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[141.146.126.69]) by mx.google.com with ESMTPS id 64si3604386edl.473.2017.11.08.17.41.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 08 Nov 2017 17:41:38 -0800 (PST) From: Mike Kravetz Subject: [RFC PATCH 3/3] mm: memfd: remove memfd code from shmem files and use new memfd files Date: Wed, 8 Nov 2017 17:41:09 -0800 Message-Id: <20171109014109.21077-4-mike.kravetz@oracle.com> In-Reply-To: <20171109014109.21077-1-mike.kravetz@oracle.com> References: <20171109014109.21077-1-mike.kravetz@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Hugh Dickins , Andrea Arcangeli , Michal Hocko , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , David Herrmann , Andrew Morton , Mike Kravetz Remove memfd and file sealing routines from shmem.c and enable the use of the new files (memfd.c and memfd.h). A new config option MEMFD_CREATE is defined that is enabled if TMPFS -or- HUGETLBFS is defined. Signed-off-by: Mike Kravetz --- fs/Kconfig | 3 + fs/fcntl.c | 2 +- include/linux/shmem_fs.h | 13 -- mm/Makefile | 1 + mm/shmem.c | 323 ----------------------------------------------- 5 files changed, 5 insertions(+), 337 deletions(-) diff --git a/fs/Kconfig b/fs/Kconfig index 7aee6d699fd6..a480ea0c7a44 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -200,6 +200,9 @@ config HUGETLBFS config HUGETLB_PAGE def_bool HUGETLBFS +config MEMFD_CREATE + def_bool TMPFS || HUGETLBFS + config ARCH_HAS_GIGANTIC_PAGE bool diff --git a/fs/fcntl.c b/fs/fcntl.c index 752c23743616..eedb898abe06 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -22,7 +22,7 @@ #include #include #include -#include +#include #include #include diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index 0dac8c0f4aa4..098f8882e83b 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -107,19 +107,6 @@ static inline bool shmem_file(struct file *file) extern bool shmem_charge(struct inode *inode, long pages); extern void shmem_uncharge(struct inode *inode, long pages); -#ifdef CONFIG_TMPFS - -extern long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg); - -#else - -static inline long memfd_fcntl(struct file *f, unsigned int c, unsigned long a) -{ - return -EINVAL; -} - -#endif - #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE extern bool shmem_huge_enabled(struct vm_area_struct *vma); #else diff --git a/mm/Makefile b/mm/Makefile index e3ac3aeb533b..b3ff66e29d5b 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -105,3 +105,4 @@ obj-$(CONFIG_DEBUG_PAGE_REF) += debug_page_ref.o obj-$(CONFIG_HARDENED_USERCOPY) += usercopy.o obj-$(CONFIG_PERCPU_STATS) += percpu-stats.o obj-$(CONFIG_HMM) += hmm.o +obj-$(CONFIG_MEMFD_CREATE) += memfd.o diff --git a/mm/shmem.c b/mm/shmem.c index b08ba5d84d84..99262a963f8f 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2604,241 +2604,6 @@ static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence) return offset; } -/* - * We need a tag: a new tag would expand every radix_tree_node by 8 bytes, - * so reuse a tag which we firmly believe is never set or cleared on shmem. - */ -#define SHMEM_TAG_PINNED PAGECACHE_TAG_TOWRITE -#define LAST_SCAN 4 /* about 150ms max */ - -static void shmem_tag_pins(struct address_space *mapping) -{ - struct radix_tree_iter iter; - void **slot; - pgoff_t start; - struct page *page; - - lru_add_drain(); - start = 0; - rcu_read_lock(); - - radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { - page = radix_tree_deref_slot(slot); - if (!page || radix_tree_exception(page)) { - if (radix_tree_deref_retry(page)) { - slot = radix_tree_iter_retry(&iter); - continue; - } - } else if (page_count(page) - page_mapcount(page) > 1) { - spin_lock_irq(&mapping->tree_lock); - radix_tree_tag_set(&mapping->page_tree, iter.index, - SHMEM_TAG_PINNED); - spin_unlock_irq(&mapping->tree_lock); - } - - if (need_resched()) { - slot = radix_tree_iter_resume(slot, &iter); - cond_resched_rcu(); - } - } - rcu_read_unlock(); -} - -/* - * Setting SEAL_WRITE requires us to verify there's no pending writer. However, - * via get_user_pages(), drivers might have some pending I/O without any active - * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all pages - * and see whether it has an elevated ref-count. If so, we tag them and wait for - * them to be dropped. - * The caller must guarantee that no new user will acquire writable references - * to those pages to avoid races. - */ -static int shmem_wait_for_pins(struct address_space *mapping) -{ - struct radix_tree_iter iter; - void **slot; - pgoff_t start; - struct page *page; - int error, scan; - - shmem_tag_pins(mapping); - - error = 0; - for (scan = 0; scan <= LAST_SCAN; scan++) { - if (!radix_tree_tagged(&mapping->page_tree, SHMEM_TAG_PINNED)) - break; - - if (!scan) - lru_add_drain_all(); - else if (schedule_timeout_killable((HZ << scan) / 200)) - scan = LAST_SCAN; - - start = 0; - rcu_read_lock(); - radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, - start, SHMEM_TAG_PINNED) { - - page = radix_tree_deref_slot(slot); - if (radix_tree_exception(page)) { - if (radix_tree_deref_retry(page)) { - slot = radix_tree_iter_retry(&iter); - continue; - } - - page = NULL; - } - - if (page && - page_count(page) - page_mapcount(page) != 1) { - if (scan < LAST_SCAN) - goto continue_resched; - - /* - * On the last scan, we clean up all those tags - * we inserted; but make a note that we still - * found pages pinned. - */ - error = -EBUSY; - } - - spin_lock_irq(&mapping->tree_lock); - radix_tree_tag_clear(&mapping->page_tree, - iter.index, SHMEM_TAG_PINNED); - spin_unlock_irq(&mapping->tree_lock); -continue_resched: - if (need_resched()) { - slot = radix_tree_iter_resume(slot, &iter); - cond_resched_rcu(); - } - } - rcu_read_unlock(); - } - - return error; -} - -static unsigned int *memfd_file_seals_ptr(struct file *file) -{ - if (file->f_op == &shmem_file_operations) - return &SHMEM_I(file_inode(file))->seals; - -#ifdef CONFIG_HUGETLBFS - if (file->f_op == &hugetlbfs_file_operations) - return &HUGETLBFS_I(file_inode(file))->seals; -#endif - - return NULL; -} - -#define F_ALL_SEALS (F_SEAL_SEAL | \ - F_SEAL_SHRINK | \ - F_SEAL_GROW | \ - F_SEAL_WRITE) - -static int memfd_add_seals(struct file *file, unsigned int seals) -{ - struct inode *inode = file_inode(file); - unsigned int *file_seals; - int error; - - /* - * SEALING - * Sealing allows multiple parties to share a shmem-file but restrict - * access to a specific subset of file operations. Seals can only be - * added, but never removed. This way, mutually untrusted parties can - * share common memory regions with a well-defined policy. A malicious - * peer can thus never perform unwanted operations on a shared object. - * - * Seals are only supported on special shmem-files and always affect - * the whole underlying inode. Once a seal is set, it may prevent some - * kinds of access to the file. Currently, the following seals are - * defined: - * SEAL_SEAL: Prevent further seals from being set on this file - * SEAL_SHRINK: Prevent the file from shrinking - * SEAL_GROW: Prevent the file from growing - * SEAL_WRITE: Prevent write access to the file - * - * As we don't require any trust relationship between two parties, we - * must prevent seals from being removed. Therefore, sealing a file - * only adds a given set of seals to the file, it never touches - * existing seals. Furthermore, the "setting seals"-operation can be - * sealed itself, which basically prevents any further seal from being - * added. - * - * Semantics of sealing are only defined on volatile files. Only - * anonymous shmem files support sealing. More importantly, seals are - * never written to disk. Therefore, there's no plan to support it on - * other file types. - */ - - if (!