mirror of
https://github.com/libfuse/libfuse.git
synced 2026-07-07 14:47:41 +08:00
Bernd Schubert
3a3dd7b02d
fuse_set_conn_flag() collects the libfuse-side connection hints that are not negotiated with the kernel. no_interrupt was the one such hint still set only by direct field assignment. Define FUSE_CONN_FLAG_NO_INTERRUPT alongside FUSE_CONN_FLAG_SINGLE_ISSUER and map it onto conn->no_interrupt in the same switch, and convert the example init() handlers to set it through the setter. Signed-off-by: Bernd Schubert <bernd@bsbernd.com>
430 lines
12 KiB
C
430 lines
12 KiB
C
/*
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FUSE: Filesystem in Userspace
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Copyright (C) 2016 Nikolaus Rath <Nikolaus@rath.org>
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This program can be distributed under the terms of the GNU GPLv2.
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See the file GPL2.txt.
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*/
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/** @file
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*
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* This example implements a file system with a single file whose
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* file name changes dynamically to reflect the current time.
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*
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* It illustrates the use of the fuse_lowlevel_notify_inval_entry() and
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* fuse_lowlevel_notify_expire_entry() functions.
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*
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* To see the effect, first start the file system with the
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* ``--no-notify``
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*
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* $ notify_inval_entry --update-interval=1 --timeout=30 --no-notify mnt/
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*
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* Observe that `ls` always prints the correct directory contents
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* (since `readdir` output is not cached)::
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*
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* $ ls mnt; sleep 1; ls mnt; sleep 1; ls mnt
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* Time_is_15h_48m_33s current_time
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* Time_is_15h_48m_34s current_time
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* Time_is_15h_48m_35s current_time
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*
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* However, if you try to access a file by name the kernel will
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* report that it still exists:
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*
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* $ file=$(ls mnt/); echo $file
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* Time_is_15h_50m_09s
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* $ sleep 5; stat mnt/$file
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* File: ‘mnt/Time_is_15h_50m_09s’
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* Size: 32 Blocks: 0 IO Block: 4096 regular file
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* Device: 2ah/42d Inode: 3 Links: 1
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* Access: (0444/-r--r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
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* Access: 1969-12-31 16:00:00.000000000 -0800
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* Modify: 1969-12-31 16:00:00.000000000 -0800
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* Change: 1969-12-31 16:00:00.000000000 -0800
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* Birth: -
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*
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* Only once the kernel cache timeout has been reached will the stat
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* call fail:
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*
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* $ sleep 30; stat mnt/$file
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* stat: cannot stat ‘mnt/Time_is_15h_50m_09s’: No such file or directory
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*
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* In contrast, if you enable notifications you will be unable to stat
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* the file as soon as the file system updates its name:
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*
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* $ notify_inval_entry --update-interval=1 --timeout=30 mnt/
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* $ file=$(ls mnt/); stat mnt/$file
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* File: ‘mnt/Time_is_20h_42m_11s’
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* Size: 0 Blocks: 0 IO Block: 4096 regular empty file
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* Device: 2ah/42d Inode: 2 Links: 1
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* Access: (0000/----------) Uid: ( 0/ root) Gid: ( 0/ root)
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* Access: 1969-12-31 16:00:00.000000000 -0800
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* Modify: 1969-12-31 16:00:00.000000000 -0800
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* Change: 1969-12-31 16:00:00.000000000 -0800
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* Birth: -
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* $ sleep 1; stat mnt/$file
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* stat: cannot stat ‘mnt/Time_is_20h_42m_11s’: No such file or directory
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*
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* To use the function fuse_lowlevel_notify_expire_entry() instead of
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* fuse_lowlevel_notify_inval_entry(), use the command line option --only-expire
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*
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* Another possible command-line option is --inc-epoch, which will use the FUSE
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* low-level function fuse_lowlevel_notify_increment_epoch() instead. This will
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* function will force the invalidation of all dentries next time they are
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* revalidated. Note that --inc-epoch and --only-expire options are mutually
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* exclusive.
