From: Sage Weil <sage@inktank.com>
To: "Yan, Zheng" <ukernel@gmail.com>
Cc: Sha Zhengju <handai.szj@gmail.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
ceph-devel <ceph-devel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
cgroups@vger.kernel.org, mhocko@suse.cz,
kamezawa.hiroyu@jp.fujitsu.com, glommer@gmail.com,
Greg Thelen <gthelen@google.com>,
Wu Fengguang <fengguang.wu@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Sha Zhengju <handai.szj@taobao.com>
Subject: Re: [PATCH V5 2/8] fs/ceph: vfs __set_page_dirty_nobuffers interface instead of doing it inside filesystem
Date: Thu, 1 Aug 2013 11:27:49 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1308011121080.22584@cobra.newdream.net> (raw)
In-Reply-To: <CAAM7YAmxmmA6g2WPVtGN1-42rtDBYzLhF-gvNXxcBN6dUveBYQ@mail.gmail.com>
[-- Attachment #1: Type: TEXT/PLAIN, Size: 3697 bytes --]
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.
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
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
>
next prev parent reply other threads:[~2013-08-01 18:27 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1375357402-9811-1-git-send-email-handai.szj@taobao.com>
2013-08-01 11:51 ` [PATCH V5 2/8] fs/ceph: vfs __set_page_dirty_nobuffers interface instead of doing it inside filesystem Sha Zhengju
2013-08-01 15:19 ` Yan, Zheng
2013-08-01 18:27 ` Sage Weil [this message]
2013-08-02 10:04 ` Sha Zhengju
[not found] ` <CAFj3OHVXvtr5BDMrGatHZi7M9y+dh1ZKRMQZGjZmNBcg3pNQtw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-08-02 20:30 ` Sage Weil
2013-08-03 8:58 ` Sha Zhengju
2013-08-02 9:04 ` Sha Zhengju
2013-08-02 13:11 ` Yan, Zheng
2013-08-01 11:53 ` [PATCH V5 4/8] memcg: add per cgroup dirty pages accounting Sha Zhengju
2013-08-01 11:54 ` [PATCH V5 5/8] memcg: add per cgroup writeback " Sha Zhengju
2013-08-01 14:53 ` Michal Hocko
[not found] ` <20130801145302.GJ5198-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2013-08-03 9:25 ` Sha Zhengju
[not found] ` <CAFj3OHV-VCKJfe6bv4UMvv+uj4LELDXsieRZFJD06Yrdyy=XxA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-08-04 10:08 ` Michal Hocko
2013-08-22 9:46 ` Fwd: " Sha Zhengju
2013-08-22 9:50 ` [PATCH 1/4] memcg: remove MEMCG_NR_FILE_MAPPED Sha Zhengju
2013-08-22 9:52 ` [PATCH 2/4] memcg: check for proper lock held in mem_cgroup_update_page_stat Sha Zhengju
2013-08-22 9:53 ` [PATCH 3/4] memcg: add per cgroup writeback pages accounting Sha Zhengju
2013-08-22 22:40 ` Andrew Morton
2013-08-23 16:11 ` Sha Zhengju
2013-08-22 9:53 ` [PATCH 4/4] memcg: Document cgroup dirty/writeback memory statistics Sha Zhengju
2013-08-04 18:51 ` [PATCH V5 5/8] memcg: add per cgroup writeback pages accounting Greg Thelen
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