On Tue, 6 Feb 2007 09:02:23 +0100 (CET) Nick Piggin <npiggin@xxxxxxx> wrote:
> __block_write_full_page is calling SetPageUptodate without the page locked.
> This is unusual, but not incorrect, as PG_writeback is still set.
>
> However with the previous patch, this is now a problem: so don't bother
> setting the page uptodate in this case (it is weird that the write path
> does such a thing anyway). Instead just leave it to the read side to bring
> the page uptodate when it notices that all buffers are uptodate.
>
> Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
>
> Index: linux-2.6/fs/buffer.c
> ===================================================================
> --- linux-2.6.orig/fs/buffer.c
> +++ linux-2.6/fs/buffer.c
> @@ -1679,6 +1679,7 @@ static int __block_write_full_page(struc
> */
> BUG_ON(PageWriteback(page));
> set_page_writeback(page);
> + unlock_page(page);
>
> do {
> struct buffer_head *next = bh->b_this_page;
> @@ -1688,7 +1689,6 @@ static int __block_write_full_page(struc
> }
> bh = next;
> } while (bh != head);
> - unlock_page(page);
>
> err = 0;
> done:
Why this change? Without looking at it too hard, it seems that if
submit_bh() completes synchronously, this thread can end up playing with
the buffers on a non-locked, non-PageWriteback page. Someone else could
whip the buffers away and oops?
-
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