svn commit: r354194 - head/sys/vm

[Konstantin Belousov]

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)