[PATCH] f2fs: use bio count instead of F2FS_WRITEBACK page count

[PATCH] f2fs: use bio count instead of F2FS_WRITEBACK page count

[Jaegeuk Kim]

This can reduce page counting overhead.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/checkpoint.c |  2 +-
 fs/f2fs/data.c       | 26 +++++++++++++++-----------
 fs/f2fs/debug.c      |  6 +++---
 fs/f2fs/f2fs.h       |  4 ++--
 fs/f2fs/super.c      |  2 +-
 5 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index d04113b..447e2a9 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -914,7 +914,7 @@ static void wait_on_all_pages_writeback(struct f2fs_sb_info *sbi)
 	for (;;) {
 		prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
 
-		if (!get_pages(sbi, F2FS_WRITEBACK))
+		if (!atomic_read(&sbi->nr_wb_bios))
 			break;
 
 		io_schedule_timeout(5*HZ);
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 1013836..faef666 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -71,10 +71,9 @@ static void f2fs_write_end_io(struct bio *bio)
 			f2fs_stop_checkpoint(sbi);
 		}
 		end_page_writeback(page);
-		dec_page_count(sbi, F2FS_WRITEBACK);
 	}
-
-	if (!get_pages(sbi, F2FS_WRITEBACK) && wq_has_sleeper(&sbi->cp_wait))
+	if (atomic_dec_and_test(&sbi->nr_wb_bios) &&
+				wq_has_sleeper(&sbi->cp_wait))
 		wake_up(&sbi->cp_wait);
 
 	bio_put(bio);
@@ -98,6 +97,14 @@ static struct bio *__bio_alloc(struct f2fs_sb_info *sbi, block_t blk_addr,
 	return bio;
 }
 
+static inline void __submit_bio(struct f2fs_sb_info *sbi, int rw,
+						struct bio *bio)
+{
+	if (!is_read_io(rw))
+		atomic_inc(&sbi->nr_wb_bios);
+	submit_bio(rw, bio);
+}
+
 static void __submit_merged_bio(struct f2fs_bio_info *io)
 {
 	struct f2fs_io_info *fio = &io->fio;
@@ -110,7 +117,7 @@ static void __submit_merged_bio(struct f2fs_bio_info *io)
 	else
 		trace_f2fs_submit_write_bio(io->sbi->sb, fio, io->bio);
 
-	submit_bio(fio->rw, io->bio);
+	__submit_bio(io->sbi, fio->rw, io->bio);
 	io->bio = NULL;
 }
 
@@ -228,7 +235,7 @@ int f2fs_submit_page_bio(struct f2fs_io_info *fio)
 		return -EFAULT;
 	}
 
-	submit_bio(fio->rw, bio);
+	__submit_bio(fio->sbi, fio->rw, bio);
 	return 0;
 }
 
@@ -248,9 +255,6 @@ void f2fs_submit_page_mbio(struct f2fs_io_info *fio)
 
 	down_write(&io->io_rwsem);
 
-	if (!is_read)
-		inc_page_count(sbi, F2FS_WRITEBACK);
-
 	if (io->bio && (io->last_block_in_bio != fio->new_blkaddr - 1 ||
 						io->fio.rw != fio->rw))
 		__submit_merged_bio(io);
@@ -1047,7 +1051,7 @@ got_it:
 		 */
 		if (bio && (last_block_in_bio != block_nr - 1)) {
 submit_and_realloc:
-			submit_bio(READ, bio);
+			__submit_bio(F2FS_I_SB(inode), READ, bio);
 			bio = NULL;
 		}
 		if (bio == NULL) {
@@ -1090,7 +1094,7 @@ set_error_page:
 		goto next_page;
 confused:
 		if (bio) {
-			submit_bio(READ, bio);
+			__submit_bio(F2FS_I_SB(inode), READ, bio);
 			bio = NULL;
 		}
 		unlock_page(page);
@@ -1100,7 +1104,7 @@ next_page:
 	}
 	BUG_ON(pages && !list_empty(pages));
 	if (bio)
-		submit_bio(READ, bio);
+		__submit_bio(F2FS_I_SB(inode), READ, bio);
 	return 0;
 }
 
