Re: [PATCH v3] f2fs: submit cached bio to avoid endless PageWriteback

[Chao Yu <yuchao0@huawei.com>]

On 2018/9/26 8:20, Jaegeuk Kim wrote:
> On 09/21, Chao Yu wrote:
>> On 2018/9/18 10:14, Chao Yu wrote:
>>> On 2018/9/18 10:02, Jaegeuk Kim wrote:
>>>> On 09/18, Chao Yu wrote:
>>>>> On 2018/9/18 9:37, Jaegeuk Kim wrote:
>>>>>> On 09/18, Chao Yu wrote:
>>>>>>> On 2018/9/18 9:04, Jaegeuk Kim wrote:
>>>>>>>> On 09/13, Chao Yu wrote:
>>>>>>>>> From: Chao Yu <yuchao0@huawei.com>
>>>>>>>>>
>>>>>>>>> When migrating encrypted block from background GC thread, we only add
>>>>>>>>> them into f2fs inner bio cache, but forget to submit the cached bio, it
>>>>>>>>> may cause potential deadlock when we are waiting page writebacked, fix
>>>>>>>>> it.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>>>>>>>> ---
>>>>>>>>> v3:
>>>>>>>>> clean up codes suggested by Jaegeuk.
>>>>>>>>>  fs/f2fs/f2fs.h |  2 +-
>>>>>>>>>  fs/f2fs/gc.c   | 71 +++++++++++++++++++++++++++++++++++---------------
>>>>>>>>>  fs/f2fs/node.c | 13 ++++++---
>>>>>>>>>  3 files changed, 61 insertions(+), 25 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>>>> index b676b82312e0..917b2ca76aac 100644
>>>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>>>> @@ -2869,7 +2869,7 @@ struct page *f2fs_new_node_page(struct dnode_of_data *dn, unsigned int ofs);
>>>>>>>>>  void f2fs_ra_node_page(struct f2fs_sb_info *sbi, nid_t nid);
>>>>>>>>>  struct page *f2fs_get_node_page(struct f2fs_sb_info *sbi, pgoff_t nid);
>>>>>>>>>  struct page *f2fs_get_node_page_ra(struct page *parent, int start);
>>>>>>>>> -void f2fs_move_node_page(struct page *node_page, int gc_type);
>>>>>>>>> +int f2fs_move_node_page(struct page *node_page, int gc_type);
>>>>>>>>>  int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
>>>>>>>>>  			struct writeback_control *wbc, bool atomic,
>>>>>>>>>  			unsigned int *seq_id);
>>>>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>>>>>>> index a4c1a419611d..f57622cfe058 100644
>>>>>>>>> --- a/fs/f2fs/gc.c
>>>>>>>>> +++ b/fs/f2fs/gc.c
>>>>>>>>> @@ -461,7 +461,7 @@ static int check_valid_map(struct f2fs_sb_info *sbi,
>>>>>>>>>   * On validity, copy that node with cold status, otherwise (invalid node)
>>>>>>>>>   * ignore that.
>>>>>>>>>   */
>>>>>>>>> -static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>> +static int gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>  		struct f2fs_summary *sum, unsigned int segno, int gc_type)
>>>>>>>>>  {
>>>>>>>>>  	struct f2fs_summary *entry;
>>>>>>>>> @@ -469,6 +469,7 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>  	int off;
>>>>>>>>>  	int phase = 0;
>>>>>>>>>  	bool fggc = (gc_type == FG_GC);
>>>>>>>>> +	int submitted = 0;
>>>>>>>>>  
>>>>>>>>>  	start_addr = START_BLOCK(sbi, segno);
>>>>>>>>>  
>>>>>>>>> @@ -482,10 +483,11 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>  		nid_t nid = le32_to_cpu(entry->nid);
>>>>>>>>>  		struct page *node_page;
>>>>>>>>>  		struct node_info ni;
>>>>>>>>> +		int err;
>>>>>>>>>  
>>>>>>>>>  		/* stop BG_GC if there is not enough free sections. */
>>>>>>>>>  		if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0))
>>>>>>>>> -			return;
>>>>>>>>> +			return submitted;
>>>>>>>>>  
>>>>>>>>>  		if (check_valid_map(sbi, segno, off) == 0)
>>>>>>>>>  			continue;
>>>>>>>>> @@ -522,7 +524,9 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>  			continue;
>>>>>>>>>  		}
>>>>>>>>>  
>>>>>>>>> -		f2fs_move_node_page(node_page, gc_type);
>>>>>>>>> +		err = f2fs_move_node_page(node_page, gc_type);
>>>>>>>>> +		if (!err && gc_type == FG_GC)
>>>>>>>>> +			submitted++;
>>>>>>>>>  		stat_inc_node_blk_count(sbi, 1, gc_type);
>>>>>>>>>  	}
>>>>>>>>>  
>>>>>>>>> @@ -531,6 +535,7 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>  
>>>>>>>>>  	if (fggc)
>>>>>>>>>  		atomic_dec(&sbi->wb_sync_req[NODE]);
>>>>>>>>> +	return submitted;
>>>>>>>>>  }
>>>>>>>>>  
>>>>>>>>>  /*
>>>>>>>>> @@ -666,7 +671,7 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>>>>>>>>>   * Move data block via META_MAPPING while keeping locked data page.
