block: fix scan partition for exclusively open device again

[ Upstream commit e5cfefa97bccf956ea0bb6464c1f6c84fd7a8d9f ]

As explained in commit 36369f46e917 ("block: Do not reread partition table
on exclusively open device"), reread partition on the device that is
exclusively opened by someone else is problematic.

This patch will make sure partition scan will only be proceed if current
thread open the device exclusively, or the device is not opened
exclusively, and in the later case, other scanners and exclusive openers
will be blocked temporarily until partition scan is done.

Fixes: 10c70d95c0f2 ("block: remove the bd_openers checks in blk_drop_partitions")
Cc: <stable@vger.kernel.org>
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230217022200.3092987-3-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/block/genhd.c b/block/genhd.c
index 647f7d8d8831245a26ca477875a6b75813c9109c..85ae755913e9e7d2e89c2fe5c8f4554f7b23bd98 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -359,6 +359,7 @@ EXPORT_SYMBOL_GPL(disk_uevent);
 int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
 {
        struct block_device *bdev;
+       int ret = 0;
 
        if (disk->flags & (GENHD_FL_NO_PART | GENHD_FL_HIDDEN))
                return -EINVAL;
@@ -368,11 +369,27 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
                return -EBUSY;
 
        set_bit(GD_NEED_PART_SCAN, &disk->state);
-       bdev = blkdev_get_by_dev(disk_devt(disk), mode, NULL);
+       /*
+        * If the device is opened exclusively by current thread already, it's
+        * safe to scan partitons, otherwise, use bd_prepare_to_claim() to
+        * synchronize with other exclusive openers and other partition
+        * scanners.
+        */
+       if (!(mode & FMODE_EXCL)) {
+               ret = bd_prepare_to_claim(disk->part0, disk_scan_partitions);
+               if (ret)
+                       return ret;
+       }
+
+       bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL);
        if (IS_ERR(bdev))
-               return PTR_ERR(bdev);
-       blkdev_put(bdev, mode);
-       return 0;
+               ret =  PTR_ERR(bdev);
+       else
+               blkdev_put(bdev, mode);
+
+       if (!(mode & FMODE_EXCL))
+               bd_abort_claiming(disk->part0, disk_scan_partitions);
+       return ret;
 }
 
 /**
@@ -498,6 +515,11 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
                if (ret)
                        goto out_unregister_bdi;
 
+               /* Make sure the first partition scan will be proceed */
+               if (get_capacity(disk) && !(disk->flags & GENHD_FL_NO_PART) &&
+                   !test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
+                       set_bit(GD_NEED_PART_SCAN, &disk->state);
+
                bdev_add(disk->part0, ddev->devt);
                if (get_capacity(disk))
                        disk_scan_partitions(disk, FMODE_READ);

diff --git a/block/ioctl.c b/block/ioctl.c
index 6dd49d877584a30d48cac3e53f71b463c8e134cd..9c5f637ff153f8b0010a6812ab8565fdacfbc5fe 100644 (file)
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -528,7 +528,7 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
                        return -EACCES;
                if (bdev_is_partition(bdev))
                        return -EINVAL;
-               return disk_scan_partitions(bdev->bd_disk, mode & ~FMODE_EXCL);
+               return disk_scan_partitions(bdev->bd_disk, mode);
        case BLKTRACESTART:
        case BLKTRACESTOP:
        case BLKTRACETEARDOWN: