Re: [PATCH v3 3/4] nfsd: pass info about the legacy recoverydir in environment variables

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Oct 24, 2012 at 10:30:17AM -0400, Jeff Layton wrote:
> The usermodehelper upcall program can then decide to use this info as
> a (one-way) transition mechanism to the new scheme. When a "check"
> upcall occurs and the client doesn't exist in the database, we can
> look to see whether the directory exists. If it does, then we'd add
> the client to the database, remove the legacy recdir, and return
> success to the kernel to allow the recovery to proceed.
> 
> For gracedone, we simply pass the v4recovery "topdir" so that the
> upcall can clean it out prior to returning to the kernel.

I don't understand why the kernel needs to be involved here--can't
userspace find the old directory on its own?

--b.

> 
> A module parm is also added to disable the legacy conversion if
> the admin chooses.
> 
> Signed-off-by: Jeff Layton <jlayton@redhat.com>
> ---
>  fs/nfsd/nfs4recover.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 82 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
> index aa165fd..782168d 100644
> --- a/fs/nfsd/nfs4recover.c
> +++ b/fs/nfsd/nfs4recover.c
> @@ -932,10 +932,75 @@ module_param_string(cltrack_prog, cltrack_prog, sizeof(cltrack_prog),
>  			S_IRUGO|S_IWUSR);
>  MODULE_PARM_DESC(cltrack_prog, "Path to the nfsdcltrack upcall program");
>  
> +static bool cltrack_legacy_disable;
> +module_param(cltrack_legacy_disable, bool, S_IRUGO|S_IWUSR);
> +MODULE_PARM_DESC(cltrack_legacy_disable,
> +		"Disable legacy recoverydir conversion. Default: false");
> +
> +#define LEGACY_TOPDIR_ENV_PREFIX "NFSDCLTRACK_LEGACY_TOPDIR="
> +#define LEGACY_RECDIR_ENV_PREFIX "NFSDCLTRACK_LEGACY_RECDIR="
> +
> +static char *
> +nfsd4_cltrack_legacy_topdir(void)
> +{
> +	int copied;
> +	size_t len;
> +	char *result;
> +
> +	if (cltrack_legacy_disable)
> +		return NULL;
> +
> +	len = strlen(LEGACY_TOPDIR_ENV_PREFIX) +
> +		strlen(nfs4_recoverydir()) + 1;
> +
> +	result = kmalloc(len, GFP_KERNEL);
> +	if (!result)
> +		return result;
> +
> +	copied = snprintf(result, len, LEGACY_TOPDIR_ENV_PREFIX "%s",
> +				nfs4_recoverydir());
> +	if (copied >= len) {
> +		/* just return nothing if output was truncated */
> +		kfree(result);
> +		return NULL;
> +	}
> +
> +	return result;
> +}
> +
> +static char *
> +nfsd4_cltrack_legacy_recdir(const char *recdir)
> +{
> +	int copied;
> +	size_t len;
> +	char *result;
> +
> +	if (cltrack_legacy_disable)
> +		return NULL;
> +
> +	/* +1 is for '/' between "topdir" and "recdir" */
> +	len = strlen(LEGACY_RECDIR_ENV_PREFIX) +
> +		strlen(nfs4_recoverydir()) + 1 + HEXDIR_LEN;
> +
> +	result = kmalloc(len, GFP_KERNEL);
> +	if (!result)
> +		return result;
> +
> +	copied = snprintf(result, len, LEGACY_RECDIR_ENV_PREFIX "%s/%s",
> +				nfs4_recoverydir(), recdir);
> +	if (copied >= len) {
> +		/* just return nothing if output was truncated */
> +		kfree(result);
> +		return NULL;
> +	}
> +
> +	return result;
> +}
> +
>  static int
> -nfsd4_umh_cltrack_upcall(char *cmd, char *arg)
> +nfsd4_umh_cltrack_upcall(char *cmd, char *arg, char *legacy)
>  {
> -	char *envp[] = { NULL };
> +	char *envp[2];
>  	char *argv[4];
>  	int ret;
>  
> @@ -946,6 +1011,10 @@ nfsd4_umh_cltrack_upcall(char *cmd, char *arg)
>  
>  	dprintk("%s: cmd: %s\n", __func__, cmd);
>  	dprintk("%s: arg: %s\n", __func__, arg ? arg : "(null)");
> +	dprintk("%s: legacy: %s\n", __func__, legacy ? legacy : "(null)");
> +
> +	envp[0] = legacy;
> +	envp[1] = NULL;
>  
>  	argv[0] = (char *)cltrack_prog;
>  	argv[1] = cmd;
> @@ -991,7 +1060,7 @@ bin_to_hex_dup(const unsigned char *src, int srclen)
>  static int
>  nfsd4_umh_cltrack_init(struct net __attribute__((unused)) *net)
>  {
> -	return nfsd4_umh_cltrack_upcall("init", NULL);
> +	return nfsd4_umh_cltrack_upcall("init", NULL, NULL);
>  }
>  
>  static void
> @@ -1004,7 +1073,7 @@ nfsd4_umh_cltrack_create(struct nfs4_client *clp)
>  		dprintk("%s: can't allocate memory for upcall!\n", __func__);
>  		return;
>  	}
> -	nfsd4_umh_cltrack_upcall("create", hexid);
> +	nfsd4_umh_cltrack_upcall("create", hexid, NULL);
>  	kfree(hexid);
>  }
>  
> @@ -1018,7 +1087,7 @@ nfsd4_umh_cltrack_remove(struct nfs4_client *clp)
>  		dprintk("%s: can't allocate memory for upcall!\n", __func__);
>  		return;
>  	}
> -	nfsd4_umh_cltrack_upcall("remove", hexid);
> +	nfsd4_umh_cltrack_upcall("remove", hexid, NULL);
>  	kfree(hexid);
>  }
>  
> @@ -1026,14 +1095,16 @@ static int
>  nfsd4_umh_cltrack_check(struct nfs4_client *clp)
>  {
>  	int ret;
> -	char *hexid;
> +	char *hexid, *legacy;
>  
>  	hexid = bin_to_hex_dup(clp->cl_name.data, clp->cl_name.len);
>  	if (!hexid) {
>  		dprintk("%s: can't allocate memory for upcall!\n", __func__);
>  		return -ENOMEM;
>  	}
> -	ret = nfsd4_umh_cltrack_upcall("check", hexid);
> +	legacy = nfsd4_cltrack_legacy_recdir(clp->cl_recdir);
> +	ret = nfsd4_umh_cltrack_upcall("check", hexid, legacy);
> +	kfree(legacy);
>  	kfree(hexid);
>  	return ret;
>  }
> @@ -1042,10 +1113,13 @@ static void
>  nfsd4_umh_cltrack_grace_done(struct net __attribute__((unused)) *net,
>  				time_t boot_time)
>  {
> +	char *legacy;
>  	char timestr[22]; /* FIXME: better way to determine max size? */
>  
>  	sprintf(timestr, "%ld", boot_time);
> -	nfsd4_umh_cltrack_upcall("gracedone", timestr);
> +	legacy = nfsd4_cltrack_legacy_topdir();
> +	nfsd4_umh_cltrack_upcall("gracedone", timestr, legacy);
> +	kfree(legacy);
>  }
>  
>  static struct nfsd4_client_tracking_ops nfsd4_umh_tracking_ops = {
> -- 
> 1.7.11.7
>