raid5.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 1,920 行 · 第 1/4 页

			bi = sh->dev[i].written;
			sh->dev[i].written = NULL;
			while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS) {
				struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
				clear_bit(BIO_UPTODATE, &bi->bi_flags);
				if (--bi->bi_phys_segments == 0) {
					md_write_end(conf->mddev);
					bi->bi_next = return_bi;
					return_bi = bi;
				}
				bi = bi2;
			}

			/* fail any reads if this device is non-operational */
			if (!test_bit(R5_Insync, &sh->dev[i].flags)) {
				bi = sh->dev[i].toread;
				sh->dev[i].toread = NULL;
				if (bi) to_read--;
				while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS){
					struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
					clear_bit(BIO_UPTODATE, &bi->bi_flags);
					if (--bi->bi_phys_segments == 0) {
						bi->bi_next = return_bi;
						return_bi = bi;
					}
					bi = nextbi;
				}
			}
		}
		spin_unlock_irq(&conf->device_lock);
	}
	if (failed > 1 && syncing) {
		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
		clear_bit(STRIPE_SYNCING, &sh->state);
		syncing = 0;
	}

	/* might be able to return some write requests if the parity block
	 * is safe, or on a failed drive
	 */
	dev = &sh->dev[sh->pd_idx];
	if ( written &&
	     ( (test_bit(R5_Insync, &dev->flags) && !test_bit(R5_LOCKED, &dev->flags) &&
		test_bit(R5_UPTODATE, &dev->flags))
	       || (failed == 1 && failed_num == sh->pd_idx))
	    ) {
	    /* any written block on an uptodate or failed drive can be returned.
	     * Note that if we 'wrote' to a failed drive, it will be UPTODATE, but 
	     * never LOCKED, so we don't need to test 'failed' directly.
	     */
	    for (i=disks; i--; )
		if (sh->dev[i].written) {
		    dev = &sh->dev[i];
		    if (!test_bit(R5_LOCKED, &dev->flags) &&
			 test_bit(R5_UPTODATE, &dev->flags) ) {
			/* We can return any write requests */
			    struct bio *wbi, *wbi2;
			    PRINTK("Return write for disc %d\n", i);
			    spin_lock_irq(&conf->device_lock);
			    wbi = dev->written;
			    dev->written = NULL;
			    while (wbi && wbi->bi_sector < dev->sector + STRIPE_SECTORS) {
				    wbi2 = r5_next_bio(wbi, dev->sector);
				    if (--wbi->bi_phys_segments == 0) {
					    md_write_end(conf->mddev);
					    wbi->bi_next = return_bi;
					    return_bi = wbi;
				    }
				    wbi = wbi2;
			    }
			    spin_unlock_irq(&conf->device_lock);
		    }
		}
	}

	/* Now we might consider reading some blocks, either to check/generate
	 * parity, or to satisfy requests
	 * or to load a block that is being partially written.
	 */
	if (to_read || non_overwrite || (syncing && (uptodate < disks))) {
		for (i=disks; i--;) {
			dev = &sh->dev[i];
			if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
			    (dev->toread ||
			     (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
			     syncing ||
			     (failed && (sh->dev[failed_num].toread ||
					 (sh->dev[failed_num].towrite && !test_bit(R5_OVERWRITE, &sh->dev[failed_num].flags))))
				    )
				) {
				/* we would like to get this block, possibly
				 * by computing it, but we might not be able to
				 */
				if (uptodate == disks-1) {
					PRINTK("Computing block %d\n", i);
					compute_block(sh, i);
					uptodate++;
				} else if (test_bit(R5_Insync, &dev->flags)) {
					set_bit(R5_LOCKED, &dev->flags);
					set_bit(R5_Wantread, &dev->flags);
#if 0
					/* if I am just reading this block and we don't have
					   a failed drive, or any pending writes then sidestep the cache */
					if (sh->bh_read[i] && !sh->bh_read[i]->b_reqnext &&
					    ! syncing && !failed && !to_write) {
						sh->bh_cache[i]->b_page =  sh->bh_read[i]->b_page;
						sh->bh_cache[i]->b_data =  sh->bh_read[i]->b_data;
					}
#endif
					locked++;
					PRINTK("Reading block %d (sync=%d)\n", 
						i, syncing);
					if (syncing)
						md_sync_acct(conf->disks[i].rdev->bdev,
							     STRIPE_SECTORS);
				}
			}
		}
		set_bit(STRIPE_HANDLE, &sh->state);
	}

