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[PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data

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  [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data Jaegeuk Kim <jaegeuk@kernel.org> - 2016-01-23 21:20 +0100
    RE: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due  to inline_data Chao Yu <chao2.yu@samsung.com> - 2016-01-25 10:50 +0100
      Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due  to inline_data Jaegeuk Kim <jaegeuk@kernel.org> - 2016-01-25 20:20 +0100
        RE: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due  to inline_data Chao Yu <chao2.yu@samsung.com> - 2016-01-26 08:10 +0100
          Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due  to inline_data Jaegeuk Kim <jaegeuk@kernel.org> - 2016-01-26 19:40 +0100

#1315747 — [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data

The sceanrio is:
1. create fully node blocks
2. flush node blocks
3. write inline_data for all the node blocks again
4. flush node blocks redundantly

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/data.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 8d0d9ec..011456e 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1622,14 +1622,22 @@ static int f2fs_write_end(struct file *file,
 
 	trace_f2fs_write_end(inode, pos, len, copied);
 
-	set_page_dirty(page);
-
 	if (pos + copied > i_size_read(inode)) {
 		i_size_write(inode, pos + copied);
 		mark_inode_dirty(inode);
-		update_inode_page(inode);
 	}
 
+	if (f2fs_has_inline_data(inode) &&
+			is_inode_flag_set(F2FS_I(inode), FI_DATA_EXIST)) {
+		int err = f2fs_write_inline_data(inode, page);
+		if (err)
+			set_page_dirty(page);
+	} else {
+		set_page_dirty(page);
+	}
+
+	f2fs_write_inode(inode, NULL);
+
 	f2fs_put_page(page, 1);
 	f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
 	return copied;
-- 
2.6.3

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#1316342 — RE: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data

Hi Jaegeuk,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> Sent: Sunday, January 24, 2016 4:16 AM
> To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> linux-f2fs-devel@lists.sourceforge.net
> Cc: Jaegeuk Kim
> Subject: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data
> 
> The sceanrio is:
> 1. create fully node blocks
> 2. flush node blocks
> 3. write inline_data for all the node blocks again
> 4. flush node blocks redundantly
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/data.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 8d0d9ec..011456e 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1622,14 +1622,22 @@ static int f2fs_write_end(struct file *file,
> 
>  	trace_f2fs_write_end(inode, pos, len, copied);
> 
> -	set_page_dirty(page);
> -
>  	if (pos + copied > i_size_read(inode)) {
>  		i_size_write(inode, pos + copied);
>  		mark_inode_dirty(inode);
> -		update_inode_page(inode);
>  	}
> 
> +	if (f2fs_has_inline_data(inode) &&
> +			is_inode_flag_set(F2FS_I(inode), FI_DATA_EXIST)) {
> +		int err = f2fs_write_inline_data(inode, page);

Oh, I'm sure this can fix that issue, but IMO:
a) this implementation has side-effect, it triggers inline data copying
between data page and node page whenever user write inline datas, so if
user updates inline data frequently, write-through approach would cause
memory copy overhead.
b) inline storm should be a rare case, as we didn't get any report about
problem for long time until Dave's, and write_end is a hot path, I think
it's better to be cautious to change our inline data cache policy for
fixing a rare issue in hot path.

What about delaying the merge operation? like:
1) as I proposed before, merging inline page into inode page when
detecting free_sections <= (node_secs + 2 * dent_secs + inline_secs).
2) merge inline page into inode page before writeback inode page in
sync_node_pages.

