Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Date:   Tue, 12 Apr 2022 09:21:32 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, Chao Yu <chao.yu@oppo.com>
Subject: Re: [PATCH v3] f2fs: give priority to select unpinned section for
 foreground GC
Message-ID: <YlWnDD2H+AueUYcK@google.com>
References: <20220406152651.5142-1-chao@kernel.org>
 <YlSNjgQwoiENx5EK@google.com>
 <1eee9abe-f468-ce32-cdb9-3a706404de2f@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1eee9abe-f468-ce32-cdb9-3a706404de2f@kernel.org>
Precedence: bulk

On 04/12, Chao Yu wrote:
> On 2022/4/12 4:20, Jaegeuk Kim wrote:
> > On 04/06, Chao Yu wrote:
> > > Previously, during foreground GC, if victims contain data of pinned file,
> > > it will fail migration of the data, and meanwhile i_gc_failures of that
> > > pinned file may increase, and when it exceeds threshold, GC will unpin
> > > the file, result in breaking pinfile's semantics.
> > > 
> > > In order to mitigate such condition, let's record and skip section which
> > > has pinned file's data and give priority to select unpinned one.
> > > 
> > > Signed-off-by: Chao Yu <chao.yu@oppo.com>
> > > ---
> > > v3:
> > > - check pin status before pinning section in pin_section().
> > >   fs/f2fs/gc.c      | 56 ++++++++++++++++++++++++++++++++++++++++++++---
> > >   fs/f2fs/segment.c |  7 ++++++
> > >   fs/f2fs/segment.h |  2 ++
> > >   3 files changed, 62 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > > index 6a7e4148ff9d..df23824ae3c2 100644
> > > --- a/fs/f2fs/gc.c
> > > +++ b/fs/f2fs/gc.c
> > > @@ -646,6 +646,37 @@ static void release_victim_entry(struct f2fs_sb_info *sbi)
> > >   	f2fs_bug_on(sbi, !list_empty(&am->victim_list));
> > >   }
> > > +static void pin_section(struct f2fs_sb_info *sbi, unsigned int segno)
> > 
> > Need f2fs_...?
> 
> Sure, I can add prefix...
> 
> It's a local function, it won't pollute global namespace w/o f2fs_ prefix
> though.
> 
> > 
> > > +{
> > > +	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
> > > +	unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
> > > +
> > > +	if (test_bit(secno, dirty_i->pinned_secmap))
> > > +		return;
> > > +	set_bit(secno, dirty_i->pinned_secmap);
> > > +	dirty_i->pinned_secmap_cnt++;
> > > +}
> > > +
> > > +static bool pinned_section_exists(struct dirty_seglist_info *dirty_i)
> > > +{
> > > +	return dirty_i->pinned_secmap_cnt;
> > > +}
> > > +
> > > +static bool section_is_pinned(struct dirty_seglist_info *dirty_i,
> > > +						unsigned int secno)
> > > +{
> > > +	return pinned_section_exists(dirty_i) &&
> > > +			test_bit(secno, dirty_i->pinned_secmap);
> > > +}
> > > +
> > > +static void unpin_all_sections(struct f2fs_sb_info *sbi)
> > > +{
> > > +	unsigned int bitmap_size = f2fs_bitmap_size(MAIN_SECS(sbi));
> > > +
> > > +	memset(DIRTY_I(sbi)->pinned_secmap, 0, bitmap_size);
> > > +	DIRTY_I(sbi)->pinned_secmap_cnt = 0;
> > > +}
> > > +
> > >   /*
> > >    * This function is called from two paths.
> > >    * One is garbage collection and the other is SSR segment selection.
> > > @@ -787,6 +818,9 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
> > >   		if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
> > >   			goto next;
> > > +		if (gc_type == FG_GC && section_is_pinned(dirty_i, secno))
> > > +			goto next;
> > > +
> > >   		if (is_atgc) {
> > >   			add_victim_entry(sbi, &p, segno);
> > >   			goto next;
> > > @@ -1202,8 +1236,10 @@ static int move_data_block(struct inode *inode, block_t bidx,
> > >   	}
> > >   	if (f2fs_is_pinned_file(inode)) {
> > > -		if (gc_type == FG_GC)
> > > +		if (gc_type == FG_GC) {
> > >   			f2fs_pin_file_control(inode, true);
> > > +			pin_section(F2FS_I_SB(inode), segno);
> > 
> > Do we need to check unpinning the inode?
> > 			if (!f2fs_pin_file_control())
> > 				f2fs_set_pin_section();
> 
> I'm thinking that it needs to avoid increasing GC_FAILURE_PIN AMAP,
> so could you please check below logic:
> 
> From 7cb1ee0df32ede44b17c503b81930dae25d287eb Mon Sep 17 00:00:00 2001
> From: Chao Yu <chao@kernel.org>
> Date: Wed, 6 Apr 2022 23:26:51 +0800
> Subject: [PATCH v4] f2fs: give priority to select unpinned section for
>  foreground GC
> 
> Previously, during foreground GC, if victims contain data of pinned file,
> it will fail migration of the data, and meanwhile i_gc_failures of that
> pinned file may increase, and when it exceeds threshold, GC will unpin
> the file, result in breaking pinfile's semantics.
> 
> In order to mitigate such condition, let's record and skip section which
> has pinned file's data and give priority to select unpinned one.
> 
> Signed-off-by: Chao Yu <chao.yu@oppo.com>
> ---
> v4:
> - add f2fs_ prefix for newly introduced functions
> - add bool type variable for functionality switch
> - increase GC_FAILURE_PIN only if it disable pinning section
>  fs/f2fs/gc.c      | 66 ++++++++++++++++++++++++++++++++++++++++++-----
>  fs/f2fs/segment.c |  8 ++++++
>  fs/f2fs/segment.h |  3 +++
>  3 files changed, 71 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 6a7e4148ff9d..296b31e28d3d 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -646,6 +646,41 @@ static void release_victim_entry(struct f2fs_sb_info *sbi)
>  	f2fs_bug_on(sbi, !list_empty(&am->victim_list));
>  }
> 
> +static bool f2fs_pin_section(struct f2fs_sb_info *sbi, unsigned int segno)
> +{
> +	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
> +	unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
> +
> +	if (!dirty_i->enable_pin_section)
> +		return false;
> +	if (test_bit(secno, dirty_i->pinned_secmap))
> +		return true;
> +	set_bit(secno, dirty_i->pinned_secmap);
> +	dirty_i->pinned_secmap_cnt++;