>>>>>>>>>   * This can be used to move blocks, aka LBAs, directly on disk.
>>>>>>>>>   */
>>>>>>>>> -static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>> +static int move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>  				int gc_type, unsigned int segno, int off)
>>>>>>>>
>>>>>>>> We don't need to submit IOs in this case.
>>>>>>>
>>>>>>> Actually, previously, we missed to submit IOs for encrypted block only in
>>>>>>> BGGC, so we fix to submit for this case, all other codes are cleanups. Right?
>>>>>>
>>>>>> The move_data_block migrates encrypted blocks all the time with meta page IOs.
>>>>>> I don't know what you're saying about BGGC.
>>>>>
>>>>> In move_data_block(), we use f2fs_submit_page_write() to add encrypted page
>>>>> in to sbi->write_io[META].bio cache, so before exit GC, we need to submit
>>>>> this cache by f2fs_submit_merged_write(), otherwise bio with encrypted page
>>>>> will be cached in sbi->write_io[META].bio for long time, since we only
>>>>> submmit this bio cache in foreground GC.
>>>>>
>>>>> if (gc_type == FG_GC)
>>>>> 	f2fs_submit_merged_write(sbi,
>>>>> 				(type == SUM_TYPE_NODE) ? NODE : DATA);
>>>>
>>>> Does this issue pending META IOs? I think META won't block any NODE/DATA
>>>> pages. Moreover checkpoint or reading the moved block make the IOs be flushed,
>>>> so it doesn't hurt the consistency.
>>
>> It may cause long latency before someone flushes the meta IO, how about flushing
>> IO like other flows, like writepages?
>>
>> Or is there any benefit that we still cache meta IO after GC?
>>
>>>
>>> I just guess below endless waiting for page writeback is cased by this case
>>
>> Any thoughts?
> 
> I'm waiting for the previous reported issue. Do we have this in products?

I didn't see such stack in products.

BTW, I added one patch in my tree, although this patch is not correct now
since it is missing to submit bio in some cases, it can easily reproduce
such stack, so I guess there is still at least one place we didn't submit
bio correctly.

https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git/commit/?h=f2fs-dev&id=2ca666658fc1958ab176030d435efa2ce325aa52

Thanks,

> 
>>
>>>
>>> -000|__switch_to()
>>>
>>> -001|__schedule()
>>>
>>> -002|need_resched(inline)
>>>
>>> -002|schedule()
>>>
>>> -003|schedule_timeout()
>>>
>>> -004|get_current(inline)
>>>
>>> -004|io_schedule_timeout()
>>>
>>> -005|bit_wait_io()
>>>
>>> -006|__wait_on_bit()
>>>
>>> -007|wait_on_page_bit()
>>>
>>> -008|PageWriteback(inline)
>>>
>>> -008|wait_on_page_writeback(inline)
>>>
>>> -008|__filemap_fdatawait_range()
>>>
>>> -009|filemap_fdatawait_keep_errors()
>>>
>>> -010|sync_inodes_sb()
>>>
>>> -011|__sync_filesystem(inline)
>>>
>>> -011|sync_filesystem()
>>>
>>> -012|generic_shutdown_super()
>>>
>>> -013|kill_block_super()
>>>
>>> -014|kill_f2fs_super()
>>>
>>> -015|deactivate_locked_super()
>>>
>>> -016|deactivate_super()
>>>
>>> -017|mnt_free_id(inline)
>>>
>>> -017|cleanup_mnt()
>>>
>>> -018|__cleanup_mnt()
>>>
>>> -019|task_work_run()
>>>
>>> -020|do_notify_resume()
>>>
>>> -021|work_pending(asm)
>>>
>>> -->|exception
>>>
>>> -022|NUX:0x539E58(asm)
>>>
>>> ---|end of frame
>>>
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>>>
>>>>>>>>>  {
>>>>>>>>>  	struct f2fs_io_info fio = {
>>>>>>>>> @@ -685,25 +690,29 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>  	struct node_info ni;
>>>>>>>>>  	struct page *page, *mpage;
>>>>>>>>>  	block_t newaddr;
>>>>>>>>> -	int err;
>>>>>>>>> +	int err = 0;
>>>>>>>>>  	bool lfs_mode = test_opt(fio.sbi, LFS);
>>>>>>>>>  
>>>>>>>>>  	/* do not read out */
