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Message-id: <1375265195.26443.78.camel@kjgkr>
Subject: Re: [PATCH] f2fs: add a wait step when submit bio with
 {READ,WRITE}_SYNC
From: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Reply-to: jaegeuk.kim@samsung.com
To: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: f2fs <linux-f2fs-devel@lists.sourceforge.net>,
        fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
Date: Wed, 31 Jul 2013 19:06:35 +0900
In-reply-to: <51F86F67.1070605@cn.fujitsu.com>
References: <51F7901E.3010204@cn.fujitsu.com> <1375187398.26443.69.camel@kjgkr>
 <51F86F67.1070605@cn.fujitsu.com>
Organization: Samsung
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2013-07-31 (수), 09:59 +0800, Gu Zheng:
> 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?

Correct, the READ_SYNC is also used for IO priority.
The basic read policy here is that the caller should lock the page only
when it wants to manipulate there-in data.
Otherwise, we don't need to unnecessary lock and unlocks.
Thanks,

> 
> > 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@cn.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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-- 
Jaegeuk Kim
Samsung

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