[PATCH 5.10 197/199] kernfs: implement ->write_iter

Greg Kroah-Hartman
2021-01-25T19:29:46Z

From: Christoph Hellwig <hch@lst.de>

commit cc099e0b399889c6485c88368b19824b087c9f8c upstream.

Switch kernfs to implement the write_iter method instead of plain old
write to prepare to supporting splice and sendfile again.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210120204631.274206-3-hch@lst.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/file.c | 28 ++++++++++------------------
1 file changed, 10 insertions(+), 18 deletions(-)

--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -242,13 +242,7 @@ static ssize_t kernfs_fop_read_iter(stru
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.
*
@@ -258,20 +252,18 @@ static ssize_t kernfs_fop_read_iter(stru
* 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;
@@ -282,7 +274,7 @@ static ssize_t kernfs_fop_write(struct f
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;
}
@@ -301,7 +293,7 @@ static ssize_t kernfs_fop_write(struct f

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;

@@ -309,7 +301,7 @@ static ssize_t kernfs_fop_write(struct f
mutex_unlock(&of->mutex);

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

out_free:
if (buf == of->prealloc_buf)
@@ -662,7 +654,7 @@ static int kernfs_fop_open(struct inode

/*
* Write path needs to atomic_write_len outside active reference.
- * Cache it in open_file. See kernfs_fop_write() for details.
+ * Cache it in open_file. See kernfs_fop_write_iter() for details.
*/
of->atomic_write_len = ops->atomic_write_len;

@@ -950,7 +942,7 @@ EXPORT_SYMBOL_GPL(kernfs_notify);

const struct file_operations kernfs_file_fops = {
.read_iter = kernfs_fop_read_iter,
- .write = kernfs_fop_write,
+ .write_iter = kernfs_fop_write_iter,
.llseek = generic_file_llseek,
.mmap = kernfs_fop_mmap,
.open = kernfs_fop_open,