>>>>>>>>>  	page = f2fs_grab_cache_page(inode->i_mapping, bidx, false);
>>>>>>>>>  	if (!page)
>>>>>>>>> -		return;
>>>>>>>>> +		return -ENOMEM;
>>>>>>>>>  
>>>>>>>>> -	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>>>>>>>>> +	if (!check_valid_map(F2FS_I_SB(inode), segno, off)) {
>>>>>>>>> +		err = -ENOENT;
>>>>>>>>>  		goto out;
>>>>>>>>> +	}
>>>>>>>>>  
>>>>>>>>>  	if (f2fs_is_atomic_file(inode)) {
>>>>>>>>>  		F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
>>>>>>>>>  		F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>  		goto out;
>>>>>>>>>  	}
>>>>>>>>>  
>>>>>>>>>  	if (f2fs_is_pinned_file(inode)) {
>>>>>>>>>  		f2fs_pin_file_control(inode, true);
>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>  		goto out;
>>>>>>>>>  	}
>>>>>>>>>  
>>>>>>>>> @@ -714,6 +723,7 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>  
>>>>>>>>>  	if (unlikely(dn.data_blkaddr == NULL_ADDR)) {
>>>>>>>>>  		ClearPageUptodate(page);
>>>>>>>>> +		err = -ENOENT;
>>>>>>>>>  		goto put_out;
>>>>>>>>>  	}
>>>>>>>>>  
>>>>>>>>> @@ -796,6 +806,7 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>  	fio.new_blkaddr = newaddr;
>>>>>>>>>  	f2fs_submit_page_write(&fio);
>>>>>>>>>  	if (fio.retry) {
>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>  		if (PageWriteback(fio.encrypted_page))
>>>>>>>>>  			end_page_writeback(fio.encrypted_page);
>>>>>>>>>  		goto put_page_out;
>>>>>>>>> @@ -819,34 +830,42 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>  	f2fs_put_dnode(&dn);
>>>>>>>>>  out:
>>>>>>>>>  	f2fs_put_page(page, 1);
>>>>>>>>> +	return err;
>>>>>>>>>  }
>>>>>>>>>  
>>>>>>>>> -static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>> +static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>>  							unsigned int segno, int off)
>>>>>>>>>  {
>>>>>>>>>  	struct page *page;
>>>>>>>>> +	int err = 0;
>>>>>>>>>  
>>>>>>>>>  	page = f2fs_get_lock_data_page(inode, bidx, true);
>>>>>>>>>  	if (IS_ERR(page))
>>>>>>>>> -		return;
>>>>>>>>> +		return PTR_ERR(page);
>>>>>>>>>  
>>>>>>>>> -	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>>>>>>>>> +	if (!check_valid_map(F2FS_I_SB(inode), segno, off)) {
>>>>>>>>> +		err = -ENOENT;
>>>>>>>>>  		goto out;
>>>>>>>>> +	}
>>>>>>>>>  
>>>>>>>>>  	if (f2fs_is_atomic_file(inode)) {
>>>>>>>>>  		F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
>>>>>>>>>  		F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>  		goto out;
>>>>>>>>>  	}
>>>>>>>>>  	if (f2fs_is_pinned_file(inode)) {
>>>>>>>>>  		if (gc_type == FG_GC)
>>>>>>>>>  			f2fs_pin_file_control(inode, true);
>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>  		goto out;
>>>>>>>>>  	}
>>>>>>>>>  
>>>>>>>>>  	if (gc_type == BG_GC) {
>>>>>>>>> -		if (PageWriteback(page))
>>>>>>>>> +		if (PageWriteback(page)) {
>>>>>>>>> +			err = -EAGAIN;
>>>>>>>>>  			goto out;
>>>>>>>>> +		}
>>>>>>>>>  		set_page_dirty(page);
>>>>>>>>>  		set_cold_data(page);
>>>>>>>>>  	} else {
>>>>>>>>> @@ -864,7 +883,6 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>>  			.io_type = FS_GC_DATA_IO,
>>>>>>>>>  		};
>>>>>>>>>  		bool is_dirty = PageDirty(page);
>>>>>>>>> -		int err;
>>>>>>>>>  
>>>>>>>>>  retry:
>>>>>>>>>  		set_page_dirty(page);
>>>>>>>>> @@ -889,6 +907,7 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>>  	}
>>>>>>>>>  out:
>>>>>>>>>  	f2fs_put_page(page, 1);
>>>>>>>>> +	return err;
>>>>>>>>>  }
>>>>>>>>>  
>>>>>>>>>  /*
>>>>>>>>> @@ -898,7 +917,7 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>>   * If the parent node is not valid or the data block address is different,
>>>>>>>>>   * the victim data block is ignored.
