61 lines
2.1 KiB
Diff
61 lines
2.1 KiB
Diff
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From 2bce6faed017df8da3e659eff3f42f39d25c7f09 Mon Sep 17 00:00:00 2001
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From: David Teigland <teigland@redhat.com>
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Date: Wed, 2 Jun 2021 16:29:54 -0500
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Subject: [PATCH 12/33] pvchange: fix file locking deadlock
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Calling clear_hint_file() to invalidate hints would acquire
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the hints flock before the global flock which could cause deadlock.
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The lock order requires the global lock to be taken first.
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pvchange was always invalidating hints, which was unnecessary;
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only invalidate hints when changing a PV uuid. Because of the
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lock ordering, take the global lock before clear_hint_file which
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locks the hints file.
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Signed-off-by: Heming Zhao <heming.zhao@suse.com>
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---
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tools/pvchange.c | 27 ++++++++++++++++++++++++++-
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1 file changed, 26 insertions(+), 1 deletion(-)
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diff --git a/tools/pvchange.c b/tools/pvchange.c
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index d6e35d66f9cc..04cbb428dde1 100644
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--- a/tools/pvchange.c
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+++ b/tools/pvchange.c
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@@ -248,7 +248,32 @@ int pvchange(struct cmd_context *cmd, int argc, char **argv)
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set_pv_notify(cmd);
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- clear_hint_file(cmd);
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+ /*
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+ * Changing a PV uuid is the only pvchange that invalidates hints.
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+ * Invalidating hints (clear_hint_file) is called at the start of
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+ * the command and takes the hints lock.
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+ * The global lock must always be taken first, then the hints lock
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+ * (the required lock ordering.)
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+ *
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+ * Because of these constraints, the global lock is taken ex here
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+ * for any PV uuid change, even though the global lock is technically
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+ * required only for changing an orphan PV (we don't know until later
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+ * if the PV is an orphan). The VG lock is used when changing
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+ * non-orphan PVs.
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+ *
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+ * For changes other than uuid on an orphan PV, the global lock is
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+ * taken sh by process_each, then converted to ex in pvchange_single,
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+ * which works because the hints lock is not held.
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+ *
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+ * (Eventually, perhaps always do lock_global(ex) here to simplify.)
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+ */
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+ if (arg_is_set(cmd, uuid_ARG)) {
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+ if (!lock_global(cmd, "ex")) {
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+ ret = ECMD_FAILED;
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+ goto out;
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+ }
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+ clear_hint_file(cmd);
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+ }
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ret = process_each_pv(cmd, argc, argv, NULL, 0, READ_FOR_UPDATE, handle, _pvchange_single);
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--
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1.8.3.1
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