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index 37615b2..a188973 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -48,7 +48,7 @@ static void update_general_status(struct f2fs_sb_info *sbi)
 	si->ndirty_dirs = sbi->ndirty_inode[DIR_INODE];
 	si->ndirty_files = sbi->ndirty_inode[FILE_INODE];
 	si->inmem_pages = get_pages(sbi, F2FS_INMEM_PAGES);
-	si->wb_pages = get_pages(sbi, F2FS_WRITEBACK);
+	si->wb_bios = atomic_read(&sbi->nr_wb_bios);
 	si->total_count = (int)sbi->user_block_count / sbi->blocks_per_seg;
 	si->rsvd_segs = reserved_segments(sbi);
 	si->overp_segs = overprovision_segments(sbi);
@@ -299,8 +299,8 @@ static int stat_show(struct seq_file *s, void *v)
 		seq_printf(s, "  - Inner Struct Count: tree: %d(%d), node: %d\n",
 				si->ext_tree, si->zombie_tree, si->ext_node);
 		seq_puts(s, "\nBalancing F2FS Async:\n");
-		seq_printf(s, "  - inmem: %4d, wb: %4d\n",
-			   si->inmem_pages, si->wb_pages);
+		seq_printf(s, "  - inmem: %4d, wb_bios: %4d\n",
+			   si->inmem_pages, si->wb_bios);
 		seq_printf(s, "  - nodes: %4d in %4d\n",
 			   si->ndirty_node, si->node_pages);
 		seq_printf(s, "  - dents: %4d in dirs:%4d\n",
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 1351178..bc45a2c 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -650,7 +650,6 @@ struct f2fs_sm_info {
  * dirty dentry blocks, dirty node blocks, and dirty meta blocks.
  */
 enum count_type {
-	F2FS_WRITEBACK,
 	F2FS_DIRTY_DENTS,
 	F2FS_DIRTY_DATA,
 	F2FS_DIRTY_NODES,
@@ -813,6 +812,7 @@ struct f2fs_sb_info {
 	block_t discard_blks;			/* discard command candidats */
 	block_t last_valid_block_count;		/* for recovery */
 	u32 s_next_generation;			/* for NFS support */
+	atomic_t nr_wb_bios;			/* # of writeback bios */
 	atomic_t nr_pages[NR_COUNT_TYPE];	/* # of pages, see count_type */
 
 	struct f2fs_mount_info mount_opt;	/* mount options */
@@ -2017,7 +2017,7 @@ struct f2fs_stat_info {
 	int ndirty_dent, ndirty_dirs, ndirty_data, ndirty_files;
 	int nats, dirty_nats, sits, dirty_sits, fnids;
 	int total_count, utilization;
-	int bg_gc, inmem_pages, wb_pages;
+	int bg_gc, inmem_pages, wb_bios;
 	int inline_xattr, inline_inode, inline_dir, orphans;
 	unsigned int valid_count, valid_node_count, valid_inode_count;
 	unsigned int bimodal, avg_vblocks;
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 9df6d72..c21e662 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -649,7 +649,7 @@ static void f2fs_put_super(struct super_block *sb)
 	mutex_unlock(&sbi->umount_mutex);
 
 	/* our cp_error case, we can wait for any writeback page */
-	if (get_pages(sbi, F2FS_WRITEBACK))
+	if (atomic_read(&sbi->nr_wb_bios))
 		f2fs_flush_merged_bios(sbi);
 
 	iput(sbi->node_inode);
-- 
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Re: [f2fs-dev] [PATCH] f2fs: use bio count instead of F2FS_WRITEBACK page count

[Chao Yu]

Hi Jaegeuk,

On 2016/5/18 8:44, Jaegeuk Kim wrote:
> This can reduce page counting overhead.

We change to increase one reference for one bio, but block layer can split or
merge bios by itself, and write_end will be called per bio, so the reference may
be maintained incorrectly?

