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Date: Wed, 04 Jul 2012 16:11:48 +0800
From: Sha Zhengju <handai.szj@...il.com>
To: Sage Weil <sage@...tank.com>
CC: linux-mm@...ck.org, cgroups@...r.kernel.org,
kamezawa.hiroyu@...fujitsu.com, gthelen@...gle.com,
yinghan@...gle.com, akpm@...ux-foundation.org, mhocko@...e.cz,
linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
sage@...dream.net, ceph-devel@...r.kernel.org,
Sha Zhengju <handai.szj@...bao.com>
Subject: Re: [PATCH 4/7] Use vfs __set_page_dirty interface instead of doing
it inside filesystem
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@...bao.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@...bao.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@...tank.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.
> It looks like invalidatepage won't get called if private isn't set, and
> presumably it handles the truncate race with __set_page_dirty() properly
> (right?). What about writeback? Do we need to worry about writepage[s]
> getting called with a NULL page->private?
__set_page_dirty does handle racing conditions with truncate and
writeback writepage[s] also take page->private into consideration
which is done inside specific filesystems. I notice that ceph has handled
this in ceph_writepage().
Sorry, not vfs expert and maybe I've not caught your point...
Thanks,
Sha
> Thanks!
> sage
>
>
>
>>
>>
>> Thanks,
>> Sha
>>
>>>> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
>>>> index 8b67304..d028fbe 100644
>>>> --- a/fs/ceph/addr.c
>>>> +++ b/fs/ceph/addr.c
>>>> @@ -5,6 +5,7 @@
>>>> #include<linux/mm.h>
>>>> #include<linux/pagemap.h>
>>>> #include<linux/writeback.h> /* generic_writepages */
>>>> +#include<linux/buffer_head.h>
>>>> #include<linux/slab.h>
>>>> #include<linux/pagevec.h>
>>>> #include<linux/task_io_accounting_ops.h>
>>>> @@ -73,14 +74,8 @@ static int ceph_set_page_dirty(struct page *page)
>>>> int undo = 0;
>>>> struct ceph_snap_context *snapc;
>>>>
>>>> - if (unlikely(!mapping))
>>>> - return !TestSetPageDirty(page);
>>>> -
>>>> - if (TestSetPageDirty(page)) {
>>>> - dout("%p set_page_dirty %p idx %lu -- already dirty\n",
>>>> - mapping->host, page, page->index);
>>>> + if (!__set_page_dirty(page, mapping, 1))
>>>> return 0;
>>>> - }
>>>>
>>>> inode = mapping->host;
>>>> ci = ceph_inode(inode);
>>>> @@ -107,14 +102,7 @@ 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);
>>>> -
>>>> /*
>>>> * Reference snap context in page->private. Also set
>>>> * PagePrivate so that we get invalidatepage callback.
>>>> @@ -126,14 +114,10 @@ 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;
>>>> }
>>>> diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
>>>> index 458f497..0a331a8 100644
>>>> --- a/include/linux/buffer_head.h
>>>> +++ b/include/linux/buffer_head.h
>>>> @@ -336,6 +336,8 @@ static inline void lock_buffer(struct buffer_head *bh)
>>>> }
>>>>
>>>> extern int __set_page_dirty_buffers(struct page *page);
>>>> +extern int __set_page_dirty(struct page *page,
>>>> + struct address_space *mapping, int warn);
>>>>
>>>> #else /* CONFIG_BLOCK */
>>>>
>>>> --
>>>> 1.7.1
>>>>
>>>> --
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>>>>
>>>>
>>
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