[PATCH 5/5] block: remove (__)blkdev_reread_part as an exported API

Christoph Hellwig
2019-11-06T15:14:53Z

In general drivers should never mess with partition tables directly.
Unfortunately s390 and loop do for somewhat historic reasons, but they
can use bdev_disk_changed directly instead when we export it as they
satisfy the sanity checks we have in __blkdev_reread_part.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/ioctl.c | 35 +++++----------------------------
drivers/block/loop.c | 13 +++++++-----
drivers/s390/block/dasd_genhd.c | 4 +++-
fs/block_dev.c | 7 +++++++
include/linux/fs.h | 2 --
5 files changed, 23 insertions(+), 38 deletions(-)

diff --git a/block/ioctl.c b/block/ioctl.c
index 52380c337078..2ed907ef0f01 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -155,46 +155,21 @@ static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user
}
}

-/*
- * 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)
+static int blkdev_reread_part(struct block_device *bdev)
{
+ int ret;
+
if (!disk_part_scan_enabled(bdev->bd_disk) || bdev != bdev->bd_contains)
return -EINVAL;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;

- lockdep_assert_held(&bdev->bd_mutex);
-
- return bdev_disk_changed(bdev, false);
-}
-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().
- *
- * Make sure the held locks in current context aren't required
- * in open()/close() handler and I/O path for avoiding ABBA deadlock:
- * - bd_mutex is held before calling block driver's open/close
- * handler
- * - reading partition table may submit I/O to the block device
- */
-int blkdev_reread_part(struct block_device *bdev)
-{
- int res;
-
mutex_lock(&bdev->bd_mutex);
- res = __blkdev_reread_part(bdev);
+ ret = bdev_disk_changed(bdev, false);
mutex_unlock(&bdev->bd_mutex);

- return res;
+ return ret;
}
-EXPORT_SYMBOL(blkdev_reread_part);

static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
unsigned long arg, unsigned long flags)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index f6f77eaa7217..64b16abee280 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -630,7 +630,9 @@ static void loop_reread_partitions(struct loop_device *lo,
{
int rc;

- rc = blkdev_reread_part(bdev);
+ mutex_lock(&bdev->bd_mutex);
+ rc = bdev_disk_changed(bdev, false);
+ mutex_unlock(&bdev->bd_mutex);
if (rc)
pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
__func__, lo->lo_number, lo->lo_file_name, rc);
@@ -1154,10 +1156,11 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
* must be at least one and it can only become zero when the
* current holder is released.
*/
- if (release)
- err = __blkdev_reread_part(bdev);
- else
- err = blkdev_reread_part(bdev);
+ if (!release)
+ mutex_lock(&bdev->bd_mutex);
+ err = bdev_disk_changed(bdev, false);
+ if (!release)
+ mutex_unlock(&bdev->bd_mutex);
if (err)
pr_warn("%s: partition scan of loop%d failed (rc=%d)\n",
__func__, lo_number, err);
diff --git a/drivers/s390/block/dasd_genhd.c b/drivers/s390/block/dasd_genhd.c
index 5542d9eadfe0..7d079154f849 100644
--- a/drivers/s390/block/dasd_genhd.c
+++ b/drivers/s390/block/dasd_genhd.c
@@ -116,7 +116,9 @@ int dasd_scan_partitions(struct dasd_block *block)
return -ENODEV;
}

- rc = blkdev_reread_part(bdev);
+ mutex_lock(&bdev->bd_mutex);
+ rc = bdev_disk_changed(bdev, false);
+ mutex_unlock(&bdev->bd_mutex);
if (rc)
DBF_DEV_EVENT(DBF_ERR, block->base,
"scan partitions error, rc %d", rc);
diff --git a/fs/block_dev.c b/fs/block_dev.c
index ae16466a67f7..9558a2f064b1 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1513,6 +1513,8 @@ int bdev_disk_changed(struct block_device *bdev, bool invalidate)
struct gendisk *disk = bdev->bd_disk;
int ret;

+ lockdep_assert_held(&bdev->bd_mutex);
+
rescan:
ret = blk_drop_partitions(disk, bdev);
if (ret)
@@ -1540,6 +1542,11 @@ int bdev_disk_changed(struct block_device *bdev, bool invalidate)

return ret;
}
+/*
+ * Only exported for for loop and dasd for historic reasons. Don't use in new
+ * code!
+ */
+EXPORT_SYMBOL_GPL(bdev_disk_changed);

/*
* bd_mutex locking:
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d233dd661df7..ae6c5c37f3ae 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2632,8 +2632,6 @@ extern void bd_finish_claiming(struct block_device *bdev,
extern void bd_abort_claiming(struct block_device *bdev,
struct block_device *whole, 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);
--
2.20.1