[PATCH 1/2] f2fs: conduct f2fs_gc as explicit gc_type

[PATCH 1/2] f2fs: conduct f2fs_gc as explicit gc_type

[Changman Lee]

f2fs has 2 gc_type; foreground gc and background gc.
In the case of foreground gc, f2fs will select victim as greedy.
Otherwise, as cost-benefit. And also it runs as greedy in SSR mode.
Until now, f2fs_gc conducted with BG_GC as default. So we couldn't
expect how it runs; BG_GC or FG_GC and GREEDY or COST_BENEFIT.
Therefore sometimes it runs as BG_GC/COST_BENEFIT although gc_thread
don't put f2fs_gc to work.

Signed-off-by: Changman Lee <cm224.lee@samsung.com>
---
 fs/f2fs/f2fs.h    | 2 +-
 fs/f2fs/gc.c      | 5 ++---
 fs/f2fs/segment.c | 6 +++---
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index ae6dfb6..c956535 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1476,7 +1476,7 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *, u64, u64);
 int start_gc_thread(struct f2fs_sb_info *);
 void stop_gc_thread(struct f2fs_sb_info *);
 block_t start_bidx_of_node(unsigned int, struct f2fs_inode_info *);
-int f2fs_gc(struct f2fs_sb_info *);
+int f2fs_gc(struct f2fs_sb_info *, int);
 void build_gc_manager(struct f2fs_sb_info *);
 int __init create_gc_caches(void);
 void destroy_gc_caches(void);
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index eec0933..e1fa53a 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -80,7 +80,7 @@ static int gc_thread_func(void *data)
 		stat_inc_bggc_count(sbi);
 
 		/* if return value is not zero, no victim was selected */
-		if (f2fs_gc(sbi))
+		if (f2fs_gc(sbi, BG_GC))
 			wait_ms = gc_th->no_gc_sleep_time;
 
 		/* balancing f2fs's metadata periodically */
@@ -691,10 +691,9 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 	f2fs_put_page(sum_page, 1);
 }
 
-int f2fs_gc(struct f2fs_sb_info *sbi)
+int f2fs_gc(struct f2fs_sb_info *sbi, int gc_type)
 {
 	unsigned int segno, i;
-	int gc_type = BG_GC;
 	int nfree = 0;
 	int ret = -1;
 	struct cp_control cpc;
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index fd9bc96..3b32404 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -281,7 +281,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi)
 	 */
 	if (has_not_enough_free_secs(sbi, 0)) {
 		mutex_lock(&sbi->gc_mutex);
-		f2fs_gc(sbi);
+		f2fs_gc(sbi, FG_GC);
 	}
 }
 
@@ -994,12 +994,12 @@ static int get_ssr_segment(struct f2fs_sb_info *sbi, int type)
 
 	if (IS_NODESEG(type) || !has_not_enough_free_secs(sbi, 0))
 		return v_ops->get_victim(sbi,
-				&(curseg)->next_segno, BG_GC, type, SSR);
+				&(curseg)->next_segno, FG_GC, type, SSR);
 
 	/* For data segments, let's do SSR more intensively */
 	for (; type >= CURSEG_HOT_DATA; type--)
 		if (v_ops->get_victim(sbi, &(curseg)->next_segno,
-						BG_GC, type, SSR))
+						FG_GC, type, SSR))
 			return 1;
 	return 0;
 }
-- 
1.9.1

[PATCH 2/2] f2fs: add stat info for moved blocks by background gc

[Changman Lee]

This patch is for looking into gc performance of f2fs in detail.

