diff options
| -rw-r--r-- | fs/buffer.c | 47 | ||||
| -rw-r--r-- | include/linux/buffer_head.h | 2 |
2 files changed, 49 insertions, 0 deletions
diff --git a/fs/buffer.c b/fs/buffer.c index 0f900671423..02ebb1f1d3b 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2194,6 +2194,52 @@ int generic_commit_write(struct file *file, struct page *page, return 0; } +/* + * block_page_mkwrite() is not allowed to change the file size as it gets + * called from a page fault handler when a page is first dirtied. Hence we must + * be careful to check for EOF conditions here. We set the page up correctly + * for a written page which means we get ENOSPC checking when writing into + * holes and correct delalloc and unwritten extent mapping on filesystems that + * support these features. + * + * We are not allowed to take the i_mutex here so we have to play games to + * protect against truncate races as the page could now be beyond EOF. Because + * vmtruncate() writes the inode size before removing pages, once we have the + * page lock we can determine safely if the page is beyond EOF. If it is not + * beyond EOF, then the page is guaranteed safe against truncation until we + * unlock the page. + */ +int +block_page_mkwrite(struct vm_area_struct *vma, struct page *page, + get_block_t get_block) +{ + struct inode *inode = vma->vm_file->f_path.dentry->d_inode; + unsigned long end; + loff_t size; + int ret = -EINVAL; + + lock_page(page); + size = i_size_read(inode); + if ((page->mapping != inode->i_mapping) || + ((page->index << PAGE_CACHE_SHIFT) > size)) { + /* page got truncated out from underneath us */ + goto out_unlock; + } + + /* page is wholly or partially inside EOF */ + if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) + end = size & ~PAGE_CACHE_MASK; + else + end = PAGE_CACHE_SIZE; + + ret = block_prepare_write(page, 0, end, get_block); + if (!ret) + ret = block_commit_write(page, 0, end); + +out_unlock: + unlock_page(page); + return ret; +} /* * nobh_prepare_write()'s prereads are special: the buffer_heads are freed @@ -2977,6 +3023,7 @@ EXPORT_SYMBOL(__brelse); EXPORT_SYMBOL(__wait_on_buffer); EXPORT_SYMBOL(block_commit_write); EXPORT_SYMBOL(block_prepare_write); +EXPORT_SYMBOL(block_page_mkwrite); EXPORT_SYMBOL(block_read_full_page); EXPORT_SYMBOL(block_sync_page); EXPORT_SYMBOL(block_truncate_page); diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index 5c6e12853a9..35cadad84b1 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -209,6 +209,8 @@ int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*, int generic_cont_expand(struct inode *inode, loff_t size); int generic_cont_expand_simple(struct inode *inode, loff_t size); int block_commit_write(struct page *page, unsigned from, unsigned to); +int block_page_mkwrite(struct vm_area_struct *vma, struct page *page, + get_block_t get_block); void block_sync_page(struct page *); sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *); int generic_commit_write(struct file *, struct page *, unsigned, unsigned); |