The patch titled
mm: fix xip issue with /dev/zero
has been added to the -mm tree. Its filename is
mm-fix-xip-issue-with-dev-zero.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: mm: fix xip issue with /dev/zero
From: Carsten Otte <cotte@xxxxxxxxxx>
Fix the bug, that reading into xip mapping from /dev/zero fills the user
page table with ZERO_PAGE() entries. Later on, xip cannot tell which pages
have been ZERO_PAGE() filled by access to a sparse mapping, and which ones
origin from /dev/zero. It will unmap ZERO_PAGE from all mappings when
filling the sparse hole with data. xip does now use its own zeroed page
for its sparse mappings. Please apply.
Signed-off-by: Carsten Otte <cotte@xxxxxxxxxx>
Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap_xip.c | 38 ++++++++++++++++++++++++++++++++++----
1 files changed, 34 insertions(+), 4 deletions(-)
diff -puN mm/filemap_xip.c~mm-fix-xip-issue-with-dev-zero mm/filemap_xip.c
--- a/mm/filemap_xip.c~mm-fix-xip-issue-with-dev-zero
+++ a/mm/filemap_xip.c
@@ -17,6 +17,29 @@
#include "filemap.h"
/*
+ * We do use our own empty page to avoid interference with other users
+ * of ZERO_PAGE(), such as /dev/zero
+ */
+static struct page *__xip_sparse_page;
+
+static struct page *xip_sparse_page(void)
+{
+ if (!__xip_sparse_page) {
+ unsigned long zeroes = get_zeroed_page(GFP_HIGHUSER);
+ if (zeroes) {
+ static DEFINE_SPINLOCK(xip_alloc_lock);
+ spin_lock(&xip_alloc_lock);
+ if (!__xip_sparse_page)
+ __xip_sparse_page = virt_to_page(zeroes);
+ else
+ free_page(zeroes);
+ spin_unlock(&xip_alloc_lock);
+ }
+ }
+ return __xip_sparse_page;
+}
+
+/*
* This is a file read routine for execute in place files, and uses
* the mapping->a_ops->get_xip_page() function for the actual low-level
* stuff.
@@ -162,7 +185,7 @@ EXPORT_SYMBOL_GPL(xip_file_sendfile);
* xip_write
*
* This function walks all vmas of the address_space and unmaps the
- * ZERO_PAGE when found at pgoff. Should it go in rmap.c?
+ * __xip_sparse_page when found at pgoff.
*/
static void
__xip_unmap (struct address_space * mapping,
@@ -177,13 +200,16 @@ __xip_unmap (struct address_space * mapp
spinlock_t *ptl;
struct page *page;
+ page = __xip_sparse_page;
+ if (!page)
+ return;
+
spin_lock(&mapping->i_mmap_lock);
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
mm = vma->vm_mm;
address = vma->vm_start +
((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
BUG_ON(address < vma->vm_start || address >= vma->vm_end);
- page = ZERO_PAGE(0);
pte = page_check_address(page, mm, address, &ptl);
if (pte) {
/* Nuke the page table entry. */
@@ -245,8 +271,12 @@ static struct page *xip_file_fault(struc
/* unmap page at pgoff from all other vmas */
__xip_unmap(mapping, fdata->pgoff);
} else {
- /* not shared and writable, use ZERO_PAGE() */
- page = ZERO_PAGE(0);
+ /* not shared and writable, use xip_sparse_page() */
+ page = xip_sparse_page();
+ if (!page) {
+ fdata->type = VM_FAULT_OOM;
+ return NULL;
+ }
}
out:
_
Patches currently in -mm which might be from cotte@xxxxxxxxxx are
mm-fix-xip-issue-with-dev-zero.patch
-
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