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

[nbd.git] / nbd-server.c

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;
        }