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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id d129sm539530qkf.136.2021.07.30.01.13.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Jul 2021 01:13:02 -0700 (PDT) Date: Fri, 30 Jul 2021 01:13:00 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.anvils To: Andrew Morton cc: Hugh Dickins , Shakeel Butt , "Kirill A. Shutemov" , Yang Shi , Miaohe Lin , Mike Kravetz , Michal Hocko , Rik van Riel , Christoph Hellwig , Matthew Wilcox , "Eric W. Biederman" , Alexey Gladkov , Chris Wilson , Matthew Auld , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 16/16] memfd: memfd_create(name, MFD_MEM_LOCK) for memlocked shmem In-Reply-To: <2862852d-badd-7486-3a8e-c5ea9666d6fb@google.com> Message-ID: References: <2862852d-badd-7486-3a8e-c5ea9666d6fb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now that the size of a memlocked file can be changed, memfd_create() can accept an MFD_MEM_LOCK flag to request memlocking, even though the initial size is of course 0. Signed-off-by: Hugh Dickins --- include/uapi/linux/memfd.h | 1 + mm/memfd.c | 7 +++++-- mm/shmem.c | 13 ++++++++++++- 3 files changed, 18 insertions(+), 3 deletions(-) diff --git a/include/uapi/linux/memfd.h b/include/uapi/linux/memfd.h index 8358a69e78cc..9113b5aa1763 100644 --- a/include/uapi/linux/memfd.h +++ b/include/uapi/linux/memfd.h @@ -9,6 +9,7 @@ #define MFD_ALLOW_SEALING 0x0002U #define MFD_HUGETLB 0x0004U /* Use hugetlbfs */ #define MFD_HUGEPAGE 0x0008U /* Use huge tmpfs */ +#define MFD_MEM_LOCK 0x0010U /* Memlock tmpfs */ /* * Huge page size encoding when MFD_HUGETLB is specified, and a huge page diff --git a/mm/memfd.c b/mm/memfd.c index 0d1a504d2fc9..e39f9eed55d2 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -248,7 +248,8 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg) #define MFD_ALL_FLAGS (MFD_CLOEXEC | \ MFD_ALLOW_SEALING | \ MFD_HUGETLB | \ - MFD_HUGEPAGE) + MFD_HUGEPAGE | \ + MFD_MEM_LOCK) SYSCALL_DEFINE2(memfd_create, const char __user *, uname, @@ -262,7 +263,7 @@ SYSCALL_DEFINE2(memfd_create, if (flags & MFD_HUGETLB) { /* Disallow huge tmpfs when choosing hugetlbfs */ - if (flags & MFD_HUGEPAGE) + if (flags & (MFD_HUGEPAGE | MFD_MEM_LOCK)) return -EINVAL; /* Allow huge page size encoding in flags. */ if (flags & ~(unsigned int)(MFD_ALL_FLAGS | @@ -314,6 +315,8 @@ SYSCALL_DEFINE2(memfd_create, if (flags & MFD_HUGEPAGE) vm_flags |= VM_HUGEPAGE; + if (flags & MFD_MEM_LOCK) + vm_flags |= VM_LOCKED; file = shmem_file_setup(name, 0, vm_flags); } diff --git a/mm/shmem.c b/mm/shmem.c index fa4a264453bf..a0a83e59ae07 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2395,7 +2395,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode spin_lock_init(&info->lock); atomic_set(&info->stop_eviction, 0); info->seals = F_SEAL_SEAL; - info->flags = flags & VM_NORESERVE; + info->flags = flags & (VM_NORESERVE | VM_LOCKED); if ((flags & VM_HUGEPAGE) && transparent_hugepage_allowed(sbinfo) && !test_bit(MMF_DISABLE_THP, ¤t->mm->flags)) @@ -4254,6 +4254,17 @@ static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, l inode->i_size = size; clear_nlink(inode); /* It is unlinked */ res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size)); + if (!IS_ERR(res) && (flags & VM_LOCKED)) { + struct ucounts *ucounts = current_ucounts(); + /* + * Only memfd_create() may pass VM_LOCKED, and it passes + * size 0; but avoid that assumption in case it changes. + */ + if (user_shm_lock(size, ucounts, true)) + SHMEM_I(inode)->mlock_ucounts = ucounts; + else + res = ERR_PTR(-EPERM); + } if (!IS_ERR(res)) res = alloc_file_pseudo(inode, mnt, name, O_RDWR, &shmem_file_operations); -- 2.26.2