[PATCH] block: Don't reread partitions of disk which already mouted.

[majianpeng <majianpeng@gmail.com>]

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If reread partitions of disk, the paths are:
blkdev_ioctl->blkdev_reread_part->rescan_partitions->drop_partitions
->invalidate_partition->__invalidate_device
In func __invalidate_device, if disk already mounted, it will do
shrink_dcache_sb and invalidate_inodes.
This operation will effect the fs.
So add a judgement before doing rescan_partiontions to judge disk
whether mounted.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
---
 block/ioctl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/block/ioctl.c b/block/ioctl.c
index a31d91d..374af7e 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -154,11 +154,19 @@ static int blkdev_reread_part(struct block_device *bdev)
 {
 	struct gendisk *disk = bdev->bd_disk;
 	int res;
+	struct super_block *sb;
 
 	if (!disk_part_scan_enabled(disk) || bdev != bdev->bd_contains)
 		return -EINVAL;
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
+
+	sb = get_super(bdev);
+	if (sb) {
+		drop_super(sb);
+		return -EBUSY;
+	}
+
 	if (!mutex_trylock(&bdev->bd_mutex))
 		return -EBUSY;
 	res = rescan_partitions(disk, bdev);
-- 
1.8.4
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