svn commit: r351064 - in head: sbin/swapon share/man/man5 sys/vm

[Doug Moore]

Author: dougm
Date: Thu Aug 15 02:30:44 2019
New Revision: 351064
URL: https://svnweb.freebsd.org/changeset/base/351064

Log:
  swap_pager.c reserves 2 blocks for a bsd label.  Change that 2 to the
  expression howmany(BBSIZE, PAGE_SIZE), where BBSIZE is the size of the
  boot block area.  That can be less than 2 if PAGE_SIZE is big.
  
  swapon(8) has an option to trim (delete) all the blocks of a device at
  startup.  However, if the first of those blocks is a bsd label, then
  trimming those blocks is destructive.  Change swapon to leave the
  first BBSIZE bytes untrimmed.
  
  Update manual pages to reflect changes in how swapon and how it may be
  used, espeically in association with savecore.
  
  Reviewed by: alc
  Approved by: markj (mentor)
  MFC after: 3 days
  Differential Revision: https://reviews.freebsd.org/D21191

Modified:
  head/sbin/swapon/swapon.8
  head/sbin/swapon/swapon.c
  head/share/man/man5/fstab.5
  head/sys/vm/swap_pager.c

Modified: head/sbin/swapon/swapon.8
==============================================================================
--- head/sbin/swapon/swapon.8	Thu Aug 15 02:14:44 2019	(r351063)
+++ head/sbin/swapon/swapon.8	Thu Aug 15 02:30:44 2019	(r351064)
@@ -90,7 +90,17 @@ The
 .Fl E
 option causes each of following devices to receive a
 .Dv BIO_DELETE
-command to mark all blocks as unused.
+command.
+This command marks the device's blocks as unused, except those that
+might store a disk label.
+This marking can erase a crash dump.
+To delay
+.Nm swapon
+for a device until after
+.Nm savecore
+has copied the crash dump to another location, use the 
+.Dq late
+option.
 .Pp
 The
 .Nm swapoff

Modified: head/sbin/swapon/swapon.c
==============================================================================
--- head/sbin/swapon/swapon.c	Thu Aug 15 02:14:44 2019	(r351063)
+++ head/sbin/swapon/swapon.c	Thu Aug 15 02:30:44 2019	(r351064)
@@ -45,6 +45,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/disk.h>
+#include <sys/disklabel.h>
 #include <sys/mdioctl.h>
 #include <sys/stat.h>
 #include <sys/sysctl.h>
@@ -761,8 +762,8 @@ swapon_trim(const char *name)
 	} else
 		errx(1, "%s has an invalid file type", name);
 	/* Trim the device. */
-	ioarg[0] = 0;
-	ioarg[1] = sz;
+	ioarg[0] = BBSIZE;
+	ioarg[1] = sz - BBSIZE;
 	if (ioctl(fd, DIOCGDELETE, ioarg) != 0)
 		warn("ioctl(DIOCGDELETE)");
 

Modified: head/share/man/man5/fstab.5
==============================================================================
--- head/share/man/man5/fstab.5	Thu Aug 15 02:14:44 2019	(r351063)
+++ head/share/man/man5/fstab.5	Thu Aug 15 02:30:44 2019	(r351064)
@@ -246,8 +246,17 @@ For swap devices, the keyword
 .Dq trimonce
 triggers the delivery of a
 .Dv BIO_DELETE
-command to the device to mark
-all blocks as unused.
+command to the device.
+This command marks the device's blocks as unused, except those that
+might store a disk label.
+This marking can erase a crash dump.
+To delay
+.Nm swapon
+for a device until after
+.Nm savecore
+has copied the crash dump to another location, use the 
+.Dq late
+option.
 For vnode-backed swap spaces,
 .Dq file
 is supported in the

Modified: head/sys/vm/swap_pager.c
==============================================================================
--- head/sys/vm/swap_pager.c	Thu Aug 15 02:14:44 2019	(r351063)
+++ head/sys/vm/swap_pager.c	Thu Aug 15 02:30:44 2019	(r351064)
@@ -79,6 +79,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/buf.h>
 #include <sys/conf.h>
 #include <sys/disk.h>
+#include <sys/disklabel.h>
 #include <sys/eventhandler.h>
 #include <sys/fcntl.h>
 #include <sys/lock.h>
@@ -2298,10 +2299,11 @@ swaponsomething(struct vnode *vp, void *id, u_long nbl
 
 	sp->sw_blist = blist_create(nblks, M_WAITOK);
 	/*
-	 * Do not free the first two block in order to avoid overwriting
+	 * Do not free the first blocks in order to avoid overwriting
 	 * any bsd label at the front of the partition
 	 */
-	blist_free(sp->sw_blist, 2, nblks - 2);
+	blist_free(sp->sw_blist, howmany(BBSIZE, PAGE_SIZE),
+	    nblks - howmany(BBSIZE, PAGE_SIZE));
 
 	dvbase = 0;
 	mtx_lock(&sw_dev_mtx);
@@ -2319,7 +2321,7 @@ swaponsomething(struct vnode *vp, void *id, u_long nbl
 	sp->sw_end = dvbase + nblks;
 	TAILQ_INSERT_TAIL(&swtailq, sp, sw_list);
 	nswapdev++;
-	swap_pager_avail += nblks - 2;
+	swap_pager_avail += nblks - howmany(BBSIZE, PAGE_SIZE);
 	swap_total += nblks;
 	swapon_check_swzone();
 	swp_sizecheck();