[parisc-linux] [akpm@digeo.com: arch changes for file-offset-in-pte's]
Matthew Wilcox
willy@debian.org
Sat, 22 Mar 2003 01:20:10 +0000
FYI. jsm, any comments?
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Envelope-to: willy@ftp.uk.linux.org
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Date: Fri, 21 Mar 2003 17:56:26 -0800
From: Andrew Morton <akpm@digeo.com>
To: "David S. Miller" <davem@redhat.com>, paulus@au.ibm.com,
benh@kernel.crashing.org, rth@twiddle.net, davidm@hpl.hp.com,
ralf@linux-mips.org, schwidefsky@de.ibm.com,
Russell King
<rmk@arm.linux.org.uk>, bjornw@axis.com,
geert@linux-m68k.org, Matthew
Wilcox <willy@debian.org>,
gniibe@m17n.org, linux-sh@m17n.org, jdike@karaya.com,
uclinux-v850@lsi.nec.co.jp
Cc: Ingo Molnar <mingo@elte.hu>, linux-mm@kvack.org
Subject: arch changes for file-offset-in-pte's
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hi,
I'd like to submit Ingo's remap_file_pages() enhancements soon. His patch
allows pages in "nonlinear" mappings to be reestablished by the kernel's
pagefault handler.
It does this by embedding the page's ->index into the pte which wants to map
the page. This is arch-specific, and I only have ia32, ppc64 and x86_64 done.
So if&when this hits the tree, it will break other architectures. It's a
five-minute-fix.
Four things need to be provided:
pte_t pgoff_to_pte(unsigned long pgoff)
Return a pte_t which contains as many of the lower bits of pgoff as
you can feasibly pack into a pte.
You'll probably need to reserve at least two bits - one for
not-present and one to say "this is a pte_file pte".
unsigned long pte_to_pgoff(pte_t pte)
Extract the unsigned long from a pte.
int pte_file(pte_t)
Return true if the pte is a "file pte". This is where you'll need to
use the magical reserved bit to distinguish this from a swapped out pte.
PTE_FILE_MAX_BITS (a constant)
Tells the kernel how many bits of the file offset the architecture is
capable of placing in the pte, via pgoff_to_pte(). ia32 sets this to 29
in non-PAE mode, 32 in PAE mode (CONFIG_HIGHMEM64G)
As an example, here is the x86_64 implementation (the comment next to
_PAGE_FILE is wrong, btw. These are not swapcache pages)
The ia32 version of this code is right at the start of the the main patch, at
http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.5/2.5.65/2.5.65-mm3/broken-out/remap-file-pages-2.5.63-a1.patch
Thanks.
diff -puN include/asm-x86_64/pgtable.h~file-offset-in-pte-x86_64 include/asm-x86_64/pgtable.h
--- 25/include/asm-x86_64/pgtable.h~file-offset-in-pte-x86_64 2003-03-13 04:45:57.000000000 -0800
+++ 25-akpm/include/asm-x86_64/pgtable.h 2003-03-13 04:45:57.000000000 -0800
@@ -151,6 +151,7 @@ static inline void set_pml4(pml4_t *dst,
#define _PAGE_ACCESSED 0x020
#define _PAGE_DIRTY 0x040
#define _PAGE_PSE 0x080 /* 2MB page */
+#define _PAGE_FILE 0x040 /* pagecache or swap */
#define _PAGE_GLOBAL 0x100 /* Global TLB entry */
#define _PAGE_PROTNONE 0x080 /* If not present */
@@ -245,6 +246,7 @@ extern inline int pte_exec(pte_t pte) {
extern inline int pte_dirty(pte_t pte) { return pte_val(pte) & _PAGE_DIRTY; }
extern inline int pte_young(pte_t pte) { return pte_val(pte) & _PAGE_ACCESSED; }
extern inline int pte_write(pte_t pte) { return pte_val(pte) & _PAGE_RW; }
+static inline int pte_file(pte_t pte) { return pte_val(pte) & _PAGE_FILE; }
extern inline pte_t pte_rdprotect(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_USER)); return pte; }
extern inline pte_t pte_exprotect(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_USER)); return pte; }
@@ -330,6 +332,11 @@ static inline pgd_t *current_pgd_offset_
#define pmd_bad(x) ((pmd_val(x) & (~PTE_MASK & ~_PAGE_USER)) != _KERNPG_TABLE )
#define pfn_pmd(nr,prot) (__pmd(((nr) << PAGE_SHIFT) | pgprot_val(prot)))
+
+#define pte_to_pgoff(pte) ((pte_val(pte) & PHYSICAL_PAGE_MASK) >> PAGE_SHIFT)
+#define pgoff_to_pte(off) ((pte_t) { ((off) << PAGE_SHIFT) | _PAGE_FILE })
+#define PTE_FILE_MAX_BITS __PHYSICAL_MASK_SHIFT
+
/* PTE - Level 1 access. */
/* page, protection -> pte */
diff -puN include/asm-x86_64/page.h~file-offset-in-pte-x86_64 include/asm-x86_64/page.h
--- 25/include/asm-x86_64/page.h~file-offset-in-pte-x86_64 2003-03-13 04:45:57.000000000 -0800
+++ 25-akpm/include/asm-x86_64/page.h 2003-03-13 04:48:53.000000000 -0800
@@ -69,8 +69,9 @@ typedef struct { unsigned long pgprot; }
/* See Documentation/x86_64/mm.txt for a description of the memory map. */
#define __START_KERNEL 0xffffffff80100000
#define __START_KERNEL_map 0xffffffff80000000
-#define __PAGE_OFFSET 0x0000010000000000
-#define __PHYSICAL_MASK 0x000000ffffffffff
+#define __PAGE_OFFSET 0x0000010000000000 /* 1 << 40 */
+#define __PHYSICAL_MASK_SHIFT 40
+#define __PHYSICAL_MASK ((1UL << __PHYSICAL_MASK_SHIFT) - 1)
#define KERNEL_TEXT_SIZE (40UL*1024*1024)
#define KERNEL_TEXT_START 0xffffffff80000000UL
_
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