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Date: Sun, 28 Mar 2010 17:41:27 -0700
From: Yinghai Lu <yinghai@...nel.org>
To: Johannes Weiner <hannes@...xchg.org>
CC: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>,
David Miller <davem@...emloft.net>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [patch v5] x86: page-alin initrd area size
On 03/28/2010 04:35 PM, Johannes Weiner wrote:
> Initrd memory is freed late and page-wise, so allocate full pages and
> not share the last one with somebody else.
>
> Also add a warning and a fixup in free_init_pages() to catch unaligned
> ranges more explicitely in the future.
>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
> arch/x86/kernel/head32.c | 8 +++++++-
> arch/x86/kernel/head64.c | 8 +++++++-
> arch/x86/kernel/setup.c | 14 ++++++++++----
> arch/x86/mm/init.c | 12 ++++++++----
> 4 files changed, 32 insertions(+), 10 deletions(-)
>
> On Sat, Mar 27, 2010 at 06:58:38PM -0700, Yinghai Lu wrote:
>> please check.
>
> I am really fed up with you replying to one point of an email and
> skipping over five others. So here is my version of the patch,
> the maintainers can choose.
thought I prefer to put calculating out of if
>
> Differences:
> o only align the allocation area size, no need to also copy
> alignment bits in relocate_initrd()
good point.
> o keep the alignment fixup in free_init_pages() out of line and
> self-contained
why calulate them two times ?
also prefer to put the fat comments in one place.
also we need to align begin too, so don't confuse set_memory_np() and set_memory_rw().
Thanks
Yinghai
Subject: [PATCH -v6] x86: Make sure free_init_pages() free pages in boundary
When CONFIG_NO_BOOTMEM, it could use memory more effient, or more compact.
Example is:
Allocated new RAMDISK: 00ec2000 - 0248ce57
Move RAMDISK from 000000002ea04000 - 000000002ffcee56 to 00ec2000 - 0248ce56
The new RAMDISK's end is not page aligned.
Last page could use shared with other user.
When free_init_pages are called for initrd or .init, the page could be freed
could have chance to corrupt other data.
code segment in free_init_pages()
| for (; addr < end; addr += PAGE_SIZE) {
| ClearPageReserved(virt_to_page(addr));
| init_page_count(virt_to_page(addr));
| memset((void *)(addr & ~(PAGE_SIZE-1)),
| POISON_FREE_INITMEM, PAGE_SIZE);
| free_page(addr);
| totalram_pages++;
| }
last half page could be used as one whole free page.
Try to make the boundaries to be page aligned.
-v2: make the original initramdisk to be aligned, according to Johannes.
otherwise we have chance to lose one page.
we still need to keep initrd_end not aligned, otherwise it could
confuse decompresser.
-v3: change to WARN_ON instead according to Johannes.
-v4: use PAGE_ALIGN according to Johannes.
We may fix that MARCO name later to PAGE_ALIGN_UP, and PAGE_ALIGN_DOWN
Add comments about assuming ramdisk start is aligned
in relocate_initrd(), change to re get ramdisk_image instead of save it
to make diff smaller.
Add WARN for wrong range according Johannes.
-v6: remove one WARN
We need align begin in free_init_pages()
not copy more than ramdisk_size according to Johannes
Reported-by: Stanislaw Gruszka <sgruszka@...hat.com>
Signed-off-by: Yinghai Lu <yinghai@...nel.org>
Acked-by: Johannes Weiner <hannes@...xchg.org>
Tested-by: Stanislaw Gruszka <sgruszka@...hat.com>
---
arch/x86/kernel/head32.c | 3 ++-
arch/x86/kernel/head64.c | 3 ++-
arch/x86/kernel/setup.c | 10 ++++++----
arch/x86/mm/init.c | 32 ++++++++++++++++++++++++++------
4 files changed, 36 insertions(+), 12 deletions(-)
Index: linux-2.6/arch/x86/mm/init.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init.c
+++ linux-2.6/arch/x86/mm/init.c
@@ -331,11 +331,23 @@ int devmem_is_allowed(unsigned long page
void free_init_pages(char *what, unsigned long begin, unsigned long end)
{
- unsigned long addr = begin;
+ unsigned long addr;
+ unsigned long begin_aligned, end_aligned;
- if (addr >= end)
+ /* Make sure boundaries are page aligned */
+ begin_aligned = PAGE_ALIGN(begin);
+ end_aligned = end & PAGE_MASK;
+
+ if (WARN_ON(begin_aligned != begin || end_aligned != end)) {
+ begin = begin_aligned;
+ end = end_aligned;
+ }
+
+ if (begin >= end)
return;
+ addr = begin;
+
/*
* If debugging page accesses then do not free this memory but
