Commit a254e568 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Dave Chinner

dax: provide an iomap based dax read/write path

This is a much simpler implementation of the DAX read/write path
that makes use of the iomap infrastructure.  It does not try to
mirror the direct I/O calling conventions and thus doesn't have to
deal with i_dio_count or the end_io handler, but instead leaves
locking and filesystem-specific I/O completion to the caller.
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent b0d5e82f
......@@ -31,6 +31,8 @@
#include <linux/vmstat.h>
#include <linux/pfn_t.h>
#include <linux/sizes.h>
#include <linux/iomap.h>
#include "internal.h"
/*
* We use lowest available bit in exceptional entry for locking, other two
......@@ -1241,3 +1243,115 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
return dax_zero_page_range(inode, from, length, get_block);
}
EXPORT_SYMBOL_GPL(dax_truncate_page);
#ifdef CONFIG_FS_IOMAP
static loff_t
iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
struct iomap *iomap)
{
struct iov_iter *iter = data;
loff_t end = pos + length, done = 0;
ssize_t ret = 0;
if (iov_iter_rw(iter) == READ) {
end = min(end, i_size_read(inode));
if (pos >= end)
return 0;
if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
return iov_iter_zero(min(length, end - pos), iter);
}
if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
return -EIO;
while (pos < end) {
unsigned offset = pos & (PAGE_SIZE - 1);
struct blk_dax_ctl dax = { 0 };
ssize_t map_len;
dax.sector = iomap->blkno +
(((pos & PAGE_MASK) - iomap->offset) >> 9);
dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
map_len = dax_map_atomic(iomap->bdev, &dax);
if (map_len < 0) {
ret = map_len;
break;
}
dax.addr += offset;
map_len -= offset;
if (map_len > end - pos)
map_len = end - pos;
if (iov_iter_rw(iter) == WRITE)
map_len = copy_from_iter_pmem(dax.addr, map_len, iter);
else
map_len = copy_to_iter(dax.addr, map_len, iter);
dax_unmap_atomic(iomap->bdev, &dax);
if (map_len <= 0) {
ret = map_len ? map_len : -EFAULT;
break;
}
pos += map_len;
length -= map_len;
done += map_len;
}
return done ? done : ret;
}
/**
* iomap_dax_rw - Perform I/O to a DAX file
* @iocb: The control block for this I/O
* @iter: The addresses to do I/O from or to
* @ops: iomap ops passed from the file system
*
* This function performs read and write operations to directly mapped
* persistent memory. The callers needs to take care of read/write exclusion
* and evicting any page cache pages in the region under I/O.
*/
ssize_t
iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
struct iomap_ops *ops)
{
struct address_space *mapping = iocb->ki_filp->f_mapping;
struct inode *inode = mapping->host;
loff_t pos = iocb->ki_pos, ret = 0, done = 0;
unsigned flags = 0;
if (iov_iter_rw(iter) == WRITE)
flags |= IOMAP_WRITE;
/*
* Yes, even DAX files can have page cache attached to them: A zeroed
* page is inserted into the pagecache when we have to serve a write
* fault on a hole. It should never be dirtied and can simply be
* dropped from the pagecache once we get real data for the page.
*
* XXX: This is racy against mmap, and there's nothing we can do about
* it. We'll eventually need to shift this down even further so that
* we can check if we allocated blocks over a hole first.
*/
if (mapping->nrpages) {
ret = invalidate_inode_pages2_range(mapping,
pos >> PAGE_SHIFT,
(pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT);
WARN_ON_ONCE(ret);
}
while (iov_iter_count(iter)) {
ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
iter, iomap_dax_actor);
if (ret <= 0)
break;
pos += ret;
done += ret;
}
iocb->ki_pos += done;
return done ? done : ret;
}
EXPORT_SYMBOL_GPL(iomap_dax_rw);
#endif /* CONFIG_FS_IOMAP */
......@@ -6,9 +6,13 @@
#include <linux/radix-tree.h>
#include <asm/pgtable.h>
struct iomap_ops;
/* We use lowest available exceptional entry bit for locking */
#define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
ssize_t iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
struct iomap_ops *ops);
ssize_t dax_do_io(struct kiocb *, struct inode *, struct iov_iter *,
get_block_t, dio_iodone_t, int flags);
int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
......
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