2604b703b6
md supports multiple different RAID level, each being implemented by a
'personality' (which is often in a separate module).
These personalities have fairly artificial 'numbers'. The numbers
are use to:
1- provide an index into an array where the various personalities
are recorded
2- identify the module (via an alias) which implements are particular
personality.
Neither of these uses really justify the existence of personality numbers.
The array can be replaced by a linked list which is searched (array lookup
only happens very rarely). Module identification can be done using an alias
based on level rather than 'personality' number.
The current 'raid5' modules support two level (4 and 5) but only one
personality. This slight awkwardness (which was handled in the mapping from
level to personality) can be better handled by allowing raid5 to register 2
personalities.
With this change in place, the core md module does not need to have an
exhaustive list of all possible personalities, so other personalities can be
added independently.
This patch also moves the check for chunksize being non-zero into the ->run
routines for the personalities that need it, rather than having it in core-md.
This has a side effect of allowing 'faulty' and 'linear' not to have a
chunk-size set.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
346 lines
8.3 KiB
C
346 lines
8.3 KiB
C
/*
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* faulty.c : Multiple Devices driver for Linux
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*
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* Copyright (C) 2004 Neil Brown
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*
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* fautly-device-simulator personality for md
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*
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* You should have received a copy of the GNU General Public License
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* (for example /usr/src/linux/COPYING); if not, write to the Free
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* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*
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* The "faulty" personality causes some requests to fail.
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*
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* Possible failure modes are:
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* reads fail "randomly" but succeed on retry
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* writes fail "randomly" but succeed on retry
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* reads for some address fail and then persist until a write
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* reads for some address fail and then persist irrespective of write
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* writes for some address fail and persist
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* all writes fail
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*
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* Different modes can be active at a time, but only
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* one can be set at array creation. Others can be added later.
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* A mode can be one-shot or recurrent with the recurrance being
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* once in every N requests.
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* The bottom 5 bits of the "layout" indicate the mode. The
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* remainder indicate a period, or 0 for one-shot.
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*
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* There is an implementation limit on the number of concurrently
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* persisting-faulty blocks. When a new fault is requested that would
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* exceed the limit, it is ignored.
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* All current faults can be clear using a layout of "0".
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*
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* Requests are always sent to the device. If they are to fail,
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* we clone the bio and insert a new b_end_io into the chain.
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*/
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#define WriteTransient 0
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#define ReadTransient 1
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#define WritePersistent 2
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#define ReadPersistent 3
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#define WriteAll 4 /* doesn't go to device */
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#define ReadFixable 5
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#define Modes 6
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#define ClearErrors 31
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#define ClearFaults 30
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#define AllPersist 100 /* internal use only */
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#define NoPersist 101
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#define ModeMask 0x1f
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#define ModeShift 5
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#define MaxFault 50
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#include <linux/raid/md.h>
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static int faulty_fail(struct bio *bio, unsigned int bytes_done, int error)
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{
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struct bio *b = bio->bi_private;
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b->bi_size = bio->bi_size;
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b->bi_sector = bio->bi_sector;
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if (bio->bi_size == 0)
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bio_put(bio);
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clear_bit(BIO_UPTODATE, &b->bi_flags);
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return (b->bi_end_io)(b, bytes_done, -EIO);
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}
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typedef struct faulty_conf {
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int period[Modes];
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atomic_t counters[Modes];
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sector_t faults[MaxFault];
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int modes[MaxFault];
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int nfaults;
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mdk_rdev_t *rdev;
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} conf_t;
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static int check_mode(conf_t *conf, int mode)
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{
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if (conf->period[mode] == 0 &&
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atomic_read(&conf->counters[mode]) <= 0)
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return 0; /* no failure, no decrement */
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if (atomic_dec_and_test(&conf->counters[mode])) {
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if (conf->period[mode])
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atomic_set(&conf->counters[mode], conf->period[mode]);
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return 1;
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}
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return 0;
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}
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static int check_sector(conf_t *conf, sector_t start, sector_t end, int dir)
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{
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/* If we find a ReadFixable sector, we fix it ... */
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int i;
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for (i=0; i<conf->nfaults; i++)
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if (conf->faults[i] >= start &&
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conf->faults[i] < end) {
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/* found it ... */
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switch (conf->modes[i] * 2 + dir) {
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case WritePersistent*2+WRITE: return 1;
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case ReadPersistent*2+READ: return 1;
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case ReadFixable*2+READ: return 1;
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case ReadFixable*2+WRITE:
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conf->modes[i] = NoPersist;
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return 0;
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case AllPersist*2+READ:
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case AllPersist*2+WRITE: return 1;
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default:
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return 0;
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}
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}
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return 0;
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}
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static void add_sector(conf_t *conf, sector_t start, int mode)
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{
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int i;
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int n = conf->nfaults;
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for (i=0; i<conf->nfaults; i++)
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if (conf->faults[i] == start) {
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switch(mode) {
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case NoPersist: conf->modes[i] = mode; return;
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case WritePersistent:
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if (conf->modes[i] == ReadPersistent ||
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conf->modes[i] == ReadFixable)
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conf->modes[i] = AllPersist;
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else
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conf->modes[i] = WritePersistent;
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return;
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case ReadPersistent:
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if (conf->modes[i] == WritePersistent)
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conf->modes[i] = AllPersist;
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else
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conf->modes[i] = ReadPersistent;
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return;
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case ReadFixable:
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if (conf->modes[i] == WritePersistent ||
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conf->modes[i] == ReadPersistent)
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conf->modes[i] = AllPersist;
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else
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conf->modes[i] = ReadFixable;
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return;
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}
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} else if (conf->modes[i] == NoPersist)
