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Date:      Wed, 30 Oct 2019 17:33:17 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r354194 - head/sys/vm
Message-ID:  <201910301733.x9UHXHN9070799@repo.freebsd.org>

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Author: kib
Date: Wed Oct 30 17:33:17 2019
New Revision: 354194
URL: https://svnweb.freebsd.org/changeset/base/354194

Log:
  vm_page_wire_mapped: explain why failure does not affect correctness.
  
  Reviewed by:	markj (previous version)
  Sponsored by:	The FreeBSD Foundation
  Differential revision:	https://reviews.freebsd.org/D22196

Modified:
  head/sys/vm/vm_page.c

Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c	Wed Oct 30 17:32:35 2019	(r354193)
+++ head/sys/vm/vm_page.c	Wed Oct 30 17:33:17 2019	(r354194)
@@ -3763,6 +3763,9 @@ vm_page_wire(vm_page_t m)
 /*
  * Attempt to wire a mapped page following a pmap lookup of that page.
  * This may fail if a thread is concurrently tearing down mappings of the page.
+ * The transient failure is acceptable because it translates to the
+ * failure of the caller pmap_extract_and_hold(), which should be then
+ * followed by the vm_fault() fallback, see e.g. vm_fault_quick_hold_pages().
  */
 bool
 vm_page_wire_mapped(vm_page_t m)



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