[REGRESSION] boot regression in next-20170428

[REGRESSION] boot regression in next-20170428

[Niklas Cassel]

Hello


Since next-20170428
the ARTPEC-6 SoC (MACH_ARTPEC6) does no longer boot.

It works fine with next-20170427.


I've bisected it to the following commit:

6d684e54690caef45cf14051ddeb7c71beeb681b is the first bad commit
commit 6d684e54690caef45cf14051ddeb7c71beeb681b
Author: Herbert Xu <herbert@gondor.apana.org.au>
Date:   Thu Apr 27 13:44:51 2017 +0800

    rhashtable: Cap total number of entries to 2^31
    
    When max_size is not set or if it set to a sufficiently large
    value, the nelems counter can overflow.  This would cause havoc
    with the automatic shrinking as it would then attempt to fit a
    huge number of entries into a tiny hash table.
    
    This patch fixes this by adding max_elems to struct rhashtable
    to cap the number of elements.  This is set to 2^31 as nelems is
    not a precise count.  This is sufficiently smaller than UINT_MAX
    that it should be safe.
    
    When max_size is set max_elems will be lowered to at most twice
    max_size as is the status quo.
    
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: David S. Miller <davem@davemloft.net>




Enabling earlyprintk does not give any more info,
it simply hangs after:

JUMP dest=0x2000000 dtb=0x2900000 machine=0x1399 initrd=0x02a00000/0x0021b193 cmdline="earlyprintk debug initcall_debug=1"
Uncompressing Linux... done, booting the kernel.



Regards,
Niklas

Re: [REGRESSION] boot regression in next-20170428

[David Miller]

From: Niklas Cassel <niklas.cassel@axis.com>
Date: Fri, 28 Apr 2017 17:08:17 +0200

> Hello
> 
> 
> Since next-20170428
> the ARTPEC-6 SoC (MACH_ARTPEC6) does no longer boot.
> 
> It works fine with next-20170427.
> 
> 
> I've bisected it to the following commit:
> 
> 6d684e54690caef45cf14051ddeb7c71beeb681b is the first bad commit
> commit 6d684e54690caef45cf14051ddeb7c71beeb681b
> Author: Herbert Xu <herbert@gondor.apana.org.au>
> Date:   Thu Apr 27 13:44:51 2017 +0800
> 
>     rhashtable: Cap total number of entries to 2^31

Fixed by:

>From 2d2ab658d2debcb4c0e29c9e6f18e5683f3077bf Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Fri, 28 Apr 2017 14:10:48 +0800
Subject: [PATCH] rhashtable: Do not lower max_elems when max_size is zero

The commit 6d684e54690c ("rhashtable: Cap total number of entries
to 2^31") breaks rhashtable users that do not set max_size.  This
is because when max_size is zero max_elems is also incorrectly set
to zero instead of 2^31.

This patch fixes it by only lowering max_elems when max_size is not
zero.

Fixes: 6d684e54690c ("rhashtable: Cap total number of entries to 2^31")
Reported-by: Florian Fainelli <f.fainelli@gmail.com>
Reported-by: kernel test robot <fengguang.wu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 lib/rhashtable.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 751630b..3895486 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -958,13 +958,14 @@ int rhashtable_init(struct rhashtable *ht,
 	if (params->min_size)
 		ht->p.min_size = roundup_pow_of_two(params->min_size);
 
-	if (params->max_size)
-		ht->p.max_size = rounddown_pow_of_two(params->max_size);
-
 	/* Cap total entries at 2^31 to avoid nelems overflow. */
 	ht->max_elems = 1u << 31;
-	if (ht->p.max_size < ht->max_elems / 2)
-		ht->max_elems = ht->p.max_size * 2;
+
+	if (params->max_size) {
+		ht->p.max_size = rounddown_pow_of_two(params->max_size);
+		if (ht->p.max_size < ht->max_elems / 2)
+			ht->max_elems = ht->p.max_size * 2;
+	}
 
 	ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
 
-- 
2.4.11