559 lines
14 KiB
C
559 lines
14 KiB
C
/*
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* multipath.c : Multiple Devices driver for Linux
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*
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* Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
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*
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* Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
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*
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* MULTIPATH management functions.
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*
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* derived from raid1.c.
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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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#include <linux/blkdev.h>
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#include <linux/raid/md_u.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include "md.h"
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#include "multipath.h"
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#define MAX_WORK_PER_DISK 128
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#define NR_RESERVED_BUFS 32
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static int multipath_map (multipath_conf_t *conf)
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{
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int i, disks = conf->raid_disks;
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/*
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* Later we do read balancing on the read side
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* now we use the first available disk.
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*/
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rcu_read_lock();
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for (i = 0; i < disks; i++) {
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mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
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if (rdev && test_bit(In_sync, &rdev->flags)) {
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atomic_inc(&rdev->nr_pending);
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rcu_read_unlock();
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return i;
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}
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}
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rcu_read_unlock();
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printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
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return (-1);
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}
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static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
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{
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unsigned long flags;
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mddev_t *mddev = mp_bh->mddev;
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multipath_conf_t *conf = mddev->private;
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spin_lock_irqsave(&conf->device_lock, flags);
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list_add(&mp_bh->retry_list, &conf->retry_list);
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spin_unlock_irqrestore(&conf->device_lock, flags);
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md_wakeup_thread(mddev->thread);
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}
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/*
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* multipath_end_bh_io() is called when we have finished servicing a multipathed
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* operation and are ready to return a success/failure code to the buffer
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* cache layer.
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*/
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static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
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{
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struct bio *bio = mp_bh->master_bio;
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multipath_conf_t *conf = mp_bh->mddev->private;
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bio_endio(bio, err);
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mempool_free(mp_bh, conf->pool);
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}
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static void multipath_end_request(struct bio *bio, int error)
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{
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int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
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struct multipath_bh *mp_bh = bio->bi_private;
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multipath_conf_t *conf = mp_bh->mddev->private;
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mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
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if (uptodate)
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multipath_end_bh_io(mp_bh, 0);
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else if (!(bio->bi_rw & REQ_RAHEAD)) {
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/*
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* oops, IO error:
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*/
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char b[BDEVNAME_SIZE];
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md_error (mp_bh->mddev, rdev);
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printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
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bdevname(rdev->bdev,b),
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(unsigned long long)bio->bi_sector);
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multipath_reschedule_retry(mp_bh);
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} else
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multipath_end_bh_io(mp_bh, error);
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rdev_dec_pending(rdev, conf->mddev);
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}
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static int multipath_make_request(mddev_t *mddev, struct bio * bio)
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{
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multipath_conf_t *conf = mddev->private;
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struct multipath_bh * mp_bh;
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struct multipath_info *multipath;
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if (unlikely(bio->bi_rw & REQ_FLUSH)) {
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md_flush_request(mddev, bio);
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return 0;
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}
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mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
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mp_bh->master_bio = bio;
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mp_bh->mddev = mddev;
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mp_bh->path = multipath_map(conf);
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if (mp_bh->path < 0) {
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bio_endio(bio, -EIO);
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mempool_free(mp_bh, conf->pool);
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return 0;
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}
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multipath = conf->multipaths + mp_bh->path;
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mp_bh->bio = *bio;
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mp_bh->bio.bi_sector += multipath->rdev->data_offset;
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mp_bh->bio.bi_bdev = multipath->rdev->bdev;
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mp_bh->bio.bi_rw |= REQ_FAILFAST_TRANSPORT;
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mp_bh->bio.bi_end_io = multipath_end_request;
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mp_bh->bio.bi_private = mp_bh;
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generic_make_request(&mp_bh->bio);
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return 0;
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}
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static void multipath_status (struct seq_file *seq, mddev_t *mddev)
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{
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multipath_conf_t *conf = mddev->private;
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int i;
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seq_printf (seq, " [%d/%d] [", conf->raid_disks,
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conf->raid_disks - mddev->degraded);
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for (i = 0; i < conf->raid_disks; i++)
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seq_printf (seq, "%s",
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conf->multipaths[i].rdev &&
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test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
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seq_printf (seq, "]");
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}
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static int multipath_congested(void *data, int bits)
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{
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mddev_t *mddev = data;
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multipath_conf_t *conf = mddev->private;
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int i, ret = 0;
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if (mddev_congested(mddev, bits))
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return 1;
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rcu_read_lock();
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for (i = 0; i < mddev->raid_disks ; i++) {
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mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
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if (rdev && !test_bit(Faulty, &rdev->flags)) {
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struct request_queue *q = bdev_get_queue(rdev->bdev);
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ret |= bdi_congested(&q->backing_dev_info, bits);
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/* Just like multipath_map, we just check the
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* first available device
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*/
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break;
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}
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}
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rcu_read_unlock();
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return ret;
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}
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/*
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* Careful, this can execute in IRQ contexts as well!