Thanks,

> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/checkpoint.c |  2 +-
>  fs/f2fs/data.c       | 26 +++++++++++++++-----------
>  fs/f2fs/debug.c      |  6 +++---
>  fs/f2fs/f2fs.h       |  4 ++--
>  fs/f2fs/super.c      |  2 +-
>  5 files changed, 22 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index d04113b..447e2a9 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -914,7 +914,7 @@ static void wait_on_all_pages_writeback(struct f2fs_sb_info *sbi)
>  	for (;;) {
>  		prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
>  
> -		if (!get_pages(sbi, F2FS_WRITEBACK))
> +		if (!atomic_read(&sbi->nr_wb_bios))
>  			break;
>  
>  		io_schedule_timeout(5*HZ);
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 1013836..faef666 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -71,10 +71,9 @@ static void f2fs_write_end_io(struct bio *bio)
>  			f2fs_stop_checkpoint(sbi);
>  		}
>  		end_page_writeback(page);
> -		dec_page_count(sbi, F2FS_WRITEBACK);
>  	}
> -
> -	if (!get_pages(sbi, F2FS_WRITEBACK) && wq_has_sleeper(&sbi->cp_wait))
> +	if (atomic_dec_and_test(&sbi->nr_wb_bios) &&
> +				wq_has_sleeper(&sbi->cp_wait))
>  		wake_up(&sbi->cp_wait);
>  
>  	bio_put(bio);
> @@ -98,6 +97,14 @@ static struct bio *__bio_alloc(struct f2fs_sb_info *sbi, block_t blk_addr,
>  	return bio;
>  }
>  
> +static inline void __submit_bio(struct f2fs_sb_info *sbi, int rw,
> +						struct bio *bio)
> +{
> +	if (!is_read_io(rw))
> +		atomic_inc(&sbi->nr_wb_bios);
> +	submit_bio(rw, bio);
> +}
> +
>  static void __submit_merged_bio(struct f2fs_bio_info *io)
>  {
>  	struct f2fs_io_info *fio = &io->fio;
> @@ -110,7 +117,7 @@ static void __submit_merged_bio(struct f2fs_bio_info *io)
>  	else
>  		trace_f2fs_submit_write_bio(io->sbi->sb, fio, io->bio);
>  
> -	submit_bio(fio->rw, io->bio);
> +	__submit_bio(io->sbi, fio->rw, io->bio);
>  	io->bio = NULL;
>  }
>  
> @@ -228,7 +235,7 @@ int f2fs_submit_page_bio(struct f2fs_io_info *fio)
>  		return -EFAULT;
>  	}
>  
> -	submit_bio(fio->rw, bio);
> +	__submit_bio(fio->sbi, fio->rw, bio);
>  	return 0;
>  }
>  
> @@ -248,9 +255,6 @@ void f2fs_submit_page_mbio(struct f2fs_io_info *fio)
>  
>  	down_write(&io->io_rwsem);
>  
> -	if (!is_read)
> -		inc_page_count(sbi, F2FS_WRITEBACK);
> -
>  	if (io->bio && (io->last_block_in_bio != fio->new_blkaddr - 1 ||
>  						io->fio.rw != fio->rw))
>  		__submit_merged_bio(io);
> @@ -1047,7 +1051,7 @@ got_it:
>  		 */
>  		if (bio && (last_block_in_bio != block_nr - 1)) {
>  submit_and_realloc:
> -			submit_bio(READ, bio);
> +			__submit_bio(F2FS_I_SB(inode), READ, bio);
>  			bio = NULL;
>  		}
>  		if (bio == NULL) {
> @@ -1090,7 +1094,7 @@ set_error_page:
>  		goto next_page;
>  confused:
>  		if (bio) {
> -			submit_bio(READ, bio);
> +			__submit_bio(F2FS_I_SB(inode), READ, bio);
>  			bio = NULL;
>  		}
>  		unlock_page(page);
> @@ -1100,7 +1104,7 @@ next_page:
>  	}
>  	BUG_ON(pages && !list_empty(pages));
>  	if (bio)
> -		submit_bio(READ, bio);
> +		__submit_bio(F2FS_I_SB(inode), READ, bio);
>  	return 0;
>  }
>  
> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
> index 37615b2..a188973 100644
> --- a/fs/f2fs/debug.c
> +++ b/fs/f2fs/debug.c
> @@ -48,7 +48,7 @@ static void update_general_status(struct f2fs_sb_info *sbi)
>  	si->ndirty_dirs = sbi->ndirty_inode[DIR_INODE];
>  	si->ndirty_files = sbi->ndirty_inode[FILE_INODE];
>  	si->inmem_pages = get_pages(sbi, F2FS_INMEM_PAGES);
> -	si->wb_pages = get_pages(sbi, F2FS_WRITEBACK);
> +	si->wb_bios = atomic_read(&sbi->nr_wb_bios);
>  	si->total_count = (int)sbi->user_block_count / sbi->blocks_per_seg;
>  	si->rsvd_segs = reserved_segments(sbi);
>  	si->overp_segs = overprovision_segments(sbi);
> @@ -299,8 +299,8 @@ static int stat_show(struct seq_file *s, void *v)
>  		seq_printf(s, "  - Inner Struct Count: tree: %d(%d), node: %d\n",
>  				si->ext_tree, si->zombie_tree, si->ext_node);
>  		seq_puts(s, "\nBalancing F2FS Async:\n");
> -		seq_printf(s, "  - inmem: %4d, wb: %4d\n",
> -			   si->inmem_pages, si->wb_pages);
> +		seq_printf(s, "  - inmem: %4d, wb_bios: %4d\n",
> +			   si->inmem_pages, si->wb_bios);
>  		seq_printf(s, "  - nodes: %4d in %4d\n",
>  			   si->ndirty_node, si->node_pages);
>  		seq_printf(s, "  - dents: %4d in dirs:%4d\n",
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 1351178..bc45a2c 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -650,7 +650,6 @@ struct f2fs_sm_info {
>   * dirty dentry blocks, dirty node blocks, and dirty meta blocks.
>   */
>  enum count_type {
> -	F2FS_WRITEBACK,
>  	F2FS_DIRTY_DENTS,
>  	F2FS_DIRTY_DATA,
>  	F2FS_DIRTY_NODES,
> @@ -813,6 +812,7 @@ struct f2fs_sb_info {
>  	block_t discard_blks;			/* discard command candidats */
>  	block_t last_valid_block_count;		/* for recovery */
>  	u32 s_next_generation;			/* for NFS support */
> +	atomic_t nr_wb_bios;			/* # of writeback bios */
>  	atomic_t nr_pages[NR_COUNT_TYPE];	/* # of pages, see count_type */
>  
>  	struct f2fs_mount_info mount_opt;	/* mount options */
> @@ -2017,7 +2017,7 @@ struct f2fs_stat_info {
>  	int ndirty_dent, ndirty_dirs, ndirty_data, ndirty_files;
>  	int nats, dirty_nats, sits, dirty_sits, fnids;
>  	int total_count, utilization;
> -	int bg_gc, inmem_pages, wb_pages;
> +	int bg_gc, inmem_pages, wb_bios;
>  	int inline_xattr, inline_inode, inline_dir, orphans;
>  	unsigned int valid_count, valid_node_count, valid_inode_count;
>  	unsigned int bimodal, avg_vblocks;
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 9df6d72..c21e662 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -649,7 +649,7 @@ static void f2fs_put_super(struct super_block *sb)
>  	mutex_unlock(&sbi->umount_mutex);
>  
>  	/* our cp_error case, we can wait for any writeback page */
> -	if (get_pages(sbi, F2FS_WRITEBACK))
> +	if (atomic_read(&sbi->nr_wb_bios))
>  		f2fs_flush_merged_bios(sbi);
>  
>  	iput(sbi->node_inode);
> 

