From f89b634dec4f53482303d72d9248e93dcf4d0b1d Mon Sep 17 00:00:00 2001
From: Xiubo Li <xiubli@redhat.com>
Date: Fri, 29 Mar 2019 10:43:24 +0800
Subject: [PATCH] inotify: watch the directory not just file

Editors (such as vim, nano ..) follow different approaches to save conf file.
The two commonly followed techniques are to overwrite the existing file, or to
write to a new file (.swp, .tmp ..) and move it to actual file name later. In
the later case, the inotify fails, because the file it's been intended to watch
no longer exists, as the new file is a different file with just a same name.

To handle both the file save approaches mentioned above, it is better we watch
the directory and filter for MODIFY events.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
---
 utils/dyn-config.c | 45 +++++++++++++++++++++++++++++----------------
 utils/utils.h      |  3 ++-
 2 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/utils/dyn-config.c b/utils/dyn-config.c
index 0c1a5f3..b645f4f 100644
--- a/utils/dyn-config.c
+++ b/utils/dyn-config.c
@@ -475,7 +475,10 @@ glusterBlockDynConfigStart(void *arg)
   gbConfig *cfg = arg;
   int monitor, wd, len;
   char buf[GB_BUF_LEN];
+  char cfgDir[PATH_MAX];
   struct inotify_event *event;
+  struct timespec mtim = {0, }; /* Time of last modification.  */
+  struct stat statbuf;
   char *p;
 
 
@@ -486,16 +489,26 @@ glusterBlockDynConfigStart(void *arg)
     return NULL;
   }
 
-  wd = inotify_add_watch(monitor, cfg->configPath, IN_ALL_EVENTS);
+  snprintf(cfgDir, PATH_MAX, GB_DEF_CONFIGDIR);
+
+  /* Editors (vim, nano ..) follow different approaches to save conf file.
+   * The two commonly followed techniques are to overwrite the existing
+   * file, or to write to a new file (.swp, .tmp ..) and move it to actual
+   * file name later. In the later case, the inotify fails, because the
+   * file it's been intended to watch no longer exists, as the new file
+   * is a different file with just a same name.
+   * To handle both the file save approaches mentioned above, it is better
+   * we watch the directory and filter for MODIFY events.
+   */
+  wd = inotify_add_watch(monitor, cfgDir, IN_MODIFY);
   if (wd == -1) {
     LOG("mgmt", GB_LOG_ERROR,
-        "Failed to add \"%s\" to inotify (%d)\n", cfg->configPath, monitor);
+        "Failed to add \"%s\" to inotify (%d)\n", cfgDir, monitor);
     return NULL;
   }
 
   LOG("mgmt", GB_LOG_INFO,
-      "Inotify is watching \"%s\", wd: %d, mask: IN_ALL_EVENTS\n",
-      cfg->configPath, wd);
+      "Inotify is watching \"%s\", wd: %d, mask: IN_MODIFY\n", cfgDir, wd);
 
   while (1) {
     len = read(monitor, buf, GB_BUF_LEN);
@@ -504,7 +517,7 @@ glusterBlockDynConfigStart(void *arg)
       continue;
     }
 
-    for (p = buf; p < buf + len;) {
+    for (p = buf; p < buf + len; p += sizeof(*event) + event->len) {
       event = (struct inotify_event *)p;
 
       LOG("mgmt", GB_LOG_INFO, "event->mask: 0x%x\n", event->mask);
@@ -513,25 +526,25 @@ glusterBlockDynConfigStart(void *arg)
         continue;
       }
 
-      /*
-       * If force to write to the unwritable or crashed
-       * config file, the vi/vim will try to move and
-       * delete the config file and then recreate it again
-       * via the *.swp
-       */
-      if ((event->mask & IN_IGNORED) && !access(cfg->configPath, F_OK)) {
-        wd = inotify_add_watch(monitor, cfg->configPath, IN_ALL_EVENTS);
+      /* If stat fails we will skip the modify time check */
+      if (!stat(cfg->configPath, &statbuf)) {
+          if (statbuf.st_mtim.tv_sec == mtim.tv_sec &&
+              statbuf.st_mtim.tv_nsec == mtim.tv_nsec) {
+              continue;
+          }
       }
 
+      mtim.tv_sec = statbuf.st_mtim.tv_sec;
+      mtim.tv_nsec = statbuf.st_mtim.tv_nsec;
+
       /* Try to reload the config file */
-      if (event->mask & IN_MODIFY || event->mask & IN_IGNORED) {
+      if (event->mask & IN_MODIFY) {
         glusterBlockLoadConfig(cfg, true);
       }
-
-      p += sizeof(struct inotify_event) + event->len;
     }
   }
 
+  inotify_rm_watch(monitor, wd);
   return NULL;
 }
 
diff --git a/utils/utils.h b/utils/utils.h
index a2db9ef..a4b42b2 100644
--- a/utils/utils.h
+++ b/utils/utils.h
@@ -57,7 +57,8 @@
 
 # define  GB_METASTORE_RESERVE   10485760   /* 10 MiB reserve for block-meta */
 
-# define  GB_DEF_CONFIGPATH      "/etc/sysconfig/gluster-blockd" /* the default config file */
+# define  GB_DEF_CONFIGDIR       "/etc/sysconfig" /* the default config file directory */
+# define  GB_DEF_CONFIGPATH      GB_DEF_CONFIGDIR"/gluster-blockd" /* the default config file */
 
 # define  GB_TIME_STRING_BUFLEN  \
           (4 + 1 + 2 + 1 + 2 + 1 + 2 + 1 + 2 + 1 + 2 + 1 + 6 + 1 +   5)