/* * 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/raid/md.h> static int faulty_fail(struct bio *bio, unsigned int bytes_done, int error) { struct bio *b = bio->bi_private; b->bi_size = bio->bi_size; b->bi_sector = bio->bi_sector; if (bio->bi_size == 0) bio_put(bio); clear_bit(BIO_UPTODATE, &b->bi_flags); return (b->bi_end_io)(b, bytes_done, -EIO); } 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(request_queue_t *q, struct bio *bio) { mddev_t *mddev = q->queuedata; conf_t *conf = (conf_t*)mddev->private; int failit = 0; if (bio->bi_rw & 1) { /* write request */ if (atomic_read(&conf->counters[WriteAll])) { /* special case - don't decrement, don't generic_make_request, * just fail immediately */ bio_endio(bio, bio->bi_size, -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 reconfig(mddev_t *mddev, int layout, int chunk_size) { int mode = layout & ModeMask; int count = layout >> ModeShift; conf_t *conf = mddev->private; if (chunk_size != -1) return -EINVAL; /* 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->layout = -1; /* makes sure further changes come through */ return 0; } static int run(mddev_t *mddev) { mdk_rdev_t *rdev; struct list_head *tmp; int i; conf_t *conf = kmalloc(sizeof(*conf), GFP_KERNEL); for (i=0; i<Modes; i++) { atomic_set(&conf->counters[i], 0); conf->period[i] = 0; } conf->nfaults = 0; ITERATE_RDEV(mddev, rdev, tmp) conf->rdev = rdev; mddev->array_size = mddev->size; mddev->private = conf; reconfig(mddev, mddev->layout, -1); return 0; } static int stop(mddev_t *mddev) { conf_t *conf = (conf_t *)mddev->private; kfree(conf); mddev->private = NULL; return 0; } static mdk_personality_t faulty_personality = { .name = "faulty", .owner = THIS_MODULE, .make_request = make_request, .run = run, .stop = stop, .status = status, .reconfig = reconfig, }; static int __init raid_init(void) { return register_md_personality(FAULTY, &faulty_personality); } static void raid_exit(void) { unregister_md_personality(FAULTY); } module_init(raid_init); module_exit(raid_exit); MODULE_LICENSE("GPL"); MODULE_ALIAS("md-personality-10"); /* faulty */