linux-kernel - Re: [PATCH] erofs: set SB_NODEV sb

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Message-ID: <Zh898uJW0AFtE0Rk@debian>
Date: Wed, 17 Apr 2024 11:11:46 +0800
From: Gao Xiang <xiang@...nel.org>
To: Baokun Li <libaokun1@...wei.com>
Cc: Christian Brauner <brauner@...nel.org>, xiang@...nel.org,
	linux-erofs@...ts.ozlabs.org, chao@...nel.org, huyue2@...lpad.com,
	jefflexu@...ux.alibaba.com, viro@...iv.linux.org.uk,
	linux-kernel@...r.kernel.org, yangerkun@...wei.com,
	houtao1@...wei.com
Subject: Re: [PATCH] erofs: set SB_NODEV sb_flags when mounting with fsid

On Wed, Apr 17, 2024 at 10:59:53AM +0800, Baokun Li wrote:
> On 2024/4/16 22:49, Gao Xiang wrote:
> > On Tue, Apr 16, 2024 at 02:35:08PM +0200, Christian Brauner wrote:
> > > > > I'm not sure how to resolve it in EROFS itself, anyway...
> > > Instead of allocating the erofs_sb_info in fill_super() allocate it
> > > during erofs_get_tree() and then you can ensure that you always have the
> > > info you need available during erofs_kill_sb(). See the appended
> > > (untested) patch.
> > Hi Christian,
> > 
> > Yeah, that is a good way I think.  Although sbi will be allocated
> > unconditionally instead but that is minor.
> > 
> > I'm on OSSNA this week, will test this patch more when returning.
> > 
> > Hi Baokun,
> > 
> > Could you also check this on your side?
> > 
> > Thanks,
> > Gao Xiang
> Hi Xiang,
> 
> This patch does fix the initial problem.
> 
> 
> Hi Christian,
> 
> Thanks for the patch, this is a good idea. Just with nits below.
> Otherwise feel free to add.
> 
> Reviewed-and-tested-by: Baokun Li <libaokun1@...wei.com>
> > 
> > >  From e4f586a41748b6edc05aca36d49b7b39e55def81 Mon Sep 17 00:00:00 2001
> > > From: Christian Brauner <brauner@...nel.org>
> > > Date: Mon, 15 Apr 2024 20:17:46 +0800
> > > Subject: [PATCH] erofs: reliably distinguish block based and fscache mode
> > > 
> SNIP
> 
> > > 
> > > diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> > > index c0eb139adb07..4ed80154edf8 100644
> > > --- a/fs/erofs/super.c
> > > +++ b/fs/erofs/super.c
> > > @@ -581,7 +581,7 @@ static const struct export_operations erofs_export_ops = {
> > >   static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
> > >   {
> > >   	struct inode *inode;
> > > -	struct erofs_sb_info *sbi;
> > > +	struct erofs_sb_info *sbi = EROFS_SB(sb);
> > >   	struct erofs_fs_context *ctx = fc->fs_private;
> > >   	int err;
> > > @@ -590,15 +590,10 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
> > >   	sb->s_maxbytes = MAX_LFS_FILESIZE;
> > >   	sb->s_op = &erofs_sops;
> > > -	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
> > > -	if (!sbi)
> > > -		return -ENOMEM;
> > > -
> > >   	sb->s_fs_info = sbi;
> This line is no longer needed.
> > >   	sbi->opt = ctx->opt;
> > >   	sbi->devs = ctx->devs;
> > >   	ctx->devs = NULL;
> > > -	sbi->fsid = ctx->fsid;
> > >   	ctx->fsid = NULL;
> > >   	sbi->domain_id = ctx->domain_id;
> > >   	ctx->domain_id = NULL;
> Since erofs_sb_info is now allocated in erofs_fc_get_tree(), why not
> encapsulate the above lines as erofs_ctx_to_info() helper function
> to be called in erofs_fc_get_tree()？Then erofs_fc_fill_super() wouldn't
> have to use erofs_fs_context and would prevent the fsid from being
> freed twice.

Hi Baokun,

I'm not sure if Christian has enough time to polish the whole
codebase (I'm happy if do so).  Basically, that is just a hint
to the issue, if you have more time, I guess you could also help
revive this patch together (also because you also have a real
EROFS test environment).

Let me also check this next week after OSSNA travelling.

Thanks,
Gao Xiang