lkml.org 
[lkml]   [2017]   [Apr]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 06/17] mm: doc comment for scary spot in write_one_page
On Wed, Apr 12, 2017 at 09:01:34AM -0400, Jeff Layton wrote:
> On Wed, 2017-04-12 at 08:06 -0400, Jeff Layton wrote:
> > Not sure what to do here just yet.
> >
> > Signed-off-by: Jeff Layton <jlayton@redhat.com>
> > ---
> > mm/page-writeback.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> > index de0dbf12e2c1..3ac8399dc984 100644
> > --- a/mm/page-writeback.c
> > +++ b/mm/page-writeback.c
> > @@ -2388,6 +2388,12 @@ int write_one_page(struct page *page)
> > ret = mapping->a_ops->writepage(page, &wbc);
> > if (ret == 0) {
> > wait_on_page_writeback(page);
> > + /*
> > + * FIXME: is this racy? What guarantees that PG_error
> > + * will still be set once we get around to checking it?
> > + * What if writeback fails, but then a read is issued
> > + * before we check this, and that calls ClearPageError?
> > + */
> > if (PageError(page))
> > ret = -EIO;
> > }
>
> Ahh, we are always under the page lock here, and this is generally used
> for writing out directory pages anyway. I'm fine with dropping this
> patch unless someone else sees a problem here.

->writepage drops the page lock. We're still holding a refcount on this
page, but that's not going to prevent read being called. But maybe the
filesystem won't call read on a page that's marked as PageError?

\
 
 \ /
  Last update: 2017-04-12 16:40    [W:0.101 / U:7.612 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site