Renamed timefsN examples to fuse_notify_*

This should make it more obvious at first glance what the different
examples do.

1 files changed, 373 insertions, 0 deletions

diff --git a/example/notify_inval_inode.c b/example/notify_inval_inode.c
new file mode 100644
index 0000000..5dfc225
--- /dev/null
+++ b/example/notify_inval_inode.c
@@ -0,0 +1,373 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2016 Nikolaus Rath <Nikolaus@rath.org>
+
+  This program can be distributed under the terms of the GNU GPL.
+  See the file COPYING.
+*/
+
+/** @file
+ * @tableofcontents
+ *
+ * This example implements a file system with a single file whose
+ * contents change dynamically: it always contains the current time.
+ *
+ * While notify_store_retrieve.c uses fuse_lowlevel_notify_store() to
+ * actively push the updated data into the kernel cache, this example
+ * uses fuse_lowlevel_notify_inval_inode() to notify the kernel that
+ * the cache has to be invalidated - but the kernel still has to
+ * explicitly request the updated data on the next read.
+ *
+ * To see the effect, first start the file system with the
+ *  ``--no-notify`` option:
+ *
+ *     $ notify_inval_inode --update-interval=1 --no-notify mnt/
+ *
+ * Observe that the output never changes, even though the file system
+ * updates it once per second. This is because the contents are cached
+ * in the kernel:
+ *
+ *     $ for i in 1 2 3 4 5; do
+ *     >     cat mnt/current_time
+ *     >     sleep 1
+ *     > done
+ *     The current time is 15:58:18
+ *     The current time is 15:58:18
+ *     The current time is 15:58:18
+ *     The current time is 15:58:18
+ *     The current time is 15:58:18
+ *
+ * If you instead enable the notification functions, the changes become
+ * visible:
+ *
+ *      $ notify_inval_inode --update-interval=1 mnt/
+ *      $ for i in 1 2 3 4 5; do
+ *      >     cat mnt/current_time
+ *      >     sleep 1
+ *      > done
+ *      The current time is 15:58:40
+ *      The current time is 15:58:41
+ *      The current time is 15:58:42
+ *      The current time is 15:58:43
+ *      The current time is 15:58:44
+ *
+ * \section section_compile compiling this example
+ *
+ *     gcc -Wall notify_inval_inode.c `pkg-config fuse3 --cflags --libs` -o notify_inval_inode
+ *
+ * \section section_source the complete source
+ * \include notify_inval_inode.c
+ */
+
+
+#define FUSE_USE_VERSION 30
+
+#include <config.h>
+
+#include <fuse_lowlevel.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <stddef.h>
+#include <unistd.h>
+#include <pthread.h>
+
+/* We can't actually tell the kernel that there is no
+   timeout, so we just send a big value */
+#define NO_TIMEOUT 500000
+
+/* We cannot check directly if e.g. O_RDONLY is set, since this is not
+ * an individual bit (cf. open(2)) */
+#define ACCESS_MASK (O_RDONLY | O_WRONLY | O_RDWR)
+
+#define MAX_STR_LEN 128
+#define FILE_INO 2
+#define FILE_NAME "current_time"
+static char file_contents[MAX_STR_LEN];
+static int lookup_cnt = 0;
+static size_t file_size;
+
+/* Command line parsing */
+struct options {
+    int no_notify;
+    int update_interval;
+};
+static struct options options = {
+    .no_notify = 0,
+    .update_interval = 1,
+};
+
+#define OPTION(t, p)                           \
+    { t, offsetof(struct options, p), 1 }
+static const struct fuse_opt option_spec[] = {
+    OPTION("--no-notify", no_notify),
+    OPTION("--update-interval=%d", update_interval),
+    FUSE_OPT_END
+};
+
+static int opt_proc(void *data, const char *arg, int key,
+                    struct fuse_args *outargs) {
+    (void) outargs; (void) data; (void) arg;
+    (void) key;
+    return 1;
+}
+
+static int tfs_stat(fuse_ino_t ino, struct stat *stbuf) {
+    stbuf->st_ino = ino;
+    if (ino == FUSE_ROOT_ID) {
+        stbuf->st_mode = S_IFDIR | 0755;
+        stbuf->st_nlink = 1;
+    }
+
+    else if (ino == FILE_INO) {
+        stbuf->st_mode = S_IFREG | 0444;
+        stbuf->st_nlink = 1;
+        stbuf->st_size = file_size;
+    }
+
+    else
+        return -1;
+
+    return 0;
+}
+
+static void tfs_lookup(fuse_req_t req, fuse_ino_t parent,
+                       const char *name) {
+    struct fuse_entry_param e;
+    memset(&e, 0, sizeof(e));
+
+    if (parent != FUSE_ROOT_ID)
+        goto err_out;
+    else if (strcmp(name, FILE_NAME) == 0) {
+        e.ino = FILE_INO;
+        lookup_cnt++;
+    } else
+        goto err_out;
+
+    e.attr_timeout = NO_TIMEOUT;
+    e.entry_timeout = NO_TIMEOUT;
+    if (tfs_stat(e.ino, &e.attr) != 0)
+        goto err_out;
+    fuse_reply_entry(req, &e);
+    return;
+
+err_out:
+    fuse_reply_err(req, ENOENT);
+}
+
+static void tfs_forget (fuse_req_t req, fuse_ino_t ino,
+                        uint64_t nlookup) {
+    (void) req;
+    assert(ino == FILE_INO || ino == FUSE_ROOT_ID);
+    lookup_cnt -= nlookup;
+    fuse_reply_none(req);
+}
+
+static void tfs_getattr(fuse_req_t req, fuse_ino_t ino,
+                        struct fuse_file_info *fi) {
+    struct stat stbuf;
+
+    (void) fi;
+
+    memset(&stbuf, 0, sizeof(stbuf));
+    if (tfs_stat(ino, &stbuf) != 0)
+        fuse_reply_err(req, ENOENT);
+    else
+        fuse_reply_attr(req, &stbuf, NO_TIMEOUT);
+}
+
+struct dirbuf {
+    char *p;
+    size_t size;
+};
+
+static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
+                       fuse_ino_t ino) {
+    struct stat stbuf;
+    size_t oldsize = b->size;
+    b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
+    b->p = (char *) realloc(b->p, b->size);
+    memset(&stbuf, 0, sizeof(stbuf));
+    stbuf.st_ino = ino;
+    fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
+                      b->size);
+}
+
+#define min(x, y) ((x) < (y) ? (x) : (y))
+
+static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
+                             off_t off, size_t maxsize) {
+    if (off < bufsize)
+        return fuse_reply_buf(req, buf + off,
+                              min(bufsize - off, maxsize));
+    else
+        return fuse_reply_buf(req, NULL, 0);
+}
+
+static void tfs_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
+                        off_t off, struct fuse_file_info *fi) {
+    (void) fi;
+
+    if (ino != FUSE_ROOT_ID)
+        fuse_reply_err(req, ENOTDIR);
+    else {
+        struct dirbuf b;
+
+        memset(&b, 0, sizeof(b));
+        dirbuf_add(req, &b, FILE_NAME, FILE_INO);
+        reply_buf_limited(req, b.p, b.size, off, size);
+        free(b.p);
+    }
+}
+
+static void tfs_open(fuse_req_t req, fuse_ino_t ino,
+                     struct fuse_file_info *fi) {
+
+    /* Make cache persistent even if file is closed,
+       this makes it easier to see the effects */
+    fi->keep_cache = 1;
+
+    if (ino == FUSE_ROOT_ID)
+        fuse_reply_err(req, EISDIR);
+    else if ((fi->flags & ACCESS_MASK) != O_RDONLY)
+        fuse_reply_err(req, EACCES);
+    else if (ino == FILE_INO)
+        fuse_reply_open(req, fi);
+    else {
+        // This should not happen
+        fprintf(stderr, "Got open for non-existing inode!\n");
