From add688fbd32158440dbe62c07269a39ed969c059 Mon Sep 17 00:00:00 2001 From: malc Date: Mon, 27 Jan 2014 17:06:53 -0800 Subject: Revert "mm/vmalloc: interchage the implementation of vmalloc_to_{pfn,page}" Revert commit ece86e222db4, which was intended as a small performance improvement. Despite the claim that the patch doesn't introduce any functional changes in fact it does. The "no page" path behaves different now. Originally, vmalloc_to_page might return NULL under some conditions, with new implementation it returns pfn_to_page(0) which is not the same as NULL. Simple test shows the difference. test.c #include #include #include #include int __init myi(void) { struct page *p; void *v; v = vmalloc(PAGE_SIZE); /* trigger the "no page" path in vmalloc_to_page*/ vfree(v); p = vmalloc_to_page(v); pr_err("expected val = NULL, returned val = %p", p); return -EBUSY; } void __exit mye(void) { } module_init(myi) module_exit(mye) Before interchange: expected val = NULL, returned val = (null) After interchange: expected val = NULL, returned val = c7ebe000 Signed-off-by: Vladimir Murzin Cc: Jianyu Zhan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmalloc.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) (limited to 'mm') diff --git a/mm/vmalloc.c b/mm/vmalloc.c index e4f0db2a3eae..0fdf96803c5b 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -220,12 +220,12 @@ int is_vmalloc_or_module_addr(const void *x) } /* - * Walk a vmap address to the physical pfn it maps to. + * Walk a vmap address to the struct page it maps. */ -unsigned long vmalloc_to_pfn(const void *vmalloc_addr) +struct page *vmalloc_to_page(const void *vmalloc_addr) { unsigned long addr = (unsigned long) vmalloc_addr; - unsigned long pfn = 0; + struct page *page = NULL; pgd_t *pgd = pgd_offset_k(addr); /* @@ -244,23 +244,23 @@ unsigned long vmalloc_to_pfn(const void *vmalloc_addr) ptep = pte_offset_map(pmd, addr); pte = *ptep; if (pte_present(pte)) - pfn = pte_pfn(pte); + page = pte_page(pte); pte_unmap(ptep); } } } - return pfn; + return page; } -EXPORT_SYMBOL(vmalloc_to_pfn); +EXPORT_SYMBOL(vmalloc_to_page); /* - * Map a vmalloc()-space virtual address to the struct page. + * Map a vmalloc()-space virtual address to the physical page frame number. */ -struct page *vmalloc_to_page(const void *vmalloc_addr) +unsigned long vmalloc_to_pfn(const void *vmalloc_addr) { - return pfn_to_page(vmalloc_to_pfn(vmalloc_addr)); + return page_to_pfn(vmalloc_to_page(vmalloc_addr)); } -EXPORT_SYMBOL(vmalloc_to_page); +EXPORT_SYMBOL(vmalloc_to_pfn); /*** Global kva allocator ***/ -- cgit v1.2.3-59-g8ed1b