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*/
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static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
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{
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multipath_conf_t *conf = mddev->private;
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char b[BDEVNAME_SIZE];
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if (conf->raid_disks - mddev->degraded <= 1) {
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/*
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* Uh oh, we can do nothing if this is our last path, but
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* first check if this is a queued request for a device
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* which has just failed.
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*/
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printk(KERN_ALERT
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"multipath: only one IO path left and IO error.\n");
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/* leave it active... it's all we have */
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return;
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}
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/*
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* Mark disk as unusable
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*/
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if (test_and_clear_bit(In_sync, &rdev->flags)) {
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unsigned long flags;
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spin_lock_irqsave(&conf->device_lock, flags);
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mddev->degraded++;
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spin_unlock_irqrestore(&conf->device_lock, flags);
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}
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set_bit(Faulty, &rdev->flags);
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set_bit(MD_CHANGE_DEVS, &mddev->flags);
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printk(KERN_ALERT "multipath: IO failure on %s,"
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" disabling IO path.\n"
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"multipath: Operation continuing"
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" on %d IO paths.\n",
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bdevname(rdev->bdev, b),
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conf->raid_disks - mddev->degraded);
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}
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static void print_multipath_conf (multipath_conf_t *conf)
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{
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int i;
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struct multipath_info *tmp;
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printk("MULTIPATH conf printout:\n");
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if (!conf) {
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printk("(conf==NULL)\n");
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return;
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}
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printk(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
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conf->raid_disks);
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for (i = 0; i < conf->raid_disks; i++) {
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char b[BDEVNAME_SIZE];
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tmp = conf->multipaths + i;
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if (tmp->rdev)
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printk(" disk%d, o:%d, dev:%s\n",
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i,!test_bit(Faulty, &tmp->rdev->flags),
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bdevname(tmp->rdev->bdev,b));
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}
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}
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static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
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{
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multipath_conf_t *conf = mddev->private;
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struct request_queue *q;
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int err = -EEXIST;
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int path;
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struct multipath_info *p;
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int first = 0;
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int last = mddev->raid_disks - 1;
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if (rdev->raid_disk >= 0)
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first = last = rdev->raid_disk;
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print_multipath_conf(conf);
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for (path = first; path <= last; path++)
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if ((p=conf->multipaths+path)->rdev == NULL) {
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q = rdev->bdev->bd_disk->queue;
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disk_stack_limits(mddev->gendisk, rdev->bdev,
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rdev->data_offset << 9);
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/* as we don't honour merge_bvec_fn, we must never risk
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* violating it, so limit ->max_segments to one, lying
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* within a single page.
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* (Note: it is very unlikely that a device with
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* merge_bvec_fn will be involved in multipath.)