+        fuse_reply_err(req, ENOENT);
+    }
+}
+
+static void tfs_read(fuse_req_t req, fuse_ino_t ino, size_t size,
+                     off_t off, struct fuse_file_info *fi) {
+    (void) fi;
+
+    assert(ino == FILE_INO);
+    reply_buf_limited(req, file_contents, file_size, off, size);
+}
+
+static struct fuse_lowlevel_ops tfs_oper = {
+    .lookup	= tfs_lookup,
+    .getattr	= tfs_getattr,
+    .readdir	= tfs_readdir,
+    .open	= tfs_open,
+    .read	= tfs_read,
+    .forget     = tfs_forget,
+};
+
+static void* update_fs(void *data) {
+    struct fuse_session *se = (struct fuse_session*) data;
+    struct tm *now;
+    time_t t;
+
+    while(1) {
+        t = time(NULL);
+        now = localtime(&t);
+        assert(now != NULL);
+
+        file_size = strftime(file_contents, MAX_STR_LEN,
+                             "The current time is %H:%M:%S\n", now);
+        assert(file_size != 0);
+        if (!options.no_notify && lookup_cnt) {
+            /* Only send notification if the kernel
+               is aware of the inode */
+            assert(fuse_lowlevel_notify_inval_inode
+                   (se, FILE_INO, 0, 0) == 0);
+        }
+        sleep(options.update_interval);
+    }
+    return NULL;
+}
+
+static void show_help(const char *progname)
+{
+    printf("usage: %s [options] <mountpoint>\n\n", progname);
+    printf("File-system specific options:\n"
+               "    --update-interval=<secs>  Update-rate of file system contents\n"
+               "    --no-notify            Disable kernel notifications\n"
+               "\n");
+}
+
+int main(int argc, char *argv[]) {
+    struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
+    struct fuse_session *se;
+    struct fuse_cmdline_opts opts;
+    pthread_t updater;
+    int ret = -1;
+
+    if (fuse_opt_parse(&args, &options, option_spec,
+                       opt_proc) == -1)
+        return 1;
+
+    if (fuse_parse_cmdline(&args, &opts) != 0) {
+        ret = 1;
+        goto err_out1;
+    }
+
+    if (opts.show_help) {
+        show_help(argv[0]);
+        fuse_cmdline_help();
+        fuse_lowlevel_help();
+        fuse_mount_help();
+        ret = 0;
+        goto err_out1;
+    } else if (opts.show_version) {
+        printf("FUSE library version %s\n", fuse_pkgversion());
+        fuse_lowlevel_version();
+        fuse_mount_version();
+        ret = 0;
+        goto err_out1;
+    }
+
+    se = fuse_session_new(&args, &tfs_oper,
+                          sizeof(tfs_oper), NULL);
+    if (se == NULL)
+        goto err_out1;
+
+    if (fuse_set_signal_handlers(se) != 0)
+        goto err_out2;
+
+    if (fuse_session_mount(se, opts.mountpoint) != 0)
+        goto err_out3;
+
+    fuse_daemonize(opts.foreground);
+
+    /* Start thread to update file contents */
+    ret = pthread_create(&updater, NULL, update_fs, (void *)se);
+    if (ret != 0) {
+        fprintf(stderr, "pthread_create failed with %s\n",
+                strerror(ret));
+        goto err_out3;
+    }
+
+    /* Block until ctrl+c or fusermount -u */
+    if (opts.singlethread)
+        ret = fuse_session_loop(se);
+    else
+        ret = fuse_session_loop_mt(se);
+
+    fuse_session_unmount(se);
+err_out3:
+    fuse_remove_signal_handlers(se);
+err_out2:
+    fuse_session_destroy(se);
+err_out1:
+    fuse_opt_free_args(&args);
+    free(opts.mountpoint);
+
+    return ret ? 1 : 0;
+}
+
+
+/**
+ * Local Variables:
+ * mode: c
+ * indent-tabs-mode: nil
+ * c-basic-offset: 4
+ * End:
+ */