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n = i;
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if (n >= MaxFault)
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return;
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conf->faults[n] = start;
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conf->modes[n] = mode;
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if (conf->nfaults == n)
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conf->nfaults = n+1;
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}
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static int make_request(request_queue_t *q, struct bio *bio)
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{
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mddev_t *mddev = q->queuedata;
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conf_t *conf = (conf_t*)mddev->private;
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int failit = 0;
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if (bio->bi_rw & 1) {
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/* write request */
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if (atomic_read(&conf->counters[WriteAll])) {
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/* special case - don't decrement, don't generic_make_request,
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* just fail immediately
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*/
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bio_endio(bio, bio->bi_size, -EIO);
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return 0;
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}
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if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
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WRITE))
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failit = 1;
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if (check_mode(conf, WritePersistent)) {
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add_sector(conf, bio->bi_sector, WritePersistent);
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failit = 1;
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}
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if (check_mode(conf, WriteTransient))
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failit = 1;
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} else {
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/* read request */
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if (check_sector(conf, bio->bi_sector, bio->bi_sector + (bio->bi_size>>9),
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READ))
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failit = 1;
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if (check_mode(conf, ReadTransient))
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failit = 1;
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if (check_mode(conf, ReadPersistent)) {
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add_sector(conf, bio->bi_sector, ReadPersistent);
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failit = 1;
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}
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if (check_mode(conf, ReadFixable)) {
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add_sector(conf, bio->bi_sector, ReadFixable);
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failit = 1;
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}
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}
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if (failit) {
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struct bio *b = bio_clone(bio, GFP_NOIO);
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b->bi_bdev = conf->rdev->bdev;
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b->bi_private = bio;
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b->bi_end_io = faulty_fail;
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generic_make_request(b);
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return 0;
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} else {
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bio->bi_bdev = conf->rdev->bdev;
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return 1;
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}
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}
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static void status(struct seq_file *seq, mddev_t *mddev)
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{
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conf_t *conf = (conf_t*)mddev->private;
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int n;
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if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
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seq_printf(seq, " WriteTransient=%d(%d)",
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n, conf->period[WriteTransient]);
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if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
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seq_printf(seq, " ReadTransient=%d(%d)",
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n, conf->period[ReadTransient]);
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if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
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seq_printf(seq, " WritePersistent=%d(%d)",
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n, conf->period[WritePersistent]);
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if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
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seq_printf(seq, " ReadPersistent=%d(%d)",
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n, conf->period[ReadPersistent]);
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if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
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seq_printf(seq, " ReadFixable=%d(%d)",
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n, conf->period[ReadFixable]);
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if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
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seq_printf(seq, " WriteAll");
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seq_printf(seq, " nfaults=%d", conf->nfaults);
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}
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static int reconfig(mddev_t *mddev, int layout, int chunk_size)
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{
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int mode = layout & ModeMask;
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int count = layout >> ModeShift;
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conf_t *conf = mddev->private;
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if (chunk_size != -1)
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return -EINVAL;
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/* new layout */
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if (mode == ClearFaults)
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conf->nfaults = 0;
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else if (mode == ClearErrors) {
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int i;
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for (i=0 ; i < Modes ; i++) {
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conf->period[i] = 0;
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atomic_set(&conf->counters[i], 0);
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}
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} else if (mode < Modes) {
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conf->period[mode] = count;
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if (!count) count++;
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atomic_set(&conf->counters[mode], count);
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} else
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return -EINVAL;
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mddev->layout = -1; /* makes sure further changes come through */
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return 0;
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}
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static int run(mddev_t *mddev)
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{
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mdk_rdev_t *rdev;
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struct list_head *tmp;
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int i;
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conf_t *conf = kmalloc(sizeof(*conf), GFP_KERNEL);
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for (i=0; i<Modes; i++) {
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atomic_set(&conf->counters[i], 0);
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conf->period[i] = 0;
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}
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conf->nfaults = 0;
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ITERATE_RDEV(mddev, rdev, tmp)
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conf->rdev = rdev;
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mddev->array_size = mddev->size;
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mddev->private = conf;
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reconfig(mddev, mddev->layout, -1);
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return 0;
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}
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static int stop(mddev_t *mddev)
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{
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conf_t *conf = (conf_t *)mddev->private;
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kfree(conf);
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mddev->private = NULL;
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return 0;
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}
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static struct mdk_personality faulty_personality =
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{
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.name = "faulty",
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.level = LEVEL_FAULTY,
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.owner = THIS_MODULE,
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.make_request = make_request,
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.run = run,
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.stop = stop,
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.status = status,
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.reconfig = reconfig,
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};
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static int __init raid_init(void)
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{
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return register_md_personality(&faulty_personality);
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}
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static void raid_exit(void)
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{
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unregister_md_personality(&faulty_personality);
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}
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module_init(raid_init);
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module_exit(raid_exit);
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("md-personality-10"); /* faulty */
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MODULE_ALIAS("md-level--5");
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