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*/
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if (q->merge_bvec_fn) {
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blk_queue_max_segments(mddev->queue, 1);
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blk_queue_segment_boundary(mddev->queue,
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PAGE_CACHE_SIZE - 1);
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}
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spin_lock_irq(&conf->device_lock);
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mddev->degraded--;
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rdev->raid_disk = path;
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set_bit(In_sync, &rdev->flags);
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spin_unlock_irq(&conf->device_lock);
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rcu_assign_pointer(p->rdev, rdev);
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err = 0;
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md_integrity_add_rdev(rdev, mddev);
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break;
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}
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print_multipath_conf(conf);
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return err;
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}
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static int multipath_remove_disk(mddev_t *mddev, int number)
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{
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multipath_conf_t *conf = mddev->private;
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int err = 0;
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mdk_rdev_t *rdev;
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struct multipath_info *p = conf->multipaths + number;
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print_multipath_conf(conf);
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rdev = p->rdev;
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if (rdev) {
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if (test_bit(In_sync, &rdev->flags) ||
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atomic_read(&rdev->nr_pending)) {
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printk(KERN_ERR "hot-remove-disk, slot %d is identified"
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" but is still operational!\n", number);
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err = -EBUSY;
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goto abort;
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}
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p->rdev = NULL;
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synchronize_rcu();
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if (atomic_read(&rdev->nr_pending)) {
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/* lost the race, try later */
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err = -EBUSY;
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p->rdev = rdev;
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goto abort;
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}
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err = md_integrity_register(mddev);
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}
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abort:
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print_multipath_conf(conf);
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return err;
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}
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/*
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* This is a kernel thread which:
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*
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* 1. Retries failed read operations on working multipaths.
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* 2. Updates the raid superblock when problems encounter.
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* 3. Performs writes following reads for array syncronising.
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*/
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static void multipathd (mddev_t *mddev)
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{
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struct multipath_bh *mp_bh;
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struct bio *bio;
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unsigned long flags;
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multipath_conf_t *conf = mddev->private;
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struct list_head *head = &conf->retry_list;
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md_check_recovery(mddev);
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for (;;) {
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char b[BDEVNAME_SIZE];
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spin_lock_irqsave(&conf->device_lock, flags);
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if (list_empty(head))
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break;
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mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
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list_del(head->prev);
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spin_unlock_irqrestore(&conf->device_lock, flags);
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bio = &mp_bh->bio;
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bio->bi_sector = mp_bh->master_bio->bi_sector;
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if ((mp_bh->path = multipath_map (conf))<0) {
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printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
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" error for block %llu\n",
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bdevname(bio->bi_bdev,b),
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(unsigned long long)bio->bi_sector);
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multipath_end_bh_io(mp_bh, -EIO);
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} else {
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printk(KERN_ERR "multipath: %s: redirecting sector %llu"
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" to another IO path\n",
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bdevname(bio->bi_bdev,b),
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(unsigned long long)bio->bi_sector);
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*bio = *(mp_bh->master_bio);
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bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
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bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
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bio->bi_rw |= REQ_FAILFAST_TRANSPORT;
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bio->bi_end_io = multipath_end_request;
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bio->bi_private = mp_bh;
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generic_make_request(bio);
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}
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}
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spin_unlock_irqrestore(&conf->device_lock, flags);
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}
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static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
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{
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WARN_ONCE(sectors || raid_disks,
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"%s does not support generic reshape\n", __func__);
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return mddev->dev_sectors;
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}
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static int multipath_run (mddev_t *mddev)
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{
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multipath_conf_t *conf;
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int disk_idx;
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struct multipath_info *disk;
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mdk_rdev_t *rdev;
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int working_disks;
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if (md_check_no_bitmap(mddev))
