Re: [PATCH 2/2] xfs: stop using kmalloc in xfs_buf_get_noaddr

Timothy Shimmin
2007-03-13T00:09:06Z

Hi,

--On 9 March 2007 12:55:11 PM +0100 Christoph Hellwig <hch@lst.de> wrote:

> Ed Cashin found a bug in the error handling code for the case where
> a page allocation fails. Here's the updated version:
>
> Index: linux-2.6/fs/xfs/linux-2.6/xfs_buf.c
> ===================================================================
> --- linux-2.6.orig/fs/xfs/linux-2.6/xfs_buf.c 2007-03-08 19:08:38.000000000 +0100
> +++ linux-2.6/fs/xfs/linux-2.6/xfs_buf.c 2007-03-09 08:59:15.000000000 +0100
....
> + for (i = 0; i < page_count; i++) {
> + bp->b_pages[i] = alloc_page(GFP_KERNEL);
> + if (!bp->b_pages[i])
> + goto fail_free_mem;
> + }
> + bp->b_flags |= _XBF_PAGES;
> +
> + error = _xfs_buf_map_pages(bp, XBF_MAPPED);
> + if (unlikely(error)) {
> + printk(KERN_WARNING "%s: failed to map pages\n",
> + __FUNCTION__);
> goto fail_free_mem;
> - bp->b_flags |= _XBF_KMEM_ALLOC;
> + }
>
> xfs_buf_unlock(bp);
>
> XB_TRACE(bp, "no_daddr", data);
> return bp;
> +
> fail_free_mem:
> - kmem_free(data, malloc_len);
> + for ( ; i >= 0; i--)
> + __free_page(bp->b_pages[i]);
> fail_free_buf:
> xfs_buf_free(bp);
> fail:

It looks like you might need: for (i--; i >= 0; i--)
(or: for (j = 0; j < i; j++) etc.)

Because if the initial alloc_page loop goes to completion then:
i == pagecount
and if alloc_page loop terminates early then
bp->b_pages[i] == NULL
So we have gone 1 too far in both cases and need to
start free'ing back one.
Unless I missed something.

--Tim