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

[Siddharth Gupta]

On 1/20/2021 1:10 AM, Christoph Hellwig wrote:
> Can you give this patch a spin?
Thanks! This patch fixed the fallback mechanism for me. Attaching logs:

[   84.410162][  T244] qcom_q6v5_pas xxxxxxxx.remoteproc-cdsp: Direct 
firmware load for cdsp.bX failed with error -2
[   84.418276][  T244] qcom_q6v5_pas xxxxxxxx.remoteproc-cdsp: Falling 
back to sysfs fallback for: cdsp.bX
[   84.471558][  T393] ueventd: firmware: loading 'cdsp.bX' for 
'/devices/platform/soc/xxxxxxxx.remoteproc-cdsp/firmware/cdsp.bX'
[   84.491936][  T393] ueventd: loading 
/devices/platform/soc/xxxxxxxx.remoteproc-cdsp/firmware/cdsp.bX took 22ms
[  103.331486][  T244] remoteproc remoteproc1: remote processor 
xxxxxxxx.remoteproc-cdsp is now up


- Sid
> 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,
>   };
>   
>   /**