[dm-devel] [PATCH v5 16/22] multipath -u : set FIND_MULTIPATHS_WAIT_UNTIL from /dev/shm
Benjamin Marzinski
bmarzins at redhat.com
Mon Apr 16 19:40:47 UTC 2018
On Sat, Apr 14, 2018 at 12:00:09AM +0200, Martin Wilck wrote:
> In "find_multipaths smart" mode, use time stamps under
> /dev/shm/multipath/find_multipaths to track waiting for multipath
> siblings. When a path is first encountered and is "maybe" multipath, create
> a file under /dev/shm, set its modification time to the expiry time of the
> timer, and set the FIND_MULTIPATHS_WAIT_UNTIL variable. On later calls,
> also set FIND_MULTIPATHS_WAIT_UNTIL to the expiry time (but don't change
> the time stamp) if it's not expired yet, or 0 if it is expired. Set
> FIND_MULTIPATHS_WAIT_UNTIL even if enough evidence becomes available to
> decide if the path needs to be multipathed - this enables the udev rules to
> detect that this is a device a timer has been started for, and stop it. By
> using /dev/shm, we share information about "smart" timers between initrd
> and root file system, and thus only calculate the timeout once.
>
> Because we use major:minor to identify the devices in /dev/shm, and because
> a removed device might be replaced by a different one with the same
> major/minor number, add a rule to multipath.rules to remove the
> find_multipaths marker on remove uevents.
>
Reviewed-by: Benjamin Marzinsk <bmarzins at redhat.com>
> Signed-off-by: Martin Wilck <mwilck at suse.com>
> ---
> libmultipath/file.c | 2 +-
> libmultipath/file.h | 1 +
> multipath/main.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++
> multipath/multipath.rules | 4 +-
> 4 files changed, 137 insertions(+), 2 deletions(-)
>
> diff --git a/libmultipath/file.c b/libmultipath/file.c
> index d5165ec6..8727f160 100644
> --- a/libmultipath/file.c
> +++ b/libmultipath/file.c
> @@ -36,7 +36,7 @@
> * See the file COPYING included with this distribution for more details.
> */
>
> -static int
> +int
> ensure_directories_exist(const char *str, mode_t dir_mode)
> {
> char *pathname;
> diff --git a/libmultipath/file.h b/libmultipath/file.h
> index 70bffa53..29520c74 100644
> --- a/libmultipath/file.h
> +++ b/libmultipath/file.h
> @@ -6,6 +6,7 @@
> #define _FILE_H
>
> #define FILE_TIMEOUT 30
> +int ensure_directories_exist(const char *str, mode_t dir_mode);
> int open_file(const char *file, int *can_write, const char *header);
>
> #endif /* _FILE_H */
> diff --git a/multipath/main.c b/multipath/main.c
> index f62e18a9..5d847f08 100644
> --- a/multipath/main.c
> +++ b/multipath/main.c
> @@ -29,6 +29,7 @@
> #include <ctype.h>
> #include <libudev.h>
> #include <syslog.h>
> +#include <fcntl.h>
>
> #include "checkers.h"
> #include "prio.h"
> @@ -60,6 +61,9 @@
> #include "uxsock.h"
> #include "mpath_cmd.h"
> #include "foreign.h"
> +#include "propsel.h"
> +#include "time-util.h"
> +#include "file.h"
>
> int logsink;
> struct udev *udev;
> @@ -350,14 +354,142 @@ out:
> return r;
> }
>
> +enum {
> + FIND_MULTIPATHS_WAIT_DONE = 0,
> + FIND_MULTIPATHS_WAITING = 1,
> + FIND_MULTIPATHS_ERROR = -1,
> + FIND_MULTIPATHS_NEVER = -2,
> +};
> +
> +static const char shm_find_mp_dir[] = MULTIPATH_SHM_BASE "find_multipaths";
> +static void close_fd(void *arg)
> +{
> + close((long)arg);
> +}
> +
> +/**
> + * find_multipaths_check_timeout(wwid, tmo)
> + * Helper for "find_multipaths smart"
> + *
> + * @param[in] pp: path to check / record
> + * @param[in] tmo: configured timeout for this WWID, or value <= 0 for checking
> + * @param[out] until: timestamp until we must wait, CLOCK_REALTIME, if return
> + * value is FIND_MULTIPATHS_WAITING
> + * @returns: FIND_MULTIPATHS_WAIT_DONE, if waiting has finished
> + * @returns: FIND_MULTIPATHS_ERROR, if internal error occurred
> + * @returns: FIND_MULTIPATHS_NEVER, if tmo is 0 and we didn't wait for this
> + * device
> + * @returns: FIND_MULTIPATHS_WAITING, if timeout hasn't expired
> + */
> +static int find_multipaths_check_timeout(const struct path *pp, long tmo,
> + struct timespec *until)
> +{
> + char path[PATH_MAX];
> + struct timespec now, ftimes[2], tdiff;
> + struct stat st;
> + long fd;
> + int r, err, retries = 0;
> +
> + clock_gettime(CLOCK_REALTIME, &now);
> +
> + if (snprintf(path, sizeof(path), "%s/%s", shm_find_mp_dir, pp->dev_t)
> + >= sizeof(path)) {
> + condlog(1, "%s: path name overflow", __func__);
> + return FIND_MULTIPATHS_ERROR;
> + }
> +
> + if (ensure_directories_exist(path, 0700)) {
> + condlog(1, "%s: error creating directories", __func__);
> + return FIND_MULTIPATHS_ERROR;
> + }
> +
> +retry:
> + fd = open(path, O_RDONLY);
> + if (fd != -1) {
> + pthread_cleanup_push(close_fd, (void *)fd);
> + r = fstat(fd, &st);
> + if (r != 0)
> + err = errno;
> + pthread_cleanup_pop(1);
> +
> + } else if (tmo > 0) {
> + if (errno == ENOENT)
> + fd = open(path, O_RDWR|O_EXCL|O_CREAT, 0644);
> + if (fd == -1) {
> + if (errno == EEXIST && !retries++)
> + /* We could have raced with another process */
> + goto retry;
> + condlog(1, "%s: error opening %s: %s",
> + __func__, path, strerror(errno));
> + return FIND_MULTIPATHS_ERROR;
> + };
> +
> + pthread_cleanup_push(close_fd, (void *)fd);
> + /*
> + * We just created the file. Set st_mtim to our desired
> + * expiry time.