Signed-off-by: Changman Lee <cm224.lee@samsung.com>
---
 fs/f2fs/debug.c | 15 ++++++++++-----
 fs/f2fs/f2fs.h  | 17 ++++++++++++-----
 fs/f2fs/gc.c    |  6 +++---
 3 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index 46bef86..285cce1 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -244,11 +244,16 @@ static int stat_show(struct seq_file *s, void *v)
 		seq_printf(s, "CP calls: %d\n", si->cp_count);
 		seq_printf(s, "GC calls: %d (BG: %d)\n",
 			   si->call_count, si->bg_gc);
-		seq_printf(s, "  - data segments : %d\n", si->data_segs);
-		seq_printf(s, "  - node segments : %d\n", si->node_segs);
-		seq_printf(s, "Try to move %d blocks\n", si->tot_blks);
-		seq_printf(s, "  - data blocks : %d\n", si->data_blks);
-		seq_printf(s, "  - node blocks : %d\n", si->node_blks);
+		seq_printf(s, "  - data segments : %d (%d)\n",
+				si->data_segs, si->bg_data_segs);
+		seq_printf(s, "  - node segments : %d (%d)\n",
+				si->node_segs, si->bg_node_segs);
+		seq_printf(s, "Try to move %d blocks (BG: %d)\n", si->tot_blks,
+				si->bg_data_blks + si->bg_node_blks);
+		seq_printf(s, "  - data blocks : %d (%d)\n", si->data_blks,
+				si->bg_data_blks);
+		seq_printf(s, "  - node blocks : %d (%d)\n", si->node_blks,
+				si->bg_node_blks);
 		seq_printf(s, "\nExtent Hit Ratio: %d / %d\n",
 			   si->hit_ext, si->total_ext);
 		seq_puts(s, "\nBalancing F2FS Async:\n");
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index c956535..c88e2fc 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1508,7 +1508,9 @@ struct f2fs_stat_info {
 	int dirty_count, node_pages, meta_pages;
 	int prefree_count, call_count, cp_count;
 	int tot_segs, node_segs, data_segs, free_segs, free_secs;
+	int bg_node_segs, bg_data_segs;
 	int tot_blks, data_blks, node_blks;
+	int bg_data_blks, bg_node_blks;
 	int curseg[NR_CURSEG_TYPE];
 	int cursec[NR_CURSEG_TYPE];
 	int curzone[NR_CURSEG_TYPE];
@@ -1557,31 +1559,36 @@ static inline struct f2fs_stat_info *F2FS_STAT(struct f2fs_sb_info *sbi)
 		((sbi)->block_count[(curseg)->alloc_type]++)
 #define stat_inc_inplace_blocks(sbi)					\
 		((sbi)->inplace_count++)
-#define stat_inc_seg_count(sbi, type)					\
+#define stat_inc_seg_count(sbi, type, gc_type)				\
 	do {								\
 		struct f2fs_stat_info *si = F2FS_STAT(sbi);		\
 		(si)->tot_segs++;					\
-		if (type == SUM_TYPE_DATA)				\
+		if (type == SUM_TYPE_DATA) {				\
 			si->data_segs++;				\
-		else							\
+			si->bg_data_segs += (gc_type == BG_GC) ? 1 : 0;	\
+		} else {						\
 			si->node_segs++;				\
+			si->bg_node_segs += (gc_type == BG_GC) ? 1 : 0;	\
+		}							\
 	} while (0)
 
 #define stat_inc_tot_blk_count(si, blks)				\
 	(si->tot_blks += (blks))
 
-#define stat_inc_data_blk_count(sbi, blks)				\
+#define stat_inc_data_blk_count(sbi, blks, gc_type)			\
 	do {								\
 		struct f2fs_stat_info *si = F2FS_STAT(sbi);		\
 		stat_inc_tot_blk_count(si, blks);			\
 		si->data_blks += (blks);				\
+		si->bg_data_blks += (gc_type == BG_GC) ? (blks) : 0;	\
 	} while (0)
 
-#define stat_inc_node_blk_count(sbi, blks)				\
+#define stat_inc_node_blk_count(sbi, blks, gc_type)			\
 	do {								\
 		struct f2fs_stat_info *si = F2FS_STAT(sbi);		\
 		stat_inc_tot_blk_count(si, blks);			\
 		si->node_blks += (blks);				\
+		si->bg_node_blks += (gc_type == BG_GC) ? (blks) : 0;	\
 	} while (0)
 
 int f2fs_build_stats(struct f2fs_sb_info *);
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index e1fa53a..f67eb2a 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -440,7 +440,7 @@ next_step:
 				set_page_dirty(node_page);
 		}
 		f2fs_put_page(node_page, 1);
-		stat_inc_node_blk_count(sbi, 1);
+		stat_inc_node_blk_count(sbi, 1, gc_type);
 	}
 
 	if (initial) {
@@ -627,7 +627,7 @@ next_step:
 			if (IS_ERR(data_page))
 				continue;
 			move_data_page(inode, data_page, gc_type);
-			stat_inc_data_blk_count(sbi, 1);
+			stat_inc_data_blk_count(sbi, 1, gc_type);
 		}
 	}
 