	/* now to consider writing and what else, if anything should be read */
	if (to_write) {
		int rmw=0, rcw=0;
		for (i=disks ; i--;) {
			/* would I have to read this buffer for read_modify_write */
			dev = &sh->dev[i];
			if ((dev->towrite || i == sh->pd_idx) &&
			    (!test_bit(R5_LOCKED, &dev->flags) 
#if 0
|| sh->bh_page[i]!=bh->b_page
#endif
				    ) &&
			    !test_bit(R5_UPTODATE, &dev->flags)) {
				if (test_bit(R5_Insync, &dev->flags)
/*				    && !(!mddev->insync && i == sh->pd_idx) */
					)
					rmw++;
				else rmw += 2*disks;  /* cannot read it */
			}
			/* Would I have to read this buffer for reconstruct_write */
			if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
			    (!test_bit(R5_LOCKED, &dev->flags) 
#if 0
|| sh->bh_page[i] != bh->b_page
#endif
				    ) &&
			    !test_bit(R5_UPTODATE, &dev->flags)) {
				if (test_bit(R5_Insync, &dev->flags)) rcw++;
				else rcw += 2*disks;
			}
		}
		PRINTK("for sector %llu, rmw=%d rcw=%d\n", 
			(unsigned long long)sh->sector, rmw, rcw);
		set_bit(STRIPE_HANDLE, &sh->state);
		if (rmw < rcw && rmw > 0)
			/* prefer read-modify-write, but need to get some data */
			for (i=disks; i--;) {
				dev = &sh->dev[i];
				if ((dev->towrite || i == sh->pd_idx) &&
				    !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
				    test_bit(R5_Insync, &dev->flags)) {
					if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
					{
						PRINTK("Read_old block %d for r-m-w\n", i);
						set_bit(R5_LOCKED, &dev->flags);
						set_bit(R5_Wantread, &dev->flags);
						locked++;
					} else {
						set_bit(STRIPE_DELAYED, &sh->state);
						set_bit(STRIPE_HANDLE, &sh->state);
					}
				}
			}
		if (rcw <= rmw && rcw > 0)
			/* want reconstruct write, but need to get some data */
			for (i=disks; i--;) {
				dev = &sh->dev[i];
				if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
				    !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
				    test_bit(R5_Insync, &dev->flags)) {
					if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
					{
						PRINTK("Read_old block %d for Reconstruct\n", i);
						set_bit(R5_LOCKED, &dev->flags);
						set_bit(R5_Wantread, &dev->flags);
						locked++;
					} else {
						set_bit(STRIPE_DELAYED, &sh->state);
						set_bit(STRIPE_HANDLE, &sh->state);
					}
				}
			}
		/* now if nothing is locked, and if we have enough data, we can start a write request */
		if (locked == 0 && (rcw == 0 ||rmw == 0)) {
			PRINTK("Computing parity...\n");
			compute_parity(sh, rcw==0 ? RECONSTRUCT_WRITE : READ_MODIFY_WRITE);
			/* now every locked buffer is ready to be written */
			for (i=disks; i--;)
				if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
					PRINTK("Writing block %d\n", i);
					locked++;
					set_bit(R5_Wantwrite, &sh->dev[i].flags);
					if (!test_bit(R5_Insync, &sh->dev[i].flags)
					    || (i==sh->pd_idx && failed == 0))
						set_bit(STRIPE_INSYNC, &sh->state);
				}
			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
				atomic_dec(&conf->preread_active_stripes);
				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
					md_wakeup_thread(conf->mddev->thread);
			}
		}
	}

