diff options
| author | Hugh Dickins <hugh@veritas.com> | 2005-10-29 18:15:55 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-10-29 21:40:36 -0700 |
| commit | 72866f6f277ec0ddd6df7a3b6ecdcf59a28de115 (patch) | |
| tree | a76bb7fb8e092250c4399c20f0c7c973b77cb0bb | |
| parent | 6237bcd94851e9cf0ecd2520d744779df0f5a9a6 (diff) | |
| download | lwn-72866f6f277ec0ddd6df7a3b6ecdcf59a28de115.tar.gz lwn-72866f6f277ec0ddd6df7a3b6ecdcf59a28de115.zip | |
[PATCH] mm: anon is already wrprotected
do_anonymous_page's pte_wrprotect causes some confusion: in such a case,
vm_page_prot must already be forcing COW, so must omit write permission, and
so the pte_wrprotect is redundant. Replace it by a comment to that effect,
and reword the comment on unuse_pte which also caused confusion.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | mm/memory.c | 7 | ||||
| -rw-r--r-- | mm/swapfile.c | 7 |
2 files changed, 7 insertions, 7 deletions
diff --git a/mm/memory.c b/mm/memory.c index fd5d4c6dc762..13667681cd16 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1768,13 +1768,14 @@ do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr) { pte_t entry; - struct page * page = ZERO_PAGE(addr); - /* Read-only mapping of ZERO_PAGE. */ - entry = pte_wrprotect(mk_pte(ZERO_PAGE(addr), vma->vm_page_prot)); + /* Mapping of ZERO_PAGE - vm_page_prot is readonly */ + entry = mk_pte(ZERO_PAGE(addr), vma->vm_page_prot); /* ..except if it's a write access */ if (write_access) { + struct page *page; + /* Allocate our own private page. */ pte_unmap(page_table); spin_unlock(&mm->page_table_lock); diff --git a/mm/swapfile.c b/mm/swapfile.c index 1dcaeda039f4..05c851291241 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -398,10 +398,9 @@ void free_swap_and_cache(swp_entry_t entry) } /* - * Always set the resulting pte to be nowrite (the same as COW pages - * after one process has exited). We don't know just how many PTEs will - * share this swap entry, so be cautious and let do_wp_page work out - * what to do if a write is requested later. + * No need to decide whether this PTE shares the swap entry with others, + * just let do_wp_page work it out if a write is requested later - to + * force COW, vm_page_prot omits write permission from any private vma. * * vma->vm_mm->page_table_lock is held. */ |