[Patch v2] block: revert block_dev read-only check

From: Chuck Ebbert
Date: Wed Feb 16 2011 - 18:15:51 EST


This reverts commit 75f1dc0d076d1c1168f2115f1941ea627d38bd5a
("block: check bdev_read_only() from blkdev_get()"). That commit added
stricter checking to make sure devices that were being used read-only
were actually opened in that mode.

It turns out that the change breaks a bunch of kernel code that opens
block devices. Affected systems include dm, md, and the loop device.
Because strict checking for read-only opens of block devices was not
done before this, the code that opens the devices was opening them
read-write even if they were being used read-only. Auditing all that
code will take time, and new userspace packages for dm, mdadm, etc.
will also be required.

Signed-off-by: Chuck Ebbert <cebbert@xxxxxxxxxx>

--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1215,12 +1215,6 @@ int blkdev_get(struct block_device *bdev

res = __blkdev_get(bdev, mode, 0);

- /* __blkdev_get() may alter read only status, check it afterwards */
- if (!res && (mode & FMODE_WRITE) && bdev_read_only(bdev)) {
- __blkdev_put(bdev, mode, 0);
- res = -EACCES;
- }
-
if (whole) {
/* finish claiming */
mutex_lock(&bdev->bd_mutex);
@@ -1298,6 +1292,11 @@ struct block_device *blkdev_get_by_path(
if (err)
return ERR_PTR(err);

+ if ((mode & FMODE_WRITE) && bdev_read_only(bdev)) {
+ blkdev_put(bdev, mode);
+ return ERR_PTR(-EACCES);
+ }
+
return bdev;
}
EXPORT_SYMBOL(blkdev_get_by_path);
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