This patch add a simple functional test for the "abort" file
in fusectlfs (/sys/fs/fuse/connections/ID/about).

A simple fuse daemon is added for testing.

Related discussion can be found in the link below.

Link: 
https://lore.kernel.org/all/CAOQ4uxjKFXOKQxPpxtS6G_nR0tpw95w0GiO68UcWg_OBhmSY=q...@mail.gmail.com/
Cc: Amir Goldstein <amir7...@gmail.com>
Signed-off-by: Chen Linxuan <chenlinx...@uniontech.com>
Acked-by: Shuah Khan <sk...@linuxfoundation.org>
---
Changes in v3:
- Apply changes suggested by Amir Goldstein
  - Rename the test subdir to filesystems/fuse
  - Verify errno when connection is aborted
- Apply changes suggested by Shuah Khan
  - Update commit message
- Link to v2: 
https://lore.kernel.org/all/20250517012350.10317-2-chenlinx...@uniontech.com/
Changes in v2:
- Apply changes suggested by Amir Goldstein
   - Check errno
- Link to v1: 
https://lore.kernel.org/all/20250515073449.346774-2-chenlinx...@uniontech.com/
---
 MAINTAINERS                                   |   1 +
 tools/testing/selftests/Makefile              |   1 +
 .../selftests/filesystems/fuse/.gitignore     |   3 +
 .../selftests/filesystems/fuse/Makefile       |  21 +++
 .../selftests/filesystems/fuse/fuse_mnt.c     | 146 ++++++++++++++++++
 .../selftests/filesystems/fuse/fusectl_test.c | 116 ++++++++++++++
 6 files changed, 288 insertions(+)
 create mode 100644 tools/testing/selftests/filesystems/fuse/.gitignore
 create mode 100644 tools/testing/selftests/filesystems/fuse/Makefile
 create mode 100644 tools/testing/selftests/filesystems/fuse/fuse_mnt.c
 create mode 100644 tools/testing/selftests/filesystems/fuse/fusectl_test.c

diff --git a/MAINTAINERS b/MAINTAINERS
index dd844ac8d9107..55bf95f06dbb6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9740,6 +9740,7 @@ T:        git 
git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git
 F:     Documentation/filesystems/fuse.rst
 F:     fs/fuse/
 F:     include/uapi/linux/fuse.h
+F:     tools/testing/selftests/filesystems/fuse/
 
