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Date:   Thu, 3 Feb 2022 11:59:44 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] f2fs: adjust readahead block number during recovery
Message-ID: <Yfw0MPPdDjSP6mxk@google.com>
References: <20220129082112.1814398-1-chao@kernel.org>
 <9d450a33-41eb-0caf-aba1-427c5ae547ed@kernel.org>
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On 02/03, Chao Yu wrote:
> Jaegeuk, any comments on this patch?

Yea, looks good to me.

> 
> Thanks,
> 
> On 2022/1/29 16:21, Chao Yu wrote:
> > In a fragmented image, entries in dnode block list may locate in
> > incontiguous physical block address space, however, in recovery flow,
> > we will always readahead BIO_MAX_VECS size blocks, so in such case,
> > current readahead policy is low efficient, let's adjust readahead
> > window size dynamically based on consecutiveness of dnode blocks.
> > 
> > Signed-off-by: Chao Yu <chao@kernel.org>
> > ---
> >   fs/f2fs/checkpoint.c |  8 ++++++--
> >   fs/f2fs/f2fs.h       |  6 +++++-
> >   fs/f2fs/recovery.c   | 27 ++++++++++++++++++++++++---
> >   3 files changed, 35 insertions(+), 6 deletions(-)
> > 
> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > index 57a2d9164bee..203a1577942d 100644
> > --- a/fs/f2fs/checkpoint.c
> > +++ b/fs/f2fs/checkpoint.c
> > @@ -282,18 +282,22 @@ int f2fs_ra_meta_pages(struct f2fs_sb_info *sbi, block_t start, int nrpages,
> >   	return blkno - start;
> >   }
> > -void f2fs_ra_meta_pages_cond(struct f2fs_sb_info *sbi, pgoff_t index)
> > +void f2fs_ra_meta_pages_cond(struct f2fs_sb_info *sbi, pgoff_t index,
> > +							unsigned int ra_blocks)
> >   {
> >   	struct page *page;
> >   	bool readahead = false;
> > +	if (ra_blocks == RECOVERY_MIN_RA_BLOCKS)
> > +		return;
> > +
> >   	page = find_get_page(META_MAPPING(sbi), index);
> >   	if (!page || !PageUptodate(page))
> >   		readahead = true;
> >   	f2fs_put_page(page, 0);
> >   	if (readahead)
> > -		f2fs_ra_meta_pages(sbi, index, BIO_MAX_VECS, META_POR, true);
> > +		f2fs_ra_meta_pages(sbi, index, ra_blocks, META_POR, true);
> >   }
> >   static int __f2fs_write_meta_page(struct page *page,
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 5af415208488..1fa6b3f98a71 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -590,6 +590,9 @@ enum {
> >   /* number of extent info in extent cache we try to shrink */
> >   #define EXTENT_CACHE_SHRINK_NUMBER	128
> > +#define RECOVERY_MAX_RA_BLOCKS		BIO_MAX_VECS
> > +#define RECOVERY_MIN_RA_BLOCKS		1
> > +
> >   struct rb_entry {
> >   	struct rb_node rb_node;		/* rb node located in rb-tree */
> >   	union {
> > @@ -3655,7 +3658,8 @@ bool f2fs_is_valid_blkaddr(struct f2fs_sb_info *sbi,
> >   					block_t blkaddr, int type);
> >   int f2fs_ra_meta_pages(struct f2fs_sb_info *sbi, block_t start, int nrpages,
> >   			int type, bool sync);
> > -void f2fs_ra_meta_pages_cond(struct f2fs_sb_info *sbi, pgoff_t index);
> > +void f2fs_ra_meta_pages_cond(struct f2fs_sb_info *sbi, pgoff_t index,
> > +							unsigned int ra_blocks);
> >   long f2fs_sync_meta_pages(struct f2fs_sb_info *sbi, enum page_type type,
