Re: [RFC] vfs_parse_fs_string() calling conventions change (was Re: [PATCH v2 17/35] sanitize handling of long-term internal mounts)

[Al Viro <viro@xxxxxxxxxxxxxxxxxx>]

On Sat, Jun 28, 2025 at 05:28:25PM +0100, Al Viro wrote:
> On Sat, Jun 28, 2025 at 08:58:49AM +0100, Al Viro wrote:
> > Yes, it's a flagday change.  Compiler will immediately catch any place
> > that needs to be converted, and D/f/porting.rst part should be clear
> > enough.
> > 
> > How about something like the following (completely untested), on top of -rc3?
> > Objections, anyone?
>  
> After fixing a braino (s/QSTR_INIT/QSTR_LEN/) it even builds and seems to work...

While we are at it, there are at least some open-coded instances.  IMO
that part of do_nfs4_mount() is better this way, and I wonder if we should
add vfs_parse_fs_printf(fc, key, fmt, ...) as well...

diff --git a/fs/nfs/nfs4super.c b/fs/nfs/nfs4super.c
index b29a26923ce0..92ac12cee26e 100644
--- a/fs/nfs/nfs4super.c
+++ b/fs/nfs/nfs4super.c
@@ -158,12 +158,6 @@ static int do_nfs4_mount(struct nfs_server *server,
 		.dirfd	= -1,
 	};
 
-	struct fs_parameter param_fsc = {
-		.key	= "fsc",
-		.type	= fs_value_is_string,
-		.dirfd	= -1,
-	};
-
 	if (IS_ERR(server))
 		return PTR_ERR(server);
 
@@ -181,15 +175,7 @@ static int do_nfs4_mount(struct nfs_server *server,
 	root_ctx->server = server;
 
 	if (ctx->fscache_uniq) {
-		len = strlen(ctx->fscache_uniq);
-		param_fsc.size = len;
-		param_fsc.string = kmemdup_nul(ctx->fscache_uniq, len, GFP_KERNEL);
-		if (param_fsc.string == NULL) {
-			put_fs_context(root_fc);
-			return -ENOMEM;
-		}
-		ret = vfs_parse_fs_param(root_fc, &param_fsc);
-		kfree(param_fsc.string);
+		ret = vfs_parse_fs_string(root_fc, "fsc", ctx->fscache_uniq);
 		if (ret < 0) {
 			put_fs_context(root_fc);
 			return ret;