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/* Striped store backend
Copyright (C) 1996 Free Software Foundation, Inc.
Written by Miles Bader <miles@gnu.ai.mit.edu>
This file is part of the GNU Hurd.
The GNU Hurd is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2, or (at
your option) any later version.
The GNU Hurd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include <stdlib.h>
#include <string.h>
#include "store.h"
extern long lcm (long p, long q);
/* Return ADDR adjust for any block size difference between STORE and
STRIPE. We assume that STORE's block size is no less than STRIPE's. */
static inline off_t
addr_adj (off_t addr, struct store *store, struct store *stripe)
{
unsigned common_bs = store->log2_block_size;
unsigned stripe_bs = stripe->log2_block_size;
if (common_bs == stripe_bs)
return addr;
else
return addr << (common_bs - stripe_bs);
}
static error_t
stripe_read (struct store *store,
off_t addr, size_t index, mach_msg_type_number_t amount,
char **buf, mach_msg_type_number_t *len)
{
struct store *stripe = store->children[index];
return store_read (stripe, addr_adj (addr, store, stripe), amount, buf, len);
}
static error_t
stripe_write (struct store *store,
off_t addr, size_t index, char *buf, mach_msg_type_number_t len,
mach_msg_type_number_t *amount)
{
struct store *stripe = store->children[index];
return
store_write (stripe, addr_adj (addr, store, stripe), buf, len, amount);
}
static struct store_meths
stripe_meths = {stripe_read, stripe_write, 0, 0, 0, 0};
/* Return a new store in STORE that interleaves all the stores in STRIPES
(NUM_STRIPES of them) every INTERLEAVE bytes; INTERLEAVE must be an
integer multiple of each stripe's block size. The stores in STRIPES are
consumed -- that is, will be freed when this store is (however, the
*array* STRIPES is copied, and so should be freed by the caller). */
error_t
store_ileave_create (struct store *const *stripes, size_t num_stripes,
off_t interleave, struct store **store)
{
size_t i;
error_t err;
off_t block_size = 1, min_end = 0;
struct store_run runs[num_stripes];
/* Find a common block size. */
for (i = 0; i < num_stripes; i++)
block_size = lcm (block_size, stripes[i]->block_size);
if (interleave < block_size || (interleave % block_size) != 0)
return EINVAL;
interleave /= block_size;
for (i = 0; i < num_stripes; i++)
{
/* The stripe's end adjusted to the common block size. */
off_t end = stripes[i]->end;
runs[i].start = 0;
runs[i].length = interleave;
if (stripes[i]->block_size != block_size)
end /= (block_size / stripes[i]->block_size);
if (min_end < 0)
min_end = end;
else if (min_end > end)
/* Only use as much space as the smallest stripe has. */
min_end = end;
}
*store = _make_store (0, &stripe_meths, MACH_PORT_NULL, block_size,
runs, num_stripes, min_end);
if (! *store)
return ENOMEM;
(*store)->wrap_dst = interleave;
err = store_set_children (*store, stripes, num_stripes);
if (err)
store_free (*store);
return err;
}
/* Return a new store in STORE that concatenates all the stores in STORES
(NUM_STORES of them). The stores in STRIPES are consumed -- that is, will
be freed when this store is (however, the *array* STRIPES is copied, and
so should be freed by the caller). */
error_t
store_concat_create (struct store * const *stores, size_t num_stores,
struct store **store)
{
size_t i;
error_t err;
off_t block_size = 1;
struct store_run runs[num_stores];
/* Find a common block size. */
for (i = 0; i < num_stores; i++)
block_size = lcm (block_size, stores[i]->block_size);
for (i = 0; i < num_stores; i++)
{
runs[i].start = 0;
runs[i].length = stores[i]->end;
}
*store = _make_store (0, &stripe_meths, MACH_PORT_NULL, block_size,
runs, num_stores * 2, 0);
if (! *store)
return ENOMEM;
err = store_set_children (*store, stores, num_stores);
if (err)
store_free (*store);
return err;
}
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