Commit 4136bb64 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds

[PATCH] fix low-memory BUG in slab

cache_grow() will call kmem_freepages() if the call to alloc_slabmgmt()
fails.  But the pages have not been marked PageSlab at this stage, so
kmem_freepages() goes BUG.

It is more symmetrical to mark the pages as PageSlab in kmem_getpages().

The patch also prunes a bunch of incorrect comments.

(PageSlab doesn't actually do anything: its only value is as a debug check.
I think the LKCD patch uses it).
parent 7ae0eef7
...@@ -793,42 +793,42 @@ int __init cpucache_init(void) ...@@ -793,42 +793,42 @@ int __init cpucache_init(void)
__initcall(cpucache_init); __initcall(cpucache_init);
/* Interface to system's page allocator. No need to hold the cache-lock. /*
* Interface to system's page allocator. No need to hold the cache-lock.
*
* If we requested dmaable memory, we will get it. Even if we
* did not request dmaable memory, we might get it, but that
* would be relatively rare and ignorable.
*/ */
static inline void * kmem_getpages (kmem_cache_t *cachep, unsigned long flags) static inline void *kmem_getpages(kmem_cache_t *cachep, unsigned long flags)
{ {
void *addr; void *addr;
/*
* If we requested dmaable memory, we will get it. Even if we
* did not request dmaable memory, we might get it, but that
* would be relatively rare and ignorable.
*/
flags |= cachep->gfpflags; flags |= cachep->gfpflags;
if ( cachep->flags & SLAB_RECLAIM_ACCOUNT) if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
atomic_add(1<<cachep->gfporder, &slab_reclaim_pages); atomic_add(1<<cachep->gfporder, &slab_reclaim_pages);
addr = (void*) __get_free_pages(flags, cachep->gfporder); addr = (void*)__get_free_pages(flags, cachep->gfporder);
/* Assume that now we have the pages no one else can legally if (addr) {
* messes with the 'struct page's. int i = (1 << cachep->gfporder);
* However vm_scan() might try to test the structure to see if struct page *page = virt_to_page(addr);
* it is a named-page or buffer-page. The members it tests are
* of no interest here..... while (i--) {
*/ SetPageSlab(page);
page++;
}
}
return addr; return addr;
} }
/* Interface to system's page release. */ /*
static inline void kmem_freepages (kmem_cache_t *cachep, void *addr) * Interface to system's page release.
*/
static inline void kmem_freepages(kmem_cache_t *cachep, void *addr)
{ {
unsigned long i = (1<<cachep->gfporder); unsigned long i = (1<<cachep->gfporder);
struct page *page = virt_to_page(addr); struct page *page = virt_to_page(addr);
const unsigned long nr_freed = i; const unsigned long nr_freed = i;
/* free_pages() does not clear the type bit - we do that.
* The pages have been unlinked from their cache-slab,
* but their 'struct page's might be accessed in
* vm_scan(). Shouldn't be a worry.
*/
while (i--) { while (i--) {
if (!TestClearPageSlab(page)) if (!TestClearPageSlab(page))
BUG(); BUG();
...@@ -1608,7 +1608,6 @@ static int cache_grow (kmem_cache_t * cachep, int flags) ...@@ -1608,7 +1608,6 @@ static int cache_grow (kmem_cache_t * cachep, int flags)
do { do {
SET_PAGE_CACHE(page, cachep); SET_PAGE_CACHE(page, cachep);
SET_PAGE_SLAB(page, slabp); SET_PAGE_SLAB(page, slabp);
SetPageSlab(page);
inc_page_state(nr_slab); inc_page_state(nr_slab);
page++; page++;
} while (--i); } while (--i);
......
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