Re: [PATCH] 9p: add write-cache support to loose cache mode (take 3)

Andrew Morton
2007-02-16T20:12:38Z

On Fri, 16 Feb 2007 09:37:01 -0600 Eric Van Hensbergen <ericvh@gmail.com> wrote:

> +static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
> +{
> + char *buffer = NULL;
> + struct address_space *mapping = page->mapping;
> + int retval = -EIO;
> + loff_t offset = 0;
> + pgoff_t end_index;
> + int count = PAGE_CACHE_SIZE;
> + struct file *filp = v9fs_find_file(page);
> + struct inode *inode = mapping->host;
> +
> + dprintk(DEBUG_VFS, "page: %p\n", page);
> +
> + if ((!inode) || (!filp))
> + goto UnlockPage;
> +
> + end_index = inode->i_size >> PAGE_CACHE_SHIFT;
> +
> + /* complicated case at end of file */
> + if (page->index >= end_index) {
> + /* things got complicated... */
> + count = inode->i_size & (PAGE_CACHE_SIZE - 1);
> + if (page->index >= end_index + 1 || !count)
> + return 0; /* truncated - don't care */
> + }
> +
> + buffer = kmap(page);
> + offset = ((loff_t) page->index << PAGE_CACHE_SHIFT);
> + page_cache_get(page);
> + retval = v9fs_write(filp, NULL, buffer, count, &offset);
> +
> kunmap(page);
> +
> + UnlockPage:
> unlock_page(page);
> + page_cache_release(page);
> +
> return retval;
> }

The page_cache_get/release here aren't needed: lock_page suffices.

Are you sure the page refcounting is right if the `goto UnlockPage'
happens?

Can that goto actually happen??