[PATCH] Fix bd_claim() error code.

Problem: In some circumstances, bd_claim() is returning the wrong error
code.

If we try to swapon an unused block device that isn't swap formatted, we
get -EINVAL.  But if that same block device is already mounted, we instead
get -EBUSY, even though it still isn't a valid swap device.

This issue came up on the busybox list trying to get the error message
from "swapon -a" right.  If a swap device is already enabled, we get -EBUSY,
and we shouldn't report this as an error.  But we can't distinguish the two
-EBUSY conditions, which are very different errors.

In the code, bd_claim() returns either 0 or -EBUSY, but in this case busy
means "somebody other than sys_swapon has already claimed this", and
_that_ means this block device can't be a valid swap device.  So return
-EINVAL there.

Signed-off-by: Rob Landley <rob@landley.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 0184f510aacefd5cdce18b18a2d2f91008e255db..1dcaeda039f4b85f8bbe1b70f4ccbc80de388ade 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1381,6 +1381,7 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
                error = bd_claim(bdev, sys_swapon);
                if (error < 0) {
                        bdev = NULL;
+                       error = -EINVAL;
                        goto bad_swap;
                }
                p->old_block_size = block_size(bdev);