Sep 17 00:00:00 2001
From: Vladimir Murzin <[email protected]>
Date: Thu, 23 Jan 2014 14:54:20 +0400
Subject: [PATCH] Revert "mm/vmalloc: interchage the implementation of
vmalloc_to_{pfn,page}"
This reverts commit ece86e222db48d04bda218a2be70e384518bb08c.
Despite being claimed that 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 <[email protected]>
Cc: Jianyu Zhan <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
---
I'm a bit surprised to see this patch merged because I've already pointed [1]
at difference in behaviour introduced by the patch.
If I've lost the point here or misunderstand the patch or abuse vmalloc_to_*
interface I'd be grateful if someone let me know.
[1] https://lkml.org/lkml/2013/12/1/76
Thanks
Vladimir
mm/vmalloc.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index e4f0db2..0fdf968 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 ***/
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
