[lustre-devel] [PATCH 01/22] ext4: add i_fs_version

From: James Simmons <jsimmons@infradead.org>
To: lustre-devel@lists.lustre.org
Subject: [lustre-devel] [PATCH 01/22] ext4: add i_fs_version
Date: Tue, 23 Jul 2019 01:07:38 +0100 (BST)	[thread overview]
Message-ID: <alpine.LFD.2.21.1907230057370.23817@casper.infradead.org> (raw)
In-Reply-To: <87wogapuz2.fsf@notabene.neil.brown.name>

> > From: James Simmons <uja.ornl@yahoo.com>
> >
> > Add inode version field that osd-ldiskfs uses.
> 
> We need more words here.  What is i_fs_version used for?
> 
> (I'll probably find out as I keep reading, but I need to know
>  the intention first, or I cannot properly review the patches
>  that make use of it.
> )

Sadly these patches don't contain much in terms of why they exist.
I did some digging and it seems at one time Lustre did use the 
i_version field directly for it recovery process. It seems ext4 stomps
on its i_version independently of lustre so it can't be trusted in
use of recovery.

> NeilBrown
> 
> 
> >
> > Signed-off-by: James Simmons <uja.ornl@yahoo.com>
> > ---
> >  fs/ext4/ext4.h   | 2 ++
> >  fs/ext4/ialloc.c | 1 +
> >  fs/ext4/inode.c  | 4 ++--
> >  3 files changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> > index 1cb6785..8abbcab 100644
> > --- a/fs/ext4/ext4.h
> > +++ b/fs/ext4/ext4.h
> > @@ -1063,6 +1063,8 @@ struct ext4_inode_info {
> >  	struct dquot *i_dquot[MAXQUOTAS];
> >  #endif
> >  
> > +	u64 i_fs_version;
> > +
> >  	/* Precomputed uuid+inum+igen checksum for seeding inode checksums */
> >  	__u32 i_csum_seed;
> >  
> > diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> > index 764ff4c..09ae4a4 100644
> > --- a/fs/ext4/ialloc.c
> > +++ b/fs/ext4/ialloc.c
> > @@ -1100,6 +1100,7 @@ struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir,
> >  	ei->i_dtime = 0;
> >  	ei->i_block_group = group;
> >  	ei->i_last_alloc_group = ~0;
> > +	ei->i_fs_version = 0;
> >  
> >  	ext4_set_inode_flags(inode);
> >  	if (IS_DIRSYNC(inode))
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index c7f77c6..6e66175 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -4806,14 +4806,14 @@ static inline void ext4_inode_set_iversion_queried(struct inode *inode, u64 val)
> >  	if (unlikely(EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL))
> >  		inode_set_iversion_raw(inode, val);
> >  	else
> > -		inode_set_iversion_queried(inode, val);
> > +		EXT4_I(inode)->i_fs_version = val;
> >  }
> >  static inline u64 ext4_inode_peek_iversion(const struct inode *inode)
> >  {
> >  	if (unlikely(EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL))
> >  		return inode_peek_iversion_raw(inode);
> >  	else
> > -		return inode_peek_iversion(inode);
> > +		return EXT4_I(inode)->i_fs_version;
> >  }
> >  
> >  struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
> > -- 
> > 1.8.3.1
> 