On Wed, Sep 16, 2026 at 5:55 PM Luis Henriques <[email protected]> wrote: > > This patch adds a simple test that allows to verify that, when resolving a > symlink, user-space is called only the first time when caching is enabled > or, if caching is disabled, every time the symlink resolution is requested. > > Signed-off-by: Luis Henriques <[email protected]> > --- > .../selftests/filesystems/fuse/.gitignore | 1 + > .../selftests/filesystems/fuse/Makefile | 2 + > .../fuse/fuse_symlink_cache_test.c | 163 ++++++++++++++++++ > 3 files changed, 166 insertions(+) > create mode 100644 > tools/testing/selftests/filesystems/fuse/fuse_symlink_cache_test.c > > diff --git a/tools/testing/selftests/filesystems/fuse/.gitignore > b/tools/testing/selftests/filesystems/fuse/.gitignore > index f7f3dd345a50..ebfe7133d811 100644 > --- a/tools/testing/selftests/filesystems/fuse/.gitignore > +++ b/tools/testing/selftests/filesystems/fuse/.gitignore > @@ -3,3 +3,4 @@ fuse_mnt > fusectl_test > write_extend_eof_test > fuse_acl_cache_test > +fuse_symlink_cache_test > diff --git a/tools/testing/selftests/filesystems/fuse/Makefile > b/tools/testing/selftests/filesystems/fuse/Makefile > index 7744f796eb06..3a5a557dde7a 100644 > --- a/tools/testing/selftests/filesystems/fuse/Makefile > +++ b/tools/testing/selftests/filesystems/fuse/Makefile > @@ -5,6 +5,7 @@ CFLAGS += -Wall -O2 -g $(KHDR_INCLUDES) > TEST_GEN_PROGS := fusectl_test > TEST_GEN_PROGS += write_extend_eof_test > TEST_GEN_PROGS += fuse_acl_cache_test > +TEST_GEN_PROGS += fuse_symlink_cache_test > TEST_GEN_FILES := fuse_mnt > > include ../../lib.mk > @@ -28,5 +29,6 @@ $(OUTPUT)/fuse_mnt: CFLAGS += $(VAR_CFLAGS) > $(OUTPUT)/fuse_mnt: LDLIBS += $(VAR_LDLIBS) > > $(OUTPUT)/fuse_acl_cache_test: fuse_common.c fuse_acl_cache_test.c > +$(OUTPUT)/fuse_symlink_cache_test: fuse_common.c fuse_symlink_cache_test.c > > EXTRA_CLEAN := fuse_common.o > diff --git > a/tools/testing/selftests/filesystems/fuse/fuse_symlink_cache_test.c > b/tools/testing/selftests/filesystems/fuse/fuse_symlink_cache_test.c > new file mode 100644 > index 000000000000..dd001736ebca > --- /dev/null > +++ b/tools/testing/selftests/filesystems/fuse/fuse_symlink_cache_test.c > @@ -0,0 +1,163 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Simple filesystem to test FUSE symlink cache > + * > + * This is a simple FUSE filesystem that contains two objects: a file named > + * 'file' and a symlink to that file named 'link'. If symlink caching is > + * disabled (i.e. FUSE_CAP_CACHE_SYMLINKS is reset during FUSE_INIT), > whenever > + * the ->readlink() is executed to resolve 'link' a counter will be > incremented. > + * > + * If symlink caching is enabled (i.e. FUSE_CAP_CACHE_SYMLINKS is set during > + * FUSE_INIT), resolving a symlink will only call into user-space the first > + * time. > + */ > + > +#define FUSE_USE_VERSION 31 > + > +#include <stdio.h> > +#include <fuse_lowlevel.h> > + > +#include "kselftest_harness.h" > + > +#include "fuse_common.h" > + > +#define FILENAME "file" > +#define FILE_INO 42 > + > +#define LINKNAME "link" > +#define LINK_INO 43 > + > +#define TIMEOUT 86400.0f > + > +struct test_state { > + pthread_mutex_t lock; > + struct fuse_common_ctx ctx; > + int readlink_counter; > + bool cache; > +} test_state = { > + .lock = PTHREAD_MUTEX_INITIALIZER, > +}; > + > +static void fs_init(void *userdata, struct fuse_conn_info *conn) > +{ > + pthread_mutex_lock(&test_state.lock); > + if (test_state.cache) > + fuse_set_feature_flag(conn, FUSE_CAP_CACHE_SYMLINKS); > + else > + fuse_unset_feature_flag(conn, FUSE_CAP_CACHE_SYMLINKS); > + pthread_mutex_unlock(&test_state.lock); > +} > + > +static void fs_lookup(fuse_req_t req, fuse_ino_t parent, const char *name) > +{ > + struct fuse_entry_param e = {}; > + > + if (parent != FUSE_ROOT_ID || > + (strcmp(name, FILENAME) != 0 && strcmp(name, LINKNAME) != 0)) { > + fuse_reply_err(req, ENOENT); > + return; > + } > + > + if (!strcmp(name, FILENAME)) { > + e.ino = FILE_INO; > + e.attr.st_mode = S_IFREG | 0444; > + e.attr.st_nlink = 2; > + } else if (!strcmp(name, LINKNAME)) { > + e.ino = LINK_INO; > + e.attr.st_mode = S_IFLNK | 0444; > + e.attr.st_nlink = 1; > + e.attr.st_size = strlen(FILENAME); > + } > + e.attr_timeout = TIMEOUT; > + e.entry_timeout = TIMEOUT; > + > + fuse_reply_entry(req, &e); > +} > + > +static void fs_readlink(fuse_req_t req, fuse_ino_t ino) > +{ > + char buf[PATH_MAX]; > + size_t sz = strlen(FILENAME); > + > + if (ino != LINK_INO) { > + fuse_reply_err(req, ENOENT); > + return; > + } > + > + memcpy(buf, FILENAME, sz); > + buf[sz] = '\0'; > + pthread_mutex_lock(&test_state.lock); > + test_state.readlink_counter++; > + pthread_mutex_unlock(&test_state.lock); > + > + fuse_reply_readlink(req, buf); > +} > + > +static const struct fuse_lowlevel_ops fs_ops = { > + .init = fs_init, > + .lookup = fs_lookup, > + .readlink = fs_readlink, > +}; > + > +FIXTURE(symlink_cache) {}; > +FIXTURE_VARIANT(symlink_cache) > +{ > + const bool cache; > +}; > +FIXTURE_VARIANT_ADD(symlink_cache, symlinks_nocache) > +{ > + /* Variant with symlink cache disabled */ > + .cache = false, > +}; > +FIXTURE_VARIANT_ADD(symlink_cache, symlinks_cache) > +{ > + /* Variant with symlink cache enabled */ > + .cache = true, > +}; > + > +FIXTURE_SETUP(symlink_cache) > +{ > + char err[MAX_ERR_MSG]; > + > + pthread_mutex_lock(&test_state.lock); > + test_state.readlink_counter = 0; > + test_state.cache = variant->cache; > + > + if (fs_setup(&fs_ops, &test_state.ctx, err)) > + SKIP(goto out, err); > +out: > + pthread_mutex_unlock(&test_state.lock); > +} > + > +FIXTURE_TEARDOWN(symlink_cache) > +{ > + pthread_mutex_lock(&test_state.lock); > + fs_teardown(&test_state.ctx); > + pthread_mutex_unlock(&test_state.lock); > +} > +
Here too, unless you have a good reason not to, please put fuse_common_ctx in the test fixture object. With that fix, feel free to add Reviewed-by: Amir Goldstein <[email protected]> Thanks, Amir. > +TEST_F(symlink_cache, test_symlink_cache) > +{ > + char pathname[PATH_MAX]; > + char buf[PATH_MAX]; > + ssize_t sz; > + int counter; > + int i; > + > + sprintf(pathname, "%s/%s", test_state.ctx.mountpoint, LINKNAME); > + for (i = 0; i < 100; i++) { > + sz = readlink(pathname, buf, PATH_MAX); > + ASSERT_NE(sz, -1); > + } > + pthread_mutex_lock(&test_state.lock); > + counter = test_state.readlink_counter; > + pthread_mutex_unlock(&test_state.lock); > + > + if (variant->cache) { > + ASSERT_EQ(counter, 1); > + } else { > + ASSERT_EQ(counter, 100); > + } > +} > + > +TEST_HARNESS_MAIN
