diff options
Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index bf6aa30be58d..d3e2766216e3 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2700,6 +2700,34 @@ const struct vm_operations_struct generic_file_vm_ops = { .page_mkwrite = filemap_page_mkwrite, }; +/** + * page_mkwrite_check_truncate - check if page was truncated + * @page: the page to check + * @inode: the inode to check the page against + * + * Returns the number of bytes in the page up to EOF, + * or -EFAULT if the page was truncated. + */ +int page_mkwrite_check_truncate(struct page *page, struct inode *inode) +{ + loff_t size = i_size_read(inode); + pgoff_t index = size >> PAGE_SHIFT; + int offset = offset_in_page(size); + + if (page->mapping != inode->i_mapping) + return -EFAULT; + + /* page is wholly inside EOF */ + if (page->index < index) + return PAGE_SIZE; + /* page is wholly past EOF */ + if (page->index > index || !offset) + return -EFAULT; + /* page is partially inside EOF */ + return offset; +} +EXPORT_SYMBOL(page_mkwrite_check_truncate); + /* This is used for a general mmap of a disk file */ int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |