[PATCH TOOLS] fuse: graceful shutdown when startup fails

[PATCH TOOLS] fuse: graceful shutdown when startup fails

[Thomas Bertschinger]

When FUSE startup encounters an error after opening the filesystem--for
example because of a bad mountpoint--it exited uncleanly, which is a
bit unfriendly.

Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
---

Another mitigation could be to check access(2) for the mountpoint before
doing any work...

 c_src/cmd_fusemount.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/c_src/cmd_fusemount.c b/c_src/cmd_fusemount.c
index f43d29f5..50d35832 100644
--- a/c_src/cmd_fusemount.c
+++ b/c_src/cmd_fusemount.c
@@ -1203,6 +1203,7 @@ int cmd_fusemount(int argc, char *argv[])
 	struct bch_opts bch_opts = bch2_opts_empty();
 	struct bf_context ctx = { 0 };
 	struct bch_fs *c = NULL;
+	struct fuse_session *se = NULL;
 	int ret = 0, i;
 
 	/* Parse arguments. */
@@ -1263,17 +1264,22 @@ int cmd_fusemount(int argc, char *argv[])
 		    bch2_err_str(PTR_ERR(c)));
 
 	/* Fuse */
-	struct fuse_session *se =
-		fuse_session_new(&args, &bcachefs_fuse_ops,
-				 sizeof(bcachefs_fuse_ops), c);
-	if (!se)
-		die("fuse_lowlevel_new err: %m");
+	se = fuse_session_new(&args, &bcachefs_fuse_ops,
+				sizeof(bcachefs_fuse_ops), c);
+	if (!se) {
+		fprintf(stderr, "fuse_lowlevel_new err: %m\n");
+		goto err;
+	}
 
-	if (fuse_set_signal_handlers(se) < 0)
-		die("fuse_set_signal_handlers err: %m");
+	if (fuse_set_signal_handlers(se) < 0) {
+		fprintf(stderr, "fuse_set_signal_handlers err: %m\n");
+		goto err;
+	}
 
-	if (fuse_session_mount(se, fuse_opts.mountpoint))
-		die("fuse_mount err: %m");
+	if (fuse_session_mount(se, fuse_opts.mountpoint)) {
+		fprintf(stderr, "fuse_mount err: %m\n");
+		goto err;
+	}
 
 	/* This print statement is a trigger for tests. */
 	printf("Fuse mount initialized.\n");
@@ -1287,17 +1293,22 @@ int cmd_fusemount(int argc, char *argv[])
 
 	ret = fuse_session_loop(se);
 
-	/* Cleanup */
-	fuse_session_unmount(se);
-	fuse_remove_signal_handlers(se);
-	fuse_session_destroy(se);
-
 out:
+	if (se) {
+		fuse_session_unmount(se);
+		fuse_remove_signal_handlers(se);
+		fuse_session_destroy(se);
+	}
+
 	free(fuse_opts.mountpoint);
 	fuse_opt_free_args(&args);
 	bf_context_free(&ctx);
 
 	return ret ? 1 : 0;
+
+err:
+	bch2_fs_stop(c);
+	goto out;
 }
 
 #endif /* BCACHEFS_FUSE */
-- 
2.46.0

Re: [PATCH TOOLS] fuse: graceful shutdown when startup fails

[Kent Overstreet]

On Fri, Oct 04, 2024 at 08:06:54PM GMT, Thomas Bertschinger wrote:
> When FUSE startup encounters an error after opening the filesystem--for
> example because of a bad mountpoint--it exited uncleanly, which is a
> bit unfriendly.
> 
> Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
> ---
> 
> Another mitigation could be to check access(2) for the mountpoint before
> doing any work...

I don't like relying on access(2) because that's racy - this looks nice.

Applied

> 
>  c_src/cmd_fusemount.c | 39 +++++++++++++++++++++++++--------------
>  1 file changed, 25 insertions(+), 14 deletions(-)
> 
> diff --git a/c_src/cmd_fusemount.c b/c_src/cmd_fusemount.c
> index f43d29f5..50d35832 100644
> --- a/c_src/cmd_fusemount.c
> +++ b/c_src/cmd_fusemount.c
> @@ -1203,6 +1203,7 @@ int cmd_fusemount(int argc, char *argv[])
>  	struct bch_opts bch_opts = bch2_opts_empty();
>  	struct bf_context ctx = { 0 };
>  	struct bch_fs *c = NULL;
> +	struct fuse_session *se = NULL;
>  	int ret = 0, i;
>  
>  	/* Parse arguments. */
> @@ -1263,17 +1264,22 @@ int cmd_fusemount(int argc, char *argv[])
>  		    bch2_err_str(PTR_ERR(c)));
>  
>  	/* Fuse */
> -	struct fuse_session *se =
> -		fuse_session_new(&args, &bcachefs_fuse_ops,
> -				 sizeof(bcachefs_fuse_ops), c);
> -	if (!se)
> -		die("fuse_lowlevel_new err: %m");
> +	se = fuse_session_new(&args, &bcachefs_fuse_ops,
> +				sizeof(bcachefs_fuse_ops), c);
> +	if (!se) {
> +		fprintf(stderr, "fuse_lowlevel_new err: %m\n");
> +		goto err;
> +	}
>  
> -	if (fuse_set_signal_handlers(se) < 0)
> -		die("fuse_set_signal_handlers err: %m");
> +	if (fuse_set_signal_handlers(se) < 0) {
> +		fprintf(stderr, "fuse_set_signal_handlers err: %m\n");
> +		goto err;
> +	}
>  
> -	if (fuse_session_mount(se, fuse_opts.mountpoint))
> -		die("fuse_mount err: %m");
> +	if (fuse_session_mount(se, fuse_opts.mountpoint)) {
> +		fprintf(stderr, "fuse_mount err: %m\n");
> +		goto err;
> +	}
>  
>  	/* This print statement is a trigger for tests. */
>  	printf("Fuse mount initialized.\n");
> @@ -1287,17 +1293,22 @@ int cmd_fusemount(int argc, char *argv[])
>  
>  	ret = fuse_session_loop(se);
>  
> -	/* Cleanup */
> -	fuse_session_unmount(se);
> -	fuse_remove_signal_handlers(se);
> -	fuse_session_destroy(se);
> -
>  out:
> +	if (se) {
> +		fuse_session_unmount(se);
> +		fuse_remove_signal_handlers(se);
> +		fuse_session_destroy(se);
> +	}
> +
>  	free(fuse_opts.mountpoint);
>  	fuse_opt_free_args(&args);
>  	bf_context_free(&ctx);
>  
>  	return ret ? 1 : 0;
> +
> +err:
> +	bch2_fs_stop(c);
> +	goto out;
>  }
>  
>  #endif /* BCACHEFS_FUSE */
> -- 
> 2.46.0
>