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*
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* ## Compilation ##
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*
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* gcc -Wall notify_inval_entry.c `pkg-config fuse3 --cflags --libs` -o notify_inval_entry
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*
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* ## Source code ##
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* \include notify_inval_entry.c
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*/
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#define FUSE_USE_VERSION FUSE_MAKE_VERSION(3, 12)
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#include <fuse_lowlevel.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <assert.h>
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#include <signal.h>
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#include <stddef.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <pthread.h>
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#define MAX_STR_LEN 128
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static char file_name[MAX_STR_LEN];
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static fuse_ino_t file_ino = 2;
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static int lookup_cnt = 0;
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static pthread_t main_thread;
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/* Command line parsing */
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struct options {
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int no_notify;
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float timeout;
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int update_interval;
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int only_expire;
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int inc_epoch;
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};
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static struct options options = {
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.timeout = 5,
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.no_notify = 0,
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.update_interval = 1,
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.only_expire = 0,
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.inc_epoch = 0,
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};
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#define OPTION(t, p) \
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{ t, offsetof(struct options, p), 1 }
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static const struct fuse_opt option_spec[] = {
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OPTION("--no-notify", no_notify),
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OPTION("--update-interval=%d", update_interval),
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OPTION("--timeout=%f", timeout),
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OPTION("--only-expire", only_expire),
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OPTION("--inc-epoch", inc_epoch),
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FUSE_OPT_END
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};
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static int tfs_stat(fuse_ino_t ino, struct stat *stbuf) {
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stbuf->st_ino = ino;
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if (ino == FUSE_ROOT_ID) {
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stbuf->st_mode = S_IFDIR | 0755;
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stbuf->st_nlink = 1;
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}
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else if (ino == file_ino) {
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stbuf->st_mode = S_IFREG | 0000;
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stbuf->st_nlink = 1;
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stbuf->st_size = 0;
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}
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else
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return -1;
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return 0;
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}
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static void tfs_init(void *userdata, struct fuse_conn_info *conn) {
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(void)userdata;
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fuse_set_conn_flag(conn, FUSE_CONN_FLAG_SINGLE_ISSUER);
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/* Disable the receiving and processing of FUSE_INTERRUPT requests */
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fuse_set_conn_flag(conn, FUSE_CONN_FLAG_NO_INTERRUPT);
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}
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static void tfs_lookup(fuse_req_t req, fuse_ino_t parent,
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const char *name) {
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struct fuse_entry_param e;
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memset(&e, 0, sizeof(e));
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if (parent != FUSE_ROOT_ID)
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goto err_out;
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else if (strcmp(name, file_name) == 0) {
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e.ino = file_ino;
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lookup_cnt++;
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} else
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goto err_out;
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e.attr_timeout = options.timeout;
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e.entry_timeout = options.timeout;
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if (tfs_stat(e.ino, &e.attr) != 0)
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goto err_out;
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fuse_reply_entry(req, &e);
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return;
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err_out:
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fuse_reply_err(req, ENOENT);
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}
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static void tfs_forget (fuse_req_t req, fuse_ino_t ino,
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uint64_t nlookup) {
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(void) req;
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if(ino == file_ino)
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lookup_cnt -= nlookup;
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else
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assert(ino == FUSE_ROOT_ID);
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fuse_reply_none(req);
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}
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static void tfs_getattr(fuse_req_t req, fuse_ino_t ino,
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struct fuse_file_info *fi) {
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struct stat stbuf;
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(void) fi;
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memset(&stbuf, 0, sizeof(stbuf));
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if (tfs_stat(ino, &stbuf) != 0)
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fuse_reply_err(req, ENOENT);
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else
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fuse_reply_attr(req, &stbuf, options.timeout);
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}
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struct dirbuf {
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char *p;
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size_t size;
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};
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static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
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fuse_ino_t ino) {
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struct stat stbuf;
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size_t oldsize = b->size;
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b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
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b->p = (char *) realloc(b->p, b->size);
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memset(&stbuf, 0, sizeof(stbuf));
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stbuf.st_ino = ino;
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fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
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b->size);
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}
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#define min(x, y) ((x) < (y) ? (x) : (y))
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static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
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off_t off, size_t maxsize) {
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if (off < bufsize)
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return fuse_reply_buf(req, buf + off,
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min(bufsize - off, maxsize));
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else
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return fuse_reply_buf(req, NULL, 0);
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}
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static void tfs_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
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off_t off, struct fuse_file_info *fi) {
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(void) fi;
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if (ino != FUSE_ROOT_ID)
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fuse_reply_err(req, ENOTDIR);
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else {
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struct dirbuf b;
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memset(&b, 0, sizeof(b));
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dirbuf_add(req, &b, file_name, file_ino);
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reply_buf_limited(req, b.p, b.size, off, size);
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free(b.p);
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}
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}
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static const struct fuse_lowlevel_ops tfs_oper = {
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.init = tfs_init,
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.lookup = tfs_lookup,
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.getattr = tfs_getattr,
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.readdir = tfs_readdir,
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.forget = tfs_forget,
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};
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static void update_fs(void) {