	if (!test_and_set_bit())
		dirty_i->pinned_secmap_cnt++;

> +	return true;
> +}
> +
> +static bool f2fs_pinned_section_exists(struct dirty_seglist_info *dirty_i)
> +{
> +	return dirty_i->enable_pin_section && dirty_i->pinned_secmap_cnt;
> +}
> +
> +static bool f2fs_section_is_pinned(struct dirty_seglist_info *dirty_i,
> +						unsigned int secno)
> +{
> +	return f2fs_pinned_section_exists(dirty_i) &&
> +			test_bit(secno, dirty_i->pinned_secmap);
> +}
> +
> +static void f2fs_unpin_all_sections(struct f2fs_sb_info *sbi, bool enable)
> +{
> +	unsigned int bitmap_size = f2fs_bitmap_size(MAIN_SECS(sbi));
> +
> +	memset(DIRTY_I(sbi)->pinned_secmap, 0, bitmap_size);
> +	DIRTY_I(sbi)->pinned_secmap_cnt = 0;
> +	DIRTY_I(sbi)->enable_pin_section = enable;
> +}
> +
>  /*
>   * This function is called from two paths.
>   * One is garbage collection and the other is SSR segment selection.
> @@ -787,6 +822,9 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
>  		if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
>  			goto next;
> 
> +		if (gc_type == FG_GC && f2fs_section_is_pinned(dirty_i, secno))
> +			goto next;
> +
>  		if (is_atgc) {
>  			add_victim_entry(sbi, &p, segno);
>  			goto next;
> @@ -1202,8 +1240,10 @@ static int move_data_block(struct inode *inode, block_t bidx,
>  	}
> 

Can we make a generic function?

f2fs_gc_pinned_control()
{
	if (!f2fs_is_pinned_file(inode))
		return 0;
	if (gc_type != FG_GC)
		return 0;
	if (!f2fs_pin_section())
		f2fs_pin_file_control();
	return -EAGAIN;
}

>  	if (f2fs_is_pinned_file(inode)) {
> -		if (gc_type == FG_GC)
> -			f2fs_pin_file_control(inode, true);
> +		if (gc_type == FG_GC) {
> +			if (!f2fs_pin_section(F2FS_I_SB(inode), segno))

