diff options
| author | Carsten Otte <cotte@de.ibm.com> | 2007-03-29 01:20:39 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-03-29 08:22:26 -0700 |
| commit | a76c0b976310bbb1b6eaecaaae465af194134477 (patch) | |
| tree | 4f23a06244f7cb6689bd7ded80843c481968a283 /mm/filemap_xip.c | |
| parent | 90ed52ebe48181d3c5427b3bd1d24f659e7575ad (diff) | |
[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.c | 48 |
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: |