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Subject: Re: [PATCH v3] f2fs: add bio cache for IPU
To:     <jaegeuk@kernel.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <chao@kernel.org>
References: <20181219092956.8257-1-yuchao0@huawei.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <dcdaecd0-035b-83c7-76e3-6ca305a049cc@huawei.com>
Date:   Mon, 24 Dec 2018 14:35:34 +0800
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Jaegeuk,

Will kernel still hang with this v3?

Thanks,

On 2018/12/19 17:29, Chao Yu wrote:
> SQLite in Wal mode may trigger sequential IPU write in db-wal file, after
> commit d1b3e72d5490 ("f2fs: submit bio of in-place-update pages"), we
> lost the chance of merging page in inner managed bio cache, result in
> submitting more small-sized IO.
> 
> So let's add temporary bio in writepages() to cache mergeable write IO as
> much as possible.
> 
> Test case:
> 1. xfs_io -f /mnt/f2fs/file -c "pwrite 0 65536" -c "fsync"
> 2. xfs_io -f /mnt/f2fs/file -c "pwrite 0 65536" -c "fsync"
> 
> Before:
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65544, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65552, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65560, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65568, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65576, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65584, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65592, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65600, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65608, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65616, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65624, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65632, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65640, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65648, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65656, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65664, size = 4096
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), NODE, sector = 57352, size = 4096
> 
> After:
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), DATA, sector = 65544, size = 65536
> f2fs_submit_write_bio: dev = (251,0)/(251,0), rw = WRITE(S), NODE, sector = 57368, size = 4096
> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
> v3:
> - introduce f2fs_submit_ipu_bio() to check page Writeback status.
>  fs/f2fs/data.c    | 85 ++++++++++++++++++++++++++++++++++++++++++-----
>  fs/f2fs/f2fs.h    |  3 ++
>  fs/f2fs/segment.c |  5 ++-
>  3 files changed, 84 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index cdfe9a7b856e..e5cd3fd9e215 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -341,20 +341,20 @@ static void __submit_merged_bio(struct f2fs_bio_info *io)
>  	io->bio = NULL;
>  }
>  
> -static bool __has_merged_page(struct f2fs_bio_info *io, struct inode *inode,
> +static bool __has_merged_page(struct bio *bio, struct inode *inode,
>  						struct page *page, nid_t ino)
>  {
>  	struct bio_vec *bvec;
>  	struct page *target;
>  	int i;
>  
> -	if (!io->bio)
> +	if (!bio)
>  		return false;
>  
>  	if (!inode && !page && !ino)
>  		return true;
>  
> -	bio_for_each_segment_all(bvec, io->bio, i) {
> +	bio_for_each_segment_all(bvec, bio, i) {
>  
>  		if (bvec->bv_page->mapping)
>  			target = bvec->bv_page;
> @@ -405,7 +405,7 @@ static void __submit_merged_write_cond(struct f2fs_sb_info *sbi,
>  			struct f2fs_bio_info *io = sbi->write_io[btype] + temp;
>  
>  			down_read(&io->io_rwsem);
> -			ret = __has_merged_page(io, inode, page, ino);
> +			ret = __has_merged_page(io->bio, inode, page, ino);
>  			up_read(&io->io_rwsem);
>  		}
>  		if (ret)
> @@ -474,6 +474,59 @@ int f2fs_submit_page_bio(struct f2fs_io_info *fio)
>  	return 0;
>  }
>  
> +int f2fs_merge_page_bio(struct f2fs_io_info *fio)
> +{
> +	struct bio *bio = *fio->bio;
> +	struct page *page = fio->encrypted_page ?
> +			fio->encrypted_page : fio->page;
> +
> +	if (!f2fs_is_valid_blkaddr(fio->sbi, fio->new_blkaddr,
> +			__is_meta_io(fio) ? META_GENERIC : DATA_GENERIC))
> +		return -EFAULT;
> +
> +	trace_f2fs_submit_page_bio(page, fio);
> +	f2fs_trace_ios(fio, 0);
> +
> +	if (bio && (*fio->last_block + 1 != fio->new_blkaddr ||
> +			!__same_bdev(fio->sbi, fio->new_blkaddr, bio))) {
> +		__submit_bio(fio->sbi, bio, fio->type);
> +		bio = NULL;
> +	}
> +alloc_new:
> +	if (!bio) {
> +		bio = __bio_alloc(fio->sbi, fio->new_blkaddr, fio->io_wbc,
> +				BIO_MAX_PAGES, false, fio->type, fio->temp);
> +		*fio->last_block = fio->new_blkaddr;
> +		bio_set_op_attrs(bio, fio->op, fio->op_flags);
> +	}
> +