	/* maybe we need to check and possibly fix the parity for this stripe
	 * Any reads will already have been scheduled, so we just see if enough data
	 * is available
	 */
	if (syncing && locked == 0 &&
	    !test_bit(STRIPE_INSYNC, &sh->state) && failed <= 1) {
		set_bit(STRIPE_HANDLE, &sh->state);
		if (failed == 0) {
			char *pagea;
			if (uptodate != disks)
				BUG();
			compute_parity(sh, CHECK_PARITY);
			uptodate--;
			pagea = page_address(sh->dev[sh->pd_idx].page);
			if ((*(u32*)pagea) == 0 &&
			    !memcmp(pagea, pagea+4, STRIPE_SIZE-4)) {
				/* parity is correct (on disc, not in buffer any more) */
				set_bit(STRIPE_INSYNC, &sh->state);
			}
		}
		if (!test_bit(STRIPE_INSYNC, &sh->state)) {
			if (failed==0)
				failed_num = sh->pd_idx;
			/* should be able to compute the missing block and write it to spare */
			if (!test_bit(R5_UPTODATE, &sh->dev[failed_num].flags)) {
				if (uptodate+1 != disks)
					BUG();
				compute_block(sh, failed_num);
				uptodate++;
			}
			if (uptodate != disks)
				BUG();
			dev = &sh->dev[failed_num];
			set_bit(R5_LOCKED, &dev->flags);
			set_bit(R5_Wantwrite, &dev->flags);
			locked++;
			set_bit(STRIPE_INSYNC, &sh->state);
			set_bit(R5_Syncio, &dev->flags);
		}
	}
	if (syncing && locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
		clear_bit(STRIPE_SYNCING, &sh->state);
	}
	
	spin_unlock(&sh->lock);

	while ((bi=return_bi)) {
		int bytes = bi->bi_size;

		return_bi = bi->bi_next;
		bi->bi_next = NULL;
		bi->bi_size = 0;
		bi->bi_end_io(bi, bytes, 0);
	}
	for (i=disks; i-- ;) {
		int rw;
		struct bio *bi;
		mdk_rdev_t *rdev;
		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
			rw = 1;
		else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
			rw = 0;
		else
			continue;
 
		bi = &sh->dev[i].req;
 
		bi->bi_rw = rw;
		if (rw)
			bi->bi_end_io = raid5_end_write_request;
		else
			bi->bi_end_io = raid5_end_read_request;
 
		spin_lock_irq(&conf->device_lock);
		rdev = conf->disks[i].rdev;
		if (rdev && rdev->faulty)
			rdev = NULL;
		if (rdev)
			atomic_inc(&rdev->nr_pending);
		spin_unlock_irq(&conf->device_lock);
 
		if (rdev) {
			if (test_bit(R5_Syncio, &sh->dev[i].flags))
				md_sync_acct(rdev->bdev, STRIPE_SECTORS);

			bi->bi_bdev = rdev->bdev;
			PRINTK("for %llu schedule op %ld on disc %d\n",
				(unsigned long long)sh->sector, bi->bi_rw, i);
			atomic_inc(&sh->count);
			bi->bi_sector = sh->sector + rdev->data_offset;
			bi->bi_flags = 1 << BIO_UPTODATE;
			bi->bi_vcnt = 1;	
			bi->bi_idx = 0;
			bi->bi_io_vec = &sh->dev[i].vec;
			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
			bi->bi_io_vec[0].bv_offset = 0;
			bi->bi_size = STRIPE_SIZE;
			bi->bi_next = NULL;
			generic_make_request(bi);
		} else {
			PRINTK("skip op %ld on disc %d for sector %llu\n",
				bi->bi_rw, i, (unsigned long long)sh->sector);
			clear_bit(R5_LOCKED, &sh->dev[i].flags);
			set_bit(STRIPE_HANDLE, &sh->state);
		}
	}
}

static inline void raid5_activate_delayed(raid5_conf_t *conf)
{
	if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
		while (!list_empty(&conf->delayed_list)) {
			struct list_head *l = conf->delayed_list.next;
			struct stripe_head *sh;
			sh = list_entry(l, struct stripe_head, lru);
			list_del_init(l);
			clear_bit(STRIPE_DELAYED, &sh->state);
			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
				atomic_inc(&conf->preread_active_stripes);
			list_add_tail(&sh->lru, &conf->handle_list);
		}
	}
}

static void unplug_slaves(mddev_t *mddev)
{
	raid5_conf_t *conf = mddev_to_conf(mddev);
	int i;
	unsigned long flags;

	spin_lock_irqsave(&conf->device_lock, flags);
	for (i=0; i<mddev->raid_disks; i++) {
		mdk_rdev_t *rdev = conf->disks[i].rdev;
		if (rdev && atomic_read(&rdev->nr_pending)) {
			request_queue_t *r_queue = bdev_get_queue(rdev->bdev);

