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alistair23-linux/drivers/md/faulty.c
Andre Noll 0894cc3066 md: Move check for bitmap presence to personality code. 
If the superblock of a component device indicates the presence of a
bitmap but the corresponding raid personality does not support bitmaps
(raid0, linear, multipath, faulty), then something is seriously wrong
and we'd better refuse to run such an array.

Currently, this check is performed while the superblocks are examined,
i.e. before entering personality code. Therefore the generic md layer
must know which raid levels support bitmaps and which do not.

This patch avoids this layer violation without adding identical code
to various personalities. This is accomplished by introducing a new
public function to md.c, md_check_no_bitmap(), which replaces the
hard-coded checks in the superblock loading functions.

A call to md_check_no_bitmap() is added to the ->run method of each
personality which does not support bitmaps and assembly is aborted
if at least one component device contains a bitmap.

Signed-off-by: Andre Noll <maan@systemlinux.org>
Signed-off-by: NeilBrown <neilb@suse.de>
2009-06-18 08:49:23 +10:00

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/*
* faulty.c : Multiple Devices driver for Linux
*
* Copyright (C) 2004 Neil Brown
*
* fautly-device-simulator personality for md
*
*
* This program 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.
*
* You should have received a copy of the GNU General Public License
* (for example /usr/src/linux/COPYING); if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* The "faulty" personality causes some requests to fail.
*
* Possible failure modes are:
* reads fail "randomly" but succeed on retry
* writes fail "randomly" but succeed on retry
* reads for some address fail and then persist until a write
* reads for some address fail and then persist irrespective of write
* writes for some address fail and persist
* all writes fail
*
* Different modes can be active at a time, but only
* one can be set at array creation. Others can be added later.
* A mode can be one-shot or recurrent with the recurrance being
* once in every N requests.
* The bottom 5 bits of the "layout" indicate the mode. The
* remainder indicate a period, or 0 for one-shot.
*
* There is an implementation limit on the number of concurrently
* persisting-faulty blocks. When a new fault is requested that would
* exceed the limit, it is ignored.
* All current faults can be clear using a layout of "0".
*
* Requests are always sent to the device. If they are to fail,
* we clone the bio and insert a new b_end_io into the chain.
*/
#define WriteTransient 0
#define ReadTransient 1
#define WritePersistent 2
#define ReadPersistent 3
#define WriteAll 4 /* doesn't go to device */
#define ReadFixable 5
#define Modes 6
#define ClearErrors 31
#define ClearFaults 30
#define AllPersist 100 /* internal use only */
#define NoPersist 101
#define ModeMask 0x1f
#define ModeShift 5
#define MaxFault 50
#include <linux/blkdev.h>
#include <linux/raid/md_u.h>
#include "md.h"
#include <linux/seq_file.h>
static void faulty_fail(struct bio *bio, int error)
{
struct bio *b = bio->bi_private;
b->bi_size = bio->bi_size;
b->bi_sector = bio->bi_sector;
bio_put(bio);
bio_io_error(b);
}
typedef struct faulty_conf {
int period[Modes];
atomic_t counters[Modes];
sector_t faults[MaxFault];
int modes[MaxFault];
int nfaults;
mdk_rdev_t *rdev;
} conf_t;
static int check_mode(conf_t *conf, int mode)
{
if (conf->period[mode] == 0 &&
atomic_read(&conf->counters[mode]) <= 0)
return 0; /* no failure, no decrement */
if (atomic_dec_and_test(&conf->counters[mode])) {
if (conf->period[mode])
atomic_set(&conf->counters[mode], conf->period[mode]);
return 1;
}
return 0;
}
static int check_sector(conf_t *conf, sector_t start, sector_t end, int dir)
{
/* If we find a ReadFixable sector, we fix it ... */
int i;
for (i=0; i<conf->nfaults; i++)
if (conf->faults[i] >= start &&
conf->faults[i] < end) {
/* found it ... */
switch (conf->modes[i] * 2 + dir) {
case WritePersistent*2+WRITE: return 1;
case ReadPersistent*2+READ: return 1;
case ReadFixable*2+READ: return 1;
case ReadFixable*2+WRITE:
conf->modes[i] = NoPersist;
return 0;
case AllPersist*2+READ:
case AllPersist*2+WRITE: return 1;
default:
return 0;
}
}
return 0;
}
static void add_sector(conf_t *conf, sector_t start, int mode)
{
int i;
int n = conf->nfaults;
for (i=0; i<conf->nfaults; i++)
if (conf->faults[i] == start) {
switch(mode) {
case NoPersist: conf->modes[i] = mode; return;
case WritePersistent:
if (conf->modes[i] == ReadPersistent ||
conf->modes[i] == ReadFixable)
conf->modes[i] = AllPersist;
else