> +	if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE) {
> +		__submit_bio(fio->sbi, bio, fio->type);
> +		bio = NULL;
> +		goto alloc_new;
> +	}
> +
> +	if (fio->io_wbc)
> +		wbc_account_io(fio->io_wbc, page, PAGE_SIZE);
> +
> +	*fio->last_block = fio->new_blkaddr;
> +
> +	inc_page_count(fio->sbi, WB_DATA_TYPE(fio->page));
> +
> +	*fio->bio = bio;
> +	return 0;
> +}
> +
> +void f2fs_submit_ipu_bio(struct f2fs_sb_info *sbi, struct bio *bio,
> +							struct page *page)
> +{
> +	if (!__has_merged_page(bio, NULL, page, 0))
> +		return;
> +
> +	if (bio)
> +		__submit_bio(sbi, bio, DATA);
> +}
> +
>  void f2fs_submit_page_write(struct f2fs_io_info *fio)
>  {
>  	struct f2fs_sb_info *sbi = fio->sbi;
> @@ -1903,6 +1956,8 @@ int f2fs_do_write_data_page(struct f2fs_io_info *fio)
>  }
>  
>  static int __write_data_page(struct page *page, bool *submitted,
> +				struct bio **bio,
> +				sector_t *last_block,
>  				struct writeback_control *wbc,
>  				enum iostat_type io_type)
>  {
> @@ -1928,6 +1983,8 @@ static int __write_data_page(struct page *page, bool *submitted,
>  		.need_lock = LOCK_RETRY,
>  		.io_type = io_type,
>  		.io_wbc = wbc,
> +		.bio = bio,
> +		.last_block = last_block,
>  	};
>  
>  	trace_f2fs_writepage(page, DATA);
> @@ -2029,6 +2086,10 @@ static int __write_data_page(struct page *page, bool *submitted,
>  		f2fs_balance_fs(sbi, need_balance_fs);
>  
>  	if (unlikely(f2fs_cp_error(sbi))) {
> +		if (bio && *bio) {
> +			__submit_bio(sbi, *bio, DATA);
> +			*bio = NULL;
> +		}
>  		f2fs_submit_merged_write(sbi, DATA);
>  		submitted = NULL;
>  	}
> @@ -2055,7 +2116,7 @@ static int __write_data_page(struct page *page, bool *submitted,
>  static int f2fs_write_data_page(struct page *page,
>  					struct writeback_control *wbc)
>  {
> -	return __write_data_page(page, NULL, wbc, FS_DATA_IO);
> +	return __write_data_page(page, NULL, NULL, NULL, wbc, FS_DATA_IO);
>  }
>  
>  /*
> @@ -2071,6 +2132,8 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
>  	int done = 0;
>  	struct pagevec pvec;
>  	struct f2fs_sb_info *sbi = F2FS_M_SB(mapping);
> +	struct bio *bio = NULL;
> +	sector_t last_block;
>  	int nr_pages;
>  	pgoff_t uninitialized_var(writeback_index);
>  	pgoff_t index;
> @@ -2147,17 +2210,20 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
>  			}
>  
>  			if (PageWriteback(page)) {
> -				if (wbc->sync_mode != WB_SYNC_NONE)
> +				if (wbc->sync_mode != WB_SYNC_NONE) {
>  					f2fs_wait_on_page_writeback(page,
>  								DATA, true);
> -				else
> +					f2fs_submit_ipu_bio(sbi, bio, page);
> +				} else {
>  					goto continue_unlock;
> +				}
>  			}
>  
>  			if (!clear_page_dirty_for_io(page))
>  				goto continue_unlock;
>  
> -			ret = __write_data_page(page, &submitted, wbc, io_type);
> +			ret = __write_data_page(page, &submitted, &bio,
> +						&last_block, wbc, io_type);
>  			if (unlikely(ret)) {
>  				/*
>  				 * keep nr_to_write, since vfs uses this to
> @@ -2206,6 +2272,9 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
>  	if (nwritten)
>  		f2fs_submit_merged_write_cond(F2FS_M_SB(mapping), mapping->host,
>  								NULL, 0, DATA);
> +	/* submit cached bio of IPU write */
> +	if (bio)
> +		__submit_bio(sbi, bio, DATA);
>  
>  	return ret;
>  }
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 9e56c78fe519..eeede26339a8 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1044,6 +1044,8 @@ struct f2fs_io_info {
>  	bool retry;		/* need to reallocate block address */
>  	enum iostat_type io_type;	/* io type */
>  	struct writeback_control *io_wbc; /* writeback control */
> +	struct bio **bio;		/* bio for ipu */
> +	sector_t *last_block;		/* last block number in bio */
>  	unsigned char version;		/* version of the node */
>  };
>  
> @@ -3105,6 +3107,7 @@ void f2fs_submit_merged_write_cond(struct f2fs_sb_info *sbi,
>  				nid_t ino, enum page_type type);
>  void f2fs_flush_merged_writes(struct f2fs_sb_info *sbi);
>  int f2fs_submit_page_bio(struct f2fs_io_info *fio);
> +int f2fs_merge_page_bio(struct f2fs_io_info *fio);
>  void f2fs_submit_page_write(struct f2fs_io_info *fio);
>  struct block_device *f2fs_target_device(struct f2fs_sb_info *sbi,
>  			block_t blk_addr, struct bio *bio);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 3241e0619275..a361d61b005e 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -3163,7 +3163,10 @@ int f2fs_inplace_write_data(struct f2fs_io_info *fio)
>  
>  	stat_inc_inplace_blocks(fio->sbi);
>  
> -	err = f2fs_submit_page_bio(fio);
> +	if (fio->bio)
> +		err = f2fs_merge_page_bio(fio);
> +	else
> +		err = f2fs_submit_page_bio(fio);
>  	if (!err)
>  		update_device_state(fio);
>  
>