On Thu, 1 Aug 2013, Yan, Zheng wrote:
> On Thu, Aug 1, 2013 at 7:51 PM, Sha Zhengju <handai.szj@xxxxxxxxx> wrote:
> > From: Sha Zhengju <handai.szj@xxxxxxxxxx>
> >
> > Following we will begin to add memcg dirty page accounting around
> __set_page_dirty_
> > {buffers,nobuffers} in vfs layer, so we'd better use vfs interface to
> avoid exporting
> > those details to filesystems.
> >
> > Signed-off-by: Sha Zhengju <handai.szj@xxxxxxxxxx>
> > ---
> > fs/ceph/addr.c | 13 +------------
> > 1 file changed, 1 insertion(+), 12 deletions(-)
> >
> > diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> > index 3e68ac1..1445bf1 100644
> > --- a/fs/ceph/addr.c
> > +++ b/fs/ceph/addr.c
> > @@ -76,7 +76,7 @@ static int ceph_set_page_dirty(struct page *page)
> > if (unlikely(!mapping))
> > return !TestSetPageDirty(page);
> >
> > - if (TestSetPageDirty(page)) {
> > + if (!__set_page_dirty_nobuffers(page)) {
> it's too early to set the radix tree tag here. We should set page's snapshot
> context and increase the i_wrbuffer_ref first. This is because once the tag
> is set, writeback thread can find and start flushing the page.
Unfortunately I only remember being frustrated by this code. :) Looking
at it now, though, it seems like the minimum fix is to set the
page->private before marking the page dirty. I don't know the locking
rules around that, though. If that is potentially racy, maybe the safest
thing would be if __set_page_dirty_nobuffers() took a void* to set
page->private to atomically while holding the tree_lock.
sage
>
> > dout("%p set_page_dirty %p idx %lu -- already dirty\n",
> > mapping->host, page, page->index);
> > return 0;
> > @@ -107,14 +107,7 @@ static int ceph_set_page_dirty(struct page *page)
> > snapc, snapc->seq, snapc->num_snaps);
> > spin_unlock(&ci->i_ceph_lock);
> >
> > - /* now adjust page */
> > - spin_lock_irq(&mapping->tree_lock);
> > if (page->mapping) { /* Race with truncate? */
> > - WARN_ON_ONCE(!PageUptodate(page));
> > - account_page_dirtied(page, page->mapping);
> > - radix_tree_tag_set(&mapping->page_tree,
> > - page_index(page), PAGECACHE_TAG_DIRTY);
> > -
>
> this code was coped from __set_page_dirty_nobuffers(). I think the reason
> Sage did this is to handle the race described in
> __set_page_dirty_nobuffers()'s comment. But I'm wonder if "page->mapping ==
> NULL" can still happen here. Because truncate_inode_page() unmap page from
> processes's address spaces first, then delete page from page cache.
>
> Regards
> Yan, Zheng
>
> > /*
> > * Reference snap context in page->private. Also set
> > * PagePrivate so that we get invalidatepage callback.
> > @@ -126,14 +119,10 @@ static int ceph_set_page_dirty(struct page *page)
> > undo = 1;
> > }
> >
> > - spin_unlock_irq(&mapping->tree_lock);
>
>
>
>
> > -
> > if (undo)
> > /* whoops, we failed to dirty the page */
> > ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
> >
> > - __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
> > -
> > BUG_ON(!PageDirty(page));
> > return 1;
> > }
> > --
> > 1.7.9.5
> >
> > --
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>
>