Re: PROBLEM: Firmware loader fallback mechanism no longer works with sendfile

Christoph Hellwig
2021-01-20T10:25:01Z

Can you give this patch a spin?

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index f277d023ebcd14..4b5833b3059f9c 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -14,6 +14,7 @@
#include <linux/pagemap.h>
#include <linux/sched/mm.h>
#include <linux/fsnotify.h>
+#include <linux/uio.h>

#include "kernfs-internal.h"

@@ -180,11 +181,10 @@ static const struct seq_operations kernfs_seq_ops = {
* it difficult to use seq_file. Implement simplistic custom buffering for
* bin files.
*/
-static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
- char __user *user_buf, size_t count,
- loff_t *ppos)
+static ssize_t kernfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
- ssize_t len = min_t(size_t, count, PAGE_SIZE);
+ struct kernfs_open_file *of = kernfs_of(iocb->ki_filp);
+ ssize_t len = min_t(size_t, iov_iter_count(iter), PAGE_SIZE);
const struct kernfs_ops *ops;
char *buf;

@@ -210,7 +210,7 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
of->event = atomic_read(&of->kn->attr.open->event);
ops = kernfs_ops(of->kn);
if (ops->read)
- len = ops->read(of, buf, len, *ppos);
+ len = ops->read(of, buf, len, iocb->ki_pos);
else
len = -EINVAL;

@@ -220,12 +220,12 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
if (len < 0)
goto out_free;

- if (copy_to_user(user_buf, buf, len)) {
+ if (copy_to_iter(buf, len, iter) != len) {
len = -EFAULT;
goto out_free;
}

- *ppos += len;
+ iocb->ki_pos += len;

out_free:
if (buf == of->prealloc_buf)
@@ -235,31 +235,14 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
return len;
}

-/**
- * kernfs_fop_read - kernfs vfs read callback
- * @file: file pointer
- * @user_buf: data to write
- * @count: number of bytes
- * @ppos: starting offset
- */
-static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,
- size_t count, loff_t *ppos)
+static ssize_t kernfs_fop_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
- struct kernfs_open_file *of = kernfs_of(file);
-
- if (of->kn->flags & KERNFS_HAS_SEQ_SHOW)
- return seq_read(file, user_buf, count, ppos);
- else
- return kernfs_file_direct_read(of, user_buf, count, ppos);
+ if (kernfs_of(iocb->ki_filp)->kn->flags & KERNFS_HAS_SEQ_SHOW)
+ return seq_read_iter(iocb, iter);
+ return kernfs_file_read_iter(iocb, iter);
}

-/**
- * kernfs_fop_write - kernfs vfs write callback
- * @file: file pointer
- * @user_buf: data to write
- * @count: number of bytes
- * @ppos: starting offset
- *
+/*
* Copy data in from userland and pass it to the matching kernfs write
* operation.
*
@@ -269,20 +252,18 @@ static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,
* modify only the the value you're changing, then write entire buffer
* back.
*/
-static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
- size_t count, loff_t *ppos)
+static ssize_t kernfs_fop_write_iter(struct kiocb *iocb, struct iov_iter *iter)
{
- struct kernfs_open_file *of = kernfs_of(file);
+ struct kernfs_open_file *of = kernfs_of(iocb->ki_filp);
+ ssize_t len = iov_iter_count(iter);
const struct kernfs_ops *ops;
- ssize_t len;
char *buf;

if (of->atomic_write_len) {
- len = count;
if (len > of->atomic_write_len)
return -E2BIG;
} else {
- len = min_t(size_t, count, PAGE_SIZE);
+ len = min_t(size_t, len, PAGE_SIZE);
}

buf = of->prealloc_buf;
@@ -293,7 +274,7 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
if (!buf)
return -ENOMEM;

- if (copy_from_user(buf, user_buf, len)) {
+ if (copy_from_iter(buf, len, iter) != len) {
len = -EFAULT;
goto out_free;
}
@@ -312,7 +293,7 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,

ops = kernfs_ops(of->kn);
if (ops->write)
- len = ops->write(of, buf, len, *ppos);
+ len = ops->write(of, buf, len, iocb->ki_pos);
else
len = -EINVAL;

@@ -320,7 +301,7 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
mutex_unlock(&of->mutex);

if (len > 0)
- *ppos += len;
+ iocb->ki_pos += len;

out_free:
if (buf == of->prealloc_buf)
@@ -960,14 +941,16 @@ void kernfs_notify(struct kernfs_node *kn)
EXPORT_SYMBOL_GPL(kernfs_notify);

const struct file_operations kernfs_file_fops = {
- .read = kernfs_fop_read,
- .write = kernfs_fop_write,
+ .read_iter = kernfs_fop_read_iter,
+ .write_iter = kernfs_fop_write_iter,
.llseek = generic_file_llseek,
.mmap = kernfs_fop_mmap,
.open = kernfs_fop_open,
.release = kernfs_fop_release,
.poll = kernfs_fop_poll,
.fsync = noop_fsync,
+ .splice_read = generic_file_splice_read,
+ .splice_write = iter_file_splice_write,
};

/**