>>>>>>>>>   */
>>>>>>>>> -static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>> +static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>  		struct gc_inode_list *gc_list, unsigned int segno, int gc_type)
>>>>>>>>>  {
>>>>>>>>>  	struct super_block *sb = sbi->sb;
>>>>>>>>> @@ -906,6 +925,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>  	block_t start_addr;
>>>>>>>>>  	int off;
>>>>>>>>>  	int phase = 0;
>>>>>>>>> +	int submitted = 0;
>>>>>>>>>  
>>>>>>>>>  	start_addr = START_BLOCK(sbi, segno);
>>>>>>>>>  
>>>>>>>>> @@ -922,7 +942,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>  
>>>>>>>>>  		/* stop BG_GC if there is not enough free sections. */
>>>>>>>>>  		if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0))
>>>>>>>>> -			return;
>>>>>>>>> +			return submitted;
>>>>>>>>>  
>>>>>>>>>  		if (check_valid_map(sbi, segno, off) == 0)
>>>>>>>>>  			continue;
>>>>>>>>> @@ -994,6 +1014,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>  		if (inode) {
>>>>>>>>>  			struct f2fs_inode_info *fi = F2FS_I(inode);
>>>>>>>>>  			bool locked = false;
>>>>>>>>> +			int err;
>>>>>>>>>  
>>>>>>>>>  			if (S_ISREG(inode->i_mode)) {
>>>>>>>>>  				if (!down_write_trylock(&fi->i_gc_rwsem[READ]))
>>>>>>>>> @@ -1013,12 +1034,16 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>  			start_bidx = f2fs_start_bidx_of_node(nofs, inode)
>>>>>>>>>  								+ ofs_in_node;
>>>>>>>>>  			if (f2fs_post_read_required(inode))
>>>>>>>>> -				move_data_block(inode, start_bidx, gc_type,
>>>>>>>>> -								segno, off);
>>>>>>>>> +				err = move_data_block(inode, start_bidx,
>>>>>>>>> +							gc_type, segno, off);
>>>>>>>>>  			else
>>>>>>>>> -				move_data_page(inode, start_bidx, gc_type,
>>>>>>>>> +				err = move_data_page(inode, start_bidx, gc_type,
>>>>>>>>>  								segno, off);
>>>>>>>>>  
>>>>>>>>> +			if (!err && (gc_type == FG_GC ||
>>>>>>>>> +					f2fs_post_read_required(inode)))
>>>>>>>>> +				submitted++;
>>>>>>>>> +
>>>>>>>>>  			if (locked) {
>>>>>>>>>  				up_write(&fi->i_gc_rwsem[WRITE]);
>>>>>>>>>  				up_write(&fi->i_gc_rwsem[READ]);
>>>>>>>>> @@ -1030,6 +1055,8 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>  
>>>>>>>>>  	if (++phase < 5)
>>>>>>>>>  		goto next_step;
>>>>>>>>> +
>>>>>>>>> +	return submitted;
>>>>>>>>>  }
>>>>>>>>>  
>>>>>>>>>  static int __get_victim(struct f2fs_sb_info *sbi, unsigned int *victim,
>>>>>>>>> @@ -1057,6 +1084,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>>>>>  	int seg_freed = 0;
>>>>>>>>>  	unsigned char type = IS_DATASEG(get_seg_entry(sbi, segno)->type) ?
