On Fri, Jan 13, 2012 at 10:36:42AM -0600, Dimitri Sivanich wrote:
> On Fri, Jan 13, 2012 at 04:22:36PM +0000, Al Viro wrote:
> > On Fri, Jan 13, 2012 at 09:52:37AM -0600, Dimitri Sivanich wrote:
> > > When the number of dentry cache hash table entries gets too high
> > > (2147483648 entries), use of a signed integer in the initialization
> > > loop prevents the dentry_hashtable from getting initialized, resulting
> > > in a panic in __d_lookup. Fixing this in dcache_init and a few other
> > > spots for consistency.
> >
> > > static void __init dcache_init(void)
> > > {
> > > - int loop;
> > > + long loop;
> >
> > You've got to be kidding. Note that D_HASHMASK is at most 32bit. Use
> > of long here is an overkill and so's 2^31 hash buckets (that's what,
> > 16Gb in hash list heads alone? What kind of average chain length do
> > you expect, BTW?)
>
> Yes, long might be overkill right now, but the code is all __init time code.
> I don't have numbers showing average chain length at this point, I was
> simply fixing this one end case
>
> >
> > Can alloc_large_system_hash() produce the horrors that large, anyway?
>
> On a 16TB system, alloc_large_system_hash() produces 2^31 hash buckets, yes.
>
> Would simply capping the value in alloc_large_system_hash() be more palatable?
>
> Something like the following?
>
> Index: linux/mm/page_alloc.c
> ===================================================================
> --- linux.orig/mm/page_alloc.c
> +++ linux/mm/page_alloc.c
> @@ -5257,6 +5257,7 @@ void *__init alloc_large_system_hash(con
> if (max == 0) {
> max = ((unsigned long long)nr_all_pages << PAGE_SHIFT) >> 4;
> do_div(max, bucketsize);
> + max = min(max, 1ULL << 30);
> }
>
> if (numentries > max)
Sorry, you'd probably want something more like this:
Index: linux/mm/page_alloc.c
===================================================================
--- linux.orig/mm/page_alloc.c
+++ linux/mm/page_alloc.c
@@ -5258,6 +5258,7 @@ void *__init alloc_large_system_hash(con
max = ((unsigned long long)nr_all_pages << PAGE_SHIFT) >> 4;
do_div(max, bucketsize);
}
+ max = min(max, 1ULL << 30);
if (numentries > max)
numentries = max;
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