linux-kernel - Re: [f2fs-dev] [PATCH 4/5] f2fs: support data flush in ioctl

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Date:	Sat, 26 Dec 2015 17:26:01 +0800
From:	Chao Yu <chao@...nel.org>
To:	Jaegeuk Kim <jaegeuk@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 4/5] f2fs: support data flush in ioctl

Hi Jaegeuk,

On 12/25/15 5:06 AM, Jaegeuk Kim wrote:
> Hi Chao,
> 
> On Thu, Dec 24, 2015 at 06:10:25PM +0800, Chao Yu wrote:
>> Sometimes user want to sync all data belong to superblock into storage
>> for persistence, 'syncfs' syscall is one option, still f2fs supports
>> similar one through ioctl, difference is that sb releted kworker is
>> online for writebacking concurrently.
> 
> There is compatibility issue, since you're trying to change pre-defined
> ioctl;

Agreed.

> it needs to change F2FS_IOC_WRITE_CHECKPOINT too, right?

Yes, maybe F2FS_IOC_WRITE_CHECKPOINT_V2 if we have to change this interface.

> I'm in doubt that we really need to expose this too.

There is no obviously demands, but for Marc Lehmann's scenario I expect this can
provide less latency by concurrently writebacking when syncing the whole f2fs
partition.

Thanks,

> 
> Thanks,
> 
>>
>> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
>> ---
>>  fs/f2fs/file.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>> index a60d088..91997a5 100644
>> --- a/fs/f2fs/file.c
>> +++ b/fs/f2fs/file.c
>> @@ -1621,6 +1621,7 @@ static int f2fs_ioc_write_checkpoint(struct file *filp, unsigned long arg)
>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>  	struct cp_control cpc;
>>  	int err;
>> +	int flush_data;
>>  
>>  	if (!capable(CAP_SYS_ADMIN))
>>  		return -EPERM;
>> @@ -1628,6 +1629,15 @@ static int f2fs_ioc_write_checkpoint(struct file *filp, unsigned long arg)
>>  	if (f2fs_readonly(sbi->sb))
>>  		return -EROFS;
>>  
>> +	if (get_user(flush_data, (__u32 __user *)arg))
>> +		return -EFAULT;
>> +
>> +	if (flush_data) {
>> +		err = sync_dirty_inodes(sbi, FILE_INODE);
>> +		if (err)
>> +			return err;
>> +	}
>> +
>>  	cpc.reason = __get_cp_reason(sbi);
>>  
>>  	mutex_lock(&sbi->gc_mutex);
>> -- 
>> 2.6.3
>>
> 
> ------------------------------------------------------------------------------
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> 
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