Increase default kbufsz to 1 MiB; don't die on ENOBUFS (but spam)

Signed-off-by: Laurent Bercot <ska@appnovation.com>

5 files changed, 18 insertions, 13 deletions

diff --git a/doc/mdevd-coldplug.html b/doc/mdevd-coldplug.html
index 36654eb..b26d4c9 100644
--- a/doc/mdevd-coldplug.html
+++ b/doc/mdevd-coldplug.html
@@ -28,7 +28,7 @@ for all these devices.
 <h2> Interface </h2>
 
 <pre>
-     mdevd-coldplug [ -v <em>verbosity</em> ] [ -s <em>slashsys</em> ] [ -O <em>nlgroup</em> ] [ -b <em>kbufsize</em> ]
+     mdevd-coldplug [ -v <em>verbosity</em> ] [ -s <em>slashsys</em> ] [ -O <em>nlgroup</em> ] [ -b <em>kbufsz</em> ]
 </pre>
 
 <ul>
@@ -57,8 +57,8 @@ if <a href="mdevd.html">mdevd</a> is running with a similar <tt>-O</tt>
 option with a compatible value; else, <tt>mdevd-coldplug</tt> will wait
 forever. </li>
  <li> <tt>-b</tt>&nbsp;<em>kbufsz</em>&nbsp;: try and reserve a kernel buffer of
-<em>kbufsz</em> bytes for the netlink queue. The default is 500 kB;
-if you're getting "No buffer space available" errors, try increasing this number.
+<em>kbufsz</em> bytes for the netlink queue. The default is 1 MiB;
+if you're getting related warnings on stderr, try increasing this number.
 This option is only meaningful when paired with the <tt>-O</tt> option. </li>
 </ul>
 
diff --git a/doc/mdevd.html b/doc/mdevd.html
index ca39b02..7c2a869 100644
--- a/doc/mdevd.html
+++ b/doc/mdevd.html
@@ -119,9 +119,9 @@ cause a loop by chaining two separate instances of mdevd. mdevd will protect
 you against accidents, not against intentional stupidity.) </li>
  <li> <tt>-b</tt>&nbsp;<em>kbufsz</em>&nbsp;: try and reserve a kernel buffer of
 <em>kbufsz</em> bytes for the netlink queue. Too large a buffer wastes kernel memory;
-too small a buffer risks losing events. The default is <strong>512288</strong>,
-meaning 500 kB, which should be
-enough for most systems; if you're getting "No buffer space available" errors
+too small a buffer risks losing events. The default is <strong>1048576</strong>,
+meaning 1 MiB, which should be
+enough for most systems; if you're getting "missed events" warnings
 from mdevd at coldplug time, try increasing this number. </li>
  <li> <tt>-n</tt>&nbsp;: dry run. mdevd will not create or delete
 device nodes, and it will not spawn commands. Instead, it will print to stdout
diff --git a/src/mdevd/mdevd-coldplug.c b/src/mdevd/mdevd-coldplug.c
index 6b8953f..1dd0982 100644
--- a/src/mdevd/mdevd-coldplug.c
+++ b/src/mdevd/mdevd-coldplug.c
@@ -15,7 +15,7 @@
 
 #include "mdevd-internal.h"
 
-#define USAGE "mdevd-coldplug [ -v verbosity ] [ -s slashsys ] [ -O nlgroup ] [ -b kbufsize ]"
+#define USAGE "mdevd-coldplug [ -v verbosity ] [ -s slashsys ] [ -O nlgroup ] [ -b kbufsz ]"
 #define dieusage() strerr_dieusage(100, USAGE)
 
 static char subsystem[PATH_MAX] = "" ;
@@ -95,7 +95,7 @@ int main (int argc, char const *const *argv, char const *const *envp)
   char const *slashsys = "/sys" ;
   unsigned int verbosity = 1 ;
   unsigned int nlgroup = 0 ;
-  unsigned int kbufsz = 512288 ;
+  unsigned int kbufsz = 1048576 ;
   int nlfd = -1 ;
   PROG = "mdevd-coldplug" ;
   {
diff --git a/src/mdevd/mdevd.c b/src/mdevd/mdevd.c
index 6b82874..f5222f7 100644
--- a/src/mdevd/mdevd.c
+++ b/src/mdevd/mdevd.c
@@ -904,7 +904,7 @@ int main (int argc, char const *const *argv)
   char const *configfile = "/etc/mdev.conf" ;
   iopause_fd x[2] = { { .events = IOPAUSE_READ }, { .events = IOPAUSE_READ } } ;
   unsigned int notif = 0 ;
-  unsigned int kbufsz = 512288 ;
+  unsigned int kbufsz = 1048576 ;
   char const *slashdev = "/dev" ;
   int docoldplug = 0 ;
   unsigned int intake = 1 ;
diff --git a/src/mdevd/mdevd_uevent_read.c b/src/mdevd/mdevd_uevent_read.c
index 1c84f2d..38be5ea 100644
--- a/src/mdevd/mdevd_uevent_read.c
+++ b/src/mdevd/mdevd_uevent_read.c
@@ -38,10 +38,15 @@ static inline size_t netlink_read (int fd, char *s, uint32_t options, unsigned i
     .msg_controllen = 0,
     .msg_flags = 0
   } ;
-  ssize_t r = sanitize_read(fd_recvmsg(fd, &msg)) ;
-  if (r < 0)
-    strerr_diefu1sys(111, "receive netlink message") ;
-  if (!r) return 0 ;
+  ssize_t r ;
+  for (;;)
+  {
+    r = sanitize_read(fd_recvmsg(fd, &msg)) ;
+    if (r > 0) break ;
+    if (!r) return 0 ;
+    if (errno != ENOBUFS) strerr_diefu1sys(111, "read netlink message") ;
+    strerr_warnw1x("missed events! you should increase the -b kbufsz value") ;
+  }
   if (msg.msg_flags & MSG_TRUNC)
     strerr_diefu1x(111, "buffer too small for netlink message") ;
   if (options & 1 && nl.nl_pid)