hints: invalidate when pvscan --cache sees a new PV

An idea from Zdenek for better ensuring valid hints by invalidating
them when pvscan --cache <device> sees a new PV, which is a case
where we know that hints should be invalidated.  This is triggered
from systemd/udev logic, and there may be some cases where it would
invalidate hints that the existing methods wouldn't detect.

diff --git a/lib/label/hints.c b/lib/label/hints.c
index a9c40c223c04c7ab8992d62b418b820e6c1abff1..4fe44b0232507e483d76ce55f7511e3db8b602d3 100644 (file)
--- a/lib/label/hints.c
+++ b/lib/label/hints.c
@@ -1025,6 +1025,21 @@ void clear_hint_file(struct cmd_context *cmd)
                stack;
 }
 
+/*
+ * This is used when pvscan --cache sees a new PV, which
+ * means we should refresh hints.  It could catch some case
+ * which the other methods of detecting stale hints may miss.
+ */
+void invalidate_hints(struct cmd_context *cmd)
+{
+       /* No commands are using hints. */
+       if (!cmd->enable_hints)
+               return;
+
+       if (!_touch_newhints())
+               stack;
+}
+
 /*
  * Currently, all the commands using hints (ALLOW_HINTS) take an optional or
  * required first position arg of a VG name or LV name.  If some other command

diff --git a/lib/label/hints.h b/lib/label/hints.h
index a17214cdd6034fc7ea237941f249c5a5454bb57f..469e8c41d189e9f084e85e279f34d17befbee0a5 100644 (file)
--- a/lib/label/hints.h
+++ b/lib/label/hints.h
@@ -28,6 +28,8 @@ int write_hint_file(struct cmd_context *cmd, int newhints);
 
 void clear_hint_file(struct cmd_context *cmd);
 
+void invalidate_hints(struct cmd_context *cmd);
+
 int get_hints(struct cmd_context *cmd, struct dm_list *hints, int *newhints,
               struct dm_list *devs_in, struct dm_list *devs_out);
 

diff --git a/test/shell/hints.sh b/test/shell/hints.sh
index bdaf3be3d97e0439463b0f1904a37996f559db78..31628b0e88294e2c7b471b1b42f2748934306295 100644 (file)
--- a/test/shell/hints.sh
+++ b/test/shell/hints.sh
@@ -273,11 +273,12 @@ diff $HINTS $PREV
 #
 
 # pvs (no change), pvscan (hints are new), pvs (no change)
+rm $HINTS $PREV
 pvs
 cp $HINTS $PREV
-diff $HINTS $PREV
-cp $HINTS $PREV
+# this next pvscan recreates the hints file
 pvscan --cache
+# the only diff will be "Created by pvscan ..." vs "Created by pvs ..."
 not diff $HINTS $PREV
 cp $HINTS $PREV
 pvs
@@ -285,6 +286,8 @@ diff $HINTS $PREV
 grep 'Created by pvscan' $HINTS
 # dev4 is a PV not used by a VG, dev5 is not a PV
 # using dd to copy skirts hint tracking so dev5 won't be seen
+# (unless the dd triggers udev which triggers pvscan --cache $dev5,
+# but I've not seen that happen in tests so far.)
 dd if="$dev4" of="$dev5" bs=1M
 # this pvs won't see dev5
 pvs > foo
@@ -314,6 +317,22 @@ not grep "$dev5" foo
 grep "$dev4" $HINTS
 not grep "$dev5" $HINTS
 
+#
+# Test pvscan --cache <dev> forces refresh
+#
+
+rm $HINTS $PREV
+pvs
+cp $HINTS $PREV
+# this next pvscan creates newhints to trigger a refresh
+pvscan --cache "$dev5"
+cat $NEWHINTS
+# this next pvs creates new hints
+pvs
+# the only diff will be "Created by..."
+not diff $HINTS $PREV
+
+
 
 #
 # Test incorrect dev-to-pvid info in hints is detected

diff --git a/tools/pvscan.c b/tools/pvscan.c
index da1e4354b5520115e3705329b531d948fbfaae68..098c502610601efa48b8f4ff1f06438077a7d647 100644 (file)
--- a/tools/pvscan.c
+++ b/tools/pvscan.c
@@ -17,6 +17,7 @@
 
 #include "lib/cache/lvmcache.h"
 #include "lib/metadata/metadata.h"
+#include "lib/label/hints.h"
 
 #include <dirent.h>
 
@@ -632,6 +633,7 @@ int pvscan_cache_cmd(struct cmd_context *cmd, int argc, char **argv)
        int do_activate = arg_is_set(cmd, activate_ARG);
        int all_vgs = 0;
        int add_errors = 0;
+       int add_single_count = 0;
        int ret = ECMD_PROCESSED;
 
        dm_list_init(&single_devs);
@@ -750,6 +752,8 @@ int pvscan_cache_cmd(struct cmd_context *cmd, int argc, char **argv)
                        if (dev->flags & DEV_FILTER_OUT_SCAN)
                                continue;
 
+                       add_single_count++;
+
                        /*
                         * Devices that exist and pass the lvmetad filter
                         * are online.
@@ -801,6 +805,8 @@ int pvscan_cache_cmd(struct cmd_context *cmd, int argc, char **argv)
                        if (dev->flags & DEV_FILTER_OUT_SCAN)
                                continue;
 
+                       add_single_count++;
+
                        /*
                         * Devices that exist and pass the lvmetad filter
                         * are online.
@@ -811,6 +817,16 @@ int pvscan_cache_cmd(struct cmd_context *cmd, int argc, char **argv)
        }
 
 activate:
+       /*
+        * When a new PV appears, the system runs pvscan --cache dev.
+        * This also means that existing hints are invalid, and
+        * we can force hints to be refreshed here.  There may be
+        * cases where this detects a change that the other methods
+        * of detecting invalid hints doesn't catch.
+        */
+       if (add_single_count)
+               invalidate_hints(cmd);
+
        /*
         * Special case: pvscan --cache -aay dev 
         * where dev has no VG metadata, and it's the final device to