[Xen-devel] [PATCH 7/8] oxenstored: only process domain connections that notify us by events

[Zheng Li <dev@xxxxxxxx>]

Currently, upon receiving an event, oxenstored will scan all the xs rings (of
all domains), disregarding who sent that event. This is not very efficient, and
also it can shadow some misbehaviors of xenstore clients.

With this patch, oxenstore will only scan and process the domain connections
that have correctly notified it by events.

The function process_domains is refactored to be process_domain in order to
allow processing single domain connection. Also a mode_switch flag is added to
enable selectively processing just the input or output or both.

Signed-off-by: Zheng Li <dev@xxxxxxxx>
---
 tools/ocaml/xenstored/xenstored.ml | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/tools/ocaml/xenstored/xenstored.ml 
b/tools/ocaml/xenstored/xenstored.ml
index ea1a08f..41a188d 100644
--- a/tools/ocaml/xenstored/xenstored.ml
+++ b/tools/ocaml/xenstored/xenstored.ml
@@ -51,13 +51,17 @@ let process_connection_fds store cons domains rset wset =
        process_fdset_with rset Process.do_input;
        process_fdset_with wset Process.do_output
 
-let process_domains store cons domains =
-       let do_io_domain domain =
-               if not (Domain.is_bad_domain domain) then
-                       let con = Connections.find_domain cons (Domain.get_id 
domain) in
-                               Process.do_input store cons domains con;
-                               Process.do_output store cons domains con in
-       Domains.iter domains do_io_domain
+let process_domain ?mode_switch store cons domains c =
+       match Connection.get_domain c with
+       | None -> ()
+       | Some dom ->
+                if not (Domain.is_bad_domain dom) then
+                        let read, write = match mode_switch with
+                                | None -> true, true
+                                | Some true -> true, false
+                                | Some false -> false, true in
+                        (if read then Process.do_input store cons domains c;
+                         if write then Process.do_output store cons domains c)
 
 let sigusr1_handler store =
        try
@@ -305,6 +309,7 @@ let _ =
                        Connections.add_anonymous cons cfd can_write
                and handle_eventchn fd =
                        let port = Event.pending eventchn in
+                       debug "pending port %d" (Xeneventchn.to_int port);
                        finally (fun () ->
                                if Some port = eventchn.Event.virq_port then (
                                        let (notify, deaddom) = Domains.cleanup 
xc domains in
@@ -312,7 +317,10 @@ let _ =
                                        if deaddom <> [] || notify then
                                                Connections.fire_spec_watches 
cons "@releaseDomain"
                                )
-                       ) (fun () -> Event.unmask eventchn port);
+                               else
+                                       let c = Connections.find_domain_by_port 
cons port in
+                                       process_domain store cons domains c
+                               ) (fun () -> Event.unmask eventchn port)
                and do_if_set fd set fct =
                        if List.mem fd set then
                                fct fd in
@@ -382,7 +390,7 @@ let _ =
                        process_special_fds sfds;
                if List.length cfds > 0 || List.length wset > 0 then
                        process_connection_fds store cons domains cfds wset;
-               process_domains store cons domains
+               List.iter (process_domain store cons domains) mw
                in
 
        while not !quit
-- 
2.1.0


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