linux-kernel - [PATCH v1 1/7] block: export blkdev_reread_part() and __blkdev_reread

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Message-Id: <1428508384-29008-2-git-send-email-ming.lei@canonical.com>
Date:	Wed,  8 Apr 2015 23:52:58 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Tejun Heo <tj@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jarod Wilson <jarod@...hat.com>,
	David Herrmann <dh.herrmann@...il.com>,
	Markus Pargmann <mpa@...gutronix.de>,
	nbd-general@...ts.sourceforge.net,
	Stefan Haberland <stefan.haberland@...ibm.com>,
	Sebastian Ott <sebott@...ux.vnet.ibm.com>,
	Fabian Frederick <fabf@...net.be>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-s390@...r.kernel.org, Stefan Weinhuber <wein@...ibm.com>,
	Ming Lei <ming.lei@...onical.com>
Subject: [PATCH v1 1/7] block: export blkdev_reread_part() and __blkdev_reread_part()

From: Jarod Wilson <jarod@...hat.com>

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@...radead.org>
CC: Jens Axboe <axboe@...nel.dk>
CC: Tejun Heo <tj@...nel.org>
CC: Alexander Viro <viro@...iv.linux.org.uk>
CC: Markus Pargmann <mpa@...gutronix.de>
CC: Stefan Weinhuber <wein@...ibm.com>
CC: Stefan Haberland <stefan.haberland@...ibm.com>
CC: Sebastian Ott <sebott@...ux.vnet.ibm.com>
CC: Fabian Frederick <fabf@...net.be>
CC: Ming Lei <ming.lei@...onical.com>
CC: David Herrmann <dh.herrmann@...il.com>
CC: Andrew Morton <akpm@...ux-foundation.org>
CC: Peter Zijlstra <peterz@...radead.org>
CC: nbd-general@...ts.sourceforge.net
CC: linux-s390@...r.kernel.org
Signed-off-by: Jarod Wilson <jarod@...hat.com>
Signed-off-by: Ming Lei <ming.lei@...onical.com>
---
 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);
+}
+EXPORT_SYMBOL(__blkdev_reread_part);
+
+/*
+ * 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);
 	mutex_unlock(&bdev->bd_mutex);
+
 	return res;
 }
+EXPORT_SYMBOL(blkdev_reread_part);
 
 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);
+
 #ifdef CONFIG_SYSFS
 extern int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
 extern void bd_unlink_disk_holder(struct block_device *bdev,
-- 
1.7.9.5

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