> +				f2fs_pin_file_control(inode, true);
> +		}
>  		err = -EAGAIN;
>  		goto out;
>  	}
> @@ -1352,8 +1392,10 @@ static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
>  		goto out;
>  	}
>  	if (f2fs_is_pinned_file(inode)) {
> -		if (gc_type == FG_GC)
> -			f2fs_pin_file_control(inode, true);
> +		if (gc_type == FG_GC) {
> +			if (!f2fs_pin_section(F2FS_I_SB(inode), segno))
> +				f2fs_pin_file_control(inode, true);
> +		}
>  		err = -EAGAIN;
>  		goto out;
>  	}
> @@ -1483,7 +1525,8 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
> 
>  			if (is_inode_flag_set(inode, FI_PIN_FILE) &&
>  							gc_type == FG_GC) {
> -				f2fs_pin_file_control(inode, true);
> +				if (!f2fs_pin_section(sbi, segno))
> +					f2fs_pin_file_control(inode, true);
>  				iput(inode);
>  				return submitted;
>  			}
> @@ -1766,9 +1809,17 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  		ret = -EINVAL;
>  		goto stop;
>  	}
> +retry:
>  	ret = __get_victim(sbi, &segno, gc_type);
> -	if (ret)
> +	if (ret) {
> +		/* allow to search victim from sections has pinned data */
> +		if (ret == -ENODATA && gc_type == FG_GC &&
> +				f2fs_pinned_section_exists(DIRTY_I(sbi))) {
> +			f2fs_unpin_all_sections(sbi, false);
> +			goto retry;
> +		}
>  		goto stop;
> +	}
> 
>  	seg_freed = do_garbage_collect(sbi, segno, &gc_list, gc_type, force);
>  	if (gc_type == FG_GC &&
> @@ -1811,6 +1862,9 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  	SIT_I(sbi)->last_victim[ALLOC_NEXT] = 0;
>  	SIT_I(sbi)->last_victim[FLUSH_DEVICE] = init_segno;
> 
> +	if (gc_type == FG_GC && f2fs_pinned_section_exists(DIRTY_I(sbi)))
> +		f2fs_unpin_all_sections(sbi, true);
> +
>  	trace_f2fs_gc_end(sbi->sb, ret, total_freed, sec_freed,
>  				get_pages(sbi, F2FS_DIRTY_NODES),
>  				get_pages(sbi, F2FS_DIRTY_DENTS),
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 22dfeb991529..93c7bae57a25 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -4734,6 +4734,13 @@ static int init_victim_secmap(struct f2fs_sb_info *sbi)
>  	dirty_i->victim_secmap = f2fs_kvzalloc(sbi, bitmap_size, GFP_KERNEL);
>  	if (!dirty_i->victim_secmap)
>  		return -ENOMEM;
> +
> +	dirty_i->pinned_secmap = f2fs_kvzalloc(sbi, bitmap_size, GFP_KERNEL);
> +	if (!dirty_i->pinned_secmap)
> +		return -ENOMEM;
> +
> +	dirty_i->pinned_secmap_cnt = 0;
> +	dirty_i->enable_pin_section = true;
>  	return 0;
>  }
> 
> @@ -5322,6 +5329,7 @@ static void destroy_victim_secmap(struct f2fs_sb_info *sbi)
>  {
>  	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
> 
> +	kvfree(dirty_i->pinned_secmap);
>  	kvfree(dirty_i->victim_secmap);
>  }
> 
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 5c94caf0c0a1..8a591455d796 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -294,6 +294,9 @@ struct dirty_seglist_info {
>  	struct mutex seglist_lock;		/* lock for segment bitmaps */
>  	int nr_dirty[NR_DIRTY_TYPE];		/* # of dirty segments */
>  	unsigned long *victim_secmap;		/* background GC victims */
> +	unsigned long *pinned_secmap;		/* pinned victims from foreground GC */
> +	unsigned int pinned_secmap_cnt;		/* count of victims which has pinned data */
> +	bool enable_pin_section;		/* enable pinning section */
>  };
> 
>  /* victim selection function for cleaning and SSR */
> -- 
> 2.25.1
> 
> Thanks,
> 
> > 
> > > +		}
> > >   		err = -EAGAIN;
