kernfs: implement ->write_iter

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>

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 8276e4c..b1a5ccc 100644 (file)
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -242,13 +242,7 @@ static ssize_t kernfs_fop_read_iter(struct kiocb *iocb, struct iov_iter *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.
  *
@@ -258,20 +252,18 @@ static ssize_t kernfs_fop_read_iter(struct kiocb *iocb, struct iov_iter *iter)
  * 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 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;
        }
@@ -301,7 +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;
 
@@ -309,7 +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)
@@ -662,7 +654,7 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
 
        /*
         * 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,