 FUTEX SUBSYSTEM
 M:     Thomas Gleixner <t...@linutronix.de>
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 80fb84fa3cfcb..cadd4c217f3e0 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -36,6 +36,7 @@ TARGETS += filesystems/fat
 TARGETS += filesystems/overlayfs
 TARGETS += filesystems/statmount
 TARGETS += filesystems/mount-notify
+TARGETS += filesystems/fuse
 TARGETS += firmware
 TARGETS += fpu
 TARGETS += ftrace
diff --git a/tools/testing/selftests/filesystems/fuse/.gitignore 
b/tools/testing/selftests/filesystems/fuse/.gitignore
new file mode 100644
index 0000000000000..3e72e742d08e8
--- /dev/null
+++ b/tools/testing/selftests/filesystems/fuse/.gitignore
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+fuse_mnt
+fusectl_test
diff --git a/tools/testing/selftests/filesystems/fuse/Makefile 
b/tools/testing/selftests/filesystems/fuse/Makefile
new file mode 100644
index 0000000000000..612aad69a93aa
--- /dev/null
+++ b/tools/testing/selftests/filesystems/fuse/Makefile
@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+CFLAGS += -Wall -O2 -g $(KHDR_INCLUDES)
+
+TEST_GEN_PROGS := fusectl_test
+TEST_GEN_FILES := fuse_mnt
+
+include ../../lib.mk
+
+VAR_CFLAGS := $(shell pkg-config fuse --cflags 2>/dev/null)
+ifeq ($(VAR_CFLAGS),)
+VAR_CFLAGS := -D_FILE_OFFSET_BITS=64 -I/usr/include/fuse
+endif
+
+VAR_LDLIBS := $(shell pkg-config fuse --libs 2>/dev/null)
+ifeq ($(VAR_LDLIBS),)
+VAR_LDLIBS := -lfuse -pthread
+endif
+
+$(OUTPUT)/fuse_mnt: CFLAGS += $(VAR_CFLAGS)
+$(OUTPUT)/fuse_mnt: LDLIBS += $(VAR_LDLIBS)
diff --git a/tools/testing/selftests/filesystems/fuse/fuse_mnt.c 
b/tools/testing/selftests/filesystems/fuse/fuse_mnt.c
new file mode 100644
index 0000000000000..d12b17f30fadc
--- /dev/null
+++ b/tools/testing/selftests/filesystems/fuse/fuse_mnt.c
@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fusectl test file-system
+ * Creates a simple FUSE filesystem with a single read-write file (/test)
+ */
+
+#define FUSE_USE_VERSION 26
+
+#include <fuse.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+
+static char *content;
+static size_t content_size = 0;
+static const char test_path[] = "/test";
+
+static int test_getattr(const char *path, struct stat *st)
+{
+       memset(st, 0, sizeof(*st));
+
+       if (!strcmp(path, "/")) {
+               st->st_mode = S_IFDIR | 0755;
+               st->st_nlink = 2;
+               return 0;
+       }
+
+       if (!strcmp(path, test_path)) {
+               st->st_mode = S_IFREG | 0664;
+               st->st_nlink = 1;
+               st->st_size = content_size;
+               return 0;
+       }
+
+       return -ENOENT;
+}
+
+static int test_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
+                       off_t offset, struct fuse_file_info *fi)
+{
+       if (strcmp(path, "/"))
+               return -ENOENT;
+
+       filler(buf, ".", NULL, 0);
+       filler(buf, "..", NULL, 0);
+       filler(buf, test_path + 1, NULL, 0);
+
+       return 0;
+}
+
+static int test_open(const char *path, struct fuse_file_info *fi)
+{
+       if (strcmp(path, test_path))
+               return -ENOENT;
+
+       return 0;
+}
+
+static int test_read(const char *path, char *buf, size_t size, off_t offset,
+                    struct fuse_file_info *fi)
+{
+       if (strcmp(path, test_path) != 0)
+               return -ENOENT;
+
+       if (!content || content_size == 0)
+               return 0;
+
+       if (offset >= content_size)
+               return 0;
+
+       if (offset + size > content_size)
+               size = content_size - offset;
+
+       memcpy(buf, content + offset, size);
+
+       return size;
+}
+
+static int test_write(const char *path, const char *buf, size_t size,
+                     off_t offset, struct fuse_file_info *fi)
+{
+       size_t new_size;
+
+       if (strcmp(path, test_path) != 0)
+               return -ENOENT;
+
+       if(offset > content_size)
+               return -EINVAL;
+
+       new_size = MAX(offset + size, content_size);
+
+       if (new_size > content_size)
+               content = realloc(content, new_size);
+
+       content_size = new_size;
+
+       if (!content)
+               return -ENOMEM;
+
+       memcpy(content + offset, buf, size);
+
+       return size;
+}
+
+static int test_truncate(const char *path, off_t size)
+{
+       if (strcmp(path, test_path) != 0)
+               return -ENOENT;
+
+       if (size == 0) {
+               free(content);
+               content = NULL;
+               content_size = 0;
+               return 0;
+       }
+
+       content = realloc(content, size);
+
+       if (!content)
+               return -ENOMEM;
+
+       if (size > content_size)
+               memset(content + content_size, 0, size - content_size);
+
+       content_size = size;
+       return 0;
+}
+
+static struct fuse_operations memfd_ops = {
+       .getattr = test_getattr,
+       .readdir = test_readdir,
+       .open = test_open,
+       .read = test_read,
+       .write = test_write,
+       .truncate = test_truncate,
+};
+
+int main(int argc, char *argv[])
+{
+       return fuse_main(argc, argv, &memfd_ops, NULL);
+}
diff --git a/tools/testing/selftests/filesystems/fuse/fusectl_test.c 
b/tools/testing/selftests/filesystems/fuse/fusectl_test.c
new file mode 100644
index 0000000000000..7050fbe0970e7
--- /dev/null
+++ b/tools/testing/selftests/filesystems/fuse/fusectl_test.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright (c) 2025 Chen Linxuan <chenlinx...@uniontech.com>
+
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <linux/limits.h>
+
+#include "../../kselftest_harness.h"
+
+#define FUSECTL_MOUNTPOINT "/sys/fs/fuse/connections"
+#define FUSE_MOUNTPOINT "/tmp/fuse_mnt_XXXXXX"
+#define FUSE_DEVICE "/dev/fuse"
+#define FUSECTL_TEST_VALUE "1"
+
+FIXTURE(fusectl){
+       char fuse_mountpoint[sizeof(FUSE_MOUNTPOINT)];
+       int connection;
+};
+
+FIXTURE_SETUP(fusectl)
+{
+       const char *fuse_mnt_prog = "./fuse_mnt";
+       int status, pid;
+       struct stat statbuf;
+
+       strcpy(self->fuse_mountpoint, FUSE_MOUNTPOINT);
+
+       if (!mkdtemp(self->fuse_mountpoint))
+               SKIP(return,
+                    "Failed to create FUSE mountpoint %s",
+                    strerror(errno));
+
+       if (access(FUSECTL_MOUNTPOINT, F_OK))
+               SKIP(return,
+                    "FUSE control filesystem not mounted");
+
+       pid = fork();
+       if (pid < 0)
+               SKIP(return,
+                    "Failed to fork FUSE daemon process: %s",
+                    strerror(errno));
+
+       if (pid == 0) {
+               execlp(fuse_mnt_prog, fuse_mnt_prog, self->fuse_mountpoint, 
NULL);
+               exit(errno);
+       }
+
+       waitpid(pid, &status, 0);
+       if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+               SKIP(return,
+                    "Failed to start FUSE daemon %s",
+                    strerror(WEXITSTATUS(status)));
+       }
+
+       if (stat(self->fuse_mountpoint, &statbuf))
+               SKIP(return,
+                    "Failed to stat FUSE mountpoint %s",
+                    strerror(errno));
+
+       self->connection = statbuf.st_dev;
+}
+
+FIXTURE_TEARDOWN(fusectl)
+{
+       umount(self->fuse_mountpoint);
+       rmdir(self->fuse_mountpoint);
+}
+
+TEST_F(fusectl, abort)
+{
+       char path_buf[PATH_MAX];
+       int abort_fd, test_fd, ret;
+
+       sprintf(path_buf, "/sys/fs/fuse/connections/%d/abort", 
self->connection);
+
+       ASSERT_EQ(0, access(path_buf, F_OK));
+
+       abort_fd = open(path_buf, O_WRONLY);
+       ASSERT_GE(abort_fd, 0);
+
+       sprintf(path_buf, "%s/test", self->fuse_mountpoint);
+
+       test_fd = open(path_buf, O_RDWR);
+       ASSERT_GE(test_fd, 0);
+
+       ret = read(test_fd, path_buf, sizeof(path_buf));
+       ASSERT_EQ(ret, 0);
+
+       ret = write(test_fd, "test", sizeof("test"));
+       ASSERT_EQ(ret, sizeof("test"));
+
+       ret = lseek(test_fd, 0, SEEK_SET);
+       ASSERT_GE(ret, 0);
+
+       ret = write(abort_fd, FUSECTL_TEST_VALUE, sizeof(FUSECTL_TEST_VALUE));
+       ASSERT_GT(ret, 0);
+
+       close(abort_fd);
+
+       ret = read(test_fd, path_buf, sizeof(path_buf));
+       ASSERT_EQ(ret, -1);
+       ASSERT_EQ(errno, ENOTCONN);
+}
+
+TEST_HARNESS_MAIN
-- 
2.43.0


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