Re: [PATCH] f2fs: use bio count instead of F2FS_WRITEBACK page count

[Jaegeuk Kim]

On Wed, May 18, 2016 at 09:17:00AM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2016/5/18 8:44, Jaegeuk Kim wrote:
> > This can reduce page counting overhead.
> 
> We change to increase one reference for one bio, but block layer can split or
> merge bios by itself, and write_end will be called per bio, so the reference may
> be maintained incorrectly?

Well, block layer will merge bios in a same request, and then finally call
end_io for each original bios, no?
So far I've seen no error in any test cases.
Am I missing something?

Thanks,

> 
> Thanks,
> 
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/checkpoint.c |  2 +-
> >  fs/f2fs/data.c       | 26 +++++++++++++++-----------
> >  fs/f2fs/debug.c      |  6 +++---
> >  fs/f2fs/f2fs.h       |  4 ++--
> >  fs/f2fs/super.c      |  2 +-
> >  5 files changed, 22 insertions(+), 18 deletions(-)
> > 
> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > index d04113b..447e2a9 100644
> > --- a/fs/f2fs/checkpoint.c
> > +++ b/fs/f2fs/checkpoint.c
> > @@ -914,7 +914,7 @@ static void wait_on_all_pages_writeback(struct f2fs_sb_info *sbi)
> >  	for (;;) {
> >  		prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
> >  
> > -		if (!get_pages(sbi, F2FS_WRITEBACK))
> > +		if (!atomic_read(&sbi->nr_wb_bios))
> >  			break;
> >  
> >  		io_schedule_timeout(5*HZ);
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 1013836..faef666 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -71,10 +71,9 @@ static void f2fs_write_end_io(struct bio *bio)
> >  			f2fs_stop_checkpoint(sbi);
> >  		}
> >  		end_page_writeback(page);
> > -		dec_page_count(sbi, F2FS_WRITEBACK);
> >  	}
> > -
> > -	if (!get_pages(sbi, F2FS_WRITEBACK) && wq_has_sleeper(&sbi->cp_wait))
> > +	if (atomic_dec_and_test(&sbi->nr_wb_bios) &&
> > +				wq_has_sleeper(&sbi->cp_wait))
> >  		wake_up(&sbi->cp_wait);
> >  
> >  	bio_put(bio);
> > @@ -98,6 +97,14 @@ static struct bio *__bio_alloc(struct f2fs_sb_info *sbi, block_t blk_addr,
> >  	return bio;
> >  }
> >  
> > +static inline void __submit_bio(struct f2fs_sb_info *sbi, int rw,
> > +						struct bio *bio)
> > +{
> > +	if (!is_read_io(rw))
> > +		atomic_inc(&sbi->nr_wb_bios);
> > +	submit_bio(rw, bio);
> > +}
> > +
> >  static void __submit_merged_bio(struct f2fs_bio_info *io)
> >  {
> >  	struct f2fs_io_info *fio = &io->fio;
> > @@ -110,7 +117,7 @@ static void __submit_merged_bio(struct f2fs_bio_info *io)
> >  	else
> >  		trace_f2fs_submit_write_bio(io->sbi->sb, fio, io->bio);
> >  
> > -	submit_bio(fio->rw, io->bio);
> > +	__submit_bio(io->sbi, fio->rw, io->bio);
> >  	io->bio = NULL;
> >  }
> >  
> > @@ -228,7 +235,7 @@ int f2fs_submit_page_bio(struct f2fs_io_info *fio)
> >  		return -EFAULT;
> >  	}
> >  
> > -	submit_bio(fio->rw, bio);
> > +	__submit_bio(fio->sbi, fio->rw, bio);
> >  	return 0;
> >  }
> >  
> > @@ -248,9 +255,6 @@ void f2fs_submit_page_mbio(struct f2fs_io_info *fio)
> >  
> >  	down_write(&io->io_rwsem);
> >  
> > -	if (!is_read)
> > -		inc_page_count(sbi, F2FS_WRITEBACK);
> > -
> >  	if (io->bio && (io->last_block_in_bio != fio->new_blkaddr - 1 ||
> >  						io->fio.rw != fio->rw))
> >  		__submit_merged_bio(io);
> > @@ -1047,7 +1051,7 @@ got_it:
> >  		 */
> >  		if (bio && (last_block_in_bio != block_nr - 1)) {
> >  submit_and_realloc:
> > -			submit_bio(READ, bio);
> > +			__submit_bio(F2FS_I_SB(inode), READ, bio);