			atomic_inc(&rdev->nr_pending);
			spin_unlock_irqrestore(&conf->device_lock, flags);

			if (r_queue && r_queue->unplug_fn)
				r_queue->unplug_fn(r_queue);

			spin_lock_irqsave(&conf->device_lock, flags);
			atomic_dec(&rdev->nr_pending);
		}
	}
	spin_unlock_irqrestore(&conf->device_lock, flags);
}

static void raid5_unplug_device(request_queue_t *q)
{
	mddev_t *mddev = q->queuedata;
	raid5_conf_t *conf = mddev_to_conf(mddev);
	unsigned long flags;

	spin_lock_irqsave(&conf->device_lock, flags);

	if (blk_remove_plug(q))
		raid5_activate_delayed(conf);
	md_wakeup_thread(mddev->thread);

	spin_unlock_irqrestore(&conf->device_lock, flags);

	unplug_slaves(mddev);
}

static int raid5_issue_flush(request_queue_t *q, struct gendisk *disk,
			     sector_t *error_sector)
{
	mddev_t *mddev = q->queuedata;
	raid5_conf_t *conf = mddev_to_conf(mddev);
	int i, ret = 0;

	for (i=0; i<mddev->raid_disks; i++) {
		mdk_rdev_t *rdev = conf->disks[i].rdev;
		if (rdev && !rdev->faulty) {
			struct block_device *bdev = rdev->bdev;
			request_queue_t *r_queue;

			if (!bdev)
				continue;

			r_queue = bdev_get_queue(bdev);
			if (!r_queue)
				continue;

			if (!r_queue->issue_flush_fn) {
				ret = -EOPNOTSUPP;
				break;
			}

			ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk, error_sector);
			if (ret)
				break;
		}
	}
	return ret;
}

static inline void raid5_plug_device(raid5_conf_t *conf)
{
	spin_lock_irq(&conf->device_lock);
	blk_plug_device(conf->mddev->queue);
	spin_unlock_irq(&conf->device_lock);
}

static int make_request (request_queue_t *q, struct bio * bi)
{
	mddev_t *mddev = q->queuedata;
	raid5_conf_t *conf = mddev_to_conf(mddev);
	const unsigned int raid_disks = conf->raid_disks;
	const unsigned int data_disks = raid_disks - 1;
	unsigned int dd_idx, pd_idx;
	sector_t new_sector;
	sector_t logical_sector, last_sector;
	struct stripe_head *sh;

	if (bio_data_dir(bi)==WRITE) {
		disk_stat_inc(mddev->gendisk, writes);
		disk_stat_add(mddev->gendisk, write_sectors, bio_sectors(bi));
	} else {
		disk_stat_inc(mddev->gendisk, reads);
		disk_stat_add(mddev->gendisk, read_sectors, bio_sectors(bi));
	}

	logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
	last_sector = bi->bi_sector + (bi->bi_size>>9);
	bi->bi_next = NULL;
	bi->bi_phys_segments = 1;	/* over-loaded to count active stripes */
	if ( bio_data_dir(bi) == WRITE )
		md_write_start(mddev);
	for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
		
		new_sector = raid5_compute_sector(logical_sector,
						  raid_disks, data_disks, &dd_idx, &pd_idx, conf);

		PRINTK("raid5: make_request, sector %Lu logical %Lu\n",
			(unsigned long long)new_sector, 
			(unsigned long long)logical_sector);

		sh = get_active_stripe(conf, new_sector, pd_idx, (bi->bi_rw&RWA_MASK));
		if (sh) {

			add_stripe_bio(sh, bi, dd_idx, (bi->bi_rw&RW_MASK));

			raid5_plug_device(conf);
			handle_stripe(sh);
			release_stripe(sh);
		} else {
			/* cannot get stripe for read-ahead, just give-up */
			clear_bit(BIO_UPTODATE, &bi->bi_flags);
			break;
		}
			
	}
	spin_lock_irq(&conf->device_lock);
	if (--bi->bi_phys_segments == 0) {
		int bytes = bi->bi_size;

		if ( bio_data_dir(bi) == WRITE )
			md_write_end(mddev);
		bi->bi_size = 0;
		bi->bi_end_io(bi, bytes, 0);
	}