Merge tag 'vfs-6.10.rw' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs rw iterator updates from Christian Brauner:
 "The core fs signalfd, userfaultfd, and timerfd subsystems did still
  use f_op->read() instead of f_op->read_iter(). Convert them over since
  we should aim to get rid of f_op->read() at some point.

  Aside from that io_uring and others want to mark files as FMODE_NOWAIT
  so it can make use of per-IO nonblocking hints to enable more
  efficient IO. Converting those users to f_op->read_iter() allows them
  to be marked with FMODE_NOWAIT"

* tag 'vfs-6.10.rw' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  signalfd: convert to ->read_iter()
  userfaultfd: convert to ->read_iter()
  timerfd: convert to ->read_iter()
  new helper: copy_to_iter_full()

Author: torvalds

fs/signalfd.c

@@ -68,8 +68,7 @@ static __poll_t signalfd_poll(struct file *file, poll_table *wait)
 /*
  * Copied from copy_siginfo_to_user() in kernel/signal.c
  */
-static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
-			     kernel_siginfo_t const *kinfo)
+static int signalfd_copyinfo(struct iov_iter *to, kernel_siginfo_t const *kinfo)
 {
 	struct signalfd_siginfo new;
 
@@ -146,10 +145,10 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
 		break;
 	}
 
-	if (copy_to_user(uinfo, &new, sizeof(struct signalfd_siginfo)))
+	if (!copy_to_iter_full(&new, sizeof(struct signalfd_siginfo), to))
 		return -EFAULT;
 
-	return sizeof(*uinfo);
+	return sizeof(struct signalfd_siginfo);
 }
 
 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info,
@@ -199,28 +198,27 @@ static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info
  * error code. The "count" parameter must be at least the size of a
  * "struct signalfd_siginfo".
  */
-static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
-			     loff_t *ppos)
+static ssize_t signalfd_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
+	struct file *file = iocb->ki_filp;
 	struct signalfd_ctx *ctx = file->private_data;
-	struct signalfd_siginfo __user *siginfo;
-	int nonblock = file->f_flags & O_NONBLOCK;
+	size_t count = iov_iter_count(to);
 	ssize_t ret, total = 0;
 	kernel_siginfo_t info;
+	bool nonblock;
 
 	count /= sizeof(struct signalfd_siginfo);
 	if (!count)
 		return -EINVAL;
 
-	siginfo = (struct signalfd_siginfo __user *) buf;
+	nonblock = file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT;
 	do {
 		ret = signalfd_dequeue(ctx, &info, nonblock);
 		if (unlikely(ret <= 0))
 			break;
-		ret = signalfd_copyinfo(siginfo, &info);
+		ret = signalfd_copyinfo(to, &info);
 		if (ret < 0)
 			break;
-		siginfo++;
 		total += ret;
 		nonblock = 1;
 	} while (--count);
@@ -246,7 +244,7 @@ static const struct file_operations signalfd_fops = {
 #endif
 	.release	= signalfd_release,
 	.poll		= signalfd_poll,
-	.read		= signalfd_read,
+	.read_iter	= signalfd_read_iter,
 	.llseek		= noop_llseek,
 };
 
@@ -265,20 +263,34 @@ static int do_signalfd4(int ufd, sigset_t *mask, int flags)
 	signotset(mask);
 
 	if (ufd == -1) {
+		struct file *file;
+
 		ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
 		if (!ctx)
 			return -ENOMEM;
 
 		ctx->sigmask = *mask;
 