> > >   		goto out;
> > >   	}
> > > @@ -1352,8 +1388,10 @@ static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
> > >   		goto out;
> > >   	}
> > >   	if (f2fs_is_pinned_file(inode)) {
> > > -		if (gc_type == FG_GC)
> > > +		if (gc_type == FG_GC) {
> > >   			f2fs_pin_file_control(inode, true);
> > > +			pin_section(F2FS_I_SB(inode), segno);
> > > +		}
> > >   		err = -EAGAIN;
> > >   		goto out;
> > >   	}
> > > @@ -1485,6 +1523,7 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
> > >   							gc_type == FG_GC) {
> > >   				f2fs_pin_file_control(inode, true);
> > >   				iput(inode);
> > > +				pin_section(sbi, segno);
> > 
> > We don't have this code.
> > 
> > >   				return submitted;
> > >   			}
> > > @@ -1766,9 +1805,17 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> > >   		ret = -EINVAL;
> > >   		goto stop;
> > >   	}
> > > +retry:
> > >   	ret = __get_victim(sbi, &segno, gc_type);
> > > -	if (ret)
> > > +	if (ret) {
> > > +		/* allow to search victim from sections has pinned data */
> > > +		if (ret == -ENODATA && gc_type == FG_GC &&
> > > +				pinned_section_exists(DIRTY_I(sbi))) {
> > > +			unpin_all_sections(sbi);
> > > +			goto retry;
> > > +		}
> > >   		goto stop;
> > > +	}
> > >   	seg_freed = do_garbage_collect(sbi, segno, &gc_list, gc_type, force);
> > >   	if (gc_type == FG_GC &&
> > > @@ -1811,6 +1858,9 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> > >   	SIT_I(sbi)->last_victim[ALLOC_NEXT] = 0;
> > >   	SIT_I(sbi)->last_victim[FLUSH_DEVICE] = init_segno;
> > > +	if (gc_type == FG_GC && pinned_section_exists(DIRTY_I(sbi)))
> > > +		unpin_all_sections(sbi);
> > > +
> > >   	trace_f2fs_gc_end(sbi->sb, ret, total_freed, sec_freed,
> > >   				get_pages(sbi, F2FS_DIRTY_NODES),
> > >   				get_pages(sbi, F2FS_DIRTY_DENTS),
> > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > > index 012524db7437..1c20d7c9eca3 100644
> > > --- a/fs/f2fs/segment.c
> > > +++ b/fs/f2fs/segment.c
> > > @@ -4736,6 +4736,12 @@ static int init_victim_secmap(struct f2fs_sb_info *sbi)
> > >   	dirty_i->victim_secmap = f2fs_kvzalloc(sbi, bitmap_size, GFP_KERNEL);
> > >   	if (!dirty_i->victim_secmap)
> > >   		return -ENOMEM;
> > > +
> > > +	dirty_i->pinned_secmap = f2fs_kvzalloc(sbi, bitmap_size, GFP_KERNEL);
> > > +	if (!dirty_i->pinned_secmap)
> > > +		return -ENOMEM;
> > > +
> > > +	dirty_i->pinned_secmap_cnt = 0;
> > >   	return 0;
> > >   }
> > > @@ -5324,6 +5330,7 @@ static void destroy_victim_secmap(struct f2fs_sb_info *sbi)
> > >   {
> > >   	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
> > > +	kvfree(dirty_i->pinned_secmap);
> > >   	kvfree(dirty_i->victim_secmap);
> > >   }
> > > diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> > > index 5c94caf0c0a1..fd6f246e649c 100644
> > > --- a/fs/f2fs/segment.h
> > > +++ b/fs/f2fs/segment.h
> > > @@ -294,6 +294,8 @@ struct dirty_seglist_info {
> > >   	struct mutex seglist_lock;		/* lock for segment bitmaps */
> > >   	int nr_dirty[NR_DIRTY_TYPE];		/* # of dirty segments */
> > >   	unsigned long *victim_secmap;		/* background GC victims */
> > > +	unsigned long *pinned_secmap;		/* pinned victims from foreground GC */
> > > +	unsigned int pinned_secmap_cnt;		/* count of victims which has pinned data */
> > >   };
> > >   /* victim selection function for cleaning and SSR */
> > > -- 
> > > 2.32.0