From e2eff28aab554003bd65516241a7dc11e6825505 Mon Sep 17 00:00:00 2001
From: Davidlohr Bueso <dave@stgolabs.net>
Date: Fri, 11 Aug 2017 09:29:52 +1000
Subject: [PATCH 2/2] ipc/sem: play nicer with large nsops allocations
Patch-mainline: v4.14-rc1
Git-commit: e4243b8062c13b8cb3d91695dc353cb9e6a0da25
References: bsc#1050323
Replacing semop()'s kmalloc for kvmalloc was originally proposed by
Manfred on the premise that it can be called for large (than order-1)
sizes. For example, while Oracle recommends setting SEMOPM to a _minimum_
of 100, some distros[1] encourage the setting to be a factor of the amount
of db tasks (PROCESSES), which can get fishy for large systems (easily
going beyond 1000).
[1] An Example of Semaphore Settings
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Tuning_and_Optimizing_Red_Hat_Enterprise_Linux_for_Oracle_9i_and_10g_Databases/sect-Oracle_9i_and_10g_Tuning_Guide-Setting_Semaphores-An_Example_of_Semaphore_Settings.html
So let's just convert this to kvmalloc, just like the rest of the
allocations we do in ipc. While the fallback vmalloc obviously involves
more overhead, this by far the uncommon path, and it's better for the user
than just erroring out with kmalloc.
Link: http://lkml.kernel.org/r/20170803184136.13855-2-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
ipc/sem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/ipc/sem.c b/ipc/sem.c
index 470c49954076..b63a3fd38823 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1784,7 +1784,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
if (nsops > ns->sc_semopm)
return -E2BIG;
if (nsops > SEMOPM_FAST) {
- sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL);
+ sops = kvmalloc(sizeof(*sops)*nsops, GFP_KERNEL);
if (sops == NULL)
return -ENOMEM;
}
@@ -2016,7 +2016,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
rcu_read_unlock();
out_free:
if (sops != fast_sops)
- kfree(sops);
+ kvfree(sops);
return error;
}
--
2.12.0