linux-kernel - Re: [PATCH] f2fs: add a wait step when submit bio with {READ,WRITE}

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Message-ID: <51F86F67.1070605@cn.fujitsu.com>
Date:	Wed, 31 Jul 2013 09:59:03 +0800
From:	Gu Zheng <guz.fnst@...fujitsu.com>
To:	jaegeuk.kim@...sung.com
CC:	f2fs <linux-f2fs-devel@...ts.sourceforge.net>,
	fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: add a wait step when submit bio with {READ,WRITE}_SYNC

Hi Kim,

On 07/30/2013 08:29 PM, Jaegeuk Kim wrote:

> Hi Gu,
> 
> The original read flow was to avoid redandunt lock/unlock_page() calls.

Right, this can gain better read performance. But is the wait step after 
submitting bio with READ_SYNC needless too?

> And we should not wait for WRITE_SYNC, since it is just for write
> priority, not for synchronization of the file system.

Got it, thanks for your explanation.:) 

Best regards,
Gu

> Thanks,
> 
> 2013-07-30 (화), 18:06 +0800, Gu Zheng:
>> When we submit bio with READ_SYNC or WRITE_SYNC, we need to wait a
>> moment for the io completion, current codes only find_data_page() follows the
>> rule, other places missing this step, so add it.
>>
>> Further more, moving the PageUptodate check into f2fs_readpage() to clean up
>> the codes.
>>
>> Signed-off-by: Gu Zheng <guz.fnst@...fujitsu.com>
>> ---
>>  fs/f2fs/checkpoint.c |    1 -
>>  fs/f2fs/data.c       |   39 +++++++++++++++++----------------------
>>  fs/f2fs/node.c       |    1 -
>>  fs/f2fs/recovery.c   |    2 --
>>  fs/f2fs/segment.c    |    2 +-
>>  5 files changed, 18 insertions(+), 27 deletions(-)
>>
>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>> index fe91773..e376a42 100644
>> --- a/fs/f2fs/checkpoint.c
>> +++ b/fs/f2fs/checkpoint.c
>> @@ -64,7 +64,6 @@ repeat:
>>  	if (f2fs_readpage(sbi, page, index, READ_SYNC))
>>  		goto repeat;
>>  
>> -	lock_page(page);
>>  	if (page->mapping != mapping) {
>>  		f2fs_put_page(page, 1);
>>  		goto repeat;
>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>> index 19cd7c6..b048936 100644
>> --- a/fs/f2fs/data.c
>> +++ b/fs/f2fs/data.c
>> @@ -216,13 +216,11 @@ struct page *find_data_page(struct inode *inode, pgoff_t index, bool sync)
>>  
>>  	err = f2fs_readpage(sbi, page, dn.data_blkaddr,
>>  					sync ? READ_SYNC : READA);
>> -	if (sync) {
>> -		wait_on_page_locked(page);
>> -		if (!PageUptodate(page)) {
>> -			f2fs_put_page(page, 0);
>> -			return ERR_PTR(-EIO);
>> -		}
>> -	}
>> +	if (err)
>> +		return ERR_PTR(err);
>> +
>> +	if (sync)
>> +		unlock_page(page);
>>  	return page;
>>  }
>>  
>> @@ -267,11 +265,6 @@ repeat:
>>  	if (err)
>>  		return ERR_PTR(err);
>>  
>> -	lock_page(page);
>> -	if (!PageUptodate(page)) {
>> -		f2fs_put_page(page, 1);
>> -		return ERR_PTR(-EIO);
>> -	}
>>  	if (page->mapping != mapping) {
>>  		f2fs_put_page(page, 1);
>>  		goto repeat;
>> @@ -325,11 +318,7 @@ repeat:
>>  		err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
>>  		if (err)
>>  			return ERR_PTR(err);
>> -		lock_page(page);
>> -		if (!PageUptodate(page)) {
>> -			f2fs_put_page(page, 1);
>> -			return ERR_PTR(-EIO);
>> -		}
>> +
>>  		if (page->mapping != mapping) {
>>  			f2fs_put_page(page, 1);
>>  			goto repeat;
>> @@ -399,6 +388,16 @@ int f2fs_readpage(struct f2fs_sb_info *sbi, struct page *page,
>>  
>>  	submit_bio(type, bio);
>>  	up_read(&sbi->bio_sem);
>> +
>> +	if (type == READ_SYNC) {
>> +		wait_on_page_locked(page);
>> +		lock_page(page);
>> +		if (!PageUptodate(page)) {
>> +			f2fs_put_page(page, 1);
>> +			return -EIO;
>> +		}
>> +	}
>> +
>>  	return 0;
>>  }
>>  
>> @@ -679,11 +678,7 @@ repeat:
>>  		err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
>>  		if (err)
>>  			return err;
>> -		lock_page(page);
>> -		if (!PageUptodate(page)) {
>> -			f2fs_put_page(page, 1);
>> -			return -EIO;
>> -		}
>> +
>>  		if (page->mapping != mapping) {
>>  			f2fs_put_page(page, 1);
>>  			goto repeat;
>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>> index f5172e2..f061554 100644
>> --- a/fs/f2fs/node.c
>> +++ b/fs/f2fs/node.c
>> @@ -1534,7 +1534,6 @@ int restore_node_summary(struct f2fs_sb_info *sbi,
>>  		if (f2fs_readpage(sbi, page, addr, READ_SYNC))
>>  			goto out;
>>  
>> -		lock_page(page);
>>  		rn = F2FS_NODE(page);
>>  		sum_entry->nid = rn->footer.nid;
>>  		sum_entry->version = 0;
>> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
>> index 639eb34..ec68183 100644
>> --- a/fs/f2fs/recovery.c
>> +++ b/fs/f2fs/recovery.c
>> @@ -140,8 +140,6 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head)
>>  		if (err)
>>  			goto out;
>>  
>> -		lock_page(page);
>> -
>>  		if (cp_ver != cpver_of_node(page))
>>  			break;
>>  
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 9b74ae2..bcd19db 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -639,7 +639,7 @@ static void do_submit_bio(struct f2fs_sb_info *sbi,
>>  
>>  		trace_f2fs_do_submit_bio(sbi->sb, btype, sync, sbi->bio[btype]);
>>  
>> -		if (type == META_FLUSH) {
>> +		if ((type == META_FLUSH) || (rw & WRITE_SYNC)) {
>>  			DECLARE_COMPLETION_ONSTACK(wait);
>>  			p->is_sync = true;
>>  			p->wait = &wait;
> 


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