Date:	Wed, 10 Sep 2014 22:37:16 -0700
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	huang ying <huang.ying.caritas@...il.com>
Cc:	Huang Ying <ying.huang@...el.com>,
	Changman Lee <cm224.lee@...sung.com>,
	linux-f2fs-devel@...ts.sourceforge.net,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: Fix recover when nid of non-inode dnode < nid of
 inode

On Wed, Sep 10, 2014 at 07:08:32PM +0800, huang ying wrote:
> On Wed, Sep 10, 2014 at 3:21 PM, Jaegeuk Kim <jaegeuk@...nel.org> wrote:
> 
> > On Tue, Sep 09, 2014 at 07:31:49PM +0800, huang ying wrote:
> > > On Tue, Sep 9, 2014 at 3:09 PM, Jaegeuk Kim <jaegeuk@...nel.org> wrote:
> > >
> > > > Hi,
> > > >
> > > > On Tue, Sep 09, 2014 at 01:39:30PM +0800, Huang Ying wrote:
> > > > > On Mon, 2014-09-08 at 22:23 -0700, Jaegeuk Kim wrote:
> > > > > > Hi Huang,
> > > > > >
> > > > > > On Mon, Sep 08, 2014 at 07:38:26PM +0800, Huang Ying wrote:
> > > > > > > For fsync, if the nid of a non-inode dnode < nid of inode and the
> > > > > > > inode is not checkpointed.  The non-inode dnode may be written
> > before
> > > > > > > inode.  So in find_fsync_dnodes, f2fs_iget will fail, cause the
> > > > > > > recovery fail.
> > > > > > >
> > > > > > > Usually, inode will be allocated before non-inode dnode, so the
> > nid
> > > > of
> > > > > > > inode < nid of non-inode dnode.  But it is possible for the
> > reverse.
> > > > > > > For example, because of alloc_nid_failed.
> > > > > > >
> > > > > > > This is fixed via ignoring non-inode dnode before inode dnode in
> > > > > > > find_fsync_dnodes.
> > > > > > >
> > > > > > > The patch was tested via allocating nid reversely via a debugging
> > > > > > > patch, that is, from big number to small number.
> > > > > > >
> > > > > > > Signed-off-by: Huang, Ying <ying.huang@...el.com>
> > > > > > > ---
> > > > > > >  fs/f2fs/recovery.c |    7 ++++---
> > > > > > >  1 file changed, 4 insertions(+), 3 deletions(-)
> > > > > > >
> > > > > > > --- a/fs/f2fs/recovery.c
> > > > > > > +++ b/fs/f2fs/recovery.c
> > > > > > > @@ -172,8 +172,8 @@ static int find_fsync_dnodes(struct f2fs
> > > > > > >                   if (IS_INODE(page) && is_dent_dnode(page))
> > > > > > >                           set_inode_flag(F2FS_I(entry->inode),
> > > > > > >                                                   FI_INC_LINK);
> > > > > > > -         } else {
> > > > > > > -                 if (IS_INODE(page) && is_dent_dnode(page)) {
> > > > > >
> > > > > > If this is not inode block, we should add this inode to recover its
> > > > data blocks.
> > > > >
> > > > > Is it possible that there is only non-inode dnode but no inode when
> > > > > find_fsync_dnodes checking dnodes?  Per my understanding, any
> > changes to
> > > > > file will cause inode page dirty (for example, mtime changed), so
> > that
> > > > > we will write inode block.  Is it right?  If so, the solution in this
> > > > > patch should work too.
> > > >
> > > > Your description says that f2fs_iget will fail, which causes the
> > recovery
> > > > fail.
> > > > So, I thought it would be better to handle the f2fs_iget failure
> > directly.
> > > >
> > >
> > > Yes.  That is another way to fix the issue.
> > >
> > >
> > > > In addition, we cannot guarantee the write order of dnode and inode.
> > > > For exmaple,
> > > > 1. the inode is written by flusher or kswapd, then,
> > > > 2. f2fs_sync_file writes its dnode.
> > > >
> > > > In that case, we can get only non-inode dnode in the node chain, since
> > the
> > > > inode
> > > > has not fsync_mark.
> > > >
> > >
> > > I think your solution is better here, but does not fix all scenarios.  If
> > > the inode is checkpointed, the file can be recovered, although the inode
> > > information may be not up to date.  But if the inode is not checkpointed,
> > > f2fs_iget will fail too and recover will fail.
> >
> > Ok, let me consider your scenarios.
> >
> > Term: F: fsync_mark, D: dentry_mark
> >
> > 1. inode(x) | CP | inode(x) | dnode(F)
> >  -> Lose the latest inode(x). Need to fix.
> >
> > 2. inode(x) | CP | dnode(F) | inode(x)
> >  -> Impossible, but recover latest dnode(F)
> >
> > 3. CP | inode(x) | dnode(F)
> >  -> Need to write inode(DF) in f2fs_sync_file.
> >
> > 4. CP | dnode(F) | inode(DF)
> >  -> If f2fs_iget fails, then goto next.
> >
> > 5. CP | dnode(F) | inode(x)
> >  -> If f2fs_iget fails, then goto next. But, this is an impossible
> > scenario.
> >     Drop this dnode(F).
> >
> > Indeed, there were some missing scenarios.
> >
> > So, how about this patch?
> >
> > From 552dc68c5f07a335d7b55c197bab531efb135521 Mon Sep 17 00:00:00 2001
> > From: Jaegeuk Kim <jaegeuk@...nel.org>
> > Date: Wed, 10 Sep 2014 00:16:34 -0700
> > Subject: [PATCH] f2fs: fix roll-forward missing scenarios
> >
> > We can summarize the roll forward recovery scenarios as follows.
> >
> > [Term] F: fsync_mark, D: dentry_mark
> >
> > 1. inode(x) | CP | inode(x) | dnode(F)
> > -> Update the latest inode(x).
> >
> > 2. inode(x) | CP | inode(F) | dnode(F)
> > -> No problem.
> >
> > 3. inode(x) | CP | dnode(F) | inode(x)
> > -> Impossible, but recover latest dnode(F)
> >
> 
> I think this is possible.  If f2fs_sync_file runs concurrently with
> writeback. f2fs_sync_file written dnode(F), then writeback written inode(x).

