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Date: Tue, 25 Nov 2014 10:37:37 +0000 From: Luis Henriques <luis.henriques@...onical.com> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, kernel-team@...ts.ubuntu.com Cc: Vitaly Kuznetsov <vkuznets@...hat.com>, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, Luis Henriques <luis.henriques@...onical.com> Subject: [PATCH 3.16.y-ckt 107/254] xen/blkback: unmap all persistent grants when frontend gets disconnected 3.16.7-ckt2 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Vitaly Kuznetsov <vkuznets@...hat.com> 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@...hat.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> Signed-off-by: Luis Henriques <luis.henriques@...onical.com> --- drivers/block/xen-blkback/xenbus.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 3a8b810b4980..54f408963201 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -270,6 +270,9 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif) 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_blkif *blkif) 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); -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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