[PATCH v1 1/7] block: export blkdev_reread_part() and __blkdev_reread_part()

From: Ming Lei
Date: Wed Apr 08 2015 - 11:53:28 EST

From: Jarod Wilson <jarod@xxxxxxxxxx>

This patch exports blkdev_reread_part() for block drivers, also
introduce __blkdev_reread_part().

For some drivers, such as loop, reread of partitions can be run
from the release path, and bd_mutex may already be held prior to
calling ioctl_by_bdev(bdev, BLKRRPART, 0), so introduce
__blkdev_reread_part for use in such cases.

CC: Christoph Hellwig <hch@xxxxxxxxxxxxx>
CC: Jens Axboe <axboe@xxxxxxxxx>
CC: Tejun Heo <tj@xxxxxxxxxx>
CC: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
CC: Markus Pargmann <mpa@xxxxxxxxxxxxxx>
CC: Stefan Weinhuber <wein@xxxxxxxxxx>
CC: Stefan Haberland <stefan.haberland@xxxxxxxxxx>
CC: Sebastian Ott <sebott@xxxxxxxxxxxxxxxxxx>
CC: Fabian Frederick <fabf@xxxxxxxxx>
CC: Ming Lei <ming.lei@xxxxxxxxxxxxx>
CC: David Herrmann <dh.herrmann@xxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CC: nbd-general@xxxxxxxxxxxxxxxxxxxxx
CC: linux-s390@xxxxxxxxxxxxxxx
Signed-off-by: Jarod Wilson <jarod@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
block/ioctl.c | 28 +++++++++++++++++++++++++---
include/linux/fs.h | 3 +++
2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/block/ioctl.c b/block/ioctl.c
index 7d8befd..203cb4a 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -150,21 +150,43 @@ static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user

-static int blkdev_reread_part(struct block_device *bdev)
+ * This is an exported API for the block driver, and will not
+ * acquire bd_mutex. This API should be used in case that
+ * caller has held bd_mutex already.
+ */
+int __blkdev_reread_part(struct block_device *bdev)
struct gendisk *disk = bdev->bd_disk;
- int res;

if (!disk_part_scan_enabled(disk) || bdev != bdev->bd_contains)
return -EINVAL;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
+ lockdep_assert_held(&bdev->bd_mutex);
+ return rescan_partitions(disk, bdev);
+ * This is an exported API for the block driver, and will
+ * try to acquire bd_mutex. If bd_mutex has been held already
+ * in current context, please call __blkdev_reread_part().
+ */
+int blkdev_reread_part(struct block_device *bdev)
+ int res;
if (!mutex_trylock(&bdev->bd_mutex))
return -EBUSY;
- res = rescan_partitions(disk, bdev);
+ res = __blkdev_reread_part(bdev);
return res;

static int blk_ioctl_discard(struct block_device *bdev, uint64_t start,
uint64_t len, int secure)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4e858fd..dac6354 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2274,6 +2274,9 @@ extern struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
extern struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode,
void *holder);
extern void blkdev_put(struct block_device *bdev, fmode_t mode);
+extern int __blkdev_reread_part(struct block_device *bdev);
+extern int blkdev_reread_part(struct block_device *bdev);
extern int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
extern void bd_unlink_disk_holder(struct block_device *bdev,

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