* [PATCH] nonlinear oddities
@ 2003-03-06 16:53 Hugh Dickins
2003-03-06 19:14 ` Hugh Dickins
0 siblings, 1 reply; 5+ messages in thread
From: Hugh Dickins @ 2003-03-06 16:53 UTC (permalink / raw)
To: Andrew Morton; +Cc: Dave McCracken, Ingo Molnar, linux-kernel
1. Revert MAP_NONLINEAR and VM_NONLINEAR: I can easily imagine wanting
VM_NONLINEAR in future, warning that vma is unusual, but currently it's
not useful: install_page just needs to SetPageAnon if the page is put
somewhere try_to_unmap_obj_one wouldn't be able to find it.
2. filemap_populate and shmem_populate expect an absolute pgoff, but
try_to_unmap_one is forgetting to add in vm_pgoff when doing set_pte.
Could be done the other way round, with relative pgoff in the pte?
No, that would make splitting a vma tedious.
3. No patch included, but I believe 2.5.64-mm1 is testing Ingo's
file-offset-in-pte very much less than you imagine (I've yet to hit
a breakpoint on do_file_page, and I don't think that's down to the
patches above): Dave's work means that the file pages don't arrive
at Ingo's code to set the pte with file offset (unless you actually
use Ingo's syscall) - difficult to test both at once, I think.
Hugh
--- 2.5.64-mm1/include/asm-i386/mman.h Thu Mar 6 08:24:23 2003
+++ linux/include/asm-i386/mman.h Thu Mar 6 15:59:49 2003
@@ -20,7 +20,6 @@
#define MAP_NORESERVE 0x4000 /* don't check for reservations */
#define MAP_POPULATE 0x8000 /* populate (prefault) pagetables */
#define MAP_NONBLOCK 0x10000 /* do not block on IO */
-#define MAP_NONLINEAR 0x20000 /* will be used for remap_file_pages */
#define MS_ASYNC 1 /* sync memory asynchronously */
#define MS_INVALIDATE 2 /* invalidate the caches */
--- 2.5.64-mm1/include/asm-ppc64/mman.h Thu Mar 6 08:24:23 2003
+++ linux/include/asm-ppc64/mman.h Thu Mar 6 15:59:49 2003
@@ -36,7 +36,6 @@
#define MAP_POPULATE 0x8000 /* populate (prefault) pagetables */
#define MAP_NONBLOCK 0x10000 /* do not block on IO */
-#define MAP_NONLINEAR 0x20000 /* Mapping may use remap_file_pages */
#define MADV_NORMAL 0x0 /* default page-in behavior */
#define MADV_RANDOM 0x1 /* page-in minimum required */
--- 2.5.64-mm1/include/linux/mm.h Thu Mar 6 08:24:24 2003
+++ linux/include/linux/mm.h Thu Mar 6 15:59:49 2003
@@ -107,7 +107,6 @@
#define VM_RESERVED 0x00080000 /* Don't unmap it from swap_out */
#define VM_ACCOUNT 0x00100000 /* Is a VM accounted object */
#define VM_HUGETLB 0x00400000 /* Huge TLB Page VM */
-#define VM_NONLINEAR 0x00800000 /* Nonlinear area */
#ifdef CONFIG_STACK_GROWSUP
#define VM_STACK_FLAGS (VM_GROWSUP | VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT)
--- 2.5.64-mm1/mm/fremap.c Thu Mar 6 08:24:24 2003
+++ linux/mm/fremap.c Thu Mar 6 15:59:49 2003
@@ -1,5 +1,5 @@
/*
- * linux/mm/mpopulate.c
+ * linux/mm/fremap.c
*
* Explicit pagetable population and nonlinear (random) mappings support.
