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[2003:cb:c702:5700:cb5b:f73a:c650:1d9]) by smtp.gmail.com with ESMTPSA id k21-20020a05600c1c9500b003ee74c25f12sm7605573wms.35.2023.04.14.03.25.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Apr 2023 03:25:00 -0700 (PDT) Message-ID: Date: Fri, 14 Apr 2023 12:24:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Content-Language: en-US To: Stefan Roesch , kernel-team@fb.com Cc: linux-mm@kvack.org, riel@surriel.com, mhocko@suse.com, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, akpm@linux-foundation.org, hannes@cmpxchg.org, willy@infradead.org, Bagas Sanjaya References: <20230413233115.1878303-1-shr@devkernel.io> <20230413233115.1878303-2-shr@devkernel.io> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v7 1/3] mm: add new api to enable ksm per process In-Reply-To: <20230413233115.1878303-2-shr@devkernel.io> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Thanks! In general, Acked-by: David Hildenbrand Two nits below, after staring at some other prctl implementations. > +#define PR_SET_MEMORY_MERGE 67 > +#define PR_GET_MEMORY_MERGE 68 > #endif /* _LINUX_PRCTL_H */ > diff --git a/kernel/sys.c b/kernel/sys.c > index 495cd87d9bf4..8c2e50edeb18 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -15,6 +15,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -2661,6 +2662,30 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, > case PR_SET_VMA: > error = prctl_set_vma(arg2, arg3, arg4, arg5); > break; > +#ifdef CONFIG_KSM > + case PR_SET_MEMORY_MERGE: Looking at some other code (PR_SET_NO_NEW_PRIVS/ PR_SET_THP_DISABLE) I wonder if we also want if (arg3 || arg4 || arg5) return -EINVAL; For PR_GET_MEMORY_MERGE it looks good already. > + if (mmap_write_lock_killable(me->mm)) > + return -EINTR; > + > + if (arg2) { > + error = ksm_enable_merge_any(me->mm); > + } else { > + /* > + * TODO: we might want disable KSM on all VMAs and > + * trigger unsharing to completely disable KSM. > + */ > + clear_bit(MMF_VM_MERGE_ANY, &me->mm->flags); > + error = 0; > + } > + mmap_write_unlock(me->mm); > + break; > + case PR_GET_MEMORY_MERGE: > + if (arg2 || arg3 || arg4 || arg5) > + return -EINVAL; > + > + error = !!test_bit(MMF_VM_MERGE_ANY, &me->mm->flags); > + break; > +#endif > default: > error = -EINVAL; > break; [...] > +/** > + * ksm_enable_merge_any - Add mm to mm ksm list and enable merging on all > + * compatible VMA's > + * > + * @mm: Pointer to mm > + * > + * Returns 0 on success, otherwise error code > + */ > +int ksm_enable_merge_any(struct mm_struct *mm) > +{ > + int err; > + > + if (test_bit(MMF_VM_MERGE_ANY, &mm->flags)) > + return -EINVAL; I'm curious, why is enabling the prctl() supposed to fail if already enabled? (it would not fail if disabling and already disabled) For example, PR_SET_THP_DISABLE/PR_SET_NO_NEW_PRIVS doesn't fail if already set. -- Thanks, David / dhildenb