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

[Jaegeuk Kim]

On 09/12, Chao Yu wrote:
> Jaegeuk,
> 
> Could you update dev-test branch? so I can rebase this on yours, there are some
> pending patches in my tree, I guess it can avoid conflict when you merge this.

Done.

> 
> On 2018/9/12 6:39, Jaegeuk Kim wrote:
> > On 09/11, Chao Yu wrote:
> >> 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@xxxxxxxxxx>
> >> ---
> >>  fs/f2fs/gc.c | 42 +++++++++++++++++++++++++++++-------------
> >>  1 file changed, 29 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> >> index c4ea4009cf05..a2ea0d445345 100644
> >> --- a/fs/f2fs/gc.c
> >> +++ b/fs/f2fs/gc.c
> >> @@ -687,7 +687,7 @@ 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)
> >>  {
> >>  	struct f2fs_io_info fio = {
> >> @@ -706,25 +706,29 @@ 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;
> >>  	}
> >>  
> >> @@ -735,6 +739,7 @@ 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;
> >>  	}
> >>  
> >> @@ -817,6 +822,7 @@ 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;
> >> @@ -840,6 +846,8 @@ 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,
> >> @@ -919,7 +927,7 @@ 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;
> >> @@ -927,6 +935,7 @@ 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);
> >>  
> >> @@ -943,7 +952,7 @@ 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;
> >> @@ -1015,6 +1024,7 @@ 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]))
> >> @@ -1033,12 +1043,15 @@ 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);
> >> -			else
> >> +			if (f2fs_post_read_required(inode)) {
> >> +				err = move_data_block(inode, start_bidx,
> >> +							gc_type, segno, off);
> >> +				if (!err)
> >> +					submitted++;
> >> +			} else {
> >>  				move_data_page(inode, start_bidx, gc_type,
> >>  								segno, off);
> >> +			}
> >>  
> >>  			if (locked) {
> >>  				up_write(&fi->i_gc_rwsem[WRITE]);
> >> @@ -1051,6 +1064,8 @@ 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,
> >> @@ -1078,6 +1093,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >>  	unsigned char type = IS_DATASEG(get_seg_entry(sbi, segno)->type) ?
> >>  						SUM_TYPE_DATA : SUM_TYPE_NODE;
> >>  	unsigned int units = 0;
> >> +	int submitted = 0;
> >>  
> >>  	/* start segno may point to middle of section, so adjust it */
> >>  	if (__is_large_section(sbi))
> >> @@ -1136,8 +1152,8 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >>  		if (type == SUM_TYPE_NODE)
> >>  			gc_node_segment(sbi, sum->entries, segno, gc_type);
> >>  		else
> >> -			gc_data_segment(sbi, sum->entries, gc_list, segno,
> >> -								gc_type);
> >> +			submitted += gc_data_segment(sbi, sum->entries, gc_list,
> >> +							segno, gc_type);
> >>  
> >>  		stat_inc_seg_count(sbi, type, gc_type);
> >>  
> >> @@ -1152,7 +1168,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >>  		f2fs_put_page(sum_page, 0);
> >>  	}
> >>  
> >> -	if (gc_type == FG_GC)
> >> +	if (gc_type == FG_GC || submitted)
> > 
> > Do we need to check submitted for both of node and data? Then, we can remove
> > FG_GC case?
> 
> Yup, good idea, let me adjust.
> 
> Thanks,
> 
> > 
> >>  		f2fs_submit_merged_write(sbi,
> >>  				(type == SUM_TYPE_NODE) ? NODE : DATA);
> >>  
> >> -- 
> >> 2.18.0.rc1