Fix missing of last user info while getting DEBUG_SLAB config enabled
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From: TAO HU on 1 Apr 2010 03:10 Hi, Pekka Thanks for your feedback. The subject and comments are kind of misleading. Sorry about that. It intends to make both Red-Zone and LastUser are available even the alignment is larger than sizeof(long long). The idea is to reserve certain room ("align") to let the obj's offset is aligned to cache-line-size to address requirement of kmalloc(). Regarding align is less than sizeof(unsigned long long), I thin it is handled in previous code. Or you still expect to explicitly let align is no less than sizeof(unsigned long long)? if (flags & SLAB_RED_ZONE) { ralign = REDZONE_ALIGN; ... ... } -- Best Regards Hu Tao On Thu, Apr 1, 2010 at 2:29 PM, Pekka Enberg <penberg(a)cs.helsinki.fi> wrote: > ShiYong LI kirjoitti: >> >> Hi all, >> �For OMAP3430 chip, while getting DEBUG_SLAB config enabled, found a bug >> that last user information is missed in slab corruption log dumped by >> kernel. Actually, It's caused by ignorance of redzone and last user tag >> while calling kmem_cache_create() function if cache alignment > 16 bytes >> (unsigned long long). �Here is a patch to fix this problem. Already verified >> it on kernel 2.6.29. > > The patch is badly whitespace damaged. > >> �From 26a5a8ad2a1d7612929a91f6866cea9d1bea6077 Mon Sep 17 00:00:00 2001 >> From: Shiyong Li <shi-yong.li(a)motorola.com >> <mailto:shi-yong.li(a)motorola.com>> >> Date: Wed, 31 Mar 2010 10:09:35 +0800 >> Subject: [PATCH] Fix missing of last user info while getting DEBUG_SLAB >> config enabled. >> As OMAP3 cache line is 64 byte long, while calling kmem_cache_create() >> funtion, some cases need 64 byte alignment of requested memory space. >> But, if cache line > 16 bytes, current kernel ignore redzone >> and last user debug head/trail tag to make sure this alignment is not >> broken. >> This fix removes codes that ignorance of redzone and last user tag. >> Instead, use "align" argument value as object offset to guarantee the >> alignment. >> Signed-off-by: Shiyong Li <shi-yong.li(a)motorola.com >> <mailto:shi-yong.li(a)motorola.com>> >> --- >> �mm/slab.c | � �7 ++----- >> �1 files changed, 2 insertions(+), 5 deletions(-) >> diff --git a/mm/slab.c b/mm/slab.c >> index a8a38ca..84af997 100644 >> --- a/mm/slab.c >> +++ b/mm/slab.c >> @@ -2267,9 +2267,6 @@ kmem_cache_create (const char *name, size_t size, >> size_t align, >> �if (ralign < align) { >> � ralign = align; >> �} >> - /* disable debug if necessary */ >> - if (ralign > __alignof__(unsigned long long)) >> - �flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER); >> �/* >> � * 4) Store it. >> � */ >> @@ -2289,8 +2286,8 @@ kmem_cache_create (const char *name, size_t size, >> size_t align, >> � */ >> �if (flags & SLAB_RED_ZONE) { >> � /* add space for red zone words */ >> - �cachep->obj_offset += sizeof(unsigned long long); >> - �size += 2 * sizeof(unsigned long long); >> + �cachep->obj_offset += align; >> + �size += align + sizeof(unsigned long long); >> �} > > I don't understand what you're trying to do here. What if align is less han > sizeof(unsigned long long)? What if SLAB_RED_ZONE is not enabled but > �SLAB_STORE_USER is? > > � � � � � � � � � � � �Pekka > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo(a)kvack.org. �For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont(a)kvack.org"> email(a)kvack.org </a> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |