glusterd rebalance: handle the write failure properly

also, make sure the sizes are same before renaming the target file
to the original file, hence prevent a possible data-loss.

Change-Id: Ie88224ba62a4604f8c0149f84fa462abfbd6ad78
BUG: 3193
Reviewed-on: http://review.gluster.com/29
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vijay@gluster.com>

xlators/mgmt/glusterd/src/glusterd-rebalance.c

@@ -154,9 +154,11 @@ gf_glusterd_rebalance_move_data (glusterd_volinfo_t *volinfo, const char *dir)
         struct dirent          *entry              = NULL;
         struct stat             stbuf              = {0,};
         struct stat             new_stbuf          = {0,};
+        struct stat             dst_stbuf          = {0,};
         char                    full_path[1024]    = {0,};
         char                    tmp_filename[1024] = {0,};
         char                    value[16]          = {0,};
+        char                    file_not_copied_fully  = 0;
 
         if (!volinfo->defrag)
                 goto out;
@@ -210,24 +212,25 @@ gf_glusterd_rebalance_move_data (glusterd_volinfo_t *volinfo, const char *dir)
 
                 while (1) {
                         ret = read (src_fd, defrag->databuf, 131072);
-                        if (!ret || (ret < 0)) {
+                        if (ret < 0) {
+                                file_not_copied_fully = 1;
                                 break;
                         }
+                        /* If EOF is hit, then we get 'ret == 0' */
+                        if (!ret)
+                                break;
+
                         ret = write (dst_fd, defrag->databuf, ret);
                         if (ret < 0) {
+                                file_not_copied_fully = 1;
                                 break;
                         }
                 }
 
-                ret = lstat (full_path, &new_stbuf);
-                if (ret < 0) {
-                        close (dst_fd);
-                        close (src_fd);
-                        continue;
-                }
-                /* No need to rebalance, if there is some
-                   activity on source file */
-                if (new_stbuf.st_mtime != stbuf.st_mtime) {
+                if (file_not_copied_fully) {
+                        gf_log (THIS->name, GF_LOG_WARNING,
+                                "failed to copy the file fully : %s (%s)",
+                                full_path, strerror (errno));
                         close (dst_fd);
                         close (src_fd);
                         continue;
@@ -254,6 +257,46 @@ gf_glusterd_rebalance_move_data (glusterd_volinfo_t *volinfo, const char *dir)
                                 tmp_filename, strerror (errno));
                 }
 
+                ret = fstat (src_fd, &new_stbuf);
+                if (ret < 0) {
+                        gf_log (THIS->name, GF_LOG_WARNING,
+                                "failed to get stat: %s (%s)",
+                                full_path, strerror (errno));
+                        close (dst_fd);
+                        close (src_fd);
+                        continue;
+                }
+
+                ret = fstat (dst_fd, &dst_stbuf);
+                if (ret < 0) {
+                        gf_log (THIS->name, GF_LOG_WARNING,
+                                "failed to get stat on temp file: %s (%s)",
+                                tmp_filename, strerror (errno));
+                        close (dst_fd);
+                        close (src_fd);
+                        continue;
+                }
+
+                /* No need to rebalance, if there is some
+                   activity on source file */
+                if (new_stbuf.st_mtime != stbuf.st_mtime) {
+                        gf_log (THIS->name, GF_LOG_WARNING,
+                                "file got changed after we started copying %s",
+                                full_path);
+                        close (dst_fd);
+                        close (src_fd);
+                        continue;
+                }
+
+                if (new_stbuf.st_size != dst_stbuf.st_size) {
+                        gf_log (THIS->name, GF_LOG_WARNING,
+                                "file sizes are not same : %s",
+                                full_path);
+                        close (dst_fd);
+                        close (src_fd);
+                        continue;
+                }
+
                 ret = rename (tmp_filename, full_path);
                 if (ret != -1) {
                         LOCK (&defrag->lock);