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

Eric Van Hensbergen
2007-02-16T22:28:33Z

On 2/16/07, Andrew Morton <akpm@linux-foundation.org> wrote:
> 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??
>

It shouldn't, if it does we are probably in big trouble anyways. I'll
pull it out. Thanks.

-eric