linux/drivers/xen/xenbus
SeongJae Park fed1755b11 xen/xenbus: Allow watches discard events before queueing
If handling logics of watch events are slower than the events enqueue
logic and the events can be created from the guests, the guests could
trigger memory pressure by intensively inducing the events, because it
will create a huge number of pending events that exhausting the memory.

Fortunately, some watch events could be ignored, depending on its
handler callback.  For example, if the callback has interest in only one
single path, the watch wouldn't want multiple pending events.  Or, some
watches could ignore events to same path.

To let such watches to volutarily help avoiding the memory pressure
situation, this commit introduces new watch callback, 'will_handle'.  If
it is not NULL, it will be called for each new event just before
enqueuing it.  Then, if the callback returns false, the event will be
discarded.  No watch is using the callback for now, though.

This is part of XSA-349

Cc: stable@vger.kernel.org
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reported-by: Michael Kurth <mku@amazon.de>
Reported-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2020-12-14 10:02:45 +01:00
..
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xenbus_client.c xen/xenbus: Allow watches discard events before queueing 2020-12-14 10:02:45 +01:00
xenbus_comms.c xenbus: req->err should be updated before req->state 2020-03-05 09:42:01 -06:00
xenbus_dev_backend.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xenbus_dev_frontend.c xen/xenbus: fix self-deadlock after killing user process 2019-10-02 16:40:11 -04:00
xenbus_probe_backend.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
xenbus_probe_frontend.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
xenbus_probe.c xen: branch for v5.8-rc1 2020-06-12 11:00:45 -07:00
xenbus_xs.c xen/xenbus: Allow watches discard events before queueing 2020-12-14 10:02:45 +01:00
xenbus.h xenbus: move xenbus_dev_shutdown() into frontend code... 2019-12-20 13:44:35 +01:00