@@ -685,7 +685,7 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 	}
 	blk_finish_plug(&plug);
 
-	stat_inc_seg_count(sbi, GET_SUM_TYPE((&sum->footer)));
+	stat_inc_seg_count(sbi, GET_SUM_TYPE((&sum->footer)), gc_type);
 	stat_inc_call_count(sbi->stat_info);
 
 	f2fs_put_page(sum_page, 1);
-- 
1.9.1

Re: [f2fs-dev] [PATCH 1/2] f2fs: conduct f2fs_gc as explicit gc_type

[Jaegeuk Kim]

Hi Changman,

On Tue, Dec 23, 2014 at 08:37:38AM +0900, Changman Lee wrote:
> f2fs has 2 gc_type; foreground gc and background gc.
> In the case of foreground gc, f2fs will select victim as greedy.
> Otherwise, as cost-benefit. And also it runs as greedy in SSR mode.
> Until now, f2fs_gc conducted with BG_GC as default. So we couldn't
> expect how it runs; BG_GC or FG_GC and GREEDY or COST_BENEFIT.

What does this mean?
In f2fs_gc, the gc_type will be changed accoring to the number of free
sections.

> Therefore sometimes it runs as BG_GC/COST_BENEFIT although gc_thread
> don't put f2fs_gc to work.

You mean f2fs_balance_fs?
In this case, again, the gc_type will be assigned FG_GC.

Why do you want to set FG_GC/GREEDY for the SSR victims?

Thanks,

> 
> Signed-off-by: Changman Lee <cm224.lee@samsung.com>
> ---
>  fs/f2fs/f2fs.h    | 2 +-
>  fs/f2fs/gc.c      | 5 ++---
>  fs/f2fs/segment.c | 6 +++---
>  3 files changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index ae6dfb6..c956535 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1476,7 +1476,7 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *, u64, u64);
>  int start_gc_thread(struct f2fs_sb_info *);
>  void stop_gc_thread(struct f2fs_sb_info *);
>  block_t start_bidx_of_node(unsigned int, struct f2fs_inode_info *);
> -int f2fs_gc(struct f2fs_sb_info *);
> +int f2fs_gc(struct f2fs_sb_info *, int);
>  void build_gc_manager(struct f2fs_sb_info *);
>  int __init create_gc_caches(void);
>  void destroy_gc_caches(void);
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index eec0933..e1fa53a 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -80,7 +80,7 @@ static int gc_thread_func(void *data)
>  		stat_inc_bggc_count(sbi);
>  
>  		/* if return value is not zero, no victim was selected */
> -		if (f2fs_gc(sbi))
> +		if (f2fs_gc(sbi, BG_GC))
>  			wait_ms = gc_th->no_gc_sleep_time;
>  
>  		/* balancing f2fs's metadata periodically */
> @@ -691,10 +691,9 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
>  	f2fs_put_page(sum_page, 1);
>  }
>  
> -int f2fs_gc(struct f2fs_sb_info *sbi)
> +int f2fs_gc(struct f2fs_sb_info *sbi, int gc_type)
>  {
>  	unsigned int segno, i;
> -	int gc_type = BG_GC;
>  	int nfree = 0;
>  	int ret = -1;
>  	struct cp_control cpc;
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index fd9bc96..3b32404 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -281,7 +281,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi)
>  	 */
>  	if (has_not_enough_free_secs(sbi, 0)) {
>  		mutex_lock(&sbi->gc_mutex);
> -		f2fs_gc(sbi);
> +		f2fs_gc(sbi, FG_GC);
>  	}
>  }
>  
> @@ -994,12 +994,12 @@ static int get_ssr_segment(struct f2fs_sb_info *sbi, int type)
>  
>  	if (IS_NODESEG(type) || !has_not_enough_free_secs(sbi, 0))
>  		return v_ops->get_victim(sbi,
> -				&(curseg)->next_segno, BG_GC, type, SSR);
> +				&(curseg)->next_segno, FG_GC, type, SSR);
>  
>  	/* For data segments, let's do SSR more intensively */
>  	for (; type >= CURSEG_HOT_DATA; type--)
>  		if (v_ops->get_victim(sbi, &(curseg)->next_segno,
> -						BG_GC, type, SSR))
> +						FG_GC, type, SSR))
>  			return 1;
>  	return 0;
>  }
> -- 
> 1.9.1
> 
> 
> ------------------------------------------------------------------------------
> Dive into the World of Parallel Programming! The Go Parallel Website,
> sponsored by Intel and developed in partnership with Slashdot Media, is your
> hub for all things parallel software development, from weekly thought
> leadership blogs to news, videos, case studies, tutorials and more. Take a
> look and join the conversation now. http://goparallel.sourceforge.net
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

