[dm-devel] [PATCH 01/15] multipathd: warn when configuration has been changed.
Benjamin Marzinski
bmarzins at redhat.com
Wed Jan 22 11:59:11 UTC 2020
On Fri, Jan 17, 2020 at 03:45:34PM +0000, Martin Wilck wrote:
> On Thu, 2020-01-16 at 20:18 -0600, Benjamin Marzinski wrote:
> > It would be helpful if multipathd could log a message when
> > multipath.conf or files in the config_dir have been written to, both
> > so
> > that it can be used to send a notification to users, and to help with
> > determining after the fact if multipathd was running with an older
> > config, when the logs of multipathd's behaviour don't match with the
> > current multipath.conf.
> >
> > To do this, the multipathd uxlsnr thread now sets up inotify watches
> > on
> > both /etc/multipath.conf and the config_dir to watch if the files are
> > deleted or closed after being opened for writing. In order to keep
> > uxlsnr from polling repeatedly if the multipath.conf or the
> > config_dir
> > aren't present, it will only set up the watches once per reconfigure.
> > However, since multipath.conf is far more likely to be replaced by a
> > text editor than modified in place, if it gets removed, multipathd
> > will
> > immediately try to restart the watch on it (which will succeed if the
> > file was simply replaced by a new copy). This does mean that if
> > multipath.conf or the config_dir are actually removed and then later
> > re-added, multipathd won't log any more messages for changes until
> > the
> > next reconfigure. But that seems like a fair trade-off to avoid
> > repeatedly polling for files that aren't likely to appear.
> >
> > Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
> > ---
> > libmultipath/config.h | 1 +
> > multipathd/main.c | 1 +
> > multipathd/uxlsnr.c | 134
> > ++++++++++++++++++++++++++++++++++++++++--
> > 3 files changed, 130 insertions(+), 6 deletions(-)
>
> I know I reviewed this already, but this time I have some more remarks,
> mostly style.
Sure. I can do all these.
-Ben
>
> >
> > diff --git a/libmultipath/config.h b/libmultipath/config.h
> > index ffec3103..e69aa07c 100644
> > --- a/libmultipath/config.h
> > +++ b/libmultipath/config.h
> > @@ -188,6 +188,7 @@ struct config {
> > int find_multipaths_timeout;
> > int marginal_pathgroups;
> > unsigned int version[3];
> > + unsigned int sequence_nr;
> >
> > char * multipath_dir;
> > char * selector;
> > diff --git a/multipathd/main.c b/multipathd/main.c
> > index 34a57689..7b364cfe 100644
> > --- a/multipathd/main.c
> > +++ b/multipathd/main.c
> > @@ -2618,6 +2618,7 @@ reconfigure (struct vectors * vecs)
> > uxsock_timeout = conf->uxsock_timeout;
> >
> > old = rcu_dereference(multipath_conf);
> > + conf->sequence_nr = old->sequence_nr + 1;
> > rcu_assign_pointer(multipath_conf, conf);
> > call_rcu(&old->rcu, rcu_free_config);
> >
> > diff --git a/multipathd/uxlsnr.c b/multipathd/uxlsnr.c
> > index bc71679e..92d9a79a 100644
> > --- a/multipathd/uxlsnr.c
> > +++ b/multipathd/uxlsnr.c
> > @@ -23,6 +23,7 @@
> > #include <sys/time.h>
> > #include <signal.h>
> > #include <stdbool.h>
> > +#include <sys/inotify.h>
> > #include "checkers.h"
> > #include "memory.h"
> > #include "debug.h"
> > @@ -51,6 +52,8 @@ struct client {
> > LIST_HEAD(clients);
> > pthread_mutex_t client_lock = PTHREAD_MUTEX_INITIALIZER;
> > struct pollfd *polls;
> > +int notify_fd = -1;
> > +char *config_dir;
>
> Nit: please declare these as static, as they are used only in this
> file. Also, naming the variable differently, e.g. conf_dir, would
> decrease the number of false hits when grepping for the variable name.
>
> >
> > static bool _socket_client_is_root(int fd);
> >
> > @@ -151,6 +154,8 @@ void uxsock_cleanup(void *arg)
> > long ux_sock = (long)arg;
> >
> > close(ux_sock);
> > + close(notify_fd);
> > + free(config_dir);
> >
> > pthread_mutex_lock(&client_lock);
> > list_for_each_entry_safe(client_loop, client_tmp, &clients,
> > node) {
> > @@ -162,6 +167,106 @@ void uxsock_cleanup(void *arg)
> > free_polls();
> > }
> >
> > +/* failing to set the watch descriptor is o.k. we just miss a
> > warning
> > + * message */
> > +void reset_watch(int notify_fd, int *wds, unsigned int *sequence_nr)
>
> This function could also be static.
