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Date:      Sat, 23 Jun 2018 10:41:53 +0000 (UTC)
From:      Mark Johnston <markj@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r335580 - in head/sys: amd64/amd64 arm64/arm64
Message-ID:  <201806231041.w5NAfrAq019909@repo.freebsd.org>
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Author: markj
Date: Sat Jun 23 10:41:52 2018
New Revision: 335580
URL: https://svnweb.freebsd.org/changeset/base/335580

Log:
  Re-count available PV entries after reclaiming a PV chunk.
  
  The call to reclaim_pv_chunk() in reserve_pv_entries() may free a
  PV chunk with free entries belonging to the current pmap.  In this
  case we must account for the free entries that were reclaimed, or
  reserve_pv_entries() may return without having reserved the requested
  number of entries.
  
  Reviewed by:	alc, kib
  Tested by:	pho (previous version)
  MFC after:	2 weeks
  Differential Revision:	https://reviews.freebsd.org/D15911

Modified:
  head/sys/amd64/amd64/pmap.c
  head/sys/arm64/arm64/pmap.c

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Sat Jun 23 08:10:09 2018	(r335579)
+++ head/sys/amd64/amd64/pmap.c	Sat Jun 23 10:41:52 2018	(r335580)
@@ -3539,8 +3539,9 @@ reserve_pv_entries(pmap_t pmap, int needed, struct rwl
 {
 	struct pch new_tail;
 	struct pv_chunk *pc;
-	int avail, free;
 	vm_page_t m;
+	int avail, free;
+	bool reclaimed;
 
 	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
 	KASSERT(lockp != NULL, ("reserve_pv_entries: lockp is NULL"));
@@ -3568,13 +3569,14 @@ retry:
 		if (avail >= needed)
 			break;
 	}
-	for (; avail < needed; avail += _NPCPV) {
+	for (reclaimed = false; avail < needed; avail += _NPCPV) {
 		m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
 		    VM_ALLOC_WIRED);
 		if (m == NULL) {
 			m = reclaim_pv_chunk(pmap, lockp);
 			if (m == NULL)
 				goto retry;
+			reclaimed = true;
 		}
 		PV_STAT(atomic_add_int(&pc_chunk_count, 1));
 		PV_STAT(atomic_add_int(&pc_chunk_allocs, 1));
@@ -3587,6 +3589,14 @@ retry:
 		TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
 		TAILQ_INSERT_TAIL(&new_tail, pc, pc_lru);
 		PV_STAT(atomic_add_int(&pv_entry_spare, _NPCPV));
+
+		/*
+		 * The reclaim might have freed a chunk from the current pmap.
+		 * If that chunk contained available entries, we need to
+		 * re-count the number of available entries.
+		 */
+		if (reclaimed)
+			goto retry;
 	}
 	if (!TAILQ_EMPTY(&new_tail)) {
 		mtx_lock(&pv_chunks_mutex);

Modified: head/sys/arm64/arm64/pmap.c
==============================================================================
--- head/sys/arm64/arm64/pmap.c	Sat Jun 23 08:10:09 2018	(r335579)
+++ head/sys/arm64/arm64/pmap.c	Sat Jun 23 10:41:52 2018	(r335580)
@@ -2083,8 +2083,9 @@ reserve_pv_entries(pmap_t pmap, int needed, struct rwl
 {
 	struct pch new_tail;
 	struct pv_chunk *pc;
-	int avail, free;
 	vm_page_t m;
+	int avail, free;
+	bool reclaimed;
 
 	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
 	KASSERT(lockp != NULL, ("reserve_pv_entries: lockp is NULL"));
@@ -2107,13 +2108,14 @@ retry:
 		if (avail >= needed)
 			break;
 	}
-	for (; avail < needed; avail += _NPCPV) {
+	for (reclaimed = false; avail < needed; avail += _NPCPV) {
 		m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
 		    VM_ALLOC_WIRED);
 		if (m == NULL) {
 			m = reclaim_pv_chunk(pmap, lockp);
 			if (m == NULL)
 				goto retry;
+			reclaimed = true;
 		}
 		PV_STAT(atomic_add_int(&pc_chunk_count, 1));
 		PV_STAT(atomic_add_int(&pc_chunk_allocs, 1));
@@ -2126,6 +2128,14 @@ retry:
 		TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
 		TAILQ_INSERT_TAIL(&new_tail, pc, pc_lru);
 		PV_STAT(atomic_add_int(&pv_entry_spare, _NPCPV));
+
+		/*
+		 * The reclaim might have freed a chunk from the current pmap.
+		 * If that chunk contained available entries, we need to
+		 * re-count the number of available entries.
+		 */
+		if (reclaimed)
+			goto retry;
 	}
 	if (!TAILQ_EMPTY(&new_tail)) {
 		mtx_lock(&pv_chunks_mutex);

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