+		ufd = get_unused_fd_flags(flags & O_CLOEXEC);
+		if (ufd < 0) {
+			kfree(ctx);
+			return ufd;
+		}
+
+		file = anon_inode_getfile("[signalfd]", &signalfd_fops, ctx,
+				       O_RDWR | (flags & O_NONBLOCK));
+		if (IS_ERR(file)) {
+			put_unused_fd(ufd);
+			kfree(ctx);
+			return ufd;
+		}
+		file->f_mode |= FMODE_NOWAIT;
+
 		/*
 		 * When we call this, the initialization must be complete, since
 		 * anon_inode_getfd() will install the fd.
 		 */
-		ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
-				       O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
-		if (ufd < 0)
-			kfree(ctx);
+		fd_install(ufd, file);
 	} else {
 		struct fd f = fdget(ufd);
 		if (!f.file)

fs/timerfd.c

@@ -262,17 +262,18 @@ static __poll_t timerfd_poll(struct file *file, poll_table *wait)
 	return events;
 }
 
-static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
-			    loff_t *ppos)
+static ssize_t timerfd_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
+	struct file *file = iocb->ki_filp;
 	struct timerfd_ctx *ctx = file->private_data;
 	ssize_t res;
 	u64 ticks = 0;
 
-	if (count < sizeof(ticks))
+	if (iov_iter_count(to) < sizeof(ticks))
 		return -EINVAL;
+
 	spin_lock_irq(&ctx->wqh.lock);
-	if (file->f_flags & O_NONBLOCK)
+	if (file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT)
 		res = -EAGAIN;
 	else
 		res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
@@ -312,8 +313,11 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
 		ctx->ticks = 0;
 	}
 	spin_unlock_irq(&ctx->wqh.lock);
-	if (ticks)
-		res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
+	if (ticks) {
+		res = copy_to_iter(&ticks, sizeof(ticks), to);
+		if (!res)
+			res = -EFAULT;
+	}
 	return res;
 }
 
@@ -384,7 +388,7 @@ static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg
 static const struct file_operations timerfd_fops = {
 	.release	= timerfd_release,
 	.poll		= timerfd_poll,
-	.read		= timerfd_read,
+	.read_iter	= timerfd_read_iter,
 	.llseek		= noop_llseek,
 	.show_fdinfo	= timerfd_show,
 	.unlocked_ioctl	= timerfd_ioctl,
@@ -407,6 +411,7 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
 {
 	int ufd;
 	struct timerfd_ctx *ctx;
+	struct file *file;
 
 	/* Check the TFD_* constants for consistency.  */
 	BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
@@ -443,11 +448,22 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
 
 	ctx->moffs = ktime_mono_to_real(0);
 
-	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
-			       O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
-	if (ufd < 0)
+	ufd = get_unused_fd_flags(flags & TFD_SHARED_FCNTL_FLAGS);
+	if (ufd < 0) {
+		kfree(ctx);
+		return ufd;
+	}
+
+	file = anon_inode_getfile("[timerfd]", &timerfd_fops, ctx,
+				    O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
+	if (IS_ERR(file)) {
+		put_unused_fd(ufd);
 		kfree(ctx);
+		return PTR_ERR(file);
+	}
 
+	file->f_mode |= FMODE_NOWAIT;
+	fd_install(ufd, file);
 	return ufd;
 }
 

fs/userfaultfd.c

@@ -31,6 +31,7 @@
 #include <linux/hugetlb.h>
 #include <linux/swapops.h>
 #include <linux/miscdevice.h>
+#include <linux/uio.h>
 
 static int sysctl_unprivileged_userfaultfd __read_mostly;
 
@@ -282,7 +283,7 @@ static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
 /*
  * Verify the pagetables are still not ok after having reigstered into
  * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any
- * userfault that has already been resolved, if userfaultfd_read and
+ * userfault that has already been resolved, if userfaultfd_read_iter and
  * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different
  * threads.
  */
@@ -1181,34 +1182,34 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
 	return ret;
 }
 
-static ssize_t userfaultfd_read(struct file *file, char __user *buf,
-				size_t count, loff_t *ppos)
+static ssize_t userfaultfd_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
+	struct file *file = iocb->ki_filp;
 	struct userfaultfd_ctx *ctx = file->private_data;
 	ssize_t _ret, ret = 0;
 	struct uffd_msg msg;
-	int no_wait = file->f_flags & O_NONBLOCK;
 	struct inode *inode = file_inode(file);
+	bool no_wait;
 
 	if (!userfaultfd_is_initialized(ctx))
 		return -EINVAL;
 