*
@@ -57,6 +57,7 @@
pgd_t *pgd;
pmd_t *pmd;
struct pte_chain *pte_chain;
+ unsigned long pgidx;
pte_chain = pte_chain_alloc(GFP_KERNEL);
if (!pte_chain)
@@ -79,7 +80,10 @@
flush_icache_page(vma, page);
entry = mk_pte(page, prot);
set_pte(pte, entry);
- if (vma->vm_flags & VM_NONLINEAR)
+ pgidx = (addr - vma->vm_start) >> PAGE_SHIFT;
+ pgidx += vma->vm_pgoff;
+ pgidx >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
+ if (page->index != pgidx)
SetPageAnon(page);
pte_chain = page_add_rmap(page, pte, pte_chain);
pte_unmap(pte);
@@ -139,8 +143,7 @@
* and that the remapped range is valid and fully within
* the single existing vma:
*/
- if (vma &&
- ((vma->vm_flags & (VM_SHARED|VM_NONLINEAR)) == (VM_SHARED|VM_NONLINEAR)) &&
+ if (vma && (vma->vm_flags & VM_SHARED) &&
vma->vm_ops && vma->vm_ops->populate &&
end > start && start >= vma->vm_start &&
end <= vma->vm_end)
--- 2.5.64-mm1/mm/mmap.c Thu Mar 6 08:24:24 2003
+++ linux/mm/mmap.c Thu Mar 6 15:59:49 2003
@@ -219,7 +219,6 @@
flag_bits =
_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN) |
_trans(flags, MAP_DENYWRITE, VM_DENYWRITE) |
- _trans(flags, MAP_NONLINEAR, VM_NONLINEAR) |
_trans(flags, MAP_EXECUTABLE, VM_EXECUTABLE);
return prot_bits | flag_bits;
#undef _trans
--- 2.5.64-mm1/mm/rmap.c Thu Mar 6 08:24:24 2003
+++ linux/mm/rmap.c Thu Mar 6 15:59:49 2003
@@ -598,6 +598,8 @@
* in the pte.
*/
pgidx = (address - vma->vm_start) >> PAGE_SHIFT;
+ pgidx += vma->vm_pgoff;
+ pgidx >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
if (1 || page->index != pgidx) {
set_pte(ptep, pgoff_to_pte(page->index));
BUG_ON(!pte_file(*ptep));
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] nonlinear oddities
2003-03-06 16:53 [PATCH] nonlinear oddities Hugh Dickins
@ 2003-03-06 19:14 ` Hugh Dickins
2003-03-06 19:38 ` Dave McCracken
0 siblings, 1 reply; 5+ messages in thread
From: Hugh Dickins @ 2003-03-06 19:14 UTC (permalink / raw)
To: Andrew Morton; +Cc: Dave McCracken, Ingo Molnar, linux-kernel
On Thu, 6 Mar 2003, Hugh Dickins wrote:
> 1. Revert MAP_NONLINEAR and VM_NONLINEAR: I can easily imagine wanting
> VM_NONLINEAR in future, warning that vma is unusual, but currently it's
> not useful: install_page just needs to SetPageAnon if the page is put
> somewhere try_to_unmap_obj_one wouldn't be able to find it.
Now I think about it more, install_page's SetPageAnon is not good at all.
That (unlocked) page may already be mapped into other vmas as a shared
file page, non-zero mapcount, we can't suddenly switch it to Anon
(pte_chained) without doing the work to handle that case.
Before Ingo's file-offset-in-pte, it would have been consistent without
any SetPageAnon there, because the remapped pages would be unreliable
unless locked, and having them unfindable is equivalent to being locked.
But if we're to bother with file-offset-in-pte, then we have to bother
with finding the remapped pages, handling mapped-earlier case properly.
Hugh
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] nonlinear oddities
2003-03-06 19:14 ` Hugh Dickins
@ 2003-03-06 19:38 ` Dave McCracken
0 siblings, 0 replies; 5+ messages in thread
From: Dave McCracken @ 2003-03-06 19:38 UTC (permalink / raw)
To: Hugh Dickins, Andrew Morton; +Cc: Ingo Molnar, linux-kernel
--On Thursday, March 06, 2003 19:14:47 +0000 Hugh Dickins
<hugh@veritas.com> wrote:
> Now I think about it more, install_page's SetPageAnon is not good at all.
> That (unlocked) page may already be mapped into other vmas as a shared
> file page, non-zero mapcount, we can't suddenly switch it to Anon
> (pte_chained) without doing the work to handle that case.
Ouch. You're right. I'll go stare at it for awhile and see if any
solutions jump out at me. I suppose at worst I could write a function to
convert an object page to use pte_chains, but it'd be nice if that weren't
necessary.
Dave McCracken
======================================================================
Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059
dmccr@us.ibm.com T/L 678-3059
^ permalink raw reply [flat|nested] 5+ messages in thread
[parent not found: <fa.o2ppdof.u56795@ifi.uio.no>]
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2003-03-06 16:53 [PATCH] nonlinear oddities Hugh Dickins
2003-03-06 19:14 ` Hugh Dickins
2003-03-06 19:38 ` Dave McCracken
[not found] <fa.o2ppdof.u56795@ifi.uio.no>
[not found] ` <fa.k4ichtj.1rh0gp5@ifi.uio.no>
2003-03-09 1:37 ` Ed Tomlinson
2003-03-10 12:07 ` Hugh Dickins
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