[Devel] [PATCH RHEL7 COMMIT] ms/aio: Multiply passed nr_events in io_setup()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.18.2.vz7.14.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.18.2.vz7.14.5
------>
commit c1cb4f8b3b9ebfc9697c8b3eff7fb134556b8794
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Fri May 20 19:07:21 2016 +0400

    ms/aio: Multiply passed nr_events in io_setup()
    
    CRIU supports AIO in kernel versions >= 3.19. It expects the logic, which was
    introduced in kernel commit e1bdd5f27a5b, when it became to multiply the passed
    nr_events twice. Vz7 kernel doesn't do that, and this lead to wrong
    calculation of lenght of AIO ring in CRIU.
    
    This is a port of small part of commit e1bdd5f27a5b
    ("aio: percpu reqs_available"), to make CRIU works on Virtuozzo 7 kernel.
    
    https://jira.sw.ru/browse/PSBM-47075
    Also needed for https://jira.sw.ru/browse/PSBM-47209
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    Acked-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 fs/aio.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/aio.c b/fs/aio.c
index 29d02ab..ee72178 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -596,6 +596,9 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
 	struct ve_struct *ve = get_exec_env();
 	int err = -ENOMEM;
 
+	/* Kernel since e1bdd5f27a5b do this, and criu is tuned on that */
+	nr_events *= 2;
+
 	/* Prevent overflows */
 	if ((nr_events > (0x10000000U / sizeof(struct io_event))) ||
 	    (nr_events > (0x10000000U / sizeof(struct kiocb)))) {