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From: Alan Cox <alc@FreeBSD.org>
Date: Mon, 20 Mar 2017 05:15:55 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r315621 - head/sys/kern
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Author: alc
Date: Mon Mar 20 05:15:55 2017
New Revision: 315621
URL: https://svnweb.freebsd.org/changeset/base/315621

Log:
  Use IDX_TO_OFF(), not ptoa(), when converting the difference between two
  vm_pindex_t's into a vm_ooffset_t.
  
  The length given to shm_dotruncate() must never be negative.  Assert this.
  
  Tidy up a comment.
  
  Reviewed by:	kib
  MFC after:	1 week

Modified:
  head/sys/kern/uipc_shm.c

Modified: head/sys/kern/uipc_shm.c
==============================================================================
--- head/sys/kern/uipc_shm.c	Mon Mar 20 05:12:27 2017	(r315620)
+++ head/sys/kern/uipc_shm.c	Mon Mar 20 05:15:55 2017	(r315621)
@@ -418,6 +418,7 @@ shm_dotruncate(struct shmfd *shmfd, off_
 	vm_ooffset_t delta;
 	int base, rv;
 
+	KASSERT(length >= 0, ("shm_dotruncate: length < 0"));
 	object = shmfd->shm_object;
 	VM_OBJECT_WLOCK(object);
 	if (length == shmfd->shm_size) {
@@ -486,7 +487,7 @@ retry:
 				vm_pager_page_unswapped(m);
 			}
 		}
-		delta = ptoa(object->size - nobjsize);
+		delta = IDX_TO_OFF(object->size - nobjsize);
 
 		/* Toss in memory pages. */
 		if (nobjsize < object->size)
@@ -501,8 +502,8 @@ retry:
 		swap_release_by_cred(delta, object->cred);
 		object->charge -= delta;
 	} else {
-		/* Attempt to reserve the swap */
-		delta = ptoa(nobjsize - object->size);
+		/* Try to reserve additional swap space. */
+		delta = IDX_TO_OFF(nobjsize - object->size);
 		if (!swap_reserve_by_cred(delta, object->cred)) {
 			VM_OBJECT_WUNLOCK(object);
 			return (ENOMEM);