conf->modes[i] = WritePersistent;
return;
case ReadPersistent:
if (conf->modes[i] == WritePersistent)
conf->modes[i] = AllPersist;
else
conf->modes[i] = ReadPersistent;
return;
case ReadFixable:
if (conf->modes[i] == WritePersistent ||
conf->modes[i] == ReadPersistent)
conf->modes[i] = AllPersist;
else
conf->modes[i] = ReadFixable;
return;
}
} else if (conf->modes[i] == NoPersist)
n = i;
if (n >= MaxFault)
return;
conf->faults[n] = start;
conf->modes[n] = mode;
if (conf->nfaults == n)
conf->nfaults = n+1;
}
static int make_request(struct request_queue *q, struct bio *bio)
{
mddev_t *mddev = q->queuedata;
conf_t *conf = (conf_t*)mddev->private;
int failit = 0;
if (bio_data_dir(bio) == WRITE) {
/* write request */
if (atomic_read(&conf->counters[WriteAll])) {
/* special case - don't decrement, don't generic_make_request,
* just fail immediately
*/
bio_endio(bio, -EIO);
return 0;
}
if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
WRITE))
failit = 1;
if (check_mode(conf, WritePersistent)) {
add_sector(conf, bio->bi_sector, WritePersistent);
failit = 1;
}
if (check_mode(conf, WriteTransient))
failit = 1;
} else {
/* read request */
if (check_sector(conf, bio->bi_sector, bio->bi_sector + (bio->bi_size>>9),
READ))
failit = 1;
if (check_mode(conf, ReadTransient))
failit = 1;
if (check_mode(conf, ReadPersistent)) {
add_sector(conf, bio->bi_sector, ReadPersistent);
failit = 1;
}
if (check_mode(conf, ReadFixable)) {
add_sector(conf, bio->bi_sector, ReadFixable);
failit = 1;
}
}
if (failit) {
struct bio *b = bio_clone(bio, GFP_NOIO);
b->bi_bdev = conf->rdev->bdev;
b->bi_private = bio;
b->bi_end_io = faulty_fail;
generic_make_request(b);
return 0;
} else {
bio->bi_bdev = conf->rdev->bdev;
return 1;
}
}
static void status(struct seq_file *seq, mddev_t *mddev)
{
conf_t *conf = (conf_t*)mddev->private;
int n;
if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
seq_printf(seq, " WriteTransient=%d(%d)",
n, conf->period[WriteTransient]);
if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
seq_printf(seq, " ReadTransient=%d(%d)",
n, conf->period[ReadTransient]);
if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
seq_printf(seq, " WritePersistent=%d(%d)",
n, conf->period[WritePersistent]);
if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
seq_printf(seq, " ReadPersistent=%d(%d)",
n, conf->period[ReadPersistent]);
if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
seq_printf(seq, " ReadFixable=%d(%d)",
n, conf->period[ReadFixable]);
if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
seq_printf(seq, " WriteAll");
seq_printf(seq, " nfaults=%d", conf->nfaults);
}
static int reshape(mddev_t *mddev)
{
int mode = mddev->new_layout & ModeMask;
int count = mddev->new_layout >> ModeShift;
conf_t *conf = mddev->private;
if (mddev->new_layout < 0)
return 0;
/* new layout */
if (mode == ClearFaults)
conf->nfaults = 0;
else if (mode == ClearErrors) {
int i;
for (i=0 ; i < Modes ; i++) {
conf->period[i] = 0;
atomic_set(&conf->counters[i], 0);
}
} else if (mode < Modes) {
conf->period[mode] = count;
if (!count) count++;
atomic_set(&conf->counters[mode], count);
} else
return -EINVAL;
mddev->new_layout = -1;
mddev->layout = -1; /* makes sure further changes come through */
return 0;
}
static sector_t faulty_size(mddev_t *mddev, sector_t sectors, int raid_disks)
{
WARN_ONCE(raid_disks,
"%s does not support generic reshape\n", __func__);
if (sectors == 0)
return mddev->dev_sectors;
return sectors;
}
static int run(mddev_t *mddev)
{
mdk_rdev_t *rdev;
int i;
conf_t *conf;
if (md_check_no_bitmap(mddev))
return -EINVAL;
conf = kmalloc(sizeof(*conf), GFP_KERNEL);
if (!conf)
return -ENOMEM;
for (i=0; i<Modes; i++) {
atomic_set(&conf->counters[i], 0);
conf->period[i] = 0;
}
conf->nfaults = 0;
list_for_each_entry(rdev, &mddev->disks, same_set)
conf->rdev = rdev;
md_set_array_sectors(mddev, faulty_size(mddev, 0, 0));
mddev->private = conf;
reshape(mddev);
return 0;
}
static int stop(mddev_t *mddev)
{
conf_t *conf = (conf_t *)mddev->private;
kfree(conf);
mddev->private = NULL;
return 0;
}
static struct mdk_personality faulty_personality =
{
.name = "faulty",
.level = LEVEL_FAULTY,
.owner = THIS_MODULE,
.make_request = make_request,
.run = run,
.stop = stop,
.status = status,
.check_reshape = reshape,
.size = faulty_size,
};
static int __init raid_init(void)
{
return register_md_personality(&faulty_personality);
}
static void raid_exit(void)
{
unregister_md_personality(&faulty_personality);
}
module_init(raid_init);
module_exit(raid_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS("md-personality-10"); /* faulty */
MODULE_ALIAS("md-faulty");
MODULE_ALIAS("md-level--5");
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