Re: [f2fs-dev] [PATCH 1/2] f2fs: conduct f2fs_gc as explicit gc_type

[Changman Lee]

Hi,

On Tue, Dec 23, 2014 at 12:00:37AM -0800, Jaegeuk Kim wrote:
> Hi Changman,
> 
> On Tue, Dec 23, 2014 at 08:37:38AM +0900, Changman Lee wrote:
> > f2fs has 2 gc_type; foreground gc and background gc.
> > In the case of foreground gc, f2fs will select victim as greedy.
> > Otherwise, as cost-benefit. And also it runs as greedy in SSR mode.
> > Until now, f2fs_gc conducted with BG_GC as default. So we couldn't
> > expect how it runs; BG_GC or FG_GC and GREEDY or COST_BENEFIT.
> 
> What does this mean?
> In f2fs_gc, the gc_type will be changed accoring to the number of free
> sections.

Right, but when I turn on trace I saw 3 cases.
1. BG_GC and COST_BENEFIT
2. BG_GC and GREEDY
3. FG_GC and GREEDY

I expected that case 1 is likely to operate only by gc_thread.
But it was not.

> 
> > Therefore sometimes it runs as BG_GC/COST_BENEFIT although gc_thread
> > don't put f2fs_gc to work.
> 
> You mean f2fs_balance_fs?
> In this case, again, the gc_type will be assigned FG_GC.
> 
> Why do you want to set FG_GC/GREEDY for the SSR victims?

We should alloate a block as soon as possible.
In the case of FG_GC, it also uses invalid blocks dirtied by background gc.
In another case, if (BG_GC && test_bit(victim_secmap)), it will be
skipped.
I intended that SSR operates fastly like FG_GC.

