fs: introduce iomap infrastructure
Add infrastructure for multipage buffered writes. This is implemented
using an main iterator that applies an actor function to a range that
can be written.
This infrastucture is used to implement a buffered write helper, one
to zero file ranges and one to implement the ->page_mkwrite VM
operations. All of them borrow a fair amount of code from fs/buffers.
for now by using an internal version of __block_write_begin that
gets passed an iomap and builds the corresponding buffer head.
The file system is gets a set of paired ->iomap_begin and ->iomap_end
calls which allow it to map/reserve a range and get a notification
once the write code is finished with it.
Based on earlier code from Dave Chinner.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff --git a/fs/internal.h b/fs/internal.h
index b71deee..c0c6f49 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -11,6 +11,7 @@
struct super_block;
struct file_system_type;
+struct iomap;
struct linux_binprm;
struct path;
struct mount;
@@ -39,6 +40,8 @@
* buffer.c
*/
extern void guard_bio_eod(int rw, struct bio *bio);
+extern int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
+ get_block_t *get_block, struct iomap *iomap);
/*
* char_dev.c