Thanks,

> +		if (err)
> +			set_page_dirty(page);
> +	} else {
> +		set_page_dirty(page);
> +	}
> +
> +	f2fs_write_inode(inode, NULL);
> +
>  	f2fs_put_page(page, 1);
>  	f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
>  	return copied;
> --
> 2.6.3
> 
> 
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#1317222 — Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data

Hi Chao,

On Mon, Jan 25, 2016 at 05:42:40PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> > Sent: Sunday, January 24, 2016 4:16 AM
> > To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> > linux-f2fs-devel@lists.sourceforge.net
> > Cc: Jaegeuk Kim
> > Subject: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data
> > 
> > The sceanrio is:
> > 1. create fully node blocks
> > 2. flush node blocks
> > 3. write inline_data for all the node blocks again
> > 4. flush node blocks redundantly
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/data.c | 14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 8d0d9ec..011456e 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -1622,14 +1622,22 @@ static int f2fs_write_end(struct file *file,
> > 
> >  	trace_f2fs_write_end(inode, pos, len, copied);
> > 
> > -	set_page_dirty(page);
> > -
> >  	if (pos + copied > i_size_read(inode)) {
> >  		i_size_write(inode, pos + copied);
> >  		mark_inode_dirty(inode);
> > -		update_inode_page(inode);
> >  	}
> > 
> > +	if (f2fs_has_inline_data(inode) &&
> > +			is_inode_flag_set(F2FS_I(inode), FI_DATA_EXIST)) {
> > +		int err = f2fs_write_inline_data(inode, page);
> 
> Oh, I'm sure this can fix that issue, but IMO:
> a) this implementation has side-effect, it triggers inline data copying
> between data page and node page whenever user write inline datas, so if
> user updates inline data frequently, write-through approach would cause
> memory copy overhead.

Agreed.

> b) inline storm should be a rare case, as we didn't get any report about
> problem for long time until Dave's, and write_end is a hot path, I think
> it's better to be cautious to change our inline data cache policy for
> fixing a rare issue in hot path.
> 
> What about delaying the merge operation? like:
> 1) as I proposed before, merging inline page into inode page when
> detecting free_sections <= (node_secs + 2 * dent_secs + inline_secs).
> 2) merge inline page into inode page before writeback inode page in
> sync_node_pages.

Okay, I'm thinking more general way where we can get rid of every inlien_data
write when we flush node pages.

I've been testing this patch.

From ebddf607c64da691fef08cf68a8ecadafd5d896b Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Mon, 25 Jan 2016 05:57:05 -0800
Subject: [PATCH] f2fs: avoid multiple node page writes due to inline_data

The sceanrio is:
1. create fully node blocks
2. flush node blocks
3. write inline_data for all the node blocks again
4. flush node blocks redundantly

So, this patch tries to flush inline_data when flushing node blocks.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/data.c   |  1 +
 fs/f2fs/inline.c |  2 ++
 fs/f2fs/node.c   | 35 +++++++++++++++++++++++++++++++++++
 fs/f2fs/node.h   | 15 +++++++++++++++
 4 files changed, 53 insertions(+)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 6925c10..9043ecf 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1464,6 +1464,7 @@ restart:
 		if (pos + len <= MAX_INLINE_DATA) {
 			read_inline_data(page, ipage);
 			set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
+			set_inline_node(ipage);
 			sync_inode_page(&dn);
 		} else {
 			err = f2fs_convert_inline_page(&dn, page);
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index 8df13e5..fc4d298 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -159,6 +159,7 @@ no_update:
 
 	/* clear inline data and flag after data writeback */
 	truncate_inline_inode(dn->inode_page, 0);
+	clear_inline_node(dn->inode_page);
 clear_out:
 	stat_dec_inline_inode(dn->inode);
 	f2fs_clear_inline_inode(dn->inode);
@@ -233,6 +234,7 @@ int f2fs_write_inline_data(struct inode *inode, struct page *page)
 	set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
 
 	sync_inode_page(&dn);
+	clear_inline_node(dn.inode_page);
 	f2fs_put_dnode(&dn);
 	return 0;
 }
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 23b800d..1c5023e 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1154,6 +1154,33 @@ void sync_inode_page(struct dnode_of_data *dn)
 	dn->node_changed = ret ? true: false;
 }
 
