Commit a76c0b97 authored by Carsten Otte's avatar Carsten Otte Committed by Linus Torvalds

[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: default avatarCarsten Otte <cotte@de.ibm.com>
Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 90ed52eb
...@@ -16,6 +16,29 @@ ...@@ -16,6 +16,29 @@
#include <asm/tlbflush.h> #include <asm/tlbflush.h>
#include "filemap.h" #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 * 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 * the mapping->a_ops->get_xip_page() function for the actual low-level
...@@ -162,7 +185,7 @@ EXPORT_SYMBOL_GPL(xip_file_sendfile); ...@@ -162,7 +185,7 @@ EXPORT_SYMBOL_GPL(xip_file_sendfile);
* xip_write * xip_write
* *
* This function walks all vmas of the address_space and unmaps the * 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 static void
__xip_unmap (struct address_space * mapping, __xip_unmap (struct address_space * mapping,
...@@ -177,13 +200,16 @@ __xip_unmap (struct address_space * mapping, ...@@ -177,13 +200,16 @@ __xip_unmap (struct address_space * mapping,
spinlock_t *ptl; spinlock_t *ptl;
struct page *page; struct page *page;
page = __xip_sparse_page;
if (!page)
return;
spin_lock(&mapping->i_mmap_lock); spin_lock(&mapping->i_mmap_lock);
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
mm = vma->vm_mm; mm = vma->vm_mm;
address = vma->vm_start + address = vma->vm_start +
((pgoff - vma->vm_pgoff) << PAGE_SHIFT); ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
BUG_ON(address < vma->vm_start || address >= vma->vm_end); BUG_ON(address < vma->vm_start || address >= vma->vm_end);
page = ZERO_PAGE(0);
pte = page_check_address(page, mm, address, &ptl); pte = page_check_address(page, mm, address, &ptl);
if (pte) { if (pte) {
/* Nuke the page table entry. */ /* Nuke the page table entry. */
...@@ -222,16 +248,14 @@ xip_file_nopage(struct vm_area_struct * area, ...@@ -222,16 +248,14 @@ xip_file_nopage(struct vm_area_struct * area,
+ area->vm_pgoff; + area->vm_pgoff;
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (pgoff >= size) { if (pgoff >= size)
return NULL; return NOPAGE_SIGBUS;
}
page = mapping->a_ops->get_xip_page(mapping, pgoff*(PAGE_SIZE/512), 0); page = mapping->a_ops->get_xip_page(mapping, pgoff*(PAGE_SIZE/512), 0);
if (!IS_ERR(page)) { if (!IS_ERR(page))
goto out; goto out;
}
if (PTR_ERR(page) != -ENODATA) if (PTR_ERR(page) != -ENODATA)
return NULL; return NOPAGE_SIGBUS;
/* sparse block */ /* sparse block */
if ((area->vm_flags & (VM_WRITE | VM_MAYWRITE)) && if ((area->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
...@@ -241,12 +265,14 @@ xip_file_nopage(struct vm_area_struct * area, ...@@ -241,12 +265,14 @@ xip_file_nopage(struct vm_area_struct * area,
page = mapping->a_ops->get_xip_page (mapping, page = mapping->a_ops->get_xip_page (mapping,
pgoff*(PAGE_SIZE/512), 1); pgoff*(PAGE_SIZE/512), 1);
if (IS_ERR(page)) if (IS_ERR(page))
return NULL; return NOPAGE_SIGBUS;
/* unmap page at pgoff from all other vmas */ /* unmap page at pgoff from all other vmas */
__xip_unmap(mapping, pgoff); __xip_unmap(mapping, pgoff);
} else { } else {
/* not shared and writable, use ZERO_PAGE() */ /* not shared and writable, use xip_sparse_page() */
page = ZERO_PAGE(0); page = xip_sparse_page();
if (!page)
return NOPAGE_OOM;
} }
out: out:
......
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