Regards,
Changman

> 
> Thanks,
> 
> > 
> > Signed-off-by: Changman Lee <cm224.lee@samsung.com>
> > ---
> >  fs/f2fs/f2fs.h    | 2 +-
> >  fs/f2fs/gc.c      | 5 ++---
> >  fs/f2fs/segment.c | 6 +++---
> >  3 files changed, 6 insertions(+), 7 deletions(-)
> > 
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index ae6dfb6..c956535 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1476,7 +1476,7 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *, u64, u64);
> >  int start_gc_thread(struct f2fs_sb_info *);
> >  void stop_gc_thread(struct f2fs_sb_info *);
> >  block_t start_bidx_of_node(unsigned int, struct f2fs_inode_info *);
> > -int f2fs_gc(struct f2fs_sb_info *);
> > +int f2fs_gc(struct f2fs_sb_info *, int);
> >  void build_gc_manager(struct f2fs_sb_info *);
> >  int __init create_gc_caches(void);
> >  void destroy_gc_caches(void);
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index eec0933..e1fa53a 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -80,7 +80,7 @@ static int gc_thread_func(void *data)
> >  		stat_inc_bggc_count(sbi);
> >  
> >  		/* if return value is not zero, no victim was selected */
> > -		if (f2fs_gc(sbi))
> > +		if (f2fs_gc(sbi, BG_GC))
> >  			wait_ms = gc_th->no_gc_sleep_time;
> >  
> >  		/* balancing f2fs's metadata periodically */
> > @@ -691,10 +691,9 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
> >  	f2fs_put_page(sum_page, 1);
> >  }
> >  
> > -int f2fs_gc(struct f2fs_sb_info *sbi)
> > +int f2fs_gc(struct f2fs_sb_info *sbi, int gc_type)
> >  {
> >  	unsigned int segno, i;
> > -	int gc_type = BG_GC;
> >  	int nfree = 0;
> >  	int ret = -1;
> >  	struct cp_control cpc;
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index fd9bc96..3b32404 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -281,7 +281,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi)
> >  	 */
> >  	if (has_not_enough_free_secs(sbi, 0)) {
> >  		mutex_lock(&sbi->gc_mutex);
> > -		f2fs_gc(sbi);
> > +		f2fs_gc(sbi, FG_GC);
> >  	}
> >  }
> >  
> > @@ -994,12 +994,12 @@ static int get_ssr_segment(struct f2fs_sb_info *sbi, int type)
> >  
> >  	if (IS_NODESEG(type) || !has_not_enough_free_secs(sbi, 0))
> >  		return v_ops->get_victim(sbi,
> > -				&(curseg)->next_segno, BG_GC, type, SSR);
> > +				&(curseg)->next_segno, FG_GC, type, SSR);
> >  
> >  	/* For data segments, let's do SSR more intensively */
> >  	for (; type >= CURSEG_HOT_DATA; type--)
> >  		if (v_ops->get_victim(sbi, &(curseg)->next_segno,
> > -						BG_GC, type, SSR))
> > +						FG_GC, type, SSR))
> >  			return 1;
> >  	return 0;
> >  }
> > -- 
> > 1.9.1
> > 
> > 
> > ------------------------------------------------------------------------------
> > Dive into the World of Parallel Programming! The Go Parallel Website,
> > sponsored by Intel and developed in partnership with Slashdot Media, is your
> > hub for all things parallel software development, from weekly thought
> > leadership blogs to news, videos, case studies, tutorials and more. Take a
> > look and join the conversation now. http://goparallel.sourceforge.net
> > _______________________________________________
> > Linux-f2fs-devel mailing list
> > Linux-f2fs-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

Re: [f2fs-dev] [PATCH 1/2] f2fs: conduct f2fs_gc as explicit gc_type

[Jaegeuk Kim]

Hi,

On Tue, Dec 23, 2014 at 06:04:54PM +0900, Changman Lee wrote:
> Hi,
> 
> On Tue, Dec 23, 2014 at 12:00:37AM -0800, Jaegeuk Kim wrote:
> > Hi Changman,
> > 
> > On Tue, Dec 23, 2014 at 08:37:38AM +0900, Changman Lee wrote:
> > > f2fs has 2 gc_type; foreground gc and background gc.
> > > In the case of foreground gc, f2fs will select victim as greedy.
> > > Otherwise, as cost-benefit. And also it runs as greedy in SSR mode.
> > > Until now, f2fs_gc conducted with BG_GC as default. So we couldn't
> > > expect how it runs; BG_GC or FG_GC and GREEDY or COST_BENEFIT.
> > 
> > What does this mean?
> > In f2fs_gc, the gc_type will be changed accoring to the number of free
> > sections.
> 
> Right, but when I turn on trace I saw 3 cases.
> 1. BG_GC and COST_BENEFIT
> 2. BG_GC and GREEDY
> 3. FG_GC and GREEDY
> 
> I expected that case 1 is likely to operate only by gc_thread.
> But it was not.

One of FG_GC and BG_GC is selected according to the # of free segments.
One of CB and GREEDY is determined by select_policy().
There are orthogonal.

Please, do not expect #1 only by gc_thread.
We don't need to force it by callers, since the policy should be selected
by f2fs_gc to avoid frequent FG_GC unnecessarily.

> 
> > 
> > > Therefore sometimes it runs as BG_GC/COST_BENEFIT although gc_thread
> > > don't put f2fs_gc to work.
> > 
> > You mean f2fs_balance_fs?
> > In this case, again, the gc_type will be assigned FG_GC.
> > 
> > Why do you want to set FG_GC/GREEDY for the SSR victims?
> 
> We should alloate a block as soon as possible.
> In the case of FG_GC, it also uses invalid blocks dirtied by background gc.

