linux-kernel - Re: [PATCH 1/2] fs: use mapping_set_error instead of opencoded set

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Date:   Tue, 13 Sep 2016 08:53:01 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] fs: use mapping_set_error instead of opencoded
 set_bit

On Mon 12-09-16 15:18:23, Andrew Morton wrote:
> On Mon, 12 Sep 2016 15:11:46 -0700 Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> > > @@ -409,7 +408,7 @@ static int afs_write_back_from_locked_page(struct afs_writeback *wb,
> > >  		case -ENOMEDIUM:
> > >  		case -ENXIO:
> > >  			afs_kill_pages(wb->vnode, true, first, last);
> > > -			set_bit(AS_EIO, &wb->vnode->vfs_inode.i_mapping->flags);
> > > +			mapping_set_error(wb->vnode->vfs_inode.i_mapping, -ENXIO);
> > 
> > This one is a functional change: mapping_set_error() will rewrite
> > -ENXIO into -EIO.  Doesn't seem at all important though.
> 
> hm, OK, it's not a functional change - the code was already doing
> s/ENXIO/EIO/.

Yes the rewrite is silent but I've decided to keep the current errno
because I have no idea whether this can change in future. It doesn't
sound probable but it also sounds safer to do an overwrite at a single
place rather than all over the place /me thinks.

> Let's make it look more truthful?
> 
> --- a/fs/afs/write.c~fs-use-mapping_set_error-instead-of-opencoded-set_bit-fix
> +++ a/fs/afs/write.c
> @@ -408,7 +408,7 @@ no_more:
>  		case -ENOMEDIUM:
>  		case -ENXIO:
>  			afs_kill_pages(wb->vnode, true, first, last);
> -			mapping_set_error(wb->vnode->vfs_inode.i_mapping, -ENXIO);
> +			mapping_set_error(wb->vnode->vfs_inode.i_mapping, -EIO);
>  			break;
>  		case -EACCES:
>  		case -EPERM:
> _
> 
> 

-- 
Michal Hocko
SUSE Labs