If the inode(x) was written, f2fs_sync_file will do write the inode again with
fsync_mark. So, dnode(F) | inode(x) | inode(F) should be shown.

In f2fs_sync_file,
	...
	while (!sync_node_pages(sbi, ino, &wbc)) {
		if (fsync_mark_done(sbi, ino))
			goto out;
		mark_inode_dirty_sync(inode);
		ret = f2fs_write_inode(inode, NULL);
		if (ret)
			goto out;
	}
	...

> 
> 
> > 4. inode(x) | CP | dnode(F) | inode(F)
> > -> No problem.
> >
> > 5. CP | inode(x) | dnode(F)
> > -> Impossible. Write inode(DF) with dnode(F) by f2fs_sync_file.
> >
> 
> I think this is possible.  If inode(x) is written by writeback and then
> dnode(F) is written by f2fs_sync_file.

-> The inode(DF) was missing. Should drop this dnode(F).
Again, CP | inode(x) | dnode(F) | inode(DF) should be shown.
This is fixed by the below updated patch.

> 
> 
> > 6. CP | inode(DF) | dnode(F)
> > -> No problem.
> >
> > 7. CP | dnode(F) | inode(DF)
> > -> If f2fs_iget fails, then goto next to find inode(DF).
> >
> > 8. CP | dnode(F) | inode(x)
> > -> If f2fs_iget fails, then goto next. But, this is an impossible scenario.
> >    Drop this dnode(F).
> >
> 
> I think this is possible.  as 3.

ditto.

