linux-kernel - Re: [PATCH -V20 02/12] vfs: Add name to file handle conversion support

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Date:	Wed, 29 Sep 2010 10:26:32 -0700 (PDT)
From:	Sage Weil <sage@...dream.net>
To:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
cc:	"J. Bruce Fields" <bfields@...ldses.org>, hch@...radead.org,
	viro@...iv.linux.org.uk, adilger@....com, corbet@....net,
	neilb@...e.de, npiggin@...nel.dk, hooanon05@...oo.co.jp,
	miklos@...redi.hu, linux-fsdevel@...r.kernel.org,
	sfrench@...ibm.com, philippe.deniel@....FR,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -V20 02/12] vfs: Add name to file handle conversion
 support

Hi Aneesh,

On Wed, 29 Sep 2010, Aneesh Kumar K. V wrote:

> On Tue, 28 Sep 2010 16:30:45 -0400, "J. Bruce Fields" <bfields@...ldses.org> wrote:
> > By the way, apologies, I can't remember from last time: did you decide
> > that overflow was really the only case when 255 would be returned from
> > exportfs_encode_fs()?
> > 
> 
> All in kernel file system other than cepth return 255 on overflow.
> ceph return -ENOSPC when there is an EOVERFLOW case. (I also
> need to fix Ceph to return minimum handle size). I guess ceph usage was
> correct as per the existing documentation. But the current documentation
> is wrong and all the file system was returning 255 instead of ENOSPC
> 
> We look at the returned handle size of exportfs_encode_fh and determine
> the overflow case in open by handle code. May be i should fix that to
> include both 255 and ENOSPC ?
> 
> 	if ((handle->handle_bytes > f_handle.handle_bytes) ||
> 	    (retval == 255) || (retval == -ENOSPC)) {
> 		/* As per old exportfs_encode_fh documentation
> 		 * we could return ENOSPC to indicate overflow
> 		 * But file system returned 255 always. So handle
> 		 * both the values
> 		 */
> 		/*
> 		 * set the handle_size to zero so we copy only
> 		 * non variable part of the file_handle
> 		 */
> 		handle->handle_bytes = 0;
> 		retval = -EOVERFLOW;
>       }
> 
> Attached ceph change below

This looks good to me.  If ceph is the only one returning ENOSPC we may as 
well fix it there (and in the documentation) and avoid adding an 
additional return code check.  Unless you're worried about out of tree 
file systems?

In any case, I'll add the below patch to the ceph tree.  

Thanks!
sage




> 
> diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> index 4480cb1..e38423e 100644
> --- a/fs/ceph/export.c
> +++ b/fs/ceph/export.c
> @@ -42,32 +42,37 @@ struct ceph_nfs_confh {
>  static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
>  			  int connectable)
>  {
> +	int type;
>  	struct ceph_nfs_fh *fh = (void *)rawfh;
>  	struct ceph_nfs_confh *cfh = (void *)rawfh;
>  	struct dentry *parent = dentry->d_parent;
>  	struct inode *inode = dentry->d_inode;
> -	int type;
> +	int connected_handle_length = sizeof(*cfh)/4;
> +	int handle_length = sizeof(*fh)/4;
>  
>  	/* don't re-export snaps */
>  	if (ceph_snap(inode) != CEPH_NOSNAP)
>  		return -EINVAL;
>  
> -	if (*max_len >= sizeof(*cfh)) {
> +	if (*max_len >= connected_handle_length) {
>  		dout("encode_fh %p connectable\n", dentry);
>  		cfh->ino = ceph_ino(dentry->d_inode);
>  		cfh->parent_ino = ceph_ino(parent->d_inode);
>  		cfh->parent_name_hash = parent->d_name.hash;
> -		*max_len = sizeof(*cfh);
> +		*max_len = connected_handle_length;
>  		type = 2;
> -	} else if (*max_len > sizeof(*fh)) {
> -		if (connectable)
> -			return -ENOSPC;
> +	} else if (*max_len >= handle_length) {
> +		if (connectable) {
> +			*max_len = connected_handle_length;
> +			return 255;
> +		}
>  		dout("encode_fh %p\n", dentry);
>  		fh->ino = ceph_ino(dentry->d_inode);
> -		*max_len = sizeof(*fh);
> +		*max_len = handle_length;
>  		type = 1;
>  	} else {
> -		return -ENOSPC;
> +		*max_len = handle_length;
> +		return 255;
>  	}
>  	return type;
>  }
> 
> -aneesh
> --
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> 
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