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fs: introduce iomap infrastructure

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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
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56
include/linux/iomap.h
View file

@ -3,19 +3,65 @@
#include <linux/types.h>
/* types of block ranges for multipage write mappings. */
struct inode;
struct iov_iter;
struct kiocb;
struct vm_area_struct;
struct vm_fault;
/*
* Types of block ranges for iomap mappings:
*/
#define IOMAP_HOLE 0x01 /* no blocks allocated, need allocation */
#define IOMAP_DELALLOC 0x02 /* delayed allocation blocks */
#define IOMAP_MAPPED 0x03 /* blocks allocated @blkno */
#define IOMAP_UNWRITTEN 0x04 /* blocks allocated @blkno in unwritten state */
/*
* Magic value for blkno:
*/
#define IOMAP_NULL_BLOCK -1LL /* blkno is not valid */
struct iomap {
sector_t blkno; /* first sector of mapping */
loff_t offset; /* file offset of mapping, bytes */
u64 length; /* length of mapping, bytes */
int type; /* type of mapping */
sector_t blkno; /* 1st sector of mapping, 512b units */
loff_t offset; /* file offset of mapping, bytes */
u64 length; /* length of mapping, bytes */
int type; /* type of mapping */
struct block_device *bdev; /* block device for I/O */
};
/*
* Flags for iomap_begin / iomap_end. No flag implies a read.
*/
#define IOMAP_WRITE (1 << 0)
#define IOMAP_ZERO (1 << 1)
struct iomap_ops {
/*
* Return the existing mapping at pos, or reserve space starting at
* pos for up to length, as long as we can do it as a single mapping.
* The actual length is returned in iomap->length.
*/
int (*iomap_begin)(struct inode *inode, loff_t pos, loff_t length,
unsigned flags, struct iomap *iomap);
/*
* Commit and/or unreserve space previous allocated using iomap_begin.
* Written indicates the length of the successful write operation which
* needs to be commited, while the rest needs to be unreserved.
* Written might be zero if no data was written.
*/
int (*iomap_end)(struct inode *inode, loff_t pos, loff_t length,
ssize_t written, unsigned flags, struct iomap *iomap);
};
ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
struct iomap_ops *ops);
int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
bool *did_zero, struct iomap_ops *ops);
int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
struct iomap_ops *ops);
int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
struct iomap_ops *ops);
#endif /* LINUX_IOMAP_H */