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// SPDX-License-Identifier: GPL-2.0
/*
* dax: direct host memory access
* Copyright (C) 2020 Red Hat, Inc.
*/
#include "fuse_i.h"
#include <linux/dax.h>
#include <linux/pfn_t.h>
/*
* Default memory range size. A power of 2 so it agrees with common FUSE_INIT
* map_alignment values 4KB and 64KB.
*/
#define FUSE_DAX_SHIFT 21
#define FUSE_DAX_SZ (1 << FUSE_DAX_SHIFT)
#define FUSE_DAX_PAGES (FUSE_DAX_SZ / PAGE_SIZE)
/** Translation information for file offsets to DAX window offsets */
struct fuse_dax_mapping {
/* Will connect in fcd->free_ranges to keep track of free memory */
struct list_head list;
/** Position in DAX window */
u64 window_offset;
/** Length of mapping, in bytes */
loff_t length;
};
struct fuse_conn_dax {
/* DAX device */
struct dax_device *dev;
/* DAX Window Free Ranges */
long nr_free_ranges;
struct list_head free_ranges;
};
static void fuse_free_dax_mem_ranges(struct list_head *mem_list)
{
struct fuse_dax_mapping *range, *temp;
/* Free All allocated elements */
list_for_each_entry_safe(range, temp, mem_list, list) {
list_del(&range->list);
kfree(range);
}
}
void fuse_dax_conn_free(struct fuse_conn *fc)
{
if (fc->dax) {
fuse_free_dax_mem_ranges(&fc->dax->free_ranges);
kfree(fc->dax);
}
}
static int fuse_dax_mem_range_init(struct fuse_conn_dax *fcd)
{
long nr_pages, nr_ranges;
void *kaddr;
pfn_t pfn;
struct fuse_dax_mapping *range;
int ret, id;
size_t dax_size = -1;
unsigned long i;
INIT_LIST_HEAD(&fcd->free_ranges);
id = dax_read_lock();
nr_pages = dax_direct_access(fcd->dev, 0, PHYS_PFN(dax_size), &kaddr,
&pfn);
dax_read_unlock(id);
if (nr_pages < 0) {
pr_debug("dax_direct_access() returned %ld\n", nr_pages);
return nr_pages;
}
nr_ranges = nr_pages/FUSE_DAX_PAGES;
pr_debug("%s: dax mapped %ld pages. nr_ranges=%ld\n",
__func__, nr_pages, nr_ranges);
for (i = 0; i < nr_ranges; i++) {
range = kzalloc(sizeof(struct fuse_dax_mapping), GFP_KERNEL);
ret = -ENOMEM;
if (!range)
goto out_err;
/* TODO: This offset only works if virtio-fs driver is not
* having some memory hidden at the beginning. This needs
* better handling
*/
range->window_offset = i * FUSE_DAX_SZ;
range->length = FUSE_DAX_SZ;
list_add_tail(&range->list, &fcd->free_ranges);
}
fcd->nr_free_ranges = nr_ranges;
return 0;
out_err:
/* Free All allocated elements */
fuse_free_dax_mem_ranges(&fcd->free_ranges);
return ret;
}
int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev)
{
struct fuse_conn_dax *fcd;
int err;
if (!dax_dev)
return 0;
fcd = kzalloc(sizeof(*fcd), GFP_KERNEL);
if (!fcd)
return -ENOMEM;
fcd->dev = dax_dev;
err = fuse_dax_mem_range_init(fcd);
if (err) {
kfree(fcd);
return err;
}
fc->dax = fcd;
return 0;
}
bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment)
{
if (fc->dax && (map_alignment > FUSE_DAX_SHIFT)) {
pr_warn("FUSE: map_alignment %u incompatible with dax mem range size %u\n",
map_alignment, FUSE_DAX_SZ);
return false;
}
return true;
}
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