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

[Andrew Morton <akpm@linux-foundation.org>]

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??