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From 4e0b3de57486613c8f28ef7726df728cccd7624b Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Thu, 28 May 2020 10:59:57 +0100
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Subject: [PATCH] v2v: -it vddk: Don't use nbdkit readahead filter with VDDK
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(RHBZ#1832805).
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This filter deliberately tries to coalesce reads into larger requests.
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Unfortunately VMware has low limits on the size of requests it can
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serve to a VDDK client and the larger requests would break with errors
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like this:
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nbdkit: vddk[3]: error: [NFC ERROR] NfcFssrvrProcessErrorMsg: received NFC error 5 from server: Failed to allocate the requested 33554456 bytes
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We already increase the maximum request size by changing the
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configuration on the VMware server, but it's not sufficient for VDDK
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with the readahead filter.
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As readahead is only an optimization, the simplest solution is to
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disable this filter when we're using nbdkit-vddk-plugin.
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Thanks: Ming Xie
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(cherry picked from commit 1438174488f111fa24420758ba3bf0218dc9ee2a)
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---
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v2v/nbdkit_sources.ml | 8 ++++++--
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1 file changed, 6 insertions(+), 2 deletions(-)
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diff --git a/v2v/nbdkit_sources.ml b/v2v/nbdkit_sources.ml
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index 402dfd0e..bfda91a7 100644
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--- a/v2v/nbdkit_sources.ml
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+++ b/v2v/nbdkit_sources.ml
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@@ -97,9 +97,13 @@ let common_create ?bandwidth ?extra_debug ?extra_env plugin_name plugin_args =
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let cmd = Nbdkit.add_filter_if_available cmd "retry" in
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(* Adding the readahead filter is always a win for our access
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- * patterns. However if it doesn't exist don't worry.
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+ * patterns. If it doesn't exist don't worry. However it
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+ * breaks VMware servers (RHBZ#1832805).
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*)
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- let cmd = Nbdkit.add_filter_if_available cmd "readahead" in
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+ let cmd =
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+ if plugin_name <> "vddk" then
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+ Nbdkit.add_filter_if_available cmd "readahead"
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+ else cmd in
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(* Caching extents speeds up qemu-img, especially its consecutive
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* block_status requests with req_one=1.
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