> 
> 
> > So, this patch adds some missing points such as #1, #5, #7, and #8.
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> >  fs/f2fs/file.c     | 10 ++++++++
> >  fs/f2fs/recovery.c | 70
> > +++++++++++++++++++++++++++++++++++++++++++++---------
> >  2 files changed, 69 insertions(+), 11 deletions(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 5cde363..2660af2 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -207,6 +207,16 @@ int f2fs_sync_file(struct file *file, loff_t start,
> > loff_t end, int datasync)
> >                         up_write(&fi->i_sem);
> >                 }
> >         } else {
> > +               /*
> > +                * CP | inode(x) | dnode(F)
> > +                * We need to remain inode(DF) for roll-forward recovery.
> > +                */
> > +               if (fsync_mark_done(sbi, inode->i_ino) &&
> >
> 
> How can this happen?  We have not called sync_node_pages(sbi, inode->i_ino,
> &wbc).  Where is the fsync mark set?
> 
> 
> > +                       !is_checkpointed_node(sbi, F2FS_I(inode)->i_pino))
> > {
> >
> 
> if !is_checkpointed_node(sbi, F2FS_I(inode)->i_pino), we need to do
> checkpoint.  Right?

Yes, whole conditions were wrong.
Please, refer the following patch.
Thanks,

>From 2e70059dd680830c030f59813d4e9837cb65ecb1 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@...nel.org>
Date: Wed, 10 Sep 2014 00:16:34 -0700
Subject: [PATCH 1/2] f2fs: fix roll-forward missing scenarios

We can summarize the roll forward recovery scenarios as follows.

[Term] F: fsync_mark, D: dentry_mark

1. inode(x) | CP | inode(x) | dnode(F)
-> Update the latest inode(x).

2. inode(x) | CP | inode(F) | dnode(F)
-> No problem.

3. inode(x) | CP | dnode(F) | inode(x)
-> Impossible, but recover latest dnode(F).

4. inode(x) | CP | dnode(F) | inode(F)
-> No problem.

5. CP | inode(x) | dnode(F)
-> The inode(DF) was missing. Should drop this dnode(F).

6. CP | inode(DF) | dnode(F)
-> No problem.

7. CP | dnode(F) | inode(DF)
-> If f2fs_iget fails, then goto next to find inode(DF).

8. CP | dnode(F) | inode(x)
-> If f2fs_iget fails, then goto next to find inode(DF).
   But it will fail due to no inode(DF).

So, this patch adds some missing points such as #1, #5, #7, and #8.

Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
 fs/f2fs/file.c     | 10 ++++++++
 fs/f2fs/recovery.c | 70 +++++++++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 69 insertions(+), 11 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index e7681c3..e2a2f38 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -206,6 +206,16 @@ int f2fs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 			up_write(&fi->i_sem);
 		}
 	} else {
+		/*
+		 * CP | inode(x) | dnode(F)
+		 * We need to remain inode(DF) for roll-forward recovery.
+		 */
+		if (!fsync_mark_done(sbi, inode->i_ino) &&
+			!is_checkpointed_node(sbi, inode->i_ino)) {
+			mark_inode_dirty_sync(inode);
+			f2fs_write_inode(inode, NULL);
+		}
+
 		/* if there is no written node page, write its inode page */
 		while (!sync_node_pages(sbi, ino, &wbc)) {
 			if (fsync_mark_done(sbi, ino))
diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index 6c5a74a..eeb3785 100644
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -14,6 +14,36 @@
 #include "node.h"
 #include "segment.h"
 
+/*
+ * Roll forward recovery scenarios.
+ *
+ * [Term] F: fsync_mark, D: dentry_mark
+ *
+ * 1. inode(x) | CP | inode(x) | dnode(F)
+ * -> Update the latest inode(x).
+ *
+ * 2. inode(x) | CP | inode(F) | dnode(F)
+ * -> No problem.
+ *
+ * 3. inode(x) | CP | dnode(F) | inode(x)
+ * -> Impossible, but recover latest dnode(F)
+ *
+ * 4. inode(x) | CP | dnode(F) | inode(F)
+ * -> No problem.
+ *
+ * 5. CP | inode(x) | dnode(F)
+ * -> The inode(DF) was missing. Should drop this dnode(F).
+ *
+ * 6. CP | inode(DF) | dnode(F)
+ * -> No problem.
+ *
+ * 7. CP | dnode(F) | inode(DF)
+ * -> If f2fs_iget fails, then goto next to find inode(DF).
+ *
+ * 8. CP | dnode(F) | inode(x)
+ * -> If f2fs_iget fails, then goto next to find inode(DF).
+ *    But it will fail due to no inode(DF).
+ */
 static struct kmem_cache *fsync_entry_slab;
 
