On Wed, 15 Nov 2006 08:18:09 -0500
Trond Myklebust <[email protected]> wrote:
> The following patch allows try_to_release_page() to wait on page writeback
> instead of failing if the user specified __GFP_WAIT.
>
> The reason is that when running NetApp's simulated I/O tool (sio_ntap) on
> the NFS client, I can currently reliably trigger the WARN_ON() in
> invalidate_inode_pages2().
> Whereas we do wait on page_writeback in invalidate_inode_pages2_range(), we
> do so before we unmap the page. There is still a race which will cause the
> call to try_to_release_page() to fail the test for PageWriteback(page).
>
> Signed-off-by: Trond Myklebust <[email protected]>
> ---
>
> mm/filemap.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 7b84dc8..d37f77b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2445,7 +2445,9 @@ int try_to_release_page(struct page *pag
> struct address_space * const mapping = page->mapping;
>
> BUG_ON(!PageLocked(page));
> - if (PageWriteback(page))
> + if (gfp_mask & __GFP_WAIT)
> + wait_on_page_writeback(page);
> + else if (PageWriteback(page))
> return 0;
>
> if (mapping && mapping->a_ops->releasepage)
The change probably makes sense. Need to think about that a bit more and
review callers..
But I don't see how it can change invalidate_inode_pages2(). What we
would effectively have is:
invalidate_inode_pages2_range()
{
lock_page(page);
wait_on_page_writeback(page);
...
wait_on_page_writeback(page);
but nobody could have started another writeback after the "..." because they
couldn't have got the lock_page(), and lock_page() is required for
->writepage()?
-
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