From 1860033237d4be09c5d7382585f0c7229367a534 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Mon, 10 Jul 2017 15:48:02 -0700 Subject: mm: make PR_SET_THP_DISABLE immediately active PR_SET_THP_DISABLE has a rather subtle semantic. It doesn't affect any existing mapping because it only updated mm->def_flags which is a template for new mappings. The mappings created after prctl(PR_SET_THP_DISABLE) have VM_NOHUGEPAGE flag set. This can be quite surprising for all those applications which do not do prctl(); fork() & exec() and want to control their own THP behavior. Another usecase when the immediate semantic of the prctl might be useful is a combination of pre- and post-copy migration of containers with CRIU. In this case CRIU populates a part of a memory region with data that was saved during the pre-copy stage. Afterwards, the region is registered with userfaultfd and CRIU expects to get page faults for the parts of the region that were not yet populated. However, khugepaged collapses the pages and the expected page faults do not occur. In more general case, the prctl(PR_SET_THP_DISABLE) could be used as a temporary mechanism for enabling/disabling THP process wide. Implementation wise, a new MMF_DISABLE_THP flag is added. This flag is tested when decision whether to use huge pages is taken either during page fault of at the time of THP collapse. It should be noted, that the new implementation makes PR_SET_THP_DISABLE master override to any per-VMA setting, which was not the case previously. Fixes: a0715cc22601 ("mm, thp: add VM_INIT_DEF_MASK and PRCTL_THP_DISABLE") Link: http://lkml.kernel.org/r/1496415802-30944-1-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Michal Hocko Signed-off-by: Mike Rapoport Cc: Vlastimil Babka Cc: Andrea Arcangeli Cc: Arnd Bergmann Cc: "Kirill A. Shutemov" Cc: Pavel Emelyanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/sys.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel/sys.c') diff --git a/kernel/sys.c b/kernel/sys.c index 47d901586b4e..73fc0af147d0 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2360,7 +2360,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, case PR_GET_THP_DISABLE: if (arg2 || arg3 || arg4 || arg5) return -EINVAL; - error = !!(me->mm->def_flags & VM_NOHUGEPAGE); + error = !!test_bit(MMF_DISABLE_THP, &me->mm->flags); break; case PR_SET_THP_DISABLE: if (arg3 || arg4 || arg5) @@ -2368,9 +2368,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, if (down_write_killable(&me->mm->mmap_sem)) return -EINTR; if (arg2) - me->mm->def_flags |= VM_NOHUGEPAGE; + set_bit(MMF_DISABLE_THP, &me->mm->flags); else - me->mm->def_flags &= ~VM_NOHUGEPAGE; + clear_bit(MMF_DISABLE_THP, &me->mm->flags); up_write(&me->mm->mmap_sem); break; case PR_MPX_ENABLE_MANAGEMENT: -- cgit v1.2.3-71-gd317 From 58c7ffc0747a3a9145629d4966291f0586703767 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 12 Jul 2017 04:59:45 +0100 Subject: fix a braino in compat_sys_getrlimit() Reported-and-tested-by: Meelis Roos Fixes: commit d9e968cb9f84 "getrlimit()/setrlimit(): move compat to native" Signed-off-by: Al Viro Acked-by: David S. Miller Signed-off-by: Linus Torvalds --- kernel/sys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/sys.c') diff --git a/kernel/sys.c b/kernel/sys.c index 73fc0af147d0..2855ee73acd0 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1362,7 +1362,7 @@ COMPAT_SYSCALL_DEFINE2(getrlimit, unsigned int, resource, ret = do_prlimit(current, resource, NULL, &r); if (!ret) { - struct rlimit r32; + struct compat_rlimit r32; if (r.rlim_cur > COMPAT_RLIM_INFINITY) r32.rlim_cur = COMPAT_RLIM_INFINITY; else -- cgit v1.2.3-71-gd317