Re: [PATCH 1/8] block: add a helper function to read nr_setcs

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On 6/13/19 7:59 AM, Chaitanya Kulkarni wrote:
This patch introduces helper function to read the number of sectors
from struct block_device->bd_part member. For more details Please refer
to the comment in the include/linux/genhd.h for part_nr_sects_read().

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
---
  include/linux/blkdev.h | 12 ++++++++++++
  1 file changed, 12 insertions(+)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 592669bcc536..1ae65107182a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1475,6 +1475,18 @@ static inline void put_dev_sector(Sector p)
  	put_page(p.v);
  }
+/* Helper function to read the bdev->bd_part->nr_sects */
+static inline sector_t bdev_nr_sects(struct block_device *bdev)
+{
+	sector_t nr_sects;
+
+	rcu_read_lock();
+	nr_sects = part_nr_sects_read(bdev->bd_part);
+	rcu_read_unlock();
+
+	return nr_sects;
+}
+
  int kblockd_schedule_work(struct work_struct *work);
  int kblockd_schedule_work_on(int cpu, struct work_struct *work);
  int kblockd_mod_delayed_work_on(int cpu, struct delayed_work *dwork, unsigned long delay);


Please explain what makes you think that part_nr_sects_read() must be protected by an RCU read lock.

Thanks,

Bart.



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