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author | malc <av1474@comtv.ru> | 2014-01-27 17:06:53 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-01-27 21:02:39 -0800 |
commit | add688fbd32158440dbe62c07269a39ed969c059 (patch) | |
tree | c4bf48c0c7cf65982c11b2cf1c949f52a3750148 /mm/vmalloc.c | |
parent | fb5bb60cd004a00c1d11db680a37942ecdedb1c5 (diff) | |
download | lwn-add688fbd32158440dbe62c07269a39ed969c059.tar.gz lwn-add688fbd32158440dbe62c07269a39ed969c059.zip |
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 <linux/kernel.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
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 <murzin.v@gmail.com>
Cc: Jianyu Zhan <nasa4836@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmalloc.c')
-rw-r--r-- | mm/vmalloc.c | 20 |
1 files changed, 10 insertions, 10 deletions
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 ***/ |