+static void flush_inline_data(struct f2fs_sb_info *sbi, nid_t ino)
+{
+	struct inode *inode;
+	struct page *page;
+
+	inode = ilookup(sbi->sb, ino);
+	if (!inode)
+		return;
+
+	page = find_lock_page(inode->i_mapping, 0);
+	if (!page)
+		goto iput_out;
+
+	if (!PageDirty(page))
+		goto put_page_out;
+
+	if (!clear_page_dirty_for_io(page))
+		goto put_page_out;
+
+	if (!f2fs_write_inline_data(inode, page))
+		inode_dec_dirty_pages(inode);
+put_page_out:
+	f2fs_put_page(page, 1);
+iput_out:
+	iput(inode);
+}
+
 int sync_node_pages(struct f2fs_sb_info *sbi, nid_t ino,
 					struct writeback_control *wbc)
 {
@@ -1221,6 +1248,14 @@ continue_unlock:
 				goto continue_unlock;
 			}
 
+			/* flush inline_data */
+			if (!ino && is_inline_node(page)) {
+				clear_inline_node(page);
+				unlock_page(page);
+				flush_inline_data(sbi, ino_of_node(page));
+				continue;
+			}
+
 			if (!clear_page_dirty_for_io(page))
 				goto continue_unlock;
 
diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
index 23bd992..1f4f9d4 100644
--- a/fs/f2fs/node.h
+++ b/fs/f2fs/node.h
@@ -379,6 +379,21 @@ static inline int is_node(struct page *page, int type)
 #define is_fsync_dnode(page)	is_node(page, FSYNC_BIT_SHIFT)
 #define is_dent_dnode(page)	is_node(page, DENT_BIT_SHIFT)
 
+static inline int is_inline_node(struct page *page)
+{
+	return PageChecked(page);
+}
+
+static inline void set_inline_node(struct page *page)
+{
+	SetPageChecked(page);
+}
+
+static inline void clear_inline_node(struct page *page)
+{
+	ClearPageChecked(page);
+}
+
 static inline void set_cold_node(struct inode *inode, struct page *page)
 {
 	struct f2fs_node *rn = F2FS_NODE(page);
-- 
2.6.3

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#1317572 — RE: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data

Hi Jaegeuk,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> Sent: Tuesday, January 26, 2016 3:18 AM
> To: Chao Yu
> Cc: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> linux-f2fs-devel@lists.sourceforge.net
> Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data
> 
> Hi Chao,
> 
> On Mon, Jan 25, 2016 at 05:42:40PM +0800, Chao Yu wrote:
> > Hi Jaegeuk,
> >
> > > -----Original Message-----
> > > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> > > Sent: Sunday, January 24, 2016 4:16 AM
> > > To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> > > linux-f2fs-devel@lists.sourceforge.net
> > > Cc: Jaegeuk Kim
> > > Subject: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data
> > >
> > > The sceanrio is:
> > > 1. create fully node blocks
> > > 2. flush node blocks
> > > 3. write inline_data for all the node blocks again
> > > 4. flush node blocks redundantly
> > >
> > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > > ---
> > >  fs/f2fs/data.c | 14 +++++++++++---
> > >  1 file changed, 11 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > > index 8d0d9ec..011456e 100644
> > > --- a/fs/f2fs/data.c
> > > +++ b/fs/f2fs/data.c
> > > @@ -1622,14 +1622,22 @@ static int f2fs_write_end(struct file *file,
> > >
> > >  	trace_f2fs_write_end(inode, pos, len, copied);
> > >
> > > -	set_page_dirty(page);
> > > -
> > >  	if (pos + copied > i_size_read(inode)) {
> > >  		i_size_write(inode, pos + copied);
> > >  		mark_inode_dirty(inode);
> > > -		update_inode_page(inode);
> > >  	}
> > >
> > > +	if (f2fs_has_inline_data(inode) &&
> > > +			is_inode_flag_set(F2FS_I(inode), FI_DATA_EXIST)) {
> > > +		int err = f2fs_write_inline_data(inode, page);
> >
> > Oh, I'm sure this can fix that issue, but IMO:
> > a) this implementation has side-effect, it triggers inline data copying
> > between data page and node page whenever user write inline datas, so if
> > user updates inline data frequently, write-through approach would cause
> > memory copy overhead.
> 
> Agreed.
> 
> > b) inline storm should be a rare case, as we didn't get any report about
> > problem for long time until Dave's, and write_end is a hot path, I think
> > it's better to be cautious to change our inline data cache policy for
> > fixing a rare issue in hot path.
> >
> > What about delaying the merge operation? like:
> > 1) as I proposed before, merging inline page into inode page when
> > detecting free_sections <= (node_secs + 2 * dent_secs + inline_secs).
> > 2) merge inline page into inode page before writeback inode page in
> > sync_node_pages.
> 
> Okay, I'm thinking more general way where we can get rid of every inlien_data
> write when we flush node pages.

