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

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Message-ID: <3b488048b666f22108e7660eb32e10860a75784a.camel@kernel.org>
Date:   Wed, 23 Dec 2020 07:48:52 -0500
From:   Jeff Layton <jlayton@...nel.org>
To:     Vivek Goyal <vgoyal@...hat.com>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-unionfs@...r.kernel.org
Cc:     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 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.
 
-- 
Jeff Layton <jlayton@...nel.org>