+	no_wait = file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT;
 	for (;;) {
-		if (count < sizeof(msg))
+		if (iov_iter_count(to) < sizeof(msg))
 			return ret ? ret : -EINVAL;
 		_ret = userfaultfd_ctx_read(ctx, no_wait, &msg, inode);
 		if (_ret < 0)
 			return ret ? ret : _ret;
-		if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg)))
+		_ret = !copy_to_iter_full(&msg, sizeof(msg), to);
+		if (_ret)
 			return ret ? ret : -EFAULT;
 		ret += sizeof(msg);
-		buf += sizeof(msg);
-		count -= sizeof(msg);
 		/*
 		 * Allow to read more than one fault at time but only
 		 * block if waiting for the very first one.
 		 */
-		no_wait = O_NONBLOCK;
+		no_wait = true;
 	}
 }
 
@@ -2176,7 +2177,7 @@ static const struct file_operations userfaultfd_fops = {
 #endif
 	.release	= userfaultfd_release,
 	.poll		= userfaultfd_poll,
-	.read		= userfaultfd_read,
+	.read_iter	= userfaultfd_read_iter,
 	.unlocked_ioctl = userfaultfd_ioctl,
 	.compat_ioctl	= compat_ptr_ioctl,
 	.llseek		= noop_llseek,
@@ -2196,6 +2197,7 @@ static void init_once_userfaultfd_ctx(void *mem)
 static int new_userfaultfd(int flags)
 {
 	struct userfaultfd_ctx *ctx;
+	struct file *file;
 	int fd;
 
 	BUG_ON(!current->mm);
@@ -2219,16 +2221,26 @@ static int new_userfaultfd(int flags)
 	init_rwsem(&ctx->map_changing_lock);
 	atomic_set(&ctx->mmap_changing, 0);
 	ctx->mm = current->mm;
-	/* prevent the mm struct to be freed */
-	mmgrab(ctx->mm);
+
+	fd = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS);
+	if (fd < 0)
+		goto err_out;
 
 	/* Create a new inode so that the LSM can block the creation.  */
-	fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, ctx,
+	file = anon_inode_create_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
 			O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL);
-	if (fd < 0) {
-		mmdrop(ctx->mm);
-		kmem_cache_free(userfaultfd_ctx_cachep, ctx);
+	if (IS_ERR(file)) {
+		put_unused_fd(fd);
+		fd = PTR_ERR(file);
+		goto err_out;
 	}
+	/* prevent the mm struct to be freed */
+	mmgrab(ctx->mm);
+	file->f_mode |= FMODE_NOWAIT;
+	fd_install(fd, file);
+	return fd;
+err_out:
+	kmem_cache_free(userfaultfd_ctx_cachep, ctx);
 	return fd;
 }
 

include/linux/uio.h

@@ -205,6 +205,16 @@ size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 	return 0;
 }
 
+static __always_inline __must_check
+bool copy_to_iter_full(const void *addr, size_t bytes, struct iov_iter *i)
+{
+	size_t copied = copy_to_iter(addr, bytes, i);
+	if (likely(copied == bytes))
+		return true;
+	iov_iter_revert(i, copied);
+	return false;
+}
+
 static __always_inline __must_check
 bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
 {

include/net/udp.h

@@ -379,14 +379,7 @@ static inline bool udp_skb_is_linear(struct sk_buff *skb)
 static inline int copy_linear_skb(struct sk_buff *skb, int len, int off,
 				  struct iov_iter *to)
 {
-	int n;
-
-	n = copy_to_iter(skb->data + off, len, to);
-	if (n == len)
-		return 0;
-
-	iov_iter_revert(to, n);
-	return -EFAULT;
+	return copy_to_iter_full(skb->data + off, len, to) ? 0 : -EFAULT;
 }
 
 /*