I encountered deadlock issue, could you have a look at it?

======================================================
 [ INFO: possible circular locking dependency detected ]
 4.5.0-rc1 #45 Tainted: G           O
 -------------------------------------------------------
 fstrim/15301 is trying to acquire lock:
  (sb_internal#2){++++..}, at: [<ffffffff81216fca>] __sb_start_write+0xda/0xf0

 but task is already holding lock:
  (&sbi->cp_rwsem){++++..}, at: [<ffffffffa07d06d2>] block_operations+0x82/0x130 [f2fs]

 which lock already depends on the new lock.


 the existing dependency chain (in reverse order) is:

 -> #1 (&sbi->cp_rwsem){++++..}:
        [<ffffffff810bf827>] lock_acquire+0xb7/0x130
        [<ffffffff817de829>] down_read+0x39/0x50
        [<ffffffffa07c27af>] f2fs_evict_inode+0x26f/0x370 [f2fs]
        [<ffffffff812326cd>] evict+0xdd/0x1d0
        [<ffffffff8123323f>] iput+0x19f/0x250
        [<ffffffff81224d9d>] do_unlinkat+0x20d/0x310
        [<ffffffff81224ee2>] SyS_unlinkat+0x22/0x40
        [<ffffffff817e0957>] entry_SYSCALL_64_fastpath+0x12/0x6f

 -> #0 (sb_internal#2){++++..}:
        [<ffffffff810bf32b>] __lock_acquire+0x132b/0x1770
        [<ffffffff810bf827>] lock_acquire+0xb7/0x130
        [<ffffffff810b8fac>] percpu_down_read+0x3c/0x80
        [<ffffffff81216fca>] __sb_start_write+0xda/0xf0
        [<ffffffffa07c2761>] f2fs_evict_inode+0x221/0x370 [f2fs]
        [<ffffffff812326cd>] evict+0xdd/0x1d0
        [<ffffffff8123323f>] iput+0x19f/0x250
        [<ffffffffa07dd4d3>] sync_node_pages+0x703/0x900 [f2fs]
        [<ffffffffa07d075a>] block_operations+0x10a/0x130 [f2fs]
        [<ffffffffa07d13e4>] write_checkpoint+0xc4/0xb80 [f2fs]
        [<ffffffffa07e0af2>] f2fs_trim_fs+0x122/0x1d0 [f2fs]
        [<ffffffffa07c07da>] f2fs_ioctl+0x7fa/0x9d0 [f2fs]
        [<ffffffff81228448>] vfs_ioctl+0x18/0x40
        [<ffffffff81228b96>] do_vfs_ioctl+0x96/0x680
        [<ffffffff81229212>] SyS_ioctl+0x92/0xa0
        [<ffffffff817e0957>] entry_SYSCALL_64_fastpath+0x12/0x6f

 other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&sbi->cp_rwsem);
                                lock(sb_internal#2);
                                lock(&sbi->cp_rwsem);
   lock(sb_internal#2);