>>>>>>>>>  						SUM_TYPE_DATA : SUM_TYPE_NODE;
>>>>>>>>> +	int submitted = 0;
>>>>>>>>>  
>>>>>>>>>  	/* readahead multi ssa blocks those have contiguous address */
>>>>>>>>>  	if (sbi->segs_per_sec > 1)
>>>>>>>>> @@ -1100,10 +1128,11 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>>>>>  		 *                                  - lock_page(sum_page)
>>>>>>>>>  		 */
>>>>>>>>>  		if (type == SUM_TYPE_NODE)
>>>>>>>>> -			gc_node_segment(sbi, sum->entries, segno, gc_type);
>>>>>>>>> -		else
>>>>>>>>> -			gc_data_segment(sbi, sum->entries, gc_list, segno,
>>>>>>>>> +			submitted += gc_node_segment(sbi, sum->entries, segno,
>>>>>>>>>  								gc_type);
>>>>>>>>> +		else
>>>>>>>>> +			submitted += gc_data_segment(sbi, sum->entries, gc_list,
>>>>>>>>> +							segno, gc_type);
>>>>>>>>>  
>>>>>>>>>  		stat_inc_seg_count(sbi, type, gc_type);
>>>>>>>>>  
>>>>>>>>> @@ -1114,7 +1143,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>>>>>  		f2fs_put_page(sum_page, 0);
>>>>>>>>>  	}
>>>>>>>>>  
>>>>>>>>> -	if (gc_type == FG_GC)
>>>>>>>>> +	if (submitted)
>>>>>>>>>  		f2fs_submit_merged_write(sbi,
>>>>>>>>>  				(type == SUM_TYPE_NODE) ? NODE : DATA);
>>>>>>>>>  
>>>>>>>>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>>>>>>>>> index fa2381c0bc47..214dd6326b4b 100644
>>>>>>>>> --- a/fs/f2fs/node.c
>>>>>>>>> +++ b/fs/f2fs/node.c
>>>>>>>>> @@ -1584,8 +1584,10 @@ static int __write_node_page(struct page *page, bool atomic, bool *submitted,
>>>>>>>>>  	return AOP_WRITEPAGE_ACTIVATE;
>>>>>>>>>  }
>>>>>>>>>  
>>>>>>>>> -void f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>>>>> +int f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>>>>>  {
>>>>>>>>> +	int err = 0;
>>>>>>>>> +
>>>>>>>>>  	if (gc_type == FG_GC) {
>>>>>>>>>  		struct writeback_control wbc = {
>>>>>>>>>  			.sync_mode = WB_SYNC_ALL,
>>>>>>>>> @@ -1597,12 +1599,16 @@ void f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>>>>>  		f2fs_wait_on_page_writeback(node_page, NODE, true);
>>>>>>>>>  
>>>>>>>>>  		f2fs_bug_on(F2FS_P_SB(node_page), PageWriteback(node_page));
>>>>>>>>> -		if (!clear_page_dirty_for_io(node_page))
>>>>>>>>> +		if (!clear_page_dirty_for_io(node_page)) {
>>>>>>>>> +			err = -EAGAIN;
>>>>>>>>>  			goto out_page;
>>>>>>>>> +		}
>>>>>>>>>  
>>>>>>>>>  		if (__write_node_page(node_page, false, NULL,
>>>>>>>>> -					&wbc, false, FS_GC_NODE_IO, NULL))
>>>>>>>>> +					&wbc, false, FS_GC_NODE_IO, NULL)) {
>>>>>>>>> +			err = -EAGAIN;
>>>>>>>>>  			unlock_page(node_page);
>>>>>>>>> +		}
>>>>>>>>>  		goto release_page;
>>>>>>>>>  	} else {
>>>>>>>>>  		/* set page dirty and write it */
>>>>>>>>> @@ -1613,6 +1619,7 @@ void f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>>>>>  	unlock_page(node_page);
>>>>>>>>>  release_page:
>>>>>>>>>  	f2fs_put_page(node_page, 0);
>>>>>>>>> +	return err;
>>>>>>>>>  }
>>>>>>>>>  
>>>>>>>>>  static int f2fs_write_node_page(struct page *page,
>>>>>>>>> -- 
>>>>>>>>> 2.18.0
>>>>>>>>
>>>>>>>> .
>>>>>>>>
>>>>>>
>>>>>> .
>>>>>>
>>>>
>>>> .
>>>>
>>>
> 
> .
>