 bool space_for_roll_forward(struct f2fs_sb_info *sbi)
@@ -110,27 +140,32 @@ out:
 	return err;
 }
 
-static int recover_inode(struct inode *inode, struct page *node_page)
+static void __recover_inode(struct inode *inode, struct page *page)
 {
-	struct f2fs_inode *raw_inode = F2FS_INODE(node_page);
+	struct f2fs_inode *raw = F2FS_INODE(page);
+
+	inode->i_mode = le16_to_cpu(raw->i_mode);
+	i_size_write(inode, le64_to_cpu(raw->i_size));
+	inode->i_atime.tv_sec = le64_to_cpu(raw->i_mtime);
+	inode->i_ctime.tv_sec = le64_to_cpu(raw->i_ctime);
+	inode->i_mtime.tv_sec = le64_to_cpu(raw->i_mtime);
+	inode->i_atime.tv_nsec = le32_to_cpu(raw->i_mtime_nsec);
+	inode->i_ctime.tv_nsec = le32_to_cpu(raw->i_ctime_nsec);
+	inode->i_mtime.tv_nsec = le32_to_cpu(raw->i_mtime_nsec);
+}
 
+static int recover_inode(struct inode *inode, struct page *node_page)
+{
 	if (!IS_INODE(node_page))
 		return 0;
 
-	inode->i_mode = le16_to_cpu(raw_inode->i_mode);
-	i_size_write(inode, le64_to_cpu(raw_inode->i_size));
-	inode->i_atime.tv_sec = le64_to_cpu(raw_inode->i_mtime);
-	inode->i_ctime.tv_sec = le64_to_cpu(raw_inode->i_ctime);
-	inode->i_mtime.tv_sec = le64_to_cpu(raw_inode->i_mtime);
-	inode->i_atime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
-	inode->i_ctime.tv_nsec = le32_to_cpu(raw_inode->i_ctime_nsec);
-	inode->i_mtime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
+	__recover_inode(inode, node_page);
 
 	if (is_dent_dnode(node_page))
 		return recover_dentry(node_page, inode);
 
 	f2fs_msg(inode->i_sb, KERN_NOTICE, "recover_inode: ino = %x, name = %s",
-			ino_of_node(node_page), raw_inode->i_name);
+			ino_of_node(node_page), F2FS_INODE(node_page)->i_name);
 	return 0;
 }
 
@@ -186,10 +221,16 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head)
 				break;
 			}
 
+			/*
+			 * CP | dnode(F) | inode(DF)
+			 * For this case, we should not give up now.
+			 */
 			entry->inode = f2fs_iget(sbi->sb, ino_of_node(page));
 			if (IS_ERR(entry->inode)) {
 				err = PTR_ERR(entry->inode);
 				kmem_cache_free(fsync_entry_slab, entry);
+				if (err == -ENOENT)
+					goto next;
 				break;
 			}
 			list_add_tail(&entry->list, head);
@@ -416,6 +457,13 @@ static int recover_data(struct f2fs_sb_info *sbi,
 		entry = get_fsync_inode(head, ino_of_node(page));
 		if (!entry)
 			goto next;
+		/*
+		 * inode(x) | CP | inode(x) | dnode(F)
+		 * In this case, we can lose the latest inode(x).
+		 * So, call __recover_inode for the inode update.
+		 */
+		if (IS_INODE(page))
+			__recover_inode(entry->inode, page);
 
 		err = do_recover_data(sbi, entry->inode, page, blkaddr);
 		if (err)
-- 
1.8.5.2 (Apple Git-48)

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