xfs_healer: don't start service if kernel support unavailable

Use ExecCondition= in the system service to check if kernel support for
the health monitor is available.  If not, we don't want to run the
service, have it fail, and generate a bunch of silly log messages.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/healer/xfs_healer.c b/healer/xfs_healer.c
index d9ab53c153a456c2f237501961c85595c0d6db2a..cf26f9c04ef225bf3046a40d65ab95989545d922 100644 (file)
--- a/healer/xfs_healer.c
+++ b/healer/xfs_healer.c
@@ -195,19 +195,27 @@ healer_nproc(
        return ctx->foreground ? platform_nproc() : 1;
 }
 
+enum mon_state {
+       MON_START,
+       MON_EXIT,
+       MON_ERROR,
+       MON_UNSUPPORTED,
+};
+
 /* Set ourselves up to monitor the given mountpoint for health events. */
-static int
+static enum mon_state
 setup_monitor(
        struct healer_ctx       *ctx)
 {
        const long              BUF_SIZE = sysconf(_SC_PAGE_SIZE) * 2;
+       enum mon_state          outcome = MON_ERROR;
        int                     mon_fd;
        int                     ret;
 
        ret = xfd_open(&ctx->mnt, ctx->mntpoint, O_RDONLY);
        if (ret) {
                perror(ctx->mntpoint);
-               return -1;
+               return outcome;
        }
 
        ret = try_capture_fsinfo(ctx);
@@ -263,6 +271,7 @@ setup_monitor(
                case EOPNOTSUPP:
                        fprintf(stderr, "%s: %s\n", ctx->mntpoint,
  _("XFS health monitoring not supported."));
+                       outcome = MON_UNSUPPORTED;
                        break;
                case EEXIST:
                        fprintf(stderr, "%s: %s\n", ctx->mntpoint,
@@ -278,6 +287,16 @@ setup_monitor(
        close(ctx->mnt.fd);
        ctx->mnt.fd = -1;
 
+       /*
+        * At this point, we know that the kernel is capable of repairing the
+        * filesystem and telling us that it needs repairs.  If the user only
+        * wanted us to check for the capability, we're done.
+        */
+       if (ctx->support_check) {
+               close(mon_fd);
+               return MON_EXIT;
+       }
+
        /*
         * mon_fp consumes mon_fd.  We intentionally leave mon_fp attached to
         * the context so that we keep the monitoring fd open until we've torn
@@ -309,7 +328,7 @@ setup_monitor(
        }
        ctx->queue_active = true;
 
-       return 0;
+       return MON_START;
 
 out_mon_fp:
        if (ctx->mon_fp)
@@ -322,7 +341,7 @@ out_mnt_fd:
        if (ctx->mnt.fd >= 0)
                close(ctx->mnt.fd);
        ctx->mnt.fd = -1;
-       return -1;
+       return outcome;
 }
 
 /* Monitor the given mountpoint for health events. */
@@ -412,6 +431,7 @@ usage(void)
        fprintf(stderr, _("  --foreground  Process events as soon as possible.\n"));
        fprintf(stderr, _("  --quiet       Do not log health events to stdout.\n"));
        fprintf(stderr, _("  --repair      Repair corrupt metadata found at runtime.\n"));
+       fprintf(stderr, _("  --supported   Check that health monitoring is supported.\n"));
        fprintf(stderr, _("  -V            Print version.\n"));
 
        exit(EXIT_FAILURE);
@@ -424,6 +444,7 @@ enum long_opt_nr {
        LOPT_HELP,
        LOPT_QUIET,
        LOPT_REPAIR,
+       LOPT_SUPPORTED,
        LOPT_SVCNAME,
 
        LOPT_MAX,
@@ -456,6 +477,7 @@ main(
                [LOPT_HELP]        = {"help", no_argument, NULL, 0 },
                [LOPT_QUIET]       = {"quiet", no_argument, &ctx.log, 0 },
                [LOPT_REPAIR]      = {"repair", no_argument, &ctx.want_repair, 1 },
+               [LOPT_SUPPORTED]   = {"supported", no_argument, &ctx.support_check, 1 },
                [LOPT_SVCNAME]     = {"svcname", no_argument, &ctx.print_svcname, 1 },
 
                [LOPT_MAX]         = {NULL, 0, NULL, 0 },
@@ -507,14 +529,24 @@ main(
                return EXIT_SUCCESS;
        }
 
-       ret = setup_monitor(&ctx);
-       if (ret)
-               goto out_events;
-
-       ret = monitor(&ctx);
+       switch (setup_monitor(&ctx)) {
+       case MON_UNSUPPORTED:
+               ret = 1; /* condition not met */
+               break;
+       case MON_ERROR:
+               ret = 255; /* service failed */
+               break;
+       case MON_EXIT:
+               ret = 0;
+               break;
+       case MON_START:
+               ret = monitor(&ctx);
+               break;
+       }
 
-out_events:
        teardown_monitor(&ctx);
        free((char *)ctx.fsname);
+       if (ctx.support_check)
+               return ret;
        return systemd_service_exit(ret);
 }

diff --git a/healer/xfs_healer.h b/healer/xfs_healer.h
index 679bdc95ae48f84f489e7b16a9667337aa407206..7caa6c66a59c6fb39a9757768d0e019836cd8a46 100644 (file)
--- a/healer/xfs_healer.h
+++ b/healer/xfs_healer.h
@@ -27,6 +27,7 @@ struct healer_ctx {
        int                     foreground;
        int                     want_repair;
        int                     print_svcname;
+       int                     support_check;
 
        /* fd and fs geometry for mount */
        struct xfs_fd           mnt;

diff --git a/healer/xfs_healer@.service.in b/healer/xfs_healer@.service.in
index 385257872b0cbbee0639b34d084b935302173e59..53f89cf9c4333dbdc8adc719d1b193dc545f7dbc 100644 (file)
--- a/healer/xfs_healer@.service.in
+++ b/healer/xfs_healer@.service.in
@@ -17,6 +17,7 @@ RequiresMountsFor=%f
 [Service]
 Type=exec
 Environment=SERVICE_MODE=1
+ExecCondition=@pkg_libexec_dir@/xfs_healer --supported %f
 ExecStart=@pkg_libexec_dir@/xfs_healer %f
 SyslogIdentifier=%N