linux-kernel - Re: [f2fs-dev] [PATCH v2] f2fs: avoid cpu lockup

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Date:   Tue, 18 Jul 2017 09:40:34 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH v2] f2fs: avoid cpu lockup

On 2017/7/18 6:38, Jaegeuk Kim wrote:
> On 07/17, Chao Yu wrote:
>> On 2017/7/16 9:04, Jaegeuk Kim wrote:
>>> Before retrying to flush data or dentry pages, we need to release cpu in order
>>> to prevent watchdog.
>>>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>>
>> Reviewed-by: Chao Yu <yuchao0@...wei.com>
>>
>>> ---
>>> Change log from v1:
>>>  - timeout more specifically
>>>
>>>  fs/f2fs/checkpoint.c | 10 ++++++++++
>>>  1 file changed, 10 insertions(+)
>>>
>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>> index 56bbf592e487..5b876f6d3f6b 100644
>>> --- a/fs/f2fs/checkpoint.c
>>> +++ b/fs/f2fs/checkpoint.c
>>> @@ -879,6 +879,7 @@ int sync_dirty_inodes(struct f2fs_sb_info *sbi, enum inode_type type)
>>>  	struct inode *inode;
>>>  	struct f2fs_inode_info *fi;
>>>  	bool is_dir = (type == DIR_INODE);
>>> +	unsigned long ino = 0;
>>>  
>>>  	trace_f2fs_sync_dirty_inodes_enter(sbi->sb, is_dir,
>>>  				get_pages(sbi, is_dir ?
>>> @@ -901,8 +902,17 @@ int sync_dirty_inodes(struct f2fs_sb_info *sbi, enum inode_type type)
>>>  	inode = igrab(&fi->vfs_inode);
>>>  	spin_unlock(&sbi->inode_lock[type]);
>>>  	if (inode) {
>>> +		unsigned long cur_ino = inode->i_ino;
>>> +
>>>  		filemap_fdatawrite(inode->i_mapping);
>>>  		iput(inode);
>>> +		/* We need to give cpu to another writers. */
>>> +		if (ino == cur_ino) {
>>
>> We failed to flush dirty pages of inode due to encountering -EAGAIN of writepage?
> 
> Actually, I found this from a bug case in experimental patches which just skips
> it accidently. I think WB_SYNC_ALL doesn't return EAGAIN.

Alright, thanks for explanation. :)

Thanks,

> 
> Thanks,
> 
>>
>> Thanks,
>>
>>> +			congestion_wait(BLK_RW_ASYNC, HZ/50);
>>> +			cond_resched();
>>> +		} else {
>>> +			ino = cur_ino;
>>> +		}
>>>  	} else {
>>>  		/*
>>>  		 * We should submit bio, since it exists several
>>>
> 
> .
>