Merge branch 'hch' (patches from Christoph)

Merge procfs splice read fixes from Christoph Hellwig:
 "Greg reported a problem due to the fact that Android tests use procfs
  files to test splice, which stopped working with the changes for
  set_fs() removal.

  This series adds read_iter support for seq_file, and uses those for
  various proc files using seq_file to restore splice read support"

[ Side note: Christoph initially had a scripted "move everything over"
  patch, which looks fine, but I personally would prefer us to actively
  discourage splice() on random files.  So this does just the minimal
  basic core set of proc file op conversions.

  For completeness, and in case people care, that script was

     sed -i -e 's/\.proc_read\(\s*=\s*\)seq_read/\.proc_read_iter\1seq_read_iter/g'

  but I'll wait and see if somebody has a strong argument for using
  splice on random small /proc files before I'd run it on the whole
  kernel.   - Linus ]

* emailed patches from Christoph Hellwig <hch@lst.de>:
  proc "seq files": switch to ->read_iter
  proc "single files": switch to ->read_iter
  proc/stat: switch to ->read_iter
  proc/cpuinfo: switch to ->read_iter
  proc: wire up generic_file_splice_read for iter ops
  seq_file: add seq_read_iter

1 files changed, 32 insertions, 13 deletions

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 31219c1db17d..3b20e21604e7 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -18,6 +18,7 @@
 #include <linux/mm.h>
 #include <linux/printk.h>
 #include <linux/string_helpers.h>
+#include <linux/uio.h>
 
 #include <linux/uaccess.h>
 #include <asm/page.h>
@@ -146,7 +147,28 @@ Eoverflow:
  */
 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 {
-	struct seq_file *m = file->private_data;
+	struct iovec iov = { .iov_base = buf, .iov_len = size};
+	struct kiocb kiocb;
+	struct iov_iter iter;
+	ssize_t ret;
+
+	init_sync_kiocb(&kiocb, file);
+	iov_iter_init(&iter, READ, &iov, 1, size);
+
+	kiocb.ki_pos = *ppos;
+	ret = seq_read_iter(&kiocb, &iter);
+	*ppos = kiocb.ki_pos;
+	return ret;
+}
+EXPORT_SYMBOL(seq_read);
+
+/*
+ * Ready-made ->f_op->read_iter()
+ */
+ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct seq_file *m = iocb->ki_filp->private_data;
+	size_t size = iov_iter_count(iter);
 	size_t copied = 0;
 	size_t n;
 	void *p;
@@ -158,14 +180,14 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 	 * if request is to read from zero offset, reset iterator to first
 	 * record as it might have been already advanced by previous requests
 	 */
-	if (*ppos == 0) {
+	if (iocb->ki_pos == 0) {
 		m->index = 0;
 		m->count = 0;
 	}
 
-	/* Don't assume *ppos is where we left it */
-	if (unlikely(*ppos != m->read_pos)) {
-		while ((err = traverse(m, *ppos)) == -EAGAIN)
+	/* Don't assume ki_pos is where we left it */
+	if (unlikely(iocb->ki_pos != m->read_pos)) {
+		while ((err = traverse(m, iocb->ki_pos)) == -EAGAIN)
 			;
 		if (err) {
 			/* With prejudice... */
@@ -174,7 +196,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 			m->count = 0;
 			goto Done;
 		} else {
-			m->read_pos = *ppos;
+			m->read_pos = iocb->ki_pos;
 		}
 	}
 
@@ -187,13 +209,11 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 	/* if not empty - flush it first */
 	if (m->count) {
 		n = min(m->count, size);
-		err = copy_to_user(buf, m->buf + m->from, n);
-		if (err)
+		if (copy_to_iter(m->buf + m->from, n, iter) != n)
 			goto Efault;
 		m->count -= n;
 		m->from += n;
 		size -= n;
-		buf += n;
 		copied += n;
 		if (!size)
 			goto Done;
@@ -254,8 +274,7 @@ Fill:
 	}
 	m->op->stop(m, p);
 	n = min(m->count, size);
-	err = copy_to_user(buf, m->buf, n);
-	if (err)
+	if (copy_to_iter(m->buf, n, iter) != n)
 		goto Efault;
 	copied += n;
 	m->count -= n;
@@ -264,7 +283,7 @@ Done:
 	if (!copied)
 		copied = err;
 	else {
-		*ppos += copied;
+		iocb->ki_pos += copied;
 		m->read_pos += copied;
 	}
 	mutex_unlock(&m->lock);
@@ -276,7 +295,7 @@ Efault:
 	err = -EFAULT;
 	goto Done;
 }
-EXPORT_SYMBOL(seq_read);
+EXPORT_SYMBOL(seq_read_iter);
 
 /**
  *	seq_lseek -	->llseek() method for sequential files.