svn commit: r319612 - in head/sys: kern vm

[Alan Cox]

Author: alc
Date: Tue Jun  6 03:32:17 2017
New Revision: 319612
URL: https://svnweb.freebsd.org/changeset/base/319612

Log:
  When the function blist_fill() was added to the kernel in r107913, the swap
  pager used a different scheme for striping the allocation of swap space
  across multiple devices.  And, although blist_fill() was intended to support
  fill operations with large counts, the old striping scheme never performed a
  fill larger than the stripe size.  Consequently, the misplacement of a
  sanity check in blst_meta_fill() went undetected.  Now, moving forward in
  time to r118390, a new scheme for striping was introduced that maintained a
  blist allocator per device, but as noted in r318995, swapoff_one() was not
  fully and correctly converted to the new scheme.  This change completes what
  was started in r318995 by fixing the underlying bug in blst_meta_fill() that
  stops swapoff_one() from simply performing a single blist_fill() operation.
  
  Reviewed by:	kib
  MFC after:	5 days
  Differential Revision:	https://reviews.freebsd.org/D11043

Modified:
  head/sys/kern/subr_blist.c
  head/sys/vm/swap_pager.c

Modified: head/sys/kern/subr_blist.c
==============================================================================
--- head/sys/kern/subr_blist.c	Tue Jun  6 02:15:00 2017	(r319611)
+++ head/sys/kern/subr_blist.c	Tue Jun  6 03:32:17 2017	(r319612)
@@ -769,6 +769,8 @@ blst_meta_fill(
 	int next_skip = ((u_int)skip / BLIST_META_RADIX);
 	int nblks = 0;
 
+	if (count > radix)
+		panic("blist_meta_fill: allocation too large");
 	if (count == radix || scan->u.bmu_avail == 0)  {
 		/*
 		 * ALL-ALLOCATED special case
@@ -799,9 +801,6 @@ blst_meta_fill(
 	} else {
 		radix /= BLIST_META_RADIX;
 	}
-
-	if (count > radix)
-		panic("blist_meta_fill: allocation too large");
 
 	i = (allocBlk - blk) / radix;
 	blk += i * radix;

Modified: head/sys/vm/swap_pager.c
==============================================================================
--- head/sys/vm/swap_pager.c	Tue Jun  6 02:15:00 2017	(r319611)
+++ head/sys/vm/swap_pager.c	Tue Jun  6 03:32:17 2017	(r319612)
@@ -2271,7 +2271,7 @@ done:
 static int
 swapoff_one(struct swdevt *sp, struct ucred *cred)
 {
-	u_long nblks, dvbase;
+	u_long nblks;
 #ifdef MAC
 	int error;
 #endif
@@ -2300,14 +2300,7 @@ swapoff_one(struct swdevt *sp, struct ucred *cred)
 	 */
 	mtx_lock(&sw_dev_mtx);
 	sp->sw_flags |= SW_CLOSING;
-	for (dvbase = 0; dvbase < nblks; dvbase += BLIST_BMAP_RADIX) {
-		/*
-		 * blist_fill() cannot allocate more than BLIST_BMAP_RADIX
-		 * blocks per call.
-		 */
-		swap_pager_avail -= blist_fill(sp->sw_blist,
-		    dvbase, ulmin(nblks - dvbase, BLIST_BMAP_RADIX));
-	}
+	swap_pager_avail -= blist_fill(sp->sw_blist, 0, nblks);
 	swap_total -= (vm_ooffset_t)nblks * PAGE_SIZE;
 	mtx_unlock(&sw_dev_mtx);