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Subject[patch 17/18] remap_file_pages linear nonuniform support: (1) try_to_unmap_one fix
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From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

Since we probably will not support linear nonuniform VMAs, this will not
probably be needed. However I'm sending it just in case.

Fix try_to_unmap_one for linear VM_NONUNIFORM vma's.

When unmapping linear but non uniform VMA's in try_to_unmap_one, we must
encode the prots in the PTE.

However, we don't use the generic save_nonlinear_pte() function as it allows
for nonlinear offsets, on which we instead BUG() in this code path, by using
save_nonuniform_pte().

I've not added any TLB flush because PTE's have already been cleared and
flushed in both cases, and (I assume from existing practice and common sense,
but I don't trust CPU architects on having the latter ;-) ) TLB won't need to
know about changes in the "software" part of absent PTEs.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
---

linux-2.6.git-paolo/include/linux/pagemap.h | 11 +++++++++++
linux-2.6.git-paolo/mm/rmap.c | 3 +++
2 files changed, 14 insertions(+)

diff -puN include/linux/pagemap.h~rfp-linear-nonuniform-1 include/linux/pagemap.h
--- linux-2.6.git/include/linux/pagemap.h~rfp-linear-nonuniform-1 2005-08-25 12:46:20.000000000 +0200
+++ linux-2.6.git-paolo/include/linux/pagemap.h 2005-08-25 12:46:20.000000000 +0200
@@ -180,6 +180,17 @@ static inline void save_nonlinear_pte(pt
set_pte_at(mm, addr, ptep, pgoff_prot_to_pte(page->index, pgprot));
}

+/* For linear but nonuniform VMA's*/
+static inline void save_nonuniform_pte(pte_t pte, pte_t * ptep, struct
+ vm_area_struct *vma, struct mm_struct *mm, struct page* page,
+ unsigned long addr)
+{
+ pgprot_t pgprot = pte_to_pgprot(pte);
+ BUG_ON(linear_page_index(vma, addr) != page->index);
+ if (pgprot_val(pgprot) != pgprot_val(vma->vm_page_prot))
+ set_pte_at(mm, addr, ptep, pgoff_prot_to_pte(page->index, pgprot));
+}
+
extern void FASTCALL(__lock_page(struct page *page));
extern void FASTCALL(unlock_page(struct page *page));

diff -puN mm/rmap.c~rfp-linear-nonuniform-1 mm/rmap.c
--- linux-2.6.git/mm/rmap.c~rfp-linear-nonuniform-1 2005-08-25 12:46:20.000000000 +0200
+++ linux-2.6.git-paolo/mm/rmap.c 2005-08-25 12:46:20.000000000 +0200
@@ -543,6 +543,9 @@ static int try_to_unmap_one(struct page
flush_cache_page(vma, address, page_to_pfn(page));
pteval = ptep_clear_flush(vma, address, pte);

+ /* If nonlinear, store the file page offset in the pte. */
+ save_nonuniform_pte(pteval, pte, vma, mm, page, address);
+
/* Move the dirty bit to the physical page now the pte is gone. */
if (pte_dirty(pteval))
set_page_dirty(page);
_
-
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