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

[Gu Zheng]

On 07/31/2013 06:06 PM, Jaegeuk Kim wrote:

> 2013-07-31 (ì), 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.

Got it, it seems that I had some miss reading originally, it's
clear now, thanks very much for your explanation.:)

Regards,
Gu

> 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 (í), 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@xxxxxxxxxxxxxx>
>>>> ---
>>>>  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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> 


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