linux-kernel - [PATCH 2/9] proc: add a read_iter method to proc proc

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Message-Id: <20200626075836.1998185-3-hch@lst.de>
Date:   Fri, 26 Jun 2020 09:58:29 +0200
From:   Christoph Hellwig <hch@....de>
To:     Al Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH 2/9] proc: add a read_iter method to proc proc_ops

This will allow proc files to implement iter read semantics.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 fs/proc/inode.c         | 28 ++++++++++++++++++++++++++++
 include/linux/proc_fs.h |  1 +
 2 files changed, 29 insertions(+)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 28d6105e908e4c..fa86619cebc2be 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -297,6 +297,29 @@ static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 	return rv;
 }
 
+static ssize_t pde_read_iter(struct proc_dir_entry *pde, struct kiocb *iocb,
+		struct iov_iter *iter)
+{
+	if (!pde->proc_ops->proc_read_iter)
+		return -EINVAL;
+	return pde->proc_ops->proc_read_iter(iocb, iter);
+}
+
+static ssize_t proc_reg_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct proc_dir_entry *pde = PDE(file_inode(iocb->ki_filp));
+	ssize_t ret;
+
+	if (pde_is_permanent(pde))
+		return pde_read_iter(pde, iocb, iter);
+
+	if (!use_pde(pde))
+		return -EIO;
+	ret = pde_read_iter(pde, iocb, iter);
+	unuse_pde(pde);
+	return ret;
+}
+
 static ssize_t pde_read(struct proc_dir_entry *pde, struct file *file, char __user *buf, size_t count, loff_t *ppos)
 {
 	typeof_member(struct proc_ops, proc_read) read;
@@ -312,6 +335,9 @@ static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count,
 	struct proc_dir_entry *pde = PDE(file_inode(file));
 	ssize_t rv = -EIO;
 
+	if (pde->proc_ops->proc_read_iter)
+		return iter_read(file, buf, count, ppos, proc_reg_read_iter);
+
 	if (pde_is_permanent(pde)) {
 		return pde_read(pde, file, buf, count, ppos);
 	} else if (use_pde(pde)) {
@@ -569,6 +595,7 @@ static int proc_reg_release(struct inode *inode, struct file *file)
 static const struct file_operations proc_reg_file_ops = {
 	.llseek		= proc_reg_llseek,
 	.read		= proc_reg_read,
+	.read_iter	= proc_reg_read_iter,
 	.write		= proc_reg_write,
 	.poll		= proc_reg_poll,
 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
@@ -585,6 +612,7 @@ static const struct file_operations proc_reg_file_ops = {
 static const struct file_operations proc_reg_file_ops_no_compat = {
 	.llseek		= proc_reg_llseek,
 	.read		= proc_reg_read,
+	.read_iter	= proc_reg_read_iter,
 	.write		= proc_reg_write,
 	.poll		= proc_reg_poll,
 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index d1eed1b4365172..97b3f5f06db9d8 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -30,6 +30,7 @@ struct proc_ops {
 	unsigned int proc_flags;
 	int	(*proc_open)(struct inode *, struct file *);
 	ssize_t	(*proc_read)(struct file *, char __user *, size_t, loff_t *);
+	ssize_t (*proc_read_iter)(struct kiocb *, struct iov_iter *);
 	ssize_t	(*proc_write)(struct file *, const char __user *, size_t, loff_t *);
 	loff_t	(*proc_lseek)(struct file *, loff_t, int);
 	int	(*proc_release)(struct inode *, struct file *);
-- 
2.26.2