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![Christoph Hellwig](/assets/img/avatar_default.png)
This way we don't need a block_device structure to submit I/O. The block_device has different life time rules from the gendisk and request_queue and is usually only available when the block device node is open. Other callers need to explicitly create one (e.g. the lightnvm passthrough code, or the new nvme multipathing code). For the actual I/O path all that we need is the gendisk, which exists once per block device. But given that the block layer also does partition remapping we additionally need a partition index, which is used for said remapping in generic_make_request. Note that all the block drivers generally want request_queue or sometimes the gendisk, so this removes a layer of indirection all over the stack. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
509 lines
13 KiB
C
509 lines
13 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/module.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 (struct mpconf *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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struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
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if (rdev && test_bit(In_sync, &rdev->flags) &&
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!test_bit(Faulty, &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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pr_crit_ratelimited("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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struct mddev *mddev = mp_bh->mddev;
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struct mpconf *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, blk_status_t status)
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{
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struct bio *bio = mp_bh->master_bio;
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struct mpconf *conf = mp_bh->mddev->private;
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bio->bi_status = status;
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bio_endio(bio);
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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)
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{
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struct multipath_bh *mp_bh = bio->bi_private;
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struct mpconf *conf = mp_bh->mddev->private;
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struct md_rdev *rdev = conf->multipaths[mp_bh->path].rdev;
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if (!bio->bi_status)
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multipath_end_bh_io(mp_bh, 0);
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else if (!(bio->bi_opf & 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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pr_info("multipath: %s: rescheduling sector %llu\n",
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bdevname(rdev->bdev,b),
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(unsigned long long)bio->bi_iter.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, bio->bi_status);
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rdev_dec_pending(rdev, conf->mddev);
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}
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static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
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{
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struct mpconf *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_opf & REQ_PREFLUSH)) {
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md_flush_request(mddev, bio);
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return true;
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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_io_error(bio);
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mempool_free(mp_bh, conf->pool);
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return true;
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}
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multipath = conf->multipaths + mp_bh->path;
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bio_init(&mp_bh->bio, NULL, 0);
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__bio_clone_fast(&mp_bh->bio, bio);
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mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
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bio_set_dev(&mp_bh->bio, multipath->rdev->bdev);
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mp_bh->bio.bi_opf |= 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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mddev_check_writesame(mddev, &mp_bh->bio);
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mddev_check_write_zeroes(mddev, &mp_bh->bio);
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generic_make_request(&mp_bh->bio);
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return true;
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}
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static void multipath_status(struct seq_file *seq, struct mddev *mddev)
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{
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struct mpconf *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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rcu_read_lock();
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for (i = 0; i < conf->raid_disks; i++) {
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struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
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seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
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}
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rcu_read_unlock();
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seq_printf (seq, "]");
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}
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static int multipath_congested(struct mddev *mddev, int bits)
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{
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struct mpconf *conf = mddev->private;
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int i, ret = 0;
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rcu_read_lock();
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for (i = 0; i < mddev->raid_disks ; i++) {
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struct md_rdev *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 (struct mddev *mddev, struct md_rdev *rdev)
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{
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struct mpconf *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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pr_warn("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_SB_CHANGE_DEVS, &mddev->sb_flags);
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pr_err("multipath: IO failure on %s, disabling IO path.\n"
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"multipath: Operation continuing 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 (struct mpconf *conf)
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{
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int i;
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struct multipath_info *tmp;
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pr_debug("MULTIPATH conf printout:\n");
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if (!conf) {
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pr_debug("(conf==NULL)\n");
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return;
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}
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pr_debug(" --- 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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pr_debug(" 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(struct mddev *mddev, struct md_rdev *rdev)
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{
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struct mpconf *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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err = md_integrity_add_rdev(rdev, mddev);
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if (err)
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break;
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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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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(struct mddev *mddev, struct md_rdev *rdev)
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{
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struct mpconf *conf = mddev->private;
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int err = 0;
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int number = rdev->raid_disk;
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struct multipath_info *p = conf->multipaths + number;
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print_multipath_conf(conf);
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if (rdev == p->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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pr_warn("hot-remove-disk, slot %d is identified 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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if (!test_bit(RemoveSynchronized, &rdev->flags)) {
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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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}
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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(struct md_thread *thread)
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{
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struct mddev *mddev = thread->mddev;
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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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struct mpconf *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_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
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if ((mp_bh->path = multipath_map (conf))<0) {
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pr_err("multipath: %s: unrecoverable IO read error for block %llu\n",
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bio_devname(bio, b),
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(unsigned long long)bio->bi_iter.bi_sector);
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multipath_end_bh_io(mp_bh, BLK_STS_IOERR);
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} else {
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pr_err("multipath: %s: redirecting sector %llu to another IO path\n",
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bio_devname(bio, b),
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(unsigned long long)bio->bi_iter.bi_sector);
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*bio = *(mp_bh->master_bio);
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bio->bi_iter.bi_sector +=
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conf->multipaths[mp_bh->path].rdev->data_offset;
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bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev);
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bio->bi_opf |= 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(struct mddev *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 (struct mddev *mddev)
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{
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struct mpconf *conf;
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int disk_idx;
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struct multipath_info *disk;
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struct md_rdev *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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pr_warn("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_free()]
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*/
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conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
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mddev->private = conf;
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if (!conf)
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goto out;
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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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goto out_free_conf;
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working_disks = 0;
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rdev_for_each(rdev, mddev) {
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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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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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pr_warn("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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goto out_free_conf;
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mddev->thread = md_register_thread(multipathd, mddev,
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"multipath");
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if (!mddev->thread)
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goto out_free_conf;
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pr_info("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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if (md_integrity_register(mddev))
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goto out_free_conf;
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return 0;
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out_free_conf:
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mempool_destroy(conf->pool);
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kfree(conf->multipaths);
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kfree(conf);
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mddev->private = NULL;
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out:
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return -EIO;
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}
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static void multipath_free(struct mddev *mddev, void *priv)
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{
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struct mpconf *conf = priv;
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mempool_destroy(conf->pool);
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kfree(conf->multipaths);
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kfree(conf);
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}
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static struct md_personality multipath_personality =
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{
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.name = "multipath",
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.level = LEVEL_MULTIPATH,
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.owner = THIS_MODULE,
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.make_request = multipath_make_request,
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.run = multipath_run,
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.free = multipath_free,
|
|
.status = multipath_status,
|
|
.error_handler = multipath_error,
|
|
.hot_add_disk = multipath_add_disk,
|
|
.hot_remove_disk= multipath_remove_disk,
|
|
.size = multipath_size,
|
|
.congested = multipath_congested,
|
|
};
|
|
|
|
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");
|