> + */
> + ftimes[0].tv_sec = 0;
> + ftimes[0].tv_nsec = UTIME_OMIT;
> + ftimes[1].tv_sec = now.tv_sec + tmo;
> + ftimes[1].tv_nsec = now.tv_nsec;
> + if (futimens(fd, ftimes) != 0) {
> + condlog(1, "%s: error in futimens(%s): %s", __func__,
> + path, strerror(errno));
> + }
> + r = fstat(fd, &st);
> + if (r != 0)
> + err = errno;
> + pthread_cleanup_pop(1);
> + } else
> + return FIND_MULTIPATHS_NEVER;
> +
> + if (r != 0) {
> + condlog(1, "%s: error in fstat for %s: %s", __func__,
> + path, strerror(err));
> + return FIND_MULTIPATHS_ERROR;
> + }
> +
> + timespecsub(&st.st_mtim, &now, &tdiff);
> +
> + if (tdiff.tv_sec <= 0)
> + return FIND_MULTIPATHS_WAIT_DONE;
> +
> + *until = tdiff;
> + return FIND_MULTIPATHS_WAITING;
> +}
> +
> static int print_cmd_valid(int k, const vector pathvec,
> struct config *conf)
> {
> static const int vals[] = { 1, 0, 2 };
> + int wait = FIND_MULTIPATHS_NEVER;
> + struct timespec until;
> + struct path *pp;
>
> if (k < 0 || k >= sizeof(vals))
> return 1;
>
> + if (k == 2) {
> + /*
> + * Caller ensures that pathvec[0] is the path to
> + * examine.
> + */
> + pp = VECTOR_SLOT(pathvec, 0);
> + select_find_multipaths_timeout(conf, pp);
> + wait = find_multipaths_check_timeout(
> + pp, pp->find_multipaths_timeout, &until);
> + if (wait != FIND_MULTIPATHS_WAITING)
> + k = 1;
> + } else if (pathvec != NULL) {
> + pp = VECTOR_SLOT(pathvec, 0);
> + wait = find_multipaths_check_timeout(pp, 0, &until);
> + }
> + if (wait == FIND_MULTIPATHS_WAITING)
> + printf("FIND_MULTIPATHS_WAIT_UNTIL=\"%ld.%06ld\"\n",
> + until.tv_sec, until.tv_nsec/1000);
> + else if (wait == FIND_MULTIPATHS_WAIT_DONE)
> + printf("FIND_MULTIPATHS_WAIT_UNTIL=\"0\"\n");
> printf("DM_MULTIPATH_DEVICE_PATH=\"%d\"\n", vals[k]);
> return k == 1;
> }
> diff --git a/multipath/multipath.rules b/multipath/multipath.rules
> index aab64dc7..37f4f6d8 100644
> --- a/multipath/multipath.rules
> +++ b/multipath/multipath.rules
> @@ -1,7 +1,9 @@
> # Set DM_MULTIPATH_DEVICE_PATH if the device should be handled by multipath
> SUBSYSTEM!="block", GOTO="end_mpath"
> -ACTION!="add|change", GOTO="end_mpath"
> KERNEL!="sd*|dasd*|nvme*", GOTO="end_mpath"
> +ACTION=="remove", TEST=="/dev/shm/multipath/find_multipaths/$major:$minor", \
> + RUN+="/usr/bin/rm -f /dev/shm/multipath/find_multipaths/$major:$minor"
> +ACTION!="add|change", GOTO="end_mpath"
>
> IMPORT{cmdline}="nompath"
> ENV{nompath}=="?*", GOTO="end_mpath"
> --
> 2.16.1
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