linux-kernel - Re: [V9fs-developer] [PATCH v2 2/6] 9p: Change p9_fid

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Date:   Thu, 12 Jul 2018 13:56:16 +0200
From:   Greg Kurz <groug@...d.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Dominique Martinet <asmadeus@...ewreck.org>,
        Latchesar Ionkov <lucho@...kov.net>,
        Eric Van Hensbergen <ericvh@...il.com>,
        linux-kernel@...r.kernel.org, Ron Minnich <rminnich@...dia.gov>,
        linux-fsdevel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net
Subject: Re: [V9fs-developer] [PATCH v2 2/6] 9p: Change p9_fid_create
 calling convention

On Wed, 11 Jul 2018 14:02:21 -0700
Matthew Wilcox <willy@...radead.org> wrote:

> Return NULL instead of ERR_PTR when we can't allocate a FID.  The ENOSPC
> return value was getting all the way back to userspace, and that's
> confusing for a userspace program which isn't expecting read() to tell it
> there's no space left on the filesystem.  The best error we can return to
> indicate a temporary failure caused by lack of client resources is ENOMEM.
> 
> Maybe it would be better to sleep until a FID is available, but that's
> not a change I'm comfortable making.
> 
> Signed-off-by: Matthew Wilcox <willy@...radead.org>
> ---

Reviewed-by: Greg Kurz <groug@...d.org>

>  net/9p/client.c | 23 +++++++++--------------
>  1 file changed, 9 insertions(+), 14 deletions(-)
> 
> diff --git a/net/9p/client.c b/net/9p/client.c
> index 999eceb8af98..389a2904b7b3 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -913,13 +913,11 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
>  	p9_debug(P9_DEBUG_FID, "clnt %p\n", clnt);
>  	fid = kmalloc(sizeof(struct p9_fid), GFP_KERNEL);
>  	if (!fid)
> -		return ERR_PTR(-ENOMEM);
> +		return NULL;
>  
>  	ret = p9_idpool_get(clnt->fidpool);
> -	if (ret < 0) {
> -		ret = -ENOSPC;
> +	if (ret < 0)
>  		goto error;
> -	}
>  	fid->fid = ret;
>  
>  	memset(&fid->qid, 0, sizeof(struct p9_qid));
> @@ -935,7 +933,7 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
>  
>  error:
>  	kfree(fid);
> -	return ERR_PTR(ret);
> +	return NULL;
>  }
>  
>  static void p9_fid_destroy(struct p9_fid *fid)
> @@ -1137,9 +1135,8 @@ struct p9_fid *p9_client_attach(struct p9_client *clnt, struct p9_fid *afid,
>  	p9_debug(P9_DEBUG_9P, ">>> TATTACH afid %d uname %s aname %s\n",
>  		 afid ? afid->fid : -1, uname, aname);
>  	fid = p9_fid_create(clnt);
> -	if (IS_ERR(fid)) {
> -		err = PTR_ERR(fid);
> -		fid = NULL;
> +	if (!fid) {
> +		err = -ENOMEM;
>  		goto error;
>  	}
>  	fid->uid = n_uname;
> @@ -1188,9 +1185,8 @@ struct p9_fid *p9_client_walk(struct p9_fid *oldfid, uint16_t nwname,
>  	clnt = oldfid->clnt;
>  	if (clone) {
>  		fid = p9_fid_create(clnt);
> -		if (IS_ERR(fid)) {
> -			err = PTR_ERR(fid);
> -			fid = NULL;
> +		if (!fid) {
> +			err = -ENOMEM;
>  			goto error;
>  		}
>  
> @@ -2018,9 +2014,8 @@ struct p9_fid *p9_client_xattrwalk(struct p9_fid *file_fid,
>  	err = 0;
>  	clnt = file_fid->clnt;
>  	attr_fid = p9_fid_create(clnt);
> -	if (IS_ERR(attr_fid)) {
> -		err = PTR_ERR(attr_fid);
> -		attr_fid = NULL;
> +	if (!attr_fid) {
> +		err = -ENOMEM;
>  		goto error;
>  	}
>  	p9_debug(P9_DEBUG_9P,