(file->f_mode & FMODE_WRITE)) - return -EPERM; - if (seals & ~(unsigned int)F_ALL_SEALS) - return -EINVAL; - - inode_lock(inode); - - file_seals = memfd_file_seals_ptr(file); - if (!file_seals) { - error = -EINVAL; - goto unlock; - } - - if (*file_seals & F_SEAL_SEAL) { - error = -EPERM; - goto unlock; - } - - if ((seals & F_SEAL_WRITE) && !(*file_seals & F_SEAL_WRITE)) { - error = mapping_deny_writable(file->f_mapping); - if (error) - goto unlock; - - error = shmem_wait_for_pins(file->f_mapping); - if (error) { - mapping_allow_writable(file->f_mapping); - goto unlock; - } - } - - *file_seals |= seals; - error = 0; - -unlock: - inode_unlock(inode); - return error; -} - -static int memfd_get_seals(struct file *file) -{ - unsigned int *seals = memfd_file_seals_ptr(file); - - return seals ? *seals : -EINVAL; -} - -long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg) -{ - long error; - - switch (cmd) { - case F_ADD_SEALS: - /* disallow upper 32bit */ - if (arg > UINT_MAX) - return -EINVAL; - - error = memfd_add_seals(file, arg); - break; - case F_GET_SEALS: - error = memfd_get_seals(file); - break; - default: - error = -EINVAL; - break; - } - - return error; -} - static long shmem_fallocate(struct file *file, int mode, loff_t offset, loff_t len) { @@ -3662,94 +3427,6 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root) shmem_show_mpol(seq, sbinfo->mpol); return 0; } - -#define MFD_NAME_PREFIX "memfd:" -#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1) -#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN) - -#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB) - -SYSCALL_DEFINE2(memfd_create, - const char __user *, uname, - unsigned int, flags) -{ - unsigned int *file_seals; - struct file *file; - int fd, error; - char *name; - long len; - - if (!(flags & MFD_HUGETLB)) { - if (flags & ~(unsigned int)MFD_ALL_FLAGS) - return -EINVAL; - } else { - /* Allow huge page size encoding in flags. */ - if (flags & ~(unsigned int)(MFD_ALL_FLAGS | - (MFD_HUGE_MASK << MFD_HUGE_SHIFT))) - return -EINVAL; - } - - /* length includes terminating zero */ - len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1); - if (len <= 0) - return -EFAULT; - if (len > MFD_NAME_MAX_LEN + 1) - return -EINVAL; - - name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_KERNEL); - if (!name) - return -ENOMEM; - - strcpy(name, MFD_NAME_PREFIX); - if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) { - error = -EFAULT; - goto err_name; - } - - /* terminating-zero may have changed after strnlen_user() returned */ - if (name[len + MFD_NAME_PREFIX_LEN - 1]) { - error = -EFAULT; - goto err_name; - } - - fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0); - if (fd < 0) { - error = fd; - goto err_name; - } - - if (flags & MFD_HUGETLB) { - struct user_struct *user = NULL; - - file = hugetlb_file_setup(name, 0, VM_NORESERVE, &user, - HUGETLB_ANONHUGE_INODE, - (flags >> MFD_HUGE_SHIFT) & - MFD_HUGE_MASK); - } else - file = shmem_file_setup(name, 0, VM_NORESERVE); - if (IS_ERR(file)) { - error = PTR_ERR(file); - goto err_fd; - } - file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE; - file->f_flags |= O_RDWR | O_LARGEFILE; - - if (flags & MFD_ALLOW_SEALING) { - file_seals = memfd_file_seals_ptr(file); - *file_seals &= ~F_SEAL_SEAL; - } - - fd_install(fd, file); - kfree(name); - return fd; - -err_fd: - put_unused_fd(fd); -err_name: - kfree(name); - return error; -} - #endif /* CONFIG_TMPFS */ static void shmem_put_super(struct super_block *sb) -- 2.13.6 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . 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