From: "Yan, Zheng" <ukernel@gmail.com>
To: Sha Zhengju <handai.szj@gmail.com>
Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
ceph-devel <ceph-devel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>, Cgroups <cgroups@vger.kernel.org>,
Sage Weil <sage@inktank.com>, Michal Hocko <mhocko@suse.cz>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Glauber Costa <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: Fri, 2 Aug 2013 21:11:38 +0800 [thread overview]
Message-ID: <CAAM7YAnVYZ-=LXVuDHj38Bh88Fd+Rw9w7Efs1_efmv9X90-D1Q@mail.gmail.com> (raw)
In-Reply-To: <CAFj3OHXR=PqHwLcXCub8YezcGFF7kbKX3X2dV=6FQM78K__D8g@mail.gmail.com>
On Fri, Aug 2, 2013 at 5:04 PM, Sha Zhengju <handai.szj@gmail.com> wrote:
>
> On Thu, Aug 1, 2013 at 11:19 PM, Yan, Zheng <ukernel@gmail.com> 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.
>
> OK, thanks for pointing it out.
>
> >
> >
> >> 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.
>
> But in non-mmap case, doesn't it has no relation to 'unmap page from
> address spaces'?
In non-mmap case, page is locked when the set_page_dirty() callback is called.
truncate_inode_page() waits until the page is unlocked, then delete it from the
page cache.
Regards
Yan, Zheng
> The check is exactly avoiding racy with delete_from_page_cache(),
> since the two both need to hold mapping->tree_lock, and if truncate
> goes first then __set_page_dirty_nobuffers() may have NULL mapping.
>
>
> Thanks,
> Sha
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next prev parent reply other threads:[~2013-08-02 13:11 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
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 [this message]
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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