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Christoph Hellwiggregkh
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kernfs: implement ->read_iter
commit 4eaad21 upstream. Switch kernfs to implement the read_iter method instead of plain old read to prepare to supporting splice and sendfile again. Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20210120204631.274206-2-hch@lst.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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fs/kernfs/file.c

Lines changed: 12 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -14,6 +14,7 @@
1414
#include <linux/pagemap.h>
1515
#include <linux/sched/mm.h>
1616
#include <linux/fsnotify.h>
17+
#include <linux/uio.h>
1718

1819
#include "kernfs-internal.h"
1920

@@ -180,11 +181,10 @@ static const struct seq_operations kernfs_seq_ops = {
180181
* it difficult to use seq_file. Implement simplistic custom buffering for
181182
* bin files.
182183
*/
183-
static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
184-
char __user *user_buf, size_t count,
185-
loff_t *ppos)
184+
static ssize_t kernfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
186185
{
187-
ssize_t len = min_t(size_t, count, PAGE_SIZE);
186+
struct kernfs_open_file *of = kernfs_of(iocb->ki_filp);
187+
ssize_t len = min_t(size_t, iov_iter_count(iter), PAGE_SIZE);
188188
const struct kernfs_ops *ops;
189189
char *buf;
190190

@@ -210,7 +210,7 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
210210
of->event = atomic_read(&of->kn->attr.open->event);
211211
ops = kernfs_ops(of->kn);
212212
if (ops->read)
213-
len = ops->read(of, buf, len, *ppos);
213+
len = ops->read(of, buf, len, iocb->ki_pos);
214214
else
215215
len = -EINVAL;
216216

@@ -220,12 +220,12 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
220220
if (len < 0)
221221
goto out_free;
222222

223-
if (copy_to_user(user_buf, buf, len)) {
223+
if (copy_to_iter(buf, len, iter) != len) {
224224
len = -EFAULT;
225225
goto out_free;
226226
}
227227

228-
*ppos += len;
228+
iocb->ki_pos += len;
229229

230230
out_free:
231231
if (buf == of->prealloc_buf)
@@ -235,22 +235,11 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
235235
return len;
236236
}
237237

238-
/**
239-
* kernfs_fop_read - kernfs vfs read callback
240-
* @file: file pointer
241-
* @user_buf: data to write
242-
* @count: number of bytes
243-
* @ppos: starting offset
244-
*/
245-
static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,
246-
size_t count, loff_t *ppos)
238+
static ssize_t kernfs_fop_read_iter(struct kiocb *iocb, struct iov_iter *iter)
247239
{
248-
struct kernfs_open_file *of = kernfs_of(file);
249-
250-
if (of->kn->flags & KERNFS_HAS_SEQ_SHOW)
251-
return seq_read(file, user_buf, count, ppos);
252-
else
253-
return kernfs_file_direct_read(of, user_buf, count, ppos);
240+
if (kernfs_of(iocb->ki_filp)->kn->flags & KERNFS_HAS_SEQ_SHOW)
241+
return seq_read_iter(iocb, iter);
242+
return kernfs_file_read_iter(iocb, iter);
254243
}
255244

256245
/**
@@ -960,7 +949,7 @@ void kernfs_notify(struct kernfs_node *kn)
960949
EXPORT_SYMBOL_GPL(kernfs_notify);
961950

962951
const struct file_operations kernfs_file_fops = {
963-
.read = kernfs_fop_read,
952+
.read_iter = kernfs_fop_read_iter,
964953
.write = kernfs_fop_write,
965954
.llseek = generic_file_llseek,
966955
.mmap = kernfs_fop_mmap,

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