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Date:   Wed, 14 Nov 2018 23:52:26 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [PATCH] f2fs: add bio cache for IPU
Message-ID: <20181115075226.GA83610@jaegeuk-macbookpro.roam.corp.google.com>
References: <20181023083817.3466-1-yuchao0@huawei.com>
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Hi Chao,

I suspect this brings a system stuck by missing bio being flushed. Please check
the changes.

Thanks,

On 10/23, 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>
> ---
>  fs/f2fs/data.c    | 57 +++++++++++++++++++++++++++++++++++++++++++++--
>  fs/f2fs/f2fs.h    |  3 +++
>  fs/f2fs/segment.c |  5 ++++-
>  3 files changed, 62 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 01b7f59523dc..0c8f18dc140d 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -491,6 +491,49 @@ 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_page_write(struct f2fs_io_info *fio)
>  {
>  	struct f2fs_sb_info *sbi = fio->sbi;
> @@ -1899,6 +1942,8 @@ 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)
>  {
> @@ -1924,6 +1969,8 @@ 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);
> @@ -2051,7 +2098,7 @@ 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);
>  }
>  
>  /*
> @@ -2067,6 +2114,8 @@ 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;
> @@ -2154,7 +2203,8 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
>  			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
> @@ -2201,6 +2251,9 @@ 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 8932276015f9..6af2a105529d 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1042,6 +1042,8 @@ 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 */
>  };
>  
> @@ -3085,6 +3087,7 @@ 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 3aa2f00262b3..b51b182dd7f4 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -3194,7 +3194,10 @@ 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);
>  
> -- 
> 2.18.0.rc1