--- /dev/null
+/*
+ * 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 */
git://git.onelab.eu / linux-2.6.git / blobdiff