From: Davidlohr Bueso Date: Fri, 8 Sep 2017 23:17:52 +0000 (-0700) Subject: ipc/sem: play nicer with large nsops allocations X-Git-Tag: v4.14-rc1~83^2~1 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=e4243b8062c13b8cb3d91695dc353cb9e6a0da25;p=linux.git ipc/sem: play nicer with large nsops allocations 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 Cc: Manfred Spraul Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/ipc/sem.c b/ipc/sem.c index 16414b8a8cca..4c0cfaad560c 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; }