> >  			bio = NULL;
> >  		}
> >  		if (bio == NULL) {
> > @@ -1090,7 +1094,7 @@ set_error_page:
> >  		goto next_page;
> >  confused:
> >  		if (bio) {
> > -			submit_bio(READ, bio);
> > +			__submit_bio(F2FS_I_SB(inode), READ, bio);
> >  			bio = NULL;
> >  		}
> >  		unlock_page(page);
> > @@ -1100,7 +1104,7 @@ next_page:
> >  	}
> >  	BUG_ON(pages && !list_empty(pages));
> >  	if (bio)
> > -		submit_bio(READ, bio);
> > +		__submit_bio(F2FS_I_SB(inode), READ, bio);
> >  	return 0;
> >  }
> >  
> > diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
> > index 37615b2..a188973 100644
> > --- a/fs/f2fs/debug.c
> > +++ b/fs/f2fs/debug.c
> > @@ -48,7 +48,7 @@ static void update_general_status(struct f2fs_sb_info *sbi)
> >  	si->ndirty_dirs = sbi->ndirty_inode[DIR_INODE];
> >  	si->ndirty_files = sbi->ndirty_inode[FILE_INODE];
> >  	si->inmem_pages = get_pages(sbi, F2FS_INMEM_PAGES);
> > -	si->wb_pages = get_pages(sbi, F2FS_WRITEBACK);
> > +	si->wb_bios = atomic_read(&sbi->nr_wb_bios);
> >  	si->total_count = (int)sbi->user_block_count / sbi->blocks_per_seg;
> >  	si->rsvd_segs = reserved_segments(sbi);
> >  	si->overp_segs = overprovision_segments(sbi);
> > @@ -299,8 +299,8 @@ static int stat_show(struct seq_file *s, void *v)
> >  		seq_printf(s, "  - Inner Struct Count: tree: %d(%d), node: %d\n",
> >  				si->ext_tree, si->zombie_tree, si->ext_node);
> >  		seq_puts(s, "\nBalancing F2FS Async:\n");
> > -		seq_printf(s, "  - inmem: %4d, wb: %4d\n",
> > -			   si->inmem_pages, si->wb_pages);
> > +		seq_printf(s, "  - inmem: %4d, wb_bios: %4d\n",
> > +			   si->inmem_pages, si->wb_bios);
> >  		seq_printf(s, "  - nodes: %4d in %4d\n",
> >  			   si->ndirty_node, si->node_pages);
> >  		seq_printf(s, "  - dents: %4d in dirs:%4d\n",
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 1351178..bc45a2c 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -650,7 +650,6 @@ struct f2fs_sm_info {
> >   * dirty dentry blocks, dirty node blocks, and dirty meta blocks.
> >   */
> >  enum count_type {
> > -	F2FS_WRITEBACK,
> >  	F2FS_DIRTY_DENTS,
> >  	F2FS_DIRTY_DATA,
> >  	F2FS_DIRTY_NODES,
> > @@ -813,6 +812,7 @@ struct f2fs_sb_info {
> >  	block_t discard_blks;			/* discard command candidats */
> >  	block_t last_valid_block_count;		/* for recovery */
> >  	u32 s_next_generation;			/* for NFS support */
> > +	atomic_t nr_wb_bios;			/* # of writeback bios */
> >  	atomic_t nr_pages[NR_COUNT_TYPE];	/* # of pages, see count_type */
> >  
> >  	struct f2fs_mount_info mount_opt;	/* mount options */
> > @@ -2017,7 +2017,7 @@ struct f2fs_stat_info {
> >  	int ndirty_dent, ndirty_dirs, ndirty_data, ndirty_files;
> >  	int nats, dirty_nats, sits, dirty_sits, fnids;
> >  	int total_count, utilization;
> > -	int bg_gc, inmem_pages, wb_pages;
> > +	int bg_gc, inmem_pages, wb_bios;
> >  	int inline_xattr, inline_inode, inline_dir, orphans;
> >  	unsigned int valid_count, valid_node_count, valid_inode_count;
> >  	unsigned int bimodal, avg_vblocks;
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 9df6d72..c21e662 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -649,7 +649,7 @@ static void f2fs_put_super(struct super_block *sb)
> >  	mutex_unlock(&sbi->umount_mutex);
> >  
> >  	/* our cp_error case, we can wait for any writeback page */
> > -	if (get_pages(sbi, F2FS_WRITEBACK))
> > +	if (atomic_read(&sbi->nr_wb_bios))
> >  		f2fs_flush_merged_bios(sbi);
> >  
> >  	iput(sbi->node_inode);
> > 

