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Date:      Thu, 10 Dec 2020 20:44:29 +0000 (UTC)
From:      Bryan Drewery <bdrewery@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r368523 - head/sys/vm
Message-ID:  <202012102044.0BAKiTHh011767@repo.freebsd.org>
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Author: bdrewery
Date: Thu Dec 10 20:44:29 2020
New Revision: 368523
URL: https://svnweb.freebsd.org/changeset/base/368523

Log:
  contig allocs: Don't retry forever on M_WAITOK.
  
  This restores behavior from before domain iterators were added in
  r327895 and r327896.
  
  The vm_domainset_iter_policy() will do a vm_wait_doms() and then
  restart its iterator when M_WAITOK is set.  It will also force
  the containing loop to have M_NOWAIT.  So we get an unbounded
  retry loop rather than the intended bounded retries that
  kmem_alloc_contig_pages() already handles.
  
  This also restores M_WAITOK to the vmem_alloc() call in
  kmem_alloc_attr_domain() and kmem_alloc_contig_domain().
  
  Reviewed by:	markj, kib
  MFC after:	2 weeks
  Sponsored by:	Dell EMC
  Differential Revision:	https://reviews.freebsd.org/D27507

Modified:
  head/sys/vm/vm_kern.c

Modified: head/sys/vm/vm_kern.c
==============================================================================
--- head/sys/vm/vm_kern.c	Thu Dec 10 20:44:05 2020	(r368522)
+++ head/sys/vm/vm_kern.c	Thu Dec 10 20:44:29 2020	(r368523)
@@ -264,9 +264,15 @@ kmem_alloc_attr_domainset(struct domainset *ds, vm_siz
 {
 	struct vm_domainset_iter di;
 	vm_offset_t addr;
-	int domain;
+	int domain, iflags;
 
-	vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
+	/*
+	 * Do not allow the domainset iterator to override wait flags.  The
+	 * contiguous memory allocator defines special semantics for M_WAITOK
+	 * that do not match the iterator's implementation.
+	 */
+	iflags = (flags & ~M_WAITOK) | M_NOWAIT;
+	vm_domainset_iter_policy_init(&di, ds, &domain, &iflags);
 	do {
 		addr = kmem_alloc_attr_domain(domain, size, flags, low, high,
 		    memattr);
@@ -346,9 +352,15 @@ kmem_alloc_contig_domainset(struct domainset *ds, vm_s
 {
 	struct vm_domainset_iter di;
 	vm_offset_t addr;
-	int domain;
+	int domain, iflags;
 
-	vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
+	/*
+	 * Do not allow the domainset iterator to override wait flags.  The
+	 * contiguous memory allocator defines special semantics for M_WAITOK
+	 * that do not match the iterator's implementation.
+	 */
+	iflags = (flags & ~M_WAITOK) | M_NOWAIT;
+	vm_domainset_iter_policy_init(&di, ds, &domain, &iflags);
 	do {
 		addr = kmem_alloc_contig_domain(domain, size, flags, low, high,
 		    alignment, boundary, memattr);

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