>
> > +{
> > + struct config *conf;
> > + int dir_reset = 0;
> > + int conf_reset = 0;
> > +
> > + if (notify_fd == -1)
> > + return;
> > +
> > + conf = get_multipath_config();
> > + /* instead of repeatedly try to reset the inotify watch if
> > + * the config directory or multipath.conf isn't there, just
> > + * do it once per reconfigure */
> > + if (*sequence_nr != conf->sequence_nr) {
> > + *sequence_nr = conf->sequence_nr;
> > + if (wds[0] == -1)
> > + conf_reset = 1;
> > + if (!config_dir || !conf->config_dir ||
> > + strcmp(config_dir, conf->config_dir)) {
> > + dir_reset = 1;
> > + if (config_dir)
> > + free(config_dir);
> > + if (conf->config_dir)
> > + config_dir = strdup(conf->config_dir);
> > + else
> > + config_dir = NULL;
> > + } else if (wds[1] == -1)
> > + dir_reset = 1;
> > + }
> > + put_multipath_config(conf);
> > +
> > + if (dir_reset) {
> > + if (wds[1] != -1) {
> > + inotify_rm_watch(notify_fd, wds[1]);
> > + wds[1] = -1;
> > + }
> > + if (config_dir) {
> > + wds[1] = inotify_add_watch(notify_fd,
> > config_dir,
> > + IN_CLOSE_WRITE |
> > IN_DELETE |
> > + IN_ONLYDIR);
> > + if (wds[1] == -1)
> > + condlog(3, "didn't set up notifications
> > on %s: %s", config_dir, strerror(errno));
>
> Another nitpick: IMO we should be using "%m" for this in new code.
>
> > + }
> > + }
> > + if (conf_reset) {
> > + wds[0] = inotify_add_watch(notify_fd,
> > DEFAULT_CONFIGFILE,
> > + IN_CLOSE_WRITE);
> > + if (wds[0] == -1)
> > + condlog(3, "didn't set up notifications on
> > /etc/multipath.conf: %s", strerror(errno));
> > + }
> > + return;
> > +}
> > +
> > +void handle_inotify(int fd, int *wds)
>
> Again, static.
>
> > +{
> > + char buff[1024]
> > + __attribute__ ((aligned(__alignof__(struct
> > inotify_event))));
> > + const struct inotify_event *event;
> > + ssize_t len;
> > + char *ptr;
> > + int i, got_notify = 0;
> > +
> > + for (;;) {
> > + len = read(fd, buff, sizeof(buff));
> > + if (len <= 0) {
> > + if (len < 0 && errno != EAGAIN) {
> > + condlog(3, "error reading from
> > inotify_fd");
> > + for (i = 0; i < 2; i++) {
> > + if (wds[i] != -1) {
> > + inotify_rm_watch(fd,
> > wds[i]);
> > + wds[i] = -1;
> > + }
> > + }
> > + }
> > + break;
> > + }
> > +
> > + got_notify = 1;
> > + for (ptr = buff; ptr < buff + len;
> > + ptr += sizeof(struct inotify_event) + event->len)
> > {
> > + event = (const struct inotify_event *) ptr;
> > +
> > + if (event->mask & IN_IGNORED) {
> > + /* multipathd.conf may have been
> > overwritten.
> > + * Try once to reset the notification
> > */
> > + if (wds[0] == event->wd)
> > + wds[0] =
> > inotify_add_watch(notify_fd,
> > + DEFAULT_CONFIGF
> > ILE,
> > + IN_CLOSE_WRITE)
> > ;
> > + else if (wds[1] == event->wd)
> > + wds[1] = -1;
> > + }
> > + }
> > + }
> > + if (got_notify)
> > + condlog(1, "Multipath configuration updated.\nReload
> > multipathd for changes to take effect");
> > +}
> > +
> > /*
> > * entry point
> > */
> > @@ -173,13 +278,19 @@ void * uxsock_listen(uxsock_trigger_fn
> > uxsock_trigger, long ux_sock,
> > char *reply;
> > sigset_t mask;
> > int old_clients = MIN_POLLS;
> > + /* conf->sequence_nr will be 1 when uxsock_listen is first
> > called */
> > + unsigned int sequence_nr = 0;
> > + int wds[2] = { -1, -1 };
>
> Style issue: The code might be better readable if we used a struct for
> this,
>
> struct watch_descriptors {
> int conf_wd;
> int dir_wd;
> };
>
> --
> Dr. Martin Wilck <mwilck at suse.com>, Tel. +49 (0)911 74053 2107
> SUSE Software Solutions Germany GmbH
> HRB 36809, AG Nürnberg GF: Felix
> Imendörffer
>
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