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SubjectRe: [PATCH 4/7] Use vfs __set_page_dirty interface instead of doing it inside filesystem
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On Thu, Jul 5, 2012 at 11:20 PM, Sage Weil <sage@inktank.com> wrote:
> On Wed, 4 Jul 2012, Sha Zhengju wrote:
>> On 07/02/2012 10:49 PM, Sage Weil wrote:
>> > On Mon, 2 Jul 2012, Sha Zhengju wrote:
>> > > On 06/29/2012 01:21 PM, Sage Weil wrote:
>> > > > On Thu, 28 Jun 2012, Sha Zhengju wrote:
>> > > >
>> > > > > From: Sha Zhengju<handai.szj@taobao.com>
>> > > > >
>> > > > > Following we will treat SetPageDirty and dirty page accounting as an
>> > > > > integrated
>> > > > > operation. Filesystems had better use vfs interface directly to avoid
>> > > > > those details.
>> > > > >
>> > > > > Signed-off-by: Sha Zhengju<handai.szj@taobao.com>
>> > > > > ---
>> > > > > fs/buffer.c | 2 +-
>> > > > > fs/ceph/addr.c | 20 ++------------------
>> > > > > include/linux/buffer_head.h | 2 ++
>> > > > > 3 files changed, 5 insertions(+), 19 deletions(-)
>> > > > >
>> > > > > diff --git a/fs/buffer.c b/fs/buffer.c
>> > > > > index e8d96b8..55522dd 100644
>> > > > > --- a/fs/buffer.c
>> > > > > +++ b/fs/buffer.c
>> > > > > @@ -610,7 +610,7 @@ EXPORT_SYMBOL(mark_buffer_dirty_inode);
>> > > > > * If warn is true, then emit a warning if the page is not uptodate
>> > > > > and
>> > > > > has
>> > > > > * not been truncated.
>> > > > > */
>> > > > > -static int __set_page_dirty(struct page *page,
>> > > > > +int __set_page_dirty(struct page *page,
>> > > > > struct address_space *mapping, int warn)
>> > > > > {
>> > > > > if (unlikely(!mapping))
>> > > > This also needs an EXPORT_SYMBOL(__set_page_dirty) to allow ceph to
>> > > > continue to build as a module.
>> > > >
>> > > > With that fixed, the ceph bits are a welcome cleanup!
>> > > >
>> > > > Acked-by: Sage Weil<sage@inktank.com>
>> > > Further, I check the path again and may it be reworked as follows to avoid
>> > > undo?
>> > >
>> > > __set_page_dirty();
>> > > __set_page_dirty();
>> > > ceph operations; ==> if (page->mapping)
>> > > if (page->mapping) ceph
>> > > operations;
>> > > ;
>> > > else
>> > > undo = 1;
>> > > if (undo)
>> > > xxx;
>> > Yep. Taking another look at the original code, though, I'm worried that
>> > one reason the __set_page_dirty() actions were spread out the way they are
>> > is because we wanted to ensure that the ceph operations were always
>> > performed when PagePrivate was set.
>> >
>>
>> Sorry, I've lost something:
>>
>> __set_page_dirty(); __set_page_dirty();
>> ceph operations;
>> if(page->mapping) ==> if(page->mapping) {
>> SetPagePrivate; SetPagePrivate;
>> else ceph operations;
>> undo = 1; }
>>
>> if (undo)
>> XXX;
>>
>> I think this can ensure that ceph operations are performed together with
>> SetPagePrivate.
>
> Yeah, that looks right, as long as the ceph accounting operations happen
> before SetPagePrivate. I think it's no more or less racy than before, at
> least.
>
> The patch doesn't apply without the previous ones in the series, it looks
> like. Do you want to prepare a new version or should I?
>

Good. I'm doing some test then I'll send out a new version patchset, please
wait a bit. : )


Thanks,
Sha


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