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return -EINVAL;
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if (mddev->level != LEVEL_MULTIPATH) {
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printk("multipath: %s: raid level not set to multipath IO (%d)\n",
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mdname(mddev), mddev->level);
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goto out;
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}
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/*
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* copy the already verified devices into our private MULTIPATH
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* bookkeeping area. [whatever we allocate in multipath_run(),
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* should be freed in multipath_stop()]
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*/
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conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
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mddev->private = conf;
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if (!conf) {
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printk(KERN_ERR
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"multipath: couldn't allocate memory for %s\n",
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mdname(mddev));
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goto out;
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}
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conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
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GFP_KERNEL);
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if (!conf->multipaths) {
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printk(KERN_ERR
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"multipath: couldn't allocate memory for %s\n",
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mdname(mddev));
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goto out_free_conf;
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}
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working_disks = 0;
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list_for_each_entry(rdev, &mddev->disks, same_set) {
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disk_idx = rdev->raid_disk;
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if (disk_idx < 0 ||
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disk_idx >= mddev->raid_disks)
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continue;
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disk = conf->multipaths + disk_idx;
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disk->rdev = rdev;
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disk_stack_limits(mddev->gendisk, rdev->bdev,
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rdev->data_offset << 9);
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/* as we don't honour merge_bvec_fn, we must never risk
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* violating it, not that we ever expect a device with
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* a merge_bvec_fn to be involved in multipath */
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if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
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blk_queue_max_segments(mddev->queue, 1);
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blk_queue_segment_boundary(mddev->queue,
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PAGE_CACHE_SIZE - 1);
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}
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if (!test_bit(Faulty, &rdev->flags))
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working_disks++;
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}
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conf->raid_disks = mddev->raid_disks;
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conf->mddev = mddev;
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spin_lock_init(&conf->device_lock);
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INIT_LIST_HEAD(&conf->retry_list);
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if (!working_disks) {
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printk(KERN_ERR "multipath: no operational IO paths for %s\n",
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mdname(mddev));
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goto out_free_conf;
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}
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mddev->degraded = conf->raid_disks - working_disks;
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conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
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sizeof(struct multipath_bh));
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if (conf->pool == NULL) {
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printk(KERN_ERR
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"multipath: couldn't allocate memory for %s\n",
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mdname(mddev));
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goto out_free_conf;
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}
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{
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mddev->thread = md_register_thread(multipathd, mddev, NULL);
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if (!mddev->thread) {
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printk(KERN_ERR "multipath: couldn't allocate thread"
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" for %s\n", mdname(mddev));
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goto out_free_conf;
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}
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}
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printk(KERN_INFO
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"multipath: array %s active with %d out of %d IO paths\n",
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mdname(mddev), conf->raid_disks - mddev->degraded,
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mddev->raid_disks);
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/*
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* Ok, everything is just fine now
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*/
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md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
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mddev->queue->backing_dev_info.congested_fn = multipath_congested;
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mddev->queue->backing_dev_info.congested_data = mddev;
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if (md_integrity_register(mddev))
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goto out_free_conf;
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|
return 0;
|
|
|
|
out_free_conf:
|
|
if (conf->pool)
|
|
mempool_destroy(conf->pool);
|
|
kfree(conf->multipaths);
|
|
kfree(conf);
|
|
mddev->private = NULL;
|
|
out:
|
|
return -EIO;
|
|
}
|
|
|
|
|
|
static int multipath_stop (mddev_t *mddev)
|
|
{
|
|
multipath_conf_t *conf = mddev->private;
|
|
|
|
md_unregister_thread(mddev->thread);
|
|
mddev->thread = NULL;
|
|
blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
|
|
mempool_destroy(conf->pool);
|
|
kfree(conf->multipaths);
|
|
kfree(conf);
|
|
mddev->private = NULL;
|
|
return 0;
|
|
}
|
|
|
|
static struct mdk_personality multipath_personality =
|
|
{
|
|
.name = "multipath",
|
|
.level = LEVEL_MULTIPATH,
|
|
.owner = THIS_MODULE,
|
|
.make_request = multipath_make_request,
|
|
.run = multipath_run,
|
|
.stop = multipath_stop,
|
|
.status = multipath_status,
|
|
.error_handler = multipath_error,
|
|
.hot_add_disk = multipath_add_disk,
|
|
.hot_remove_disk= multipath_remove_disk,
|
|
.size = multipath_size,
|
|
};
|
|
|
|
static int __init multipath_init (void)
|
|
{
|
|
return register_md_personality (&multipath_personality);
|
|
}
|
|
|
|
static void __exit multipath_exit (void)
|
|
{
|
|
unregister_md_personality (&multipath_personality);
|
|
}
|
|
|
|
module_init(multipath_init);
|
|
module_exit(multipath_exit);
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_DESCRIPTION("simple multi-path personality for MD");
|
|
MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
|
|
MODULE_ALIAS("md-multipath");
|
|
MODULE_ALIAS("md-level--4");
|