From 6cfd53fc03670c7a544a56d441eb1a6cc800d72b Mon Sep 17 00:00:00 2001 From: Paul Mundt Date: Thu, 5 Jun 2008 22:46:08 -0700 Subject: [PATCH] nommu: fix kobjsize() for SLOB and SLUB kobjsize() has been abusing page->index as a method for sorting out compound order, which blows up both for page cache pages, and SLOB's reuse of the index in struct slob_page. Presently we are not able to accurately size arbitrary pointers that don't come from kmalloc(), so the best we can do is sort out the compound order from the head page if it's a compound page, or default to 0-order if it's impossible to ksize() the object. Obviously this leaves quite a bit to be desired in terms of object sizing accuracy, but the behaviour is unchanged over the existing implementation, while fixing the page->index oopses originally reported here: http://marc.info/?l=linux-mm&m=121127773325245&w=2 Accuracy could also be improved by having SLUB and SLOB both set PG_slab on ksizeable pages, rather than just handling the __GFP_COMP cases irregardless of the PG_slab setting, as made possibly with Pekka's patches: http://marc.info/?l=linux-kernel&m=121139439900534&w=2 http://marc.info/?l=linux-kernel&m=121139440000537&w=2 http://marc.info/?l=linux-kernel&m=121139440000540&w=2 This is primarily a bugfix for nommu systems for 2.6.26, with the aim being to gradually kill off kobjsize() and its particular brand of object abuse entirely. Reviewed-by: Pekka Enberg Signed-off-by: Paul Mundt Acked-by: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/nommu.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/mm/nommu.c b/mm/nommu.c index dca93fcb8b..3abd0845bd 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -104,21 +104,43 @@ EXPORT_SYMBOL(vmtruncate); unsigned int kobjsize(const void *objp) { struct page *page; + int order = 0; /* * If the object we have should not have ksize performed on it, * return size of 0 */ - if (!objp || (unsigned long)objp >= memory_end || !((page = virt_to_page(objp)))) + if (!objp) return 0; + if ((unsigned long)objp >= memory_end) + return 0; + + page = virt_to_head_page(objp); + if (!page) + return 0; + + /* + * If the allocator sets PageSlab, we know the pointer came from + * kmalloc(). + */ if (PageSlab(page)) return ksize(objp); - BUG_ON(page->index < 0); - BUG_ON(page->index >= MAX_ORDER); + /* + * The ksize() function is only guaranteed to work for pointers + * returned by kmalloc(). So handle arbitrary pointers, that we expect + * always to be compound pages, here. + */ + if (PageCompound(page)) + order = compound_order(page); - return (PAGE_SIZE << page->index); + /* + * Finally, handle arbitrary pointers that don't set PageSlab. + * Default to 0-order in the case when we're unable to ksize() + * the object. + */ + return PAGE_SIZE << order; } /* -- 2.39.5