Initial code for reporting fake fs size as suggested in #32

TODO

@@ -20,3 +20,7 @@ Minor:
 - Look at capabilities instead of uid==0 when checking for special privileges.
   Do this in a portable way and fall back to uid==0 if not available.
 
+- add real diskspace limiting (quota) besides of ability to report fake size.
+  Maybe there can be even different limit for different paths? dunno.
+  I think it's good idea to have sepparate code for faking reported size and
+  limiting size, so user can decide if he wants both or only one of them.

src/bindfs.1

@@ -277,6 +277,14 @@ only if deleting the target succeeded).  The default is \fBsymlink-only\fP.
 Note that deleting files inside symlinked directories is always possible with
 all settings, including \fBdeny\fP, unless something else protects those files.
 
+.SH SIZE LIMITS AND FAKE SIZE REPORTING
+
+.TP
+.B \-\-size=\fI...\fPM, \-o size=\fI...\fPM
+Report fake FS size of \fB...\fP Megabytes. Note this does not actually limit anything.
+It's experimental feature and it may cause your \fBdf\fP go nuts.
+Currently only \fBM\fP suffix is supported.
+Actual limiting is planned in future.
 
 .SH MISCELLANEOUS OPTIONS
 
@@ -477,6 +485,7 @@ for consistency.
 .SH AUTHOR
 Martin P\[:a]rtel <martin dot partel at gmail dot com>
 
+Contributors: Tomas 'Harvie' Mudrunka (2016 - concept of size limiting and initial code for reporting fake fs size)
 
 .SH SEE ALSO
 \fBchmod\fP(1), \fBfusermount\fP(1), \fBhttp://bindfs.org/\fP

src/bindfs.c

@@ -173,6 +173,8 @@ static struct Settings {
     uid_t uid_offset;
     gid_t gid_offset;
 
+    long bindfs_size; //Maybe it should be unsigned in future, however right now i use -1 to signal it's not used
+
 } settings;
 
 
@@ -1100,6 +1102,24 @@ static int bindfs_statfs(const char *path, struct statvfs *stbuf)
         return -errno;
 
     res = statvfs(real_path, stbuf);
+
+    if(settings.bindfs_size >= 0) {
+        //see: man 3 statvfs
+        //stbuf->f_frsize //block size (used for block to size conversion)
+
+        stbuf->f_blocks = settings.bindfs_size/stbuf->f_frsize; //total size in blocks
+	//We cannot have more free blocks than there are blocks in total:
+        stbuf->f_bfree = stbuf->f_bfree < stbuf->f_blocks ? stbuf->f_bfree : stbuf->f_blocks ; //free blocks
+        stbuf->f_bavail = stbuf->f_bavail < stbuf->f_blocks ? stbuf->f_bavail : stbuf->f_blocks ; //free blocks for unprivileged
+
+	/*
+	//TODO: same for inodes in future (when size limiting will be done)
+        stbuf->f_file = 0; //total size in inodes
+        stbuf->f_ffree = 0; //free inodes
+        stbuf->f_favail = 0; //free inodes for unprivileged
+	*/
+    }
+
     free(real_path);
     if (res == -1)
         return -errno;
@@ -1404,6 +1424,14 @@ static void print_usage(const char *progname)
            "Rate limits:\n"
            "  --read-rate=...           Limit to bytes/sec that can be read.\n"
            "  --write-rate=...          Limit to bytes/sec that can be written.\n"
+           "\n"
+           "Size limits:\n"
+           "  --size=...M               Report fake FS size of ... Megabytes\n"
+           "                            Note this does not actually limit anything\n"
+           "                            and it may cause your df go nuts.\n"
+//           "  --size-limit=...M         Limit usable FS size to ... Megabytes\n"
+//           "                            this defaults to --size, unless you want it to\n"
+//           "                            be different from value reported to df.\n"
            "\n"
            "Miscellaneous:\n"
            "  -n      --no-allow-other  Do not add -o allow_other to fuse options.\n"
@@ -1809,6 +1837,7 @@ int main(int argc, char *argv[])
         int multithreaded;
         char *uid_offset;
         char *gid_offset;
+        char *bindfs_size;
     } od;
 
     #define OPT2(one, two, key) \
@@ -1874,6 +1903,8 @@ int main(int argc, char *argv[])
 
         OPT_OFFSET2("--uid-offset=%s", "uid-offset=%s", uid_offset, 0),
         OPT_OFFSET2("--gid-offset=%s", "gid-offset=%s", gid_offset, 0),
+
+        OPT_OFFSET2("--size=%s", "size=%s", bindfs_size, 0),
         FUSE_OPT_END
     };
 
@@ -1916,6 +1947,7 @@ int main(int argc, char *argv[])
     settings.ctime_from_mtime = 0;
     settings.uid_offset = 0;
     settings.gid_offset = 0;
+    settings.bindfs_size = -1;
 
     atexit(&atexit_func);
 
@@ -2101,6 +2133,13 @@ int main(int argc, char *argv[])
         }
     }
 
+    /* parse size */
+    if (od.bindfs_size) {
+        char* bindfs_size_ptr = od.bindfs_size;
+        settings.bindfs_size = strtoul(od.bindfs_size, &bindfs_size_ptr, 10);
+        //fprintf(stderr, "Activated experimental fake size: %ldM\n", settings.bindfs_size); //Debug
+	settings.bindfs_size *= (1024*1024); //Currently only Megabytes are supported
+    }
 
     /* Single-threaded mode by default */
     if (!od.multithreaded) {