* mark them not present - any buggy init-section access will
@@ -343,7 +355,7 @@ void free_init_pages(char *what, unsigne
*/
#ifdef CONFIG_DEBUG_PAGEALLOC
printk(KERN_INFO "debug: unmapping init memory %08lx..%08lx\n",
- begin, PAGE_ALIGN(end));
+ begin, end);
set_memory_np(begin, (end - begin) >> PAGE_SHIFT);
#else
/*
@@ -358,8 +370,7 @@ void free_init_pages(char *what, unsigne
for (; addr < end; addr += PAGE_SIZE) {
ClearPageReserved(virt_to_page(addr));
init_page_count(virt_to_page(addr));
- memset((void *)(addr & ~(PAGE_SIZE-1)),
- POISON_FREE_INITMEM, PAGE_SIZE);
+ memset((void *)addr, POISON_FREE_INITMEM, PAGE_SIZE);
free_page(addr);
totalram_pages++;
}
@@ -376,6 +387,15 @@ void free_initmem(void)
#ifdef CONFIG_BLK_DEV_INITRD
void free_initrd_mem(unsigned long start, unsigned long end)
{
- free_init_pages("initrd memory", start, end);
+ /*
+ * end could be not aligned, and We can not align that,
+ * decompresser could be confused by aligned initrd_end
+ * We already reserve the end partial page before in
+ * - i386_start_kernel()
+ * - x86_64_start_kernel()
+ * - relocate_initrd()
+ * So here We can do PAGE_ALIGN() safely to get partial page to be freed
+ */
+ free_init_pages("initrd memory", start, PAGE_ALIGN(end));
}
#endif
Index: linux-2.6/arch/x86/kernel/head32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head32.c
+++ linux-2.6/arch/x86/kernel/head32.c
@@ -44,9 +44,10 @@ void __init i386_start_kernel(void)
#ifdef CONFIG_BLK_DEV_INITRD
/* Reserve INITRD */
if (boot_params.hdr.type_of_loader && boot_params.hdr.ramdisk_image) {
+ /* Assume only end is not page aligned */
u64 ramdisk_image = boot_params.hdr.ramdisk_image;
u64 ramdisk_size = boot_params.hdr.ramdisk_size;
- u64 ramdisk_end = ramdisk_image + ramdisk_size;
+ u64 ramdisk_end = PAGE_ALIGN(ramdisk_image + ramdisk_size);
reserve_early(ramdisk_image, ramdisk_end, "RAMDISK");
}
#endif
Index: linux-2.6/arch/x86/kernel/head64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head64.c
+++ linux-2.6/arch/x86/kernel/head64.c
@@ -103,9 +103,10 @@ void __init x86_64_start_reservations(ch
#ifdef CONFIG_BLK_DEV_INITRD
/* Reserve INITRD */
if (boot_params.hdr.type_of_loader && boot_params.hdr.ramdisk_image) {
+ /* Assume only end is not page aligned */
unsigned long ramdisk_image = boot_params.hdr.ramdisk_image;
unsigned long ramdisk_size = boot_params.hdr.ramdisk_size;
- unsigned long ramdisk_end = ramdisk_image + ramdisk_size;
+ unsigned long ramdisk_end = PAGE_ALIGN(ramdisk_image + ramdisk_size);
reserve_early(ramdisk_image, ramdisk_end, "RAMDISK");
}
#endif
Index: linux-2.6/arch/x86/kernel/setup.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup.c
+++ linux-2.6/arch/x86/kernel/setup.c
@@ -314,16 +314,17 @@ static void __init reserve_brk(void)
#define MAX_MAP_CHUNK (NR_FIX_BTMAPS << PAGE_SHIFT)
static void __init relocate_initrd(void)
{
-
+ /* Assume only end is not page aligned */
u64 ramdisk_image = boot_params.hdr.ramdisk_image;
u64 ramdisk_size = boot_params.hdr.ramdisk_size;
+ u64 area_size = PAGE_ALIGN(ramdisk_size);
u64 end_of_lowmem = max_low_pfn_mapped << PAGE_SHIFT;
u64 ramdisk_here;
unsigned long slop, clen, mapaddr;
char *p, *q;
/* We need to move the initrd down into lowmem */
- ramdisk_here = find_e820_area(0, end_of_lowmem, ramdisk_size,
+ ramdisk_here = find_e820_area(0, end_of_lowmem, area_size,
PAGE_SIZE);
if (ramdisk_here == -1ULL)
@@ -332,7 +333,7 @@ static void __init relocate_initrd(void)
/* Note: this includes all the lowmem currently occupied by
the initrd, we rely on that fact to keep the data intact. */
- reserve_early(ramdisk_here, ramdisk_here + ramdisk_size,
+ reserve_early(ramdisk_here, ramdisk_here + area_size,
"NEW RAMDISK");
initrd_start = ramdisk_here + PAGE_OFFSET;
initrd_end = initrd_start + ramdisk_size;
@@ -376,9 +377,10 @@ static void __init relocate_initrd(void)
static void __init reserve_initrd(void)
{
+ /* Assume only end is not page aligned */
u64 ramdisk_image = boot_params.hdr.ramdisk_image;
u64 ramdisk_size = boot_params.hdr.ramdisk_size;
- u64 ramdisk_end = ramdisk_image + ramdisk_size;
+ u64 ramdisk_end = PAGE_ALIGN(ramdisk_image + ramdisk_size);
u64 end_of_lowmem = max_low_pfn_mapped << PAGE_SHIFT;
if (!boot_params.hdr.type_of_loader ||
--
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