[linux-lvm] Kernel panic while snapshotting.

[Joe Thornber]

Hi Jay,

Drat.  I'm really sorry about this.

Can you try reversing this patch please ?  It should fix it.

Let me know if you're still having trouble afterwards.

- Joe

diff -u -r1.2.2.6 -r1.2.2.7
--- LVM/kernel/lvm-snap.c	2001/01/12 16:08:12	1.2.2.6
+++ LVM/kernel/lvm-snap.c	2001/01/17 15:20:27	1.2.2.7
@@ -45,10 +45,6 @@
 
 static char *lvm_snap_version __attribute__ ((unused)) = "LVM 0.9 snapshot code (13/11/2000)\n";
 
-#ifndef LockPage
-#define LockPage(map) set_bit(PG_locked, &(map)->flags)
-#endif
-
 extern const char *const lvm_name;
 extern int lvm_blocksizes[];
 
@@ -492,7 +488,7 @@
 		goto out;
 
 	err = -ENOMEM;
-	iobuf->locked = 1;
+	iobuf->locked = 0;
 	iobuf->nr_pages = 0;
 	for (i = 0; i < nr_pages; i++)
 	{
@@ -513,9 +509,6 @@
 #endif
 
 		iobuf->maplist[i] = page;
-		/* the only point to lock the page here is to be allowed
-		   to share unmap_kiobuf() in the fail-path */
-		LockPage(page);
 		iobuf->nr_pages++;
 	}
 	iobuf->offset = 0;


On Fri, Jan 19, 2001 at 07:56:26AM -0800, Jay Weber wrote:
> Hi,
> 
> I just got a kernel panic while snapshotting with 0.9.1beta2.  I wonder if
> anybody has seen any similar issues or I possibly fubar'd the patch on my
> end?
> 
> Panic was:
> 
> 	Kernel panic: brw_kiovec: iobuf not locked for I/O
> 
> This occured while simultanously copying 20 tarballs back and forth
> between two dirs on the source volume and performing a snapshot at that
> time.  It appears to have hung my lvcreate (snapshot) command shell.
> Oh, this was also using loop device for the source volume on my laptop in
> this case.  Hmm, actually could this panic be related to the following
> change in lvm.c?  It did work prior in 0.9.1beta1.
> 
> @@ -492,7 +488,7 @@
>                 goto out;
> 
>         err = -ENOMEM;
> -       iobuf->locked = 1;
> +       iobuf->locked = 0;
>         iobuf->nr_pages = 0;
>         for (i = 0; i < nr_pages; i++)
>         {
> 
> 
> I haven't seen this one before myself, but in testing on our bigger scsi
> based boxes in the back while snapshots are active and heavy IO is
> performed on the source volume, the box tends to hang.  I gather this is
> related to having to journal all source volume changes to the snapshot and
> when you throw massive IO at it, things get slow. Any thoughts on this one
> as well?
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm at sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
>