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/* SPDX-License-Identifier: GPL-2.0 */
/*
* xloop_file_fmt_qcow_cache.c
*
* QCOW file format driver for the xloop device module.
*
* Ported QCOW2 implementation of the QEMU project (GPL-2.0):
* L2/refcount table cache for the QCOW2 format.
*
* The copyright (C) 2010 of the original code is owned by
* Kevin Wolf <kwolf@redhat.com>
*
* Copyright (C) 2019 Manuel Bentele <development@manuel-bentele.de>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/log2.h>
#include <linux/types.h>
#include <linux/limits.h>
#include <linux/fs.h>
#include <linux/vmalloc.h>
#include <linux/math64.h>
#include "xloop_file_fmt_qcow_main.h"
#include "xloop_file_fmt_qcow_cache.h"
static inline void *__xloop_file_fmt_qcow_cache_get_table_addr(
struct xloop_file_fmt_qcow_cache *c, int table)
{
return (u8 *) c->table_array + (size_t) table * c->table_size;
}
static inline int __xloop_file_fmt_qcow_cache_get_table_idx(
struct xloop_file_fmt_qcow_cache *c, void *table)
{
ptrdiff_t table_offset = (u8 *) table - (u8 *) c->table_array;
int idx = div_s64(table_offset, c->table_size);
#ifdef ASSERT
s32 rem_table_offset_mod_table_size;
div_s64_rem(table_offset, c->table_size, &rem_table_offset_mod_table_size);
ASSERT(idx >= 0 && idx < c->size && rem_table_offset_mod_table_size == 0);
#endif
return idx;
}
static inline const char *__xloop_file_fmt_qcow_cache_get_name(
struct xloop_file_fmt *xlo_fmt, struct xloop_file_fmt_qcow_cache *c)
{
struct xloop_file_fmt_qcow_data *qcow_data = xlo_fmt->private_data;
if (c == qcow_data->refcount_block_cache) {
return "refcount block";
} else if (c == qcow_data->l2_table_cache) {
return "L2 table";
} else {
/* do not abort, because this is not critical */
return "unknown";
}
}
struct xloop_file_fmt_qcow_cache *xloop_file_fmt_qcow_cache_create(
struct xloop_file_fmt *xlo_fmt, int num_tables, unsigned table_size)
{
#ifdef CONFIG_DEBUG_DRIVER
struct xloop_file_fmt_qcow_data *qcow_data = xlo_fmt->private_data;
#endif
struct xloop_file_fmt_qcow_cache *c;
ASSERT(num_tables > 0);
ASSERT(is_power_of_2(table_size));
ASSERT(table_size >= (1 << QCOW_MIN_CLUSTER_BITS));
ASSERT(table_size <= qcow_data->cluster_size);
c = kzalloc(sizeof(*c), GFP_KERNEL);
if (!c) {
return NULL;
}
c->size = num_tables;
c->table_size = table_size;
c->entries = vzalloc(sizeof(struct xloop_file_fmt_qcow_cache_table) *
num_tables);
c->table_array = vzalloc(num_tables * c->table_size);
if (!c->entries || !c->table_array) {
vfree(c->table_array);
vfree(c->entries);
kfree(c);
c = NULL;
}
return c;
}
void xloop_file_fmt_qcow_cache_destroy(struct xloop_file_fmt *xlo_fmt)
{
struct xloop_file_fmt_qcow_data *qcow_data = xlo_fmt->private_data;
struct xloop_file_fmt_qcow_cache *c = qcow_data->l2_table_cache;
int i;
for (i = 0; i < c->size; i++) {
ASSERT(c->entries[i].ref == 0);
}
vfree(c->table_array);
vfree(c->entries);
kfree(c);
}
static int __xloop_file_fmt_qcow_cache_entry_flush(
struct xloop_file_fmt *xlo_fmt, struct xloop_file_fmt_qcow_cache *c, int i)
{
if (!c->entries[i].dirty || !c->entries[i].offset) {
return 0;
} else {
dev_err_ratelimited(xloop_file_fmt_to_dev(xlo_fmt), "flush dirty "
"cache tables is not supported yet\n");
return -ENOSYS;
}
}
static int __xloop_file_fmt_qcow_cache_do_get(struct xloop_file_fmt *xlo_fmt,
struct xloop_file_fmt_qcow_cache *c, u64 offset, void **table,
bool read_from_disk)
{
struct xloop_device *xlo = xloop_file_fmt_get_xlo(xlo_fmt);
int i;
int ret;
int lookup_index;
u64 min_lru_counter = U64_MAX;
int min_lru_index = -1;
u64 read_offset;
u64 offset_div_table_size;
size_t len;
ASSERT(offset != 0);
if (!IS_ALIGNED(offset, c->table_size)) {
dev_err_ratelimited(xloop_file_fmt_to_dev(xlo_fmt), "cannot get entry "
"from %s cache: offset %llx is unaligned\n",
__xloop_file_fmt_qcow_cache_get_name(xlo_fmt, c), offset);
return -EIO;
}
/* Check if the table is already cached */
offset_div_table_size = div_u64(offset, c->table_size) * 4;
div_u64_rem(offset_div_table_size, c->size, &lookup_index);
i = lookup_index;
do {
const struct xloop_file_fmt_qcow_cache_table *t =
&c->entries[i];
if (t->offset == offset) {
goto found;
}
if (t->ref == 0 && t->lru_counter < min_lru_counter) {
min_lru_counter = t->lru_counter;
min_lru_index = i;
}
if (++i == c->size) {
i = 0;
}
} while (i != lookup_index);
if (min_lru_index == -1) {
BUG();
panic("Oops: This can't happen in current synchronous code, "
"but leave the check here as a reminder for whoever "
"starts using AIO with the QCOW cache");
}
/* Cache miss: write a table back and replace it */
i = min_lru_index;
ret = __xloop_file_fmt_qcow_cache_entry_flush(xlo_fmt, c, i);
if (ret < 0) {
return ret;
}
c->entries[i].offset = 0;
if (read_from_disk) {
read_offset = offset;
len = kernel_read(xlo->xlo_backing_file,
__xloop_file_fmt_qcow_cache_get_table_addr(c, i),
c->table_size, &read_offset);
if (len < 0) {
len = ret;
return ret;
}
}
c->entries[i].offset = offset;
/* And return the right table */
found:
c->entries[i].ref++;
*table = __xloop_file_fmt_qcow_cache_get_table_addr(c, i);
return 0;
}
int xloop_file_fmt_qcow_cache_get(struct xloop_file_fmt *xlo_fmt, u64 offset,
void **table)
{
struct xloop_file_fmt_qcow_data *qcow_data = xlo_fmt->private_data;
struct xloop_file_fmt_qcow_cache *c = qcow_data->l2_table_cache;
return __xloop_file_fmt_qcow_cache_do_get(xlo_fmt, c, offset, table,
true);
}
void xloop_file_fmt_qcow_cache_put(struct xloop_file_fmt *xlo_fmt, void **table)
{
struct xloop_file_fmt_qcow_data *qcow_data = xlo_fmt->private_data;
struct xloop_file_fmt_qcow_cache *c = qcow_data->l2_table_cache;
int i = __xloop_file_fmt_qcow_cache_get_table_idx(c, *table);
c->entries[i].ref--;
*table = NULL;
if (c->entries[i].ref == 0) {
c->entries[i].lru_counter = ++c->lru_counter;
}
ASSERT(c->entries[i].ref >= 0);
}
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