linux-kernel - Re: [PATCH 4/7] Use vfs __set_page_dirty interface instead of doing it inside filesystem

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Date:	Mon, 02 Jul 2012 16:10:42 +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 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;



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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