Re: [External] Re: [PATCH V2 4/5] erofs: remove duplicated unregister_cookie

[Jia Zhu]

在 2022/9/9 17:55, JeffleXu 写道:
> On 9/2/22 6:53 PM, Jia Zhu wrote:
> > In erofs umount scenario, erofs_fscache_unregister_cookie() is called
> > twice in kill_sb() and put_super().
> >
> > It works for original semantics, cause 'ctx' will be set to NULL in
> > put_super() and will not be unregister again in kill_sb().
> > However, in shared domain scenario, we use refcount to maintain the
> > lifecycle of cookie. Unregister the cookie twice will cause it to be
> > released early.
> >
> > For the above reasons, this patch removes duplicate unregister_cookie
> > and move fscache_unregister_* before shotdown_super() to prevent busy
> > inode(ctx->inode) when umount.
> >
> > Signed-off-by: Jia Zhu <zhujia.zj@xxxxxxxxxxxxx>
> > ---
> >   fs/erofs/super.c | 16 ++++++++--------
> >   1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> > index 69de1731f454..667a78f0ee70 100644
> > --- a/fs/erofs/super.c
> > +++ b/fs/erofs/super.c
> > @@ -919,19 +919,20 @@ static void erofs_kill_sb(struct super_block *sb)
> >   		kill_litter_super(sb);
> >   		return;
> >   	}
> > -	if (erofs_is_fscache_mode(sb))
> > -		generic_shutdown_super(sb);
> > -	else
> > -		kill_block_super(sb);
> > -
> >   	sbi = EROFS_SB(sb);
> >   	if (!sbi)
> >   		return;
> >   
> > +	if (erofs_is_fscache_mode(sb)) {
> > +		erofs_fscache_unregister_cookie(&sbi->s_fscache);
> > +		erofs_fscache_unregister_fs(sb);
> > +		generic_shutdown_super(sb);
>
> Generally we can't do clean ups before generic_shutdown_super(), since
> generic_shutdown_super() may trigger IO, e.g. in sync_filesystem(),
> though it's not the case for erofs (read-only).
>
> How about embedding erofs_fscache_unregister_cookie() into
> erofs_fscache_unregister_fs(), and thus we can check domain_id in
> erofs_fscache_unregister_fs()?
Thanks.
> > +	} else {
> > +		kill_block_super(sb);
> > +	}
> > +
> >   	erofs_free_dev_context(sbi->devs);
> >   	fs_put_dax(sbi->dax_dev, NULL);
> > -	erofs_fscache_unregister_cookie(&sbi->s_fscache);
> > -	erofs_fscache_unregister_fs(sb);
> >   	kfree(sbi->opt.fsid);
> >   	kfree(sbi->opt.domain_id);
> >   	kfree(sbi);
> > @@ -951,7 +952,6 @@ static void erofs_put_super(struct super_block *sb)
> >   	iput(sbi->managed_cache);
> >   	sbi->managed_cache = NULL;
> >   #endif
> > -	erofs_fscache_unregister_cookie(&sbi->s_fscache);
> >   }
> >   
> >   struct file_system_type erofs_fs_type = {