  *** DEADLOCK ***

Thanks,

> 
> I've been testing this patch.
> 
> From ebddf607c64da691fef08cf68a8ecadafd5d896b Mon Sep 17 00:00:00 2001
> From: Jaegeuk Kim <jaegeuk@kernel.org>
> Date: Mon, 25 Jan 2016 05:57:05 -0800
> Subject: [PATCH] f2fs: avoid multiple node page writes due to inline_data
> 
> The sceanrio is:
> 1. create fully node blocks
> 2. flush node blocks
> 3. write inline_data for all the node blocks again
> 4. flush node blocks redundantly
> 
> So, this patch tries to flush inline_data when flushing node blocks.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/data.c   |  1 +
>  fs/f2fs/inline.c |  2 ++
>  fs/f2fs/node.c   | 35 +++++++++++++++++++++++++++++++++++
>  fs/f2fs/node.h   | 15 +++++++++++++++
>  4 files changed, 53 insertions(+)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 6925c10..9043ecf 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1464,6 +1464,7 @@ restart:
>  		if (pos + len <= MAX_INLINE_DATA) {
>  			read_inline_data(page, ipage);
>  			set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
> +			set_inline_node(ipage);
>  			sync_inode_page(&dn);
>  		} else {
>  			err = f2fs_convert_inline_page(&dn, page);
> diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> index 8df13e5..fc4d298 100644
> --- a/fs/f2fs/inline.c
> +++ b/fs/f2fs/inline.c
> @@ -159,6 +159,7 @@ no_update:
> 
>  	/* clear inline data and flag after data writeback */
>  	truncate_inline_inode(dn->inode_page, 0);
> +	clear_inline_node(dn->inode_page);
>  clear_out:
>  	stat_dec_inline_inode(dn->inode);
>  	f2fs_clear_inline_inode(dn->inode);
> @@ -233,6 +234,7 @@ int f2fs_write_inline_data(struct inode *inode, struct page *page)
>  	set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
> 
>  	sync_inode_page(&dn);
> +	clear_inline_node(dn.inode_page);
>  	f2fs_put_dnode(&dn);
>  	return 0;
>  }
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 23b800d..1c5023e 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1154,6 +1154,33 @@ void sync_inode_page(struct dnode_of_data *dn)
>  	dn->node_changed = ret ? true: false;
>  }
> 
> +static void flush_inline_data(struct f2fs_sb_info *sbi, nid_t ino)
> +{
> +	struct inode *inode;
> +	struct page *page;
> +
> +	inode = ilookup(sbi->sb, ino);
> +	if (!inode)
> +		return;
> +
> +	page = find_lock_page(inode->i_mapping, 0);
> +	if (!page)
> +		goto iput_out;
> +
> +	if (!PageDirty(page))
> +		goto put_page_out;
> +
> +	if (!clear_page_dirty_for_io(page))
> +		goto put_page_out;
> +
> +	if (!f2fs_write_inline_data(inode, page))
> +		inode_dec_dirty_pages(inode);
> +put_page_out:
> +	f2fs_put_page(page, 1);
> +iput_out:
> +	iput(inode);
> +}
> +
>  int sync_node_pages(struct f2fs_sb_info *sbi, nid_t ino,
>  					struct writeback_control *wbc)
>  {
> @@ -1221,6 +1248,14 @@ continue_unlock:
>  				goto continue_unlock;
>  			}
> 
> +			/* flush inline_data */
> +			if (!ino && is_inline_node(page)) {
> +				clear_inline_node(page);
> +				unlock_page(page);
> +				flush_inline_data(sbi, ino_of_node(page));
> +				continue;
> +			}
> +
>  			if (!clear_page_dirty_for_io(page))
>  				goto continue_unlock;
> 
> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> index 23bd992..1f4f9d4 100644
> --- a/fs/f2fs/node.h
> +++ b/fs/f2fs/node.h
> @@ -379,6 +379,21 @@ static inline int is_node(struct page *page, int type)
>  #define is_fsync_dnode(page)	is_node(page, FSYNC_BIT_SHIFT)
>  #define is_dent_dnode(page)	is_node(page, DENT_BIT_SHIFT)
> 
> +static inline int is_inline_node(struct page *page)
> +{
> +	return PageChecked(page);
> +}
> +
> +static inline void set_inline_node(struct page *page)
> +{
> +	SetPageChecked(page);
> +}
> +
> +static inline void clear_inline_node(struct page *page)
> +{
> +	ClearPageChecked(page);
> +}
> +
>  static inline void set_cold_node(struct inode *inode, struct page *page)
>  {
>  	struct f2fs_node *rn = F2FS_NODE(page);
> --
> 2.6.3
> 

