fs: add vfs_iter_{read,write} helpers

Simple helpers that pass an arbitrary iov_iter to filesystems.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 51 insertions, 14 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index c0805c93b6fa..ab4f26a7d5cb 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -333,6 +333,52 @@ out_putf:
 }
 #endif
 
+ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos)
+{
+        struct kiocb kiocb;
+        ssize_t ret;
+
+        if (!file->f_op->read_iter)
+                return -EINVAL;
+
+        init_sync_kiocb(&kiocb, file);
+        kiocb.ki_pos = *ppos;
+        kiocb.ki_nbytes = iov_iter_count(iter);
+
+        iter->type |= READ;
+        ret = file->f_op->read_iter(&kiocb, iter);
+        if (ret == -EIOCBQUEUED)
+                ret = wait_on_sync_kiocb(&kiocb);
+
+        if (ret > 0)
+                *ppos = kiocb.ki_pos;
+        return ret;
+}
+EXPORT_SYMBOL(vfs_iter_read);
+
+ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos)
+{
+        struct kiocb kiocb;
+        ssize_t ret;
+
+        if (!file->f_op->write_iter)
+                return -EINVAL;
+
+        init_sync_kiocb(&kiocb, file);
+        kiocb.ki_pos = *ppos;
+        kiocb.ki_nbytes = iov_iter_count(iter);
+
+        iter->type |= WRITE;
+        ret = file->f_op->write_iter(&kiocb, iter);
+        if (ret == -EIOCBQUEUED)
+                ret = wait_on_sync_kiocb(&kiocb);
+
+        if (ret > 0)
+                *ppos = kiocb.ki_pos;
+        return ret;
+}
+EXPORT_SYMBOL(vfs_iter_write);
+
 /*
  * rw_verify_area doesn't like huge counts. We limit
  * them to something that fits in "int" so that others
diff --git a/fs/splice.c b/fs/splice.c
index 7c7176f2d1e7..7968da96bebb 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -961,7 +961,6 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
         splice_from_pipe_begin(&sd);
         while (sd.total_len) {
                 struct iov_iter from;
-                struct kiocb kiocb;
                 size_t left;
                 int n, idx;
 
@@ -1005,26 +1004,15 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
                         left -= this_len;
                 }
 
-                /* ... iov_iter */
                 iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
                               sd.total_len - left);
-
-                /* ... and iocb */
-                init_sync_kiocb(&kiocb, out);
-                kiocb.ki_pos = sd.pos;
-                kiocb.ki_nbytes = sd.total_len - left;
-
-                /* now, send it */
-                ret = out->f_op->write_iter(&kiocb, &from);
-                if (-EIOCBQUEUED == ret)
-                        ret = wait_on_sync_kiocb(&kiocb);
-
+                ret = vfs_iter_write(out, &from, &sd.pos);
                 if (ret <= 0)
                         break;
 
                 sd.num_spliced += ret;
                 sd.total_len -= ret;
-                *ppos = sd.pos = kiocb.ki_pos;
+                *ppos = sd.pos;
 
                 /* dismiss the fully eaten buffers, adjust the partial one */
                 while (ret) {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 42efe13077b6..1f3c43952540 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2494,6 +2494,9 @@ extern ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t l
 extern ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos);
 extern ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos);
 
+ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos);
+ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos);
+
 /* fs/block_dev.c */
 extern ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to);
 extern ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from);