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configfs: implement the .read_iter and .write_iter methods
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Configfs is one of the few filesystems that does not yet support the
.read_iter and .write_iter callbacks. This patch adds support for these
methods in configfs.

Signed-off-by: Bart Van Assche <[email protected]>
[hch: split out a separate fix]
Signed-off-by: Christoph Hellwig <[email protected]>
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@bvanassche
bvanassche authored and Christoph Hellwig committed May 25, 2021
1 parent 44b9a00 commit 7fe1e79
Showing 1 changed file with 42 additions and 42 deletions.
84 changes: 42 additions & 42 deletions fs/configfs/file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@
#include <linux/mutex.h>
#include <linux/vmalloc.h>
#include <linux/uaccess.h>

#include <linux/uio.h>
#include <linux/configfs.h>
#include "configfs_internal.h"

Expand Down Expand Up @@ -77,9 +77,9 @@ static int fill_read_buffer(struct file *file, struct configfs_buffer *buffer)
return 0;
}

static ssize_t
configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
static ssize_t configfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
struct file *file = iocb->ki_filp;
struct configfs_buffer *buffer = file->private_data;
ssize_t retval = 0;

Expand All @@ -89,23 +89,24 @@ configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *pp
if (retval)
goto out;
}
pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
__func__, count, *ppos, buffer->page);
retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
buffer->count);
pr_debug("%s: count = %zd, pos = %lld, buf = %s\n",
__func__, iov_iter_count(to), iocb->ki_pos, buffer->page);
retval = copy_to_iter(buffer->page, buffer->count, to);
iocb->ki_pos += retval;
if (retval == 0)
retval = -EFAULT;
out:
mutex_unlock(&buffer->mutex);
return retval;
}

static ssize_t
configfs_read_bin_file(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
static ssize_t configfs_bin_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
struct file *file = iocb->ki_filp;
struct configfs_fragment *frag = to_frag(file);
struct configfs_buffer *buffer = file->private_data;
ssize_t retval = 0;
ssize_t len = min_t(size_t, count, PAGE_SIZE);
ssize_t len;

mutex_lock(&buffer->mutex);

Expand Down Expand Up @@ -161,31 +162,31 @@ configfs_read_bin_file(struct file *file, char __user *buf,
buffer->needs_read_fill = 0;
}

retval = simple_read_from_buffer(buf, count, ppos, buffer->bin_buffer,
buffer->bin_buffer_size);
retval = copy_to_iter(buffer->bin_buffer, buffer->bin_buffer_size, to);
iocb->ki_pos += retval;
if (retval == 0)
retval = -EFAULT;
out:
mutex_unlock(&buffer->mutex);
return retval;
}

static int
fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
static int fill_write_buffer(struct configfs_buffer *buffer,
struct iov_iter *from)
{
int error;
int copied;

if (!buffer->page)
buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
if (!buffer->page)
return -ENOMEM;

if (count >= SIMPLE_ATTR_SIZE)
count = SIMPLE_ATTR_SIZE - 1;
error = copy_from_user(buffer->page,buf,count);
copied = copy_from_iter(buffer->page, SIMPLE_ATTR_SIZE - 1, from);
buffer->needs_read_fill = 1;
/* if buf is assumed to contain a string, terminate it by \0,
* so e.g. sscanf() can scan the string easily */
buffer->page[count] = 0;
return error ? -EFAULT : count;
buffer->page[copied] = 0;
return copied ? : -EFAULT;
}

static int
Expand All @@ -209,28 +210,29 @@ flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t cou
* Hint: if you're writing a value, first read the file, modify only the value
* you're changing, then write entire buffer back.
*/
static ssize_t
configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
static ssize_t configfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct configfs_buffer *buffer = file->private_data;
ssize_t len;

mutex_lock(&buffer->mutex);
len = fill_write_buffer(buffer, buf, count);
len = fill_write_buffer(buffer, from);
if (len > 0)
len = flush_write_buffer(file, buffer, len);
if (len > 0)
*ppos += len;
iocb->ki_pos += len;
mutex_unlock(&buffer->mutex);
return len;
}

static ssize_t
configfs_write_bin_file(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
static ssize_t configfs_bin_write_iter(struct kiocb *iocb,
struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct configfs_buffer *buffer = file->private_data;
void *tbuf = NULL;
size_t end_offset;
ssize_t len;

mutex_lock(&buffer->mutex);
Expand All @@ -243,15 +245,14 @@ configfs_write_bin_file(struct file *file, const char __user *buf,
buffer->write_in_progress = true;

/* buffer grows? */
if (*ppos + count > buffer->bin_buffer_size) {

if (buffer->cb_max_size &&
*ppos + count > buffer->cb_max_size) {
end_offset = iocb->ki_pos + iov_iter_count(from);
if (end_offset > buffer->bin_buffer_size) {
if (buffer->cb_max_size && end_offset > buffer->cb_max_size) {
len = -EFBIG;
goto out;
}

tbuf = vmalloc(*ppos + count);
tbuf = vmalloc(end_offset);
if (tbuf == NULL) {
len = -ENOMEM;
goto out;
Expand All @@ -266,16 +267,15 @@ configfs_write_bin_file(struct file *file, const char __user *buf,

/* clear the new area */
memset(tbuf + buffer->bin_buffer_size, 0,
*ppos + count - buffer->bin_buffer_size);
end_offset - buffer->bin_buffer_size);
buffer->bin_buffer = tbuf;
buffer->bin_buffer_size = *ppos + count;
buffer->bin_buffer_size = end_offset;
}

len = simple_write_to_buffer(buffer->bin_buffer,
buffer->bin_buffer_size, ppos, buf, count);
len = copy_from_iter(buffer->bin_buffer, buffer->bin_buffer_size, from);
out:
mutex_unlock(&buffer->mutex);
return len;
return len ? : -EFAULT;
}

static int __configfs_open_file(struct inode *inode, struct file *file, int type)
Expand Down Expand Up @@ -420,16 +420,16 @@ static int configfs_release_bin_file(struct inode *inode, struct file *file)


const struct file_operations configfs_file_operations = {
.read = configfs_read_file,
.write = configfs_write_file,
.read_iter = configfs_read_iter,
.write_iter = configfs_write_iter,
.llseek = generic_file_llseek,
.open = configfs_open_file,
.release = configfs_release,
};

const struct file_operations configfs_bin_file_operations = {
.read = configfs_read_bin_file,
.write = configfs_write_bin_file,
.read_iter = configfs_bin_read_iter,
.write_iter = configfs_bin_write_iter,
.llseek = NULL, /* bin file is not seekable */
.open = configfs_open_bin_file,
.release = configfs_release_bin_file,
Expand Down

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