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Re: [PATCH] f2fs: use bio count instead of F2FS_WRITEBACK page count

[Chao Yu]

On 2016/5/18 9:31, Jaegeuk Kim wrote:
> On Wed, May 18, 2016 at 09:17:00AM +0800, Chao Yu wrote:
>> Hi Jaegeuk,
>>
>> On 2016/5/18 8:44, Jaegeuk Kim wrote:
>>> This can reduce page counting overhead.
>>
>> We change to increase one reference for one bio, but block layer can split or
>> merge bios by itself, and write_end will be called per bio, so the reference may
>> be maintained incorrectly?
> 
> Well, block layer will merge bios in a same request, and then finally call
> end_io for each original bios, no?

Sorry for the delay, I agree with you that end_io will be called for each bios
in the merging case, and for the spliting case, IIUC, splited bio will chain to
its parent bio, the real parent's end_io won't be called until both parent bio
and bio have completed, so I think it's safe here. :)

> So far I've seen no error in any test cases.

I haven't seen any hungtask so far too.

Thanks,

------------------------------------------------------------------------------
Mobile security can be enabling, not merely restricting. Employees who
bring their own devices (BYOD) to work are irked by the imposition of MDM
restrictions. Mobile Device Manager Plus allows you to control only the
apps on BYO-devices by containerizing them, leaving personal data untouched!
https://ad.doubleclick.net/ddm/clk/304595813;131938128;j