On Wed, Oct 24, 2012 at 09:36:27PM -0700, Hugh Dickins wrote:
> > 1148 error = shmem_add_to_page_cache(page, mapping, index,
> > 1149 gfp, swp_to_radix_entry(swap));
> > 1150 /* We already confirmed swap, and make no allocation */
> > 1151 VM_BUG_ON(error);
> > 1152 }
>
> That's very surprising. Easy enough to handle an error there, but
> of course I made it a VM_BUG_ON because it violates my assumptions:
> I rather need to understand how this can be, and I've no idea.
>
> Clutching at straws, I expect this is entirely irrelevant, but:
> there isn't a warning on line 1151 of mm/shmem.c in 3.7.0-rc2 nor
> in current linux.git; rather, there's a VM_BUG_ON on line 1149.
>
> So you've inserted a couple of lines for some reason (more useful
> trinity behaviour, perhaps)?
detritus from the recent mpol_to_str bug that I was chasing.
Shouldn't be relevant...
diff -durpN '--exclude-from=/home/davej/.exclude' src/git-trees/kernel/linux/mm>
--- src/git-trees/kernel/linux/mm/shmem.c 2012-10-12 10:01:46.613408580 ->
+++ linux-dj/mm/shmem.c 2012-10-15 12:31:32.979653309 -0400
@@ -885,13 +885,15 @@ redirty:
static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
{
char buffer[64];
+ int ret;
if (!mpol || mpol->mode == MPOL_DEFAULT)
return; /* show nothing */
- mpol_to_str(buffer, sizeof(buffer), mpol, 1);
-
- seq_printf(seq, ",mpol=%s", buffer);
+ memset(buffer, 0, sizeof(buffer));
+ ret = mpol_to_str(buffer, sizeof(buffer), mpol, 1);
+ if (ret > 0)
+ seq_printf(seq, ",mpol=%s", buffer);
}
> And have some config option I'm
> unfamiliar with, that mutates a BUG_ON or VM_BUG_ON into a warning?
Yes, I do have this..
-#define VM_BUG_ON(cond) BUG_ON(cond)
+#define VM_BUG_ON(cond) WARN_ON(cond)
because I got tired of things not going over my usb serial port when I hit them
a while ago. BUG_ON is pretty unfriendly to bug finding.
Dave
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