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#1318236 — Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data

Hi Chao,

On Tue, Jan 26, 2016 at 02:58:53PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> > Sent: Tuesday, January 26, 2016 3:18 AM
> > To: Chao Yu
> > Cc: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> > linux-f2fs-devel@lists.sourceforge.net
> > Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data
> > 
> > Hi Chao,
> > 
> > On Mon, Jan 25, 2016 at 05:42:40PM +0800, Chao Yu wrote:
> > > Hi Jaegeuk,
> > >
> > > > -----Original Message-----
> > > > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> > > > Sent: Sunday, January 24, 2016 4:16 AM
> > > > To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> > > > linux-f2fs-devel@lists.sourceforge.net
> > > > Cc: Jaegeuk Kim
> > > > Subject: [f2fs-dev] [PATCH 1/2] f2fs: avoid multiple node page writes due to inline_data
> > > >
> > > > The sceanrio is:
> > > > 1. create fully node blocks
> > > > 2. flush node blocks
> > > > 3. write inline_data for all the node blocks again
> > > > 4. flush node blocks redundantly
> > > >
> > > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > > > ---
> > > >  fs/f2fs/data.c | 14 +++++++++++---
> > > >  1 file changed, 11 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > > > index 8d0d9ec..011456e 100644
> > > > --- a/fs/f2fs/data.c
> > > > +++ b/fs/f2fs/data.c
> > > > @@ -1622,14 +1622,22 @@ static int f2fs_write_end(struct file *file,
> > > >
> > > >  	trace_f2fs_write_end(inode, pos, len, copied);
> > > >
> > > > -	set_page_dirty(page);
> > > > -
> > > >  	if (pos + copied > i_size_read(inode)) {
> > > >  		i_size_write(inode, pos + copied);
> > > >  		mark_inode_dirty(inode);
> > > > -		update_inode_page(inode);
> > > >  	}
> > > >
> > > > +	if (f2fs_has_inline_data(inode) &&
> > > > +			is_inode_flag_set(F2FS_I(inode), FI_DATA_EXIST)) {
> > > > +		int err = f2fs_write_inline_data(inode, page);
> > >
> > > Oh, I'm sure this can fix that issue, but IMO:
> > > a) this implementation has side-effect, it triggers inline data copying
> > > between data page and node page whenever user write inline datas, so if
> > > user updates inline data frequently, write-through approach would cause
> > > memory copy overhead.
> > 
> > Agreed.
> > 
> > > b) inline storm should be a rare case, as we didn't get any report about
> > > problem for long time until Dave's, and write_end is a hot path, I think
> > > it's better to be cautious to change our inline data cache policy for
> > > fixing a rare issue in hot path.
> > >
> > > What about delaying the merge operation? like:
> > > 1) as I proposed before, merging inline page into inode page when
> > > detecting free_sections <= (node_secs + 2 * dent_secs + inline_secs).
> > > 2) merge inline page into inode page before writeback inode page in
> > > sync_node_pages.
> > 
> > Okay, I'm thinking more general way where we can get rid of every inlien_data
> > write when we flush node pages.
> 
> I encountered deadlock issue, could you have a look at it?

Yeah, I've been stablizing this for a while.
Please check f2fs.git/dev-test.

