[PATCH 3/9] seq_file: add seq_read_iter

Christoph Hellwig
2020-06-26T07:59:57Z

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