| Message ID | alpine.DEB.2.00.1308021326080.1128@cobra.newdream.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, Aug 3, 2013 at 4:30 AM, Sage Weil <sage@inktank.com> wrote: > On Fri, 2 Aug 2013, Sha Zhengju wrote: >> On Fri, Aug 2, 2013 at 2:27 AM, Sage Weil <sage@inktank.com> wrote: >> > On Thu, 1 Aug 2013, Yan, Zheng wrote: >> >> On Thu, Aug 1, 2013 at 7:51 PM, Sha Zhengju <handai.szj@gmail.com> wrote: >> >> > From: Sha Zhengju <handai.szj@taobao.com> >> >> > >> >> > 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@taobao.com> >> >> > --- >> >> > 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. >> > >> >> Sorry, I don't catch the point of your last sentence... Could you >> please explain it again? > > It didn't make much sense. :) I was worried about multiple callers to > set_page_dirty, but as understand it, this all happens under page->lock, > right? (There is a mention of other special cases in mm/page-writeback.c, > but I'm hoping we don't need to worry about that.) I agree, page lock can handle the concurrent access. > > In any case, I suspect what we actually want is something like the below > (untested) patch. The snapc accounting can be ignored here because > invalidatepage will clean it up... > > sage > > > > diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c > index afb2fc2..7602e46 100644 > --- a/fs/ceph/addr.c > +++ b/fs/ceph/addr.c > @@ -76,9 +76,10 @@ static int ceph_set_page_dirty(struct page *page) > if (unlikely(!mapping)) > return !TestSetPageDirty(page); > > - if (TestSetPageDirty(page)) { > + if (PageDirty(page)) { > dout("%p set_page_dirty %p idx %lu -- already dirty\n", > mapping->host, page, page->index); > + BUG_ON(!PagePrivate(page)); > return 0; > } > > @@ -107,35 +108,16 @@ 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); > - > - /* > - * Reference snap context in page->private. Also set > - * PagePrivate so that we get invalidatepage callback. > - */ > - page->private = (unsigned long)snapc; > - SetPagePrivate(page); > - } else { > - dout("ANON set_page_dirty %p (raced truncate?)\n", 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); > + /* > + * Reference snap context in page->private. Also set > + * PagePrivate so that we get invalidatepage callback. > + */ > + BUG_ON(PagePrivate(page)); > + page->private = (unsigned long)snapc; > + SetPagePrivate(page); > > - BUG_ON(!PageDirty(page)); > - return 1; > + return __set_page_dirty_nobuffers(page); > } > > /* Looks good. Since page lock can avoid multiple access, the undo logic is also not necessary anymore. Thank you very much!
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c index afb2fc2..7602e46 100644 --- a/fs/ceph/addr.c +++ b/fs/ceph/addr.c @@ -76,9 +76,10 @@ static int ceph_set_page_dirty(struct page *page) if (unlikely(!mapping)) return !TestSetPageDirty(page); - if (TestSetPageDirty(page)) { + if (PageDirty(page)) { dout("%p set_page_dirty %p idx %lu -- already dirty\n", mapping->host, page, page->index); + BUG_ON(!PagePrivate(page)); return 0; } @@ -107,35 +108,16 @@ 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); - - /* - * Reference snap context in page->private. Also set - * PagePrivate so that we get invalidatepage callback. - */ - page->private = (unsigned long)snapc; - SetPagePrivate(page); - } else { - dout("ANON set_page_dirty %p (raced truncate?)\n", 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); + /* + * Reference snap context in page->private. Also set + * PagePrivate so that we get invalidatepage callback. + */ + BUG_ON(PagePrivate(page)); + page->private = (unsigned long)snapc; + SetPagePrivate(page); - BUG_ON(!PageDirty(page)); - return 1; + return __set_page_dirty_nobuffers(page); } /* -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in