Thanks,

> 
> ======================================================
>  [ INFO: possible circular locking dependency detected ]
>  4.5.0-rc1 #45 Tainted: G           O
>  -------------------------------------------------------
>  fstrim/15301 is trying to acquire lock:
>   (sb_internal#2){++++..}, at: [<ffffffff81216fca>] __sb_start_write+0xda/0xf0
> 
>  but task is already holding lock:
>   (&sbi->cp_rwsem){++++..}, at: [<ffffffffa07d06d2>] block_operations+0x82/0x130 [f2fs]
> 
>  which lock already depends on the new lock.
> 
> 
>  the existing dependency chain (in reverse order) is:
> 
>  -> #1 (&sbi->cp_rwsem){++++..}:
>         [<ffffffff810bf827>] lock_acquire+0xb7/0x130
>         [<ffffffff817de829>] down_read+0x39/0x50
>         [<ffffffffa07c27af>] f2fs_evict_inode+0x26f/0x370 [f2fs]
>         [<ffffffff812326cd>] evict+0xdd/0x1d0
>         [<ffffffff8123323f>] iput+0x19f/0x250
>         [<ffffffff81224d9d>] do_unlinkat+0x20d/0x310
>         [<ffffffff81224ee2>] SyS_unlinkat+0x22/0x40
>         [<ffffffff817e0957>] entry_SYSCALL_64_fastpath+0x12/0x6f
> 
>  -> #0 (sb_internal#2){++++..}:
>         [<ffffffff810bf32b>] __lock_acquire+0x132b/0x1770
>         [<ffffffff810bf827>] lock_acquire+0xb7/0x130
>         [<ffffffff810b8fac>] percpu_down_read+0x3c/0x80
>         [<ffffffff81216fca>] __sb_start_write+0xda/0xf0
>         [<ffffffffa07c2761>] f2fs_evict_inode+0x221/0x370 [f2fs]
>         [<ffffffff812326cd>] evict+0xdd/0x1d0
>         [<ffffffff8123323f>] iput+0x19f/0x250
>         [<ffffffffa07dd4d3>] sync_node_pages+0x703/0x900 [f2fs]
>         [<ffffffffa07d075a>] block_operations+0x10a/0x130 [f2fs]
>         [<ffffffffa07d13e4>] write_checkpoint+0xc4/0xb80 [f2fs]
>         [<ffffffffa07e0af2>] f2fs_trim_fs+0x122/0x1d0 [f2fs]
>         [<ffffffffa07c07da>] f2fs_ioctl+0x7fa/0x9d0 [f2fs]
>         [<ffffffff81228448>] vfs_ioctl+0x18/0x40
>         [<ffffffff81228b96>] do_vfs_ioctl+0x96/0x680
>         [<ffffffff81229212>] SyS_ioctl+0x92/0xa0
>         [<ffffffff817e0957>] entry_SYSCALL_64_fastpath+0x12/0x6f
> 
>  other info that might help us debug this:
> 
>   Possible unsafe locking scenario:
> 
>         CPU0                    CPU1
>         ----                    ----
>    lock(&sbi->cp_rwsem);
>                                 lock(sb_internal#2);
>                                 lock(&sbi->cp_rwsem);
>    lock(sb_internal#2);
> 
>   *** DEADLOCK ***
> 
> Thanks,
> 
> > 
> > I've been testing this patch.
> > 
> > From ebddf607c64da691fef08cf68a8ecadafd5d896b Mon Sep 17 00:00:00 2001
> > From: Jaegeuk Kim <jaegeuk@kernel.org>
> > Date: Mon, 25 Jan 2016 05:57:05 -0800
> > Subject: [PATCH] f2fs: avoid multiple node page writes due to inline_data
> > 
> > The sceanrio is:
> > 1. create fully node blocks
> > 2. flush node blocks
> > 3. write inline_data for all the node blocks again
> > 4. flush node blocks redundantly
> > 
> > So, this patch tries to flush inline_data when flushing node blocks.
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/data.c   |  1 +
> >  fs/f2fs/inline.c |  2 ++
> >  fs/f2fs/node.c   | 35 +++++++++++++++++++++++++++++++++++
> >  fs/f2fs/node.h   | 15 +++++++++++++++
> >  4 files changed, 53 insertions(+)
> > 
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 6925c10..9043ecf 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -1464,6 +1464,7 @@ restart:
