Merge branch 'hch' (patches from Christoph)

6b2c4d52 · Linus Torvalds <[email protected]> · 2020-11-08 10:11:31 -08:00

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 <[email protected]>:
  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

Commit: 6b2c4d52fd38e676fc9ab5d9241a056de565eb1a
Parents: 40be821d · b24c30c6

Merge commit. Changes below are compared with the first parent: 40be821d.

Changes

6 files changed · +39 −17

File	Status	Add	Del	Content
fs/proc/cpuinfo.c	modified	+1	−1	View file
fs/proc/generic.c	modified	+2	−2	View file
fs/proc/inode.c	modified	+2	−0	View file
fs/proc/stat.c	modified	+1	−1	View file
fs/seq_file.c	modified	+32	−13	View file
include/linux/seq_file.h	modified	+1	−0	View file

fs/proc/cpuinfo.c

View file

diff --git a/fs/proc/cpuinfo.c b/fs/proc/cpuinfo.c
index d0989a4..419760f 100644
--- a/fs/proc/cpuinfo.c
+++ b/fs/proc/cpuinfo.c
@@ -19,7 +19,7 @@ static int cpuinfo_open(struct inode *inode, struct file *file)
 static const struct proc_ops cpuinfo_proc_ops = {
 	.proc_flags	= PROC_ENTRY_PERMANENT,
 	.proc_open	= cpuinfo_open,
-	.proc_read	= seq_read,
+	.proc_read_iter	= seq_read_iter,
 	.proc_lseek	= seq_lseek,
 	.proc_release	= seq_release,
 };

fs/proc/generic.c

View file

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 2f9fa17..b846632 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -590,7 +590,7 @@ static int proc_seq_release(struct inode *inode, struct file *file)
 static const struct proc_ops proc_seq_ops = {
 	/* not permanent -- can call into arbitrary seq_operations */
 	.proc_open	= proc_seq_open,
-	.proc_read	= seq_read,
+	.proc_read_iter	= seq_read_iter,
 	.proc_lseek	= seq_lseek,
 	.proc_release	= proc_seq_release,
 };
@@ -621,7 +621,7 @@ static int proc_single_open(struct inode *inode, struct file *file)
 static const struct proc_ops proc_single_ops = {
 	/* not permanent -- can call into arbitrary ->single_show */
 	.proc_open	= proc_single_open,
-	.proc_read	= seq_read,
+	.proc_read_iter = seq_read_iter,
 	.proc_lseek	= seq_lseek,
 	.proc_release	= single_release,
 };

fs/proc/inode.c

View file

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 58c075e..bde6b6f 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -597,6 +597,7 @@ static const struct file_operations proc_iter_file_ops = {
 	.llseek		= proc_reg_llseek,
 	.read_iter	= proc_reg_read_iter,
 	.write		= proc_reg_write,
+	.splice_read	= generic_file_splice_read,
 	.poll		= proc_reg_poll,
 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
 	.mmap		= proc_reg_mmap,
@@ -622,6 +623,7 @@ static const struct file_operations proc_reg_file_ops_compat = {
 static const struct file_operations proc_iter_file_ops_compat = {
 	.llseek		= proc_reg_llseek,
 	.read_iter	= proc_reg_read_iter,
+	.splice_read	= generic_file_splice_read,
 	.write		= proc_reg_write,
 	.poll		= proc_reg_poll,
 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,

fs/proc/stat.c

View file

diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index 46b3293..4695b6d 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -226,7 +226,7 @@ static int stat_open(struct inode *inode, struct file *file)
 static const struct proc_ops stat_proc_ops = {
 	.proc_flags	= PROC_ENTRY_PERMANENT,
 	.proc_open	= stat_open,
-	.proc_read	= seq_read,
+	.proc_read_iter	= seq_read_iter,
 	.proc_lseek	= seq_lseek,
 	.proc_release	= single_release,
 };

fs/seq_file.c

View file

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 31219c1..3b20e21 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.

include/linux/seq_file.h

View file

diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 813614d..b83b3ae 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);