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From 9e909e2a2640b08e7bf10232321a1b1dc81df69c Mon Sep 17 00:00:00 2001
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From: John Snow <jsnow@redhat.com>
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Date: Fri, 22 Mar 2019 03:22:16 +0100
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Subject: [PATCH 049/163] nbd/client: Relax handling of large
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NBD_CMD_BLOCK_STATUS reply
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RH-Author: John Snow <jsnow@redhat.com>
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Message-id: <20190322032241.8111-4-jsnow@redhat.com>
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Patchwork-id: 85090
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O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH 03/28] nbd/client: Relax handling of large NBD_CMD_BLOCK_STATUS reply
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Bugzilla: 1691563
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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From: Eric Blake <eblake@redhat.com>
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The NBD spec is proposing a relaxation of NBD_CMD_BLOCK_STATUS
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where a server may have the final extent per context give a
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length beyond the original request, if it can easily prove that
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subsequent bytes have the same status, on the grounds that a
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client can take advantage of this information for fewer block
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status requests. Since qemu 2.12 as a client always sends
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NBD_CMD_FLAG_REQ_ONE, and rejects a server that sends extra
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length, the upstream NBD spec will probably limit this behavior
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to clients that don't request REQ_ONE semantics; but it doesn't
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hurt to relax qemu to always be permissive of this server
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behavior, even if it continues to use REQ_ONE.
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CC: qemu-stable@nongnu.org
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Signed-off-by: Eric Blake <eblake@redhat.com>
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Message-Id: <20180503222626.1303410-1-eblake@redhat.com>
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Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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(cherry picked from commit acfd8f7a5f92e703d2d046cbe3d510008a697194)
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Signed-off-by: John Snow <jsnow@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/nbd-client.c | 10 +++++++---
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1 file changed, 7 insertions(+), 3 deletions(-)
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diff --git a/block/nbd-client.c b/block/nbd-client.c
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index 80d3625..76e9ca3 100644
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--- a/block/nbd-client.c
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+++ b/block/nbd-client.c
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@@ -259,14 +259,18 @@ static int nbd_parse_blockstatus_payload(NBDClientSession *client,
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if (extent->length == 0 ||
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(client->info.min_block && !QEMU_IS_ALIGNED(extent->length,
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- client->info.min_block)) ||
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- extent->length > orig_length)
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- {
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+ client->info.min_block))) {
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error_setg(errp, "Protocol error: server sent status chunk with "
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"invalid length");
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return -EINVAL;
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}
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+ /* The server is allowed to send us extra information on the final
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+ * extent; just clamp it to the length we requested. */
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+ if (extent->length > orig_length) {
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+ extent->length = orig_length;
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+ }
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+
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return 0;
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}
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--
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1.8.3.1
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