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authorCarsten Otte <cotte@de.ibm.com>2007-03-29 01:20:39 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-03-29 08:22:26 -0700
commita76c0b976310bbb1b6eaecaaae465af194134477 (patch)
tree4f23a06244f7cb6689bd7ded80843c481968a283 /mm/filemap_xip.c
parent90ed52ebe48181d3c5427b3bd1d24f659e7575ad (diff)
downloadlinux-a76c0b976310bbb1b6eaecaaae465af194134477.tar.gz
[PATCH] mm: fix xip issue with /dev/zero
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@de.ibm.com> Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/filemap_xip.c')
-rw-r--r--mm/filemap_xip.c48
1 files changed, 37 insertions, 11 deletions
diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
index 9dd9fbb7513..cbb335813ec 100644
--- a/mm/filemap_xip.c
+++ b/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 * mapping,
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. */
@@ -222,16 +248,14 @@ xip_file_nopage(struct vm_area_struct * area,
+ area->vm_pgoff;
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
- if (pgoff >= size) {
- return NULL;
- }
+ if (pgoff >= size)
+ return NOPAGE_SIGBUS;
page = mapping->a_ops->get_xip_page(mapping, pgoff*(PAGE_SIZE/512), 0);
- if (!IS_ERR(page)) {
+ if (!IS_ERR(page))
goto out;
- }
if (PTR_ERR(page) != -ENODATA)
- return NULL;
+ return NOPAGE_SIGBUS;
/* sparse block */
if ((area->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
@@ -241,12 +265,14 @@ xip_file_nopage(struct vm_area_struct * area,
page = mapping->a_ops->get_xip_page (mapping,
pgoff*(PAGE_SIZE/512), 1);
if (IS_ERR(page))
- return NULL;
+ return NOPAGE_SIGBUS;
/* unmap page at pgoff from all other vmas */
__xip_unmap(mapping, 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)
+ return NOPAGE_OOM;
}
out: