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>
This commit is contained in:
Christoph Hellwig 2016-06-21 09:23:11 +10:00 committed by Dave Chinner
parent 199a31c6d9
commit ae259a9c85
6 changed files with 523 additions and 10 deletions

View file

@ -11,6 +11,7 @@
struct super_block;
struct file_system_type;
struct iomap;
struct linux_binprm;
struct path;
struct mount;
@ -39,6 +40,8 @@ static inline int __sync_blockdev(struct block_device *bdev, int wait)
* 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