linux-kernel - Re: [PATCH 2/3] vfs: Add a super block operation to check for writeback errors

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Message-ID: <20210104194155.GE63879@redhat.com>
Date:   Mon, 4 Jan 2021 14:41:55 -0500
From:   Vivek Goyal <vgoyal@...hat.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-unionfs@...r.kernel.org, amir73il@...il.com,
        sargun@...gun.me, miklos@...redi.hu, willy@...radead.org,
        jack@...e.cz, neilb@...e.com, viro@...iv.linux.org.uk, hch@....de
Subject: Re: [PATCH 2/3] vfs: Add a super block operation to check for
 writeback errors

On Wed, Dec 23, 2020 at 07:48:52AM -0500, Jeff Layton wrote:
> On Mon, 2020-12-21 at 14:50 -0500, Vivek Goyal wrote:
> > Right now we check for errors on super block in syncfs().
> > 
> > ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err);
> > 
> > overlayfs does not update sb->s_wb_err and it is tracked on upper filesystem.
> > So provide a superblock operation to check errors so that filesystem
> > can provide override generic method and provide its own method to
> > check for writeback errors.
> > 
> > Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
> > ---
> >  fs/sync.c          | 5 ++++-
> >  include/linux/fs.h | 1 +
> >  2 files changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/sync.c b/fs/sync.c
> > index b5fb83a734cd..57e43a16dfca 100644
> > --- a/fs/sync.c
> > +++ b/fs/sync.c
> > @@ -176,7 +176,10 @@ SYSCALL_DEFINE1(syncfs, int, fd)
> >  	ret = sync_filesystem(sb);
> >  	up_read(&sb->s_umount);
> >  
> > 
> > -	ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err);
> > +	if (sb->s_op->errseq_check_advance)
> > +		ret2 = sb->s_op->errseq_check_advance(sb, f.file);
> > +	else
> > +		ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err);
> >  
> > 
> >  	fdput(f);
> >  	return ret ? ret : ret2;
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index 8667d0cdc71e..4297b6127adf 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -1965,6 +1965,7 @@ struct super_operations {
> >  				  struct shrink_control *);
> >  	long (*free_cached_objects)(struct super_block *,
> >  				    struct shrink_control *);
> > +	int (*errseq_check_advance)(struct super_block *, struct file *);
> >  };
> >  
> > 
> >  /*
> 
> Also, the other super_operations generally don't take a superblock
> pointer when you pass in a different fs object pointer. This should
> probably just take a struct file * and then the operation can chase
> pointers to the superblock from there.

Ok, I will drop super_block * argument and just pass in "struct file *".

Vivek

>  
> -- 
> Jeff Layton <jlayton@...nel.org>
>