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time_t t;
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struct tm *now;
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ssize_t ret;
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t = time(NULL);
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now = localtime(&t);
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assert(now != NULL);
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ret = strftime(file_name, MAX_STR_LEN,
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"Time_is_%Hh_%Mm_%Ss", now);
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assert(ret != 0);
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}
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static void* update_fs_loop(void *data) {
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struct fuse_session *se = (struct fuse_session*) data;
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char *old_name;
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int ret = 0;
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while(!fuse_session_exited(se)) {
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old_name = strdup(file_name);
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update_fs();
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if (!options.no_notify && lookup_cnt) {
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if(options.only_expire) { // expire entry
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ret = fuse_lowlevel_notify_expire_entry
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(se, FUSE_ROOT_ID, old_name, strlen(old_name));
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// no kernel support
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if (ret == -ENOSYS) {
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printf("fuse_lowlevel_notify_expire_entry not supported by kernel\n");
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break;
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}
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// 1) ret == 0: successful expire of an existing entry
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// 2) ret == -ENOENT: kernel has already expired the entry /
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// entry does not exist anymore in the kernel
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assert(ret == 0 || ret == -ENOENT);
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} else if (options.inc_epoch) { // increment epoch
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ret = fuse_lowlevel_notify_increment_epoch(se);
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if (ret == -ENOSYS) {
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printf("fuse_lowlevel_notify_increment_epoch not supported by kernel\n");
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break;
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}
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assert(ret == 0);
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} else { // invalidate entry
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assert(fuse_lowlevel_notify_inval_entry
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(se, FUSE_ROOT_ID, old_name, strlen(old_name)) == 0);
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}
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}
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free(old_name);
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sleep(options.update_interval);
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}
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if (ret == -ENOSYS) {
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printf("Exiting...\n");
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fuse_session_exit(se);
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// Make sure to exit now, rather than on next request from userspace
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pthread_kill(main_thread, SIGPIPE);
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}
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return NULL;
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}
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static void show_help(const char *progname)
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{
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printf("usage: %s [options] <mountpoint>\n\n", progname);
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printf("File-system specific options:\n"
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" --timeout=<secs> Timeout for kernel caches\n"
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" --update-interval=<secs> Update-rate of file system contents\n"
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" --no-notify Disable kernel notifications\n"
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" --only-expire Expire entries instead of invalidating them\n"
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" --inc-epoch Increment epoch, invalidating all dentries\n"
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"\n");
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}
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int main(int argc, char *argv[]) {
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struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
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struct fuse_session *se;
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struct fuse_cmdline_opts opts;
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struct fuse_loop_config *config;
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pthread_t updater;
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int ret = -1;
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if (fuse_opt_parse(&args, &options, option_spec, NULL) == -1)
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return 1;
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if (fuse_parse_cmdline(&args, &opts) != 0)
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return 1;
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if (opts.show_help) {
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show_help(argv[0]);
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fuse_cmdline_help();
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fuse_lowlevel_help();
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ret = 0;
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goto err_out1;
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} else if (opts.show_version) {
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printf("FUSE library version %s\n", fuse_pkgversion());
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fuse_lowlevel_version();
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ret = 0;
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goto err_out1;
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}
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if (options.only_expire && options.inc_epoch) {
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printf("'only-expire' and 'inc-epoch' options are exclusive\n");
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ret = 0;
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goto err_out1;
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}
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/* Initial contents */
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update_fs();
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se = fuse_session_new(&args, &tfs_oper,
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sizeof(tfs_oper), &se);
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if (se == NULL)
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goto err_out1;
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if (fuse_set_signal_handlers(se) != 0)
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goto err_out2;
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if (fuse_session_mount(se, opts.mountpoint) != 0)
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goto err_out3;
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fuse_daemonize(opts.foreground);
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// Needed to ensure that the main thread continues/restarts processing as soon
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// as the fuse session ends (immediately after calling fuse_session_exit() )
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// and not only on the next request from userspace
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main_thread = pthread_self();
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/* Start thread to update file contents */
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ret = pthread_create(&updater, NULL, update_fs_loop, (void *)se);
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if (ret != 0) {
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fprintf(stderr, "pthread_create failed with %s\n",
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strerror(ret));
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goto err_out3;
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}
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/* Block until ctrl+c or fusermount -u */
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if (opts.singlethread) {
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ret = fuse_session_loop(se);
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} else {
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config = fuse_loop_cfg_create();
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fuse_loop_cfg_set_clone_fd(config, opts.clone_fd);
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fuse_loop_cfg_set_max_threads(config, opts.max_threads);
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ret = fuse_session_loop_mt(se, config);
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fuse_loop_cfg_destroy(config);
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config = NULL;
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}
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fuse_session_unmount(se);
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err_out3:
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fuse_remove_signal_handlers(se);
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err_out2:
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fuse_session_destroy(se);
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err_out1:
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free(opts.mountpoint);
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fuse_opt_free_args(&args);
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return ret ? 1 : 0;
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}
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/**
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* Local Variables:
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* mode: c
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* indent-tabs-mode: nil
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* c-basic-offset: 4
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* End:
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*/
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