Add "temporary" option, and ability to create files.

This commit:
* Adds a "temporary" option, which causes a unique file to be
  created, which is unliked as soon as it is created (and thus
  will not be present on exit). This is used for creation of
  temporary disks.
* Will create a file, if "filesize" is specified and the file
  is not present or is zero length (useful in conjunction with the
  above).

diff --git a/man/nbd-server.5.in.sgml b/man/nbd-server.5.in.sgml
index c9f618d..6947035 100644 (file)
--- a/man/nbd-server.5.in.sgml
+++ b/man/nbd-server.5.in.sgml
@@ -264,7 +264,12 @@ manpage.1: manpage.sgml
          <para>
            The name of the file (or block device) that will be
            exported. This must be a fully-qualified path and filename;
-           relative paths are not allowed.
+           relative paths are not allowed. If used in conjunction with
+           the <option>temporary</option>, this specifies a template
+           for the temporary file concerned, and thus can be used
+           to control the directory it is created in. If the file
+           does not exist, but <option>filesize</option> is set, then
+           the file will be created.
          </para>
          <para>
            Note that <command>nbd-server</command> will only try to
@@ -292,7 +297,27 @@ manpage.1: manpage.sgml
            bytes. If the <option>multifile</option> option is in
            effect, this option specifies the size of the
            <emphasis>entire</emphasis> export, not of individual
-           files.
+           files. If the file is not present, a single file is
+           created of this size.
+         </para>
+         <para>When specified on the command line, this should be the
+           third argument.
+         </para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term><option>temporary</option></term>
+       <listitem>
+         <para>Optional; boolean.</para>
+         <para>
+           Create a temporary export with a name based on exportname
+           (this can be used to set the directory). A unique filename
+           is created, which is unlinked as soon as it is created,
+           and therefore the export will not persist between
+           invocations of <command>nbd-server</command>. Se the
+           size of the file using the <command>filesize</command>
+           option. This option is incompatible with the
+           <option>multifile</option> option.
          </para>
          <para>When specified on the command line, this should be the
            third argument.

diff --git a/nbd-server.c b/nbd-server.c
index aea5d2f..5725af7 100644 (file)
--- a/nbd-server.c
+++ b/nbd-server.c
@@ -160,6 +160,7 @@ int dontfork = 0;
 #define F_FLUSH 128      /**< Whether server wants FLUSH to be sent by the client */
 #define F_FUA 256        /**< Whether server wants FUA to be sent by the client */
 #define F_ROTATIONAL 512  /**< Whether server wants the client to implement the elevator algorithm */
+#define F_TEMPORARY 1024  /**< Whether the backing file is temporary and should be created then unlinked */
 GHashTable *children;
 char pidfname[256]; /**< name of our PID file */
 char pidftemplate[256]; /**< template to be used for the filename of the PID file */
@@ -774,6 +775,7 @@ GArray* parse_cfile(gchar* f, GError** e) {
                { "flush",      FALSE,  PARAM_BOOL,     &(s.flags),             F_FLUSH },
                { "fua",        FALSE,  PARAM_BOOL,     &(s.flags),             F_FUA },
                { "rotational", FALSE,  PARAM_BOOL,     &(s.flags),             F_ROTATIONAL },
+               { "temporary",  FALSE,  PARAM_BOOL,     &(s.flags),             F_TEMPORARY },
                { "listenaddr", FALSE,  PARAM_STRING,   &(s.listenaddr),        0 },
                { "maxconnections", FALSE, PARAM_INT,   &(s.max_connections),   0 },
        };
@@ -1021,7 +1023,9 @@ off_t size_autodetect(int fhandle) {
        stat_buf.st_size = 0;
        error = fstat(fhandle, &stat_buf);
        if (!error) {
-               if(stat_buf.st_size > 0)
+               /* always believe stat if a regular file as it might really
+                * be zero length */
+               if (S_ISREG(stat_buf.st_mode) || (stat_buf.st_size > 0))
                        return (off_t)stat_buf.st_size;
         } else {
                 err("fstat failed: %m");
@@ -1644,6 +1648,8 @@ void setupexport(CLIENT* client) {
        int i;
        off_t laststartoff = 0, lastsize = 0;
        int multifile = (client->server->flags & F_MULTIFILE);
+       int temporary = (client->server->flags & F_TEMPORARY) && !multifile;
+       int cancreate = (client->server->expected_size) && !multifile;
 
        client->export = g_array_new(TRUE, TRUE, sizeof(FILE_INFO));
 
