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From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@zeniv.linux.org.uk>,
	Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	Kees Cook <keescook@chromium.org>,
	Iurii Zaikin <yzaikin@google.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH 3/9] seq_file: add seq_read_iter
Date: Fri, 26 Jun 2020 09:58:30 +0200	[thread overview]
Message-ID: <20200626075836.1998185-4-hch@lst.de> (raw)
In-Reply-To: <20200626075836.1998185-1-hch@lst.de>

iov_iter based variant for reading a seq_file.  seq_read is
reimplemented on top of the iter variant.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/seq_file.c            | 34 +++++++++++++++++++++-------------
 include/linux/seq_file.h |  1 +
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 4e6239f33c066a..159a3e12cadd30 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 +147,17 @@ static int traverse(struct seq_file *m, loff_t offset)
  */
 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 {
-	struct seq_file *m = file->private_data;
+	return iter_read(file, buf, size, ppos, seq_read_iter);
+}
+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 +169,14 @@ 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 +185,7 @@ 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 +198,11 @@ 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 +263,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 	}
 	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 +272,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 	if (!copied)
 		copied = err;
 	else {
-		*ppos += copied;
+		iocb->ki_pos += copied;
 		m->read_pos += copied;
 	}
 	mutex_unlock(&m->lock);
@@ -276,7 +284,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 	err = -EFAULT;
 	goto Done;
 }
-EXPORT_SYMBOL(seq_read);
+EXPORT_SYMBOL(seq_read_iter);
 
 /**
  *	seq_lseek -	->llseek() method for sequential files.
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 813614d4b71fbc..b83b3ae3c877f3 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -107,6 +107,7 @@ void seq_pad(struct seq_file *m, char c);
 char *mangle_path(char *s, const char *p, const char *esc);
 int seq_open(struct file *, const struct seq_operations *);
 ssize_t seq_read(struct file *, char __user *, size_t, loff_t *);
+ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter);
 loff_t seq_lseek(struct file *, loff_t, int);
 int seq_release(struct inode *, struct file *);
 int seq_write(struct seq_file *seq, const void *data, size_t len);
-- 
2.26.2


  parent reply	other threads:[~2020-06-26  7:59 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-26  7:58 [RFC] stop using ->read and ->write for kernel access v2 Christoph Hellwig
2020-06-26  7:58 ` [PATCH 1/9] fs: refactor new_sync_read Christoph Hellwig
2020-06-26  7:58 ` [PATCH 2/9] proc: add a read_iter method to proc proc_ops Christoph Hellwig
2020-06-26 12:06   ` Luis Chamberlain
2020-06-26 13:36     ` Christoph Hellwig
2020-06-26  7:58 ` Christoph Hellwig [this message]
2020-06-26  7:58 ` [PATCH 4/9] seq_file: switch over direct seq_read method calls to seq_read_iter Christoph Hellwig
2020-06-26  7:58 ` [PATCH 5/9] proc: " Christoph Hellwig
2020-06-26  7:58 ` [PATCH 6/9] sysctl: Call sysctl_head_finish on error Christoph Hellwig
2020-06-26 12:17   ` Luis Chamberlain
2020-06-26 12:27     ` Matthew Wilcox
2020-06-26  7:58 ` [PATCH 7/9] sysctl: Convert to iter interfaces Christoph Hellwig
2020-06-26  7:58 ` [PATCH 8/9] fs: don't allow kernel reads and writes without iter ops Christoph Hellwig
2020-06-26 12:27   ` Luis Chamberlain
2020-06-26 13:37     ` Christoph Hellwig
2020-06-26 13:51   ` Matthew Wilcox
2020-06-26 21:05     ` Kees Cook
2020-06-27  7:10     ` Christoph Hellwig
2020-06-26  7:58 ` [PATCH 9/9] fs: don't allow splice read/write without explicit ops Christoph Hellwig
2020-06-27 22:15 ` [RFC] stop using ->read and ->write for kernel access v2 Linus Torvalds
2020-06-28  7:20   ` Christoph Hellwig

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