> >   			long nr_to_write, enum iostat_type io_type);
> >   void f2fs_add_ino_entry(struct f2fs_sb_info *sbi, nid_t ino, int type);
> > diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
> > index f69b685fb2b2..0b88d0ce284a 100644
> > --- a/fs/f2fs/recovery.c
> > +++ b/fs/f2fs/recovery.c
> > @@ -346,6 +346,19 @@ static int recover_inode(struct inode *inode, struct page *page)
> >   	return 0;
> >   }
> > +static unsigned int adjust_por_ra_blocks(struct f2fs_sb_info *sbi,
> > +				unsigned int ra_blocks, unsigned int blkaddr,
> > +				unsigned int next_blkaddr)
> > +{
> > +	if (blkaddr + 1 == next_blkaddr)
> > +		ra_blocks = min_t(unsigned int, RECOVERY_MIN_RA_BLOCKS,
> > +							ra_blocks * 2);
> > +	else if (next_blkaddr % sbi->blocks_per_seg)
> > +		ra_blocks = max_t(unsigned int, RECOVERY_MAX_RA_BLOCKS,
> > +							ra_blocks / 2);
> > +	return ra_blocks;
> > +}
> > +
> >   static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head,
> >   				bool check_only)
> >   {
> > @@ -353,6 +366,7 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head,
> >   	struct page *page = NULL;
> >   	block_t blkaddr;
> >   	unsigned int loop_cnt = 0;
> > +	unsigned int ra_blocks = RECOVERY_MAX_RA_BLOCKS;
> >   	unsigned int free_blocks = MAIN_SEGS(sbi) * sbi->blocks_per_seg -
> >   						valid_user_blocks(sbi);
> >   	int err = 0;
> > @@ -427,11 +441,14 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head,
> >   			break;
> >   		}
> > +		ra_blocks = adjust_por_ra_blocks(sbi, ra_blocks, blkaddr,
> > +						next_blkaddr_of_node(page));
> > +
> >   		/* check next segment */
> >   		blkaddr = next_blkaddr_of_node(page);
> >   		f2fs_put_page(page, 1);
> > -		f2fs_ra_meta_pages_cond(sbi, blkaddr);
> > +		f2fs_ra_meta_pages_cond(sbi, blkaddr, ra_blocks);
> >   	}
> >   	return err;
> >   }
> > @@ -707,6 +724,7 @@ static int recover_data(struct f2fs_sb_info *sbi, struct list_head *inode_list,
> >   	struct page *page = NULL;
> >   	int err = 0;
> >   	block_t blkaddr;
> > +	unsigned int ra_blocks = RECOVERY_MAX_RA_BLOCKS;
> >   	/* get node pages in the current segment */
> >   	curseg = CURSEG_I(sbi, CURSEG_WARM_NODE);
> > @@ -718,8 +736,6 @@ static int recover_data(struct f2fs_sb_info *sbi, struct list_head *inode_list,
> >   		if (!f2fs_is_valid_blkaddr(sbi, blkaddr, META_POR))
> >   			break;
> > -		f2fs_ra_meta_pages_cond(sbi, blkaddr);
> > -
> >   		page = f2fs_get_tmp_page(sbi, blkaddr);
> >   		if (IS_ERR(page)) {
> >   			err = PTR_ERR(page);
> > @@ -762,9 +778,14 @@ static int recover_data(struct f2fs_sb_info *sbi, struct list_head *inode_list,
> >   		if (entry->blkaddr == blkaddr)
> >   			list_move_tail(&entry->list, tmp_inode_list);
> >   next:
> > +		ra_blocks = adjust_por_ra_blocks(sbi, ra_blocks, blkaddr,
> > +						next_blkaddr_of_node(page));
> > +
> >   		/* check next segment */
> >   		blkaddr = next_blkaddr_of_node(page);
> >   		f2fs_put_page(page, 1);
> > +
> > +		f2fs_ra_meta_pages_cond(sbi, blkaddr, ra_blocks);
> >   	}
> >   	if (!err)
> >   		f2fs_allocate_new_segments(sbi);