@@ -1654,24 +1660,35 @@ void setupexport(CLIENT* client) {
                FILE_INFO fi;
                gchar *tmpname;
                gchar* error_string;
-               mode_t mode = (client->server->flags & F_READONLY) ? O_RDONLY : O_RDWR;
 
-               if(multifile) {
-                       tmpname=g_strdup_printf("%s.%d", client->exportname, i);
+               if (i)
+                 cancreate = 0;
+               /* if expected_size is specified, and this is the first file, we can create the file */
+               mode_t mode = (client->server->flags & F_READONLY) ?
+                 O_RDONLY : (O_RDWR | (cancreate?O_CREAT:0));
+
+               if (temporary) {
+                       tmpname=g_strdup_printf("%s.%d-XXXXXX", client->exportname, i);
+                       DEBUG( "Opening %s\n", tmpname );
+                       fi.fhandle = mkstemp(tmpname);
                } else {
-                       tmpname=g_strdup(client->exportname);
-               }
-               DEBUG( "Opening %s\n", tmpname );
-               fi.fhandle = open(tmpname, mode);
-               if(fi.fhandle == -1 && mode == O_RDWR) {
-                       /* Try again because maybe media was read-only */
-                       fi.fhandle = open(tmpname, O_RDONLY);
-                       if(fi.fhandle != -1) {
-                               /* Opening the base file in copyonwrite mode is
-                                * okay */
-                               if(!(client->server->flags & F_COPYONWRITE)) {
-                                       client->server->flags |= F_AUTOREADONLY;
-                                       client->server->flags |= F_READONLY;
+                       if(multifile) {
+                               tmpname=g_strdup_printf("%s.%d", client->exportname, i);
+                       } else {
+                               tmpname=g_strdup(client->exportname);
+                       }
+                       DEBUG( "Opening %s\n", tmpname );
+                       fi.fhandle = open(tmpname, mode, 0x600);
+                       if(fi.fhandle == -1 && mode == O_RDWR) {
+                               /* Try again because maybe media was read-only */
+                               fi.fhandle = open(tmpname, O_RDONLY);
+                               if(fi.fhandle != -1) {
+                                       /* Opening the base file in copyonwrite mode is
+                                        * okay */
+                                       if(!(client->server->flags & F_COPYONWRITE)) {
+                                               client->server->flags |= F_AUTOREADONLY;
+                                               client->server->flags |= F_READONLY;
+                                       }
                                }
                        }
                }
@@ -1683,6 +1700,10 @@ void setupexport(CLIENT* client) {
                                tmpname);
                        err(error_string);
                }
+
+               if (temporary)
+                       unlink(tmpname); /* File will stick around whilst FD open */
+
                fi.startoff = laststartoff + lastsize;
                g_array_append_val(client->export, fi);
                g_free(tmpname);
@@ -1692,7 +1713,17 @@ void setupexport(CLIENT* client) {
                laststartoff = fi.startoff;
                lastsize = size_autodetect(fi.fhandle);
 
-               if(!multifile)
+               /* If we created the file, it will be length zero */
+               if (!lastsize && cancreate) {
+                       /* we can ignore errors as we recalculate the size */
+                       ftruncate (fi.fhandle, client->server->expected_size);
+                       lastsize = size_autodetect(fi.fhandle);
+                       if (lastsize != client->server->expected_size)
+                               err("Could not expand file");
+                       break; /* don't look for any more files */
+               }
+
+               if(!multifile || temporary)
                        break;
        }
 

diff --git a/simple_test b/simple_test
index c790311..a25eafd 100755 (executable)
--- a/simple_test
+++ b/simple_test
@@ -140,9 +140,9 @@ EOF
        flush = true
        fua = true
        rotational = true
+       filesize = 52428800
+       temporary = true
 EOF
-               # we need a bigger disk
-               dd if=/dev/zero of=$tmpnam bs=1M count=50 >/dev/null 2>&1
                ./nbd-server -C ${conffile} -p ${pidfile} &
                PID=$!
                sleep 1
@@ -158,9 +158,9 @@ EOF
        flush = true
        fua = true
        rotational = true
+       filesize = 52428800
+       temporary = true
 EOF
-               # we need a bigger disk
-               dd if=/dev/zero of=$tmpnam bs=1M count=50 >/dev/null 2>&1
                ./nbd-server -C ${conffile} -p ${pidfile} &
                PID=$!
                sleep 1