Yes, because FG_GC needs to move victim blocks.

> In another case, if (BG_GC && test_bit(victim_secmap)), it will be
> skipped.
> I intended that SSR operates fastly like FG_GC.

If FG_GC is used by SSR, we lose the effect on pre-loaded victim blocks done by
BG_GC before.

This must be a good trial to enhance SSR latencies.
Just in case, can you show how much this is serious?
If so, we need to think about different ways.

Thanks,

> 
> Regards,
> Changman
> 
> > 
> > Thanks,
> > 
> > > 
> > > Signed-off-by: Changman Lee <cm224.lee@samsung.com>
> > > ---
> > >  fs/f2fs/f2fs.h    | 2 +-
> > >  fs/f2fs/gc.c      | 5 ++---
> > >  fs/f2fs/segment.c | 6 +++---
> > >  3 files changed, 6 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > > index ae6dfb6..c956535 100644
> > > --- a/fs/f2fs/f2fs.h
> > > +++ b/fs/f2fs/f2fs.h
> > > @@ -1476,7 +1476,7 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *, u64, u64);
> > >  int start_gc_thread(struct f2fs_sb_info *);
> > >  void stop_gc_thread(struct f2fs_sb_info *);
> > >  block_t start_bidx_of_node(unsigned int, struct f2fs_inode_info *);
> > > -int f2fs_gc(struct f2fs_sb_info *);
> > > +int f2fs_gc(struct f2fs_sb_info *, int);
> > >  void build_gc_manager(struct f2fs_sb_info *);
> > >  int __init create_gc_caches(void);
> > >  void destroy_gc_caches(void);
> > > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > > index eec0933..e1fa53a 100644
> > > --- a/fs/f2fs/gc.c
> > > +++ b/fs/f2fs/gc.c
> > > @@ -80,7 +80,7 @@ static int gc_thread_func(void *data)
> > >  		stat_inc_bggc_count(sbi);
> > >  
> > >  		/* if return value is not zero, no victim was selected */
> > > -		if (f2fs_gc(sbi))
> > > +		if (f2fs_gc(sbi, BG_GC))
> > >  			wait_ms = gc_th->no_gc_sleep_time;
> > >  
> > >  		/* balancing f2fs's metadata periodically */
> > > @@ -691,10 +691,9 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
> > >  	f2fs_put_page(sum_page, 1);
> > >  }
> > >  
> > > -int f2fs_gc(struct f2fs_sb_info *sbi)
> > > +int f2fs_gc(struct f2fs_sb_info *sbi, int gc_type)
> > >  {
> > >  	unsigned int segno, i;
> > > -	int gc_type = BG_GC;
> > >  	int nfree = 0;
> > >  	int ret = -1;
> > >  	struct cp_control cpc;
> > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > > index fd9bc96..3b32404 100644
> > > --- a/fs/f2fs/segment.c
> > > +++ b/fs/f2fs/segment.c
> > > @@ -281,7 +281,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi)
> > >  	 */
> > >  	if (has_not_enough_free_secs(sbi, 0)) {
> > >  		mutex_lock(&sbi->gc_mutex);
> > > -		f2fs_gc(sbi);
> > > +		f2fs_gc(sbi, FG_GC);
> > >  	}
> > >  }
> > >  
> > > @@ -994,12 +994,12 @@ static int get_ssr_segment(struct f2fs_sb_info *sbi, int type)
> > >  
> > >  	if (IS_NODESEG(type) || !has_not_enough_free_secs(sbi, 0))
> > >  		return v_ops->get_victim(sbi,
> > > -				&(curseg)->next_segno, BG_GC, type, SSR);
> > > +				&(curseg)->next_segno, FG_GC, type, SSR);
> > >  
> > >  	/* For data segments, let's do SSR more intensively */
> > >  	for (; type >= CURSEG_HOT_DATA; type--)
> > >  		if (v_ops->get_victim(sbi, &(curseg)->next_segno,
> > > -						BG_GC, type, SSR))
> > > +						FG_GC, type, SSR))
> > >  			return 1;
> > >  	return 0;
> > >  }
> > > -- 
> > > 1.9.1
> > > 
> > > 
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