[Libguestfs] [PATCH v2v 1/4] v2v: Disable readahead for VMware curl sources too (RHBZ#1848862).

[Richard W.M. Jones]

This appears to be the cause of timeouts during the conversion step
where VMware VCenter server's Tomcat HTTPS server stops responding to
requests (or rather, responds only with 503 errors).  The server later
recovers and in fact because of the retry filter the conversion
usually succeeds, but I found that we can avoid the problem by
disabling readahead.

(cherry picked from commit 46c3d413d7b3aa6cea342df182f104045417d819)
---
 v2v/nbdkit_sources.ml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/v2v/nbdkit_sources.ml b/v2v/nbdkit_sources.ml
index f5e919116..7c177e358 100644
--- a/v2v/nbdkit_sources.ml
+++ b/v2v/nbdkit_sources.ml
@@ -99,12 +99,12 @@ let common_create ?bandwidth ?extra_debug ?extra_env password
 
   (* Adding the readahead filter is always a win for our access
    * patterns.  If it doesn't exist don't worry.  However it
-   * breaks VMware servers (RHBZ#1832805).
+   * breaks VMware servers (RHBZ#1832805, RHBZ#1848862).
    *)
   let cmd =
-    if plugin_name <> "vddk" then
-      Nbdkit.add_filter_if_available cmd "readahead"
-    else cmd in
+    match plugin_name with
+    | "vddk" | "curl" -> cmd
+    | _ -> Nbdkit.add_filter_if_available cmd "readahead" in
 
   (* Caching extents speeds up qemu-img, especially its consecutive
    * block_status requests with req_one=1.
-- 
2.27.0