This is a note to let you know that I've just added the patch titled
xen/blkback: unmap all persistent grants when frontend gets disconnected
to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-blkback-unmap-all-persistent-grants-when-frontend-gets-disconnected.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 12ea729645ace01e08f9654df155622898d3aae6 Mon Sep 17 00:00:00 2001
From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Date: Mon, 8 Sep 2014 15:21:33 +0200
Subject: xen/blkback: unmap all persistent grants when frontend gets disconnected
From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
commit 12ea729645ace01e08f9654df155622898d3aae6 upstream.
blkback does not unmap persistent grants when frontend goes to Closed
state (e.g. when blkfront module is being removed). This leads to the
following in guest's dmesg:
[ 343.243825] xen:grant_table: WARNING: g.e. 0x445 still in use!
[ 343.243825] xen:grant_table: WARNING: g.e. 0x42a still in use!
...
When load module -> use device -> unload module sequence is performed multiple times
it is possible to hit BUG() condition in blkfront module:
[ 343.243825] kernel BUG at drivers/block/xen-blkfront.c:954!
[ 343.243825] invalid opcode: 0000 [#1] SMP
[ 343.243825] Modules linked in: xen_blkfront(-) ata_generic pata_acpi [last unloaded: xen_blkfront]
...
[ 343.243825] Call Trace:
[ 343.243825] [<ffffffff814111ef>] ? unregister_xenbus_watch+0x16f/0x1e0
[ 343.243825] [<ffffffffa0016fbf>] blkfront_remove+0x3f/0x140 [xen_blkfront]
...
[ 343.243825] RIP [<ffffffffa0016aae>] blkif_free+0x34e/0x360 [xen_blkfront]
[ 343.243825] RSP <ffff88001eb8fdc0>
We don't need to keep these grants if we're disconnecting as frontend might already
forgot about them. Solve the issue by moving xen_blkbk_free_caches() call from
xen_blkif_free() to xen_blkif_disconnect().
Now we can see the following:
[ 928.590893] xen:grant_table: WARNING: g.e. 0x587 still in use!
[ 928.591861] xen:grant_table: WARNING: g.e. 0x372 still in use!
...
[ 929.592146] xen:grant_table: freeing g.e. 0x587
[ 929.597174] xen:grant_table: freeing g.e. 0x372
...
Backend does not keep persistent grants any more, reconnect works fine.
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/block/xen-blkback/xenbus.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -270,6 +270,9 @@ static int xen_blkif_disconnect(struct x
blkif->blk_rings.common.sring = NULL;
}
+ /* Remove all persistent grants and the cache of ballooned pages. */
+ xen_blkbk_free_caches(blkif);
+
return 0;
}
@@ -281,9 +284,6 @@ static void xen_blkif_free(struct xen_bl
xen_blkif_disconnect(blkif);
xen_vbd_free(&blkif->vbd);
- /* Remove all persistent grants and the cache of ballooned pages. */
- xen_blkbk_free_caches(blkif);
-
/* Make sure everything is drained before shutting down */
BUG_ON(blkif->persistent_gnt_c != 0);
BUG_ON(atomic_read(&blkif->persistent_gnt_in_use) != 0);
Patches currently in stable-queue which might be from vkuznets@xxxxxxxxxx are
queue-3.17/xen-blkback-unmap-all-persistent-grants-when-frontend-gets-disconnected.patch
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