> >  		if (pos + len <= MAX_INLINE_DATA) {
> >  			read_inline_data(page, ipage);
> >  			set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
> > +			set_inline_node(ipage);
> >  			sync_inode_page(&dn);
> >  		} else {
> >  			err = f2fs_convert_inline_page(&dn, page);
> > diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> > index 8df13e5..fc4d298 100644
> > --- a/fs/f2fs/inline.c
> > +++ b/fs/f2fs/inline.c
> > @@ -159,6 +159,7 @@ no_update:
> > 
> >  	/* clear inline data and flag after data writeback */
> >  	truncate_inline_inode(dn->inode_page, 0);
> > +	clear_inline_node(dn->inode_page);
> >  clear_out:
> >  	stat_dec_inline_inode(dn->inode);
> >  	f2fs_clear_inline_inode(dn->inode);
> > @@ -233,6 +234,7 @@ int f2fs_write_inline_data(struct inode *inode, struct page *page)
> >  	set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
> > 
> >  	sync_inode_page(&dn);
> > +	clear_inline_node(dn.inode_page);
> >  	f2fs_put_dnode(&dn);
> >  	return 0;
> >  }
> > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> > index 23b800d..1c5023e 100644
> > --- a/fs/f2fs/node.c
> > +++ b/fs/f2fs/node.c
> > @@ -1154,6 +1154,33 @@ void sync_inode_page(struct dnode_of_data *dn)
> >  	dn->node_changed = ret ? true: false;
> >  }
> > 
> > +static void flush_inline_data(struct f2fs_sb_info *sbi, nid_t ino)
> > +{
> > +	struct inode *inode;
> > +	struct page *page;
> > +
> > +	inode = ilookup(sbi->sb, ino);
> > +	if (!inode)
> > +		return;
> > +
> > +	page = find_lock_page(inode->i_mapping, 0);
> > +	if (!page)
> > +		goto iput_out;
> > +
> > +	if (!PageDirty(page))
> > +		goto put_page_out;
> > +
> > +	if (!clear_page_dirty_for_io(page))
> > +		goto put_page_out;
> > +
> > +	if (!f2fs_write_inline_data(inode, page))
> > +		inode_dec_dirty_pages(inode);
> > +put_page_out:
> > +	f2fs_put_page(page, 1);
> > +iput_out:
> > +	iput(inode);
> > +}
> > +
> >  int sync_node_pages(struct f2fs_sb_info *sbi, nid_t ino,
> >  					struct writeback_control *wbc)
> >  {
> > @@ -1221,6 +1248,14 @@ continue_unlock:
> >  				goto continue_unlock;
> >  			}
> > 
> > +			/* flush inline_data */
> > +			if (!ino && is_inline_node(page)) {
> > +				clear_inline_node(page);
> > +				unlock_page(page);
> > +				flush_inline_data(sbi, ino_of_node(page));
> > +				continue;
> > +			}
> > +
> >  			if (!clear_page_dirty_for_io(page))
> >  				goto continue_unlock;
> > 
> > diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> > index 23bd992..1f4f9d4 100644
> > --- a/fs/f2fs/node.h
> > +++ b/fs/f2fs/node.h
> > @@ -379,6 +379,21 @@ static inline int is_node(struct page *page, int type)
> >  #define is_fsync_dnode(page)	is_node(page, FSYNC_BIT_SHIFT)
> >  #define is_dent_dnode(page)	is_node(page, DENT_BIT_SHIFT)
> > 
> > +static inline int is_inline_node(struct page *page)
> > +{
> > +	return PageChecked(page);
> > +}
> > +
> > +static inline void set_inline_node(struct page *page)
> > +{
> > +	SetPageChecked(page);
> > +}
> > +
> > +static inline void clear_inline_node(struct page *page)
> > +{
> > +	ClearPageChecked(page);
> > +}
> > +
> >  static inline void set_cold_node(struct inode *inode, struct page *page)
> >  {
> >  	struct f2fs_node *rn = F2FS_NODE(page);
> > --
> > 2.6.3
> > 
> 

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