[PATCH v6 1/6] libfs: define simple_read_iter_from_buffer
Mimi Zohar
zohar at linux.vnet.ibm.com
Tue Aug 15 14:43:52 UTC 2017
In preparation for defining an integrity_read file operation
method for efivarfs, define a simple_read_iter_from_buffer()
function.
(Based on Al's code as posted in thread.)
Suggested-by: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
Cc: Matthew Garrett <mjg59 at srcf.ucam.org>
---
Changelog v6:
- defined as a separate patch
fs/libfs.c | 32 ++++++++++++++++++++++++++++++++
include/linux/fs.h | 2 ++
2 files changed, 34 insertions(+)
diff --git a/fs/libfs.c b/fs/libfs.c
index 3aabe553fc45..b6e304c6828b 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -16,6 +16,7 @@
#include <linux/exportfs.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h> /* sync_mapping_buffers */
+#include <linux/uio.h>
#include <linux/uaccess.h>
@@ -676,6 +677,37 @@ ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
EXPORT_SYMBOL(simple_write_to_buffer);
/**
+ * simple_read_iter_from_buffer - copy data from the buffer to user space
+ * @iocb: struct containing the file, the current position and other info
+ * @to: the user space buffer to read to
+ * @from: the buffer to read from
+ * @available: the size of the buffer
+ *
+ * The simple_read_iter_from_buffer() function reads up to @available bytes
+ * from the current buffer into the user space buffer.
+ *
+ * On success, the current buffer offset is advanced by the number of bytes
+ * read, or a negative value is returned on error.
+ **/
+ssize_t simple_read_iter_from_buffer(struct kiocb *iocb, struct iov_iter *to,
+ const void *from, size_t available)
+{
+ loff_t pos = iocb->ki_pos;
+ size_t ret;
+
+ if (pos < 0)
+ return -EINVAL;
+ if (pos >= available)
+ return 0;
+ ret = copy_to_iter(from + pos, available - pos, to);
+ if (!ret && iov_iter_count(to))
+ return -EFAULT;
+ iocb->ki_pos = pos + ret;
+ return ret;
+}
+EXPORT_SYMBOL(simple_read_iter_from_buffer);
+
+/**
* memory_read_from_buffer - copy data from the buffer
* @to: the kernel space buffer to read to
* @count: the maximum number of bytes to read
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6e1fd5d21248..fdec9b763b54 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3097,6 +3097,8 @@ extern void simple_release_fs(struct vfsmount **mount, int *count);
extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
loff_t *ppos, const void *from, size_t available);
+extern ssize_t simple_read_iter_from_buffer(struct kiocb *iocb,
+ struct iov_iter *to, const void *from, size_t available);
extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
const void __user *from, size_t count);
--
2.7.4
--
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