static struct block_device *psblk_get_bdev(void *holder,
 			return bdev;
 	}
 
-	nr_sects = part_nr_sects_read(bdev->bd_part);
+	nr_sects = bdev_nr_sectors(bdev);
 	if (!nr_sects) {
 		pr_err("not enough space for '%s'\n", blkdev);
 		blkdev_put(bdev, mode);
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index ab5fca99764e7a..e01618dfafc05c 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -52,15 +52,6 @@  struct partition_meta_info {
 
 struct hd_struct {
 	sector_t start_sect;
-	/*
-	 * nr_sects is protected by sequence counter. One might extend a
-	 * partition while IO is happening to it and update of nr_sects
-	 * can be non-atomic on 32bit machines with 64bit sector_t.
-	 */
-	sector_t nr_sects;
-#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
-	seqcount_t nr_sects_seq;
-#endif
 	unsigned long stamp;
 	struct disk_stats __percpu *dkstats;
 	struct percpu_ref ref;
@@ -259,13 +250,6 @@  static inline void disk_put_part(struct hd_struct *part)
 		put_device(part_to_dev(part));
 }
 
-static inline void hd_sects_seq_init(struct hd_struct *p)
-{
-#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
-	seqcount_init(&p->nr_sects_seq);
-#endif
-}
-
 /*
  * Smarter partition iterator without context limits.
  */
@@ -323,13 +307,15 @@  static inline sector_t get_start_sect(struct block_device *bdev)
 {
 	return bdev->bd_part->start_sect;
 }
-static inline sector_t get_capacity(struct gendisk *disk)
+	
+static inline sector_t bdev_nr_sectors(struct block_device *bdev)
 {
-	return disk->part0.nr_sects;
+	return i_size_read(bdev->bd_inode) >> 9;
 }
-static inline void set_capacity(struct gendisk *disk, sector_t size)
+	
+static inline sector_t get_capacity(struct gendisk *disk)
 {
-	disk->part0.nr_sects = size;
+	return bdev_nr_sectors(disk->part0.bdev);
 }
 
 int bdev_disk_changed(struct block_device *bdev, bool invalidate);
@@ -363,10 +349,9 @@  int __register_blkdev(unsigned int major, const char *name,
 	__register_blkdev(major, name, NULL)
 void unregister_blkdev(unsigned int major, const char *name);
 
-void revalidate_disk_size(struct gendisk *disk, bool verbose);
 bool bdev_check_media_change(struct block_device *bdev);
 int __invalidate_device(struct block_device *bdev, bool kill_dirty);
-void bd_set_nr_sectors(struct block_device *bdev, sector_t sectors);
+void set_capacity(struct gendisk *disk, sector_t size);
 
 /* for drivers/char/raw.c: */
 int blkdev_ioctl(struct block_device *, fmode_t, unsigned, unsigned long);
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index f1022945e3460b..7076d588a50d69 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -465,7 +465,7 @@  static void blk_trace_setup_lba(struct blk_trace *bt,
 
 	if (part) {
 		bt->start_lba = part->start_sect;
-		bt->end_lba = part->start_sect + part->nr_sects;
+		bt->end_lba = part->start_sect + bdev_nr_sectors(bdev);
 	} else {
 		bt->start_lba = 0;
 		bt->end_lba = -1ULL;