From patchwork Fri Jun 9 11:58:55 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergei Shtepa X-Patchwork-Id: 13273827 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 03DF3C87FDC for ; Fri, 9 Jun 2023 12:21:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238697AbjFIMVp (ORCPT ); Fri, 9 Jun 2023 08:21:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239459AbjFIMVm (ORCPT ); Fri, 9 Jun 2023 08:21:42 -0400 Received: from mx1.veeam.com (mx1.veeam.com [216.253.77.21]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BD3F930CD; Fri, 9 Jun 2023 05:21:36 -0700 (PDT) Received: from mail.veeam.com (prgmbx01.amust.local [172.24.128.102]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.veeam.com (Postfix) with ESMTPS id 0057742543; Fri, 9 Jun 2023 08:06:13 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=veeam.com; s=mx1-2022; t=1686312373; bh=w41iDVc5LKMZ73O5cZY/nfU0O2QCnXg1jdgooADFqMk=; h=From:To:CC:Subject:Date:In-Reply-To:References:From; b=tjdqmr0SeuRcez0d7Vsxm/JvxE6XxmYIgDESdbSeoR7s2ZAlF5JXS/73XaBe+HYfr LI/T2qw4erfKLr/Q0/ER2K0BOevdoOUJ4ctYi+iWTPNdr+h607FQzPk/51yg13sBm8 aBQBsqujWahKuQFP9eI/GIQ2hi/aM9UerlY/F6iMKSSGVwOjghGp4f1XMhVITIWwSm E9Ccqvx6AMpgjma5rpelhOF5GmcR1I48B7Z1YkeZey8YPJbvfVvwFibXUiQWQV6bJr gidLDXrJt+0vs2ttQVjJXoVz/VqKGwVSC3LZD+/79k2/tkS86dX2Uyjpa96MP6XmDU 0lBeRmqJxFmyA== Received: from ssh-deb10-ssd-vb.amust.local (172.24.10.107) by prgmbx01.amust.local (172.24.128.102) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.26; Fri, 9 Jun 2023 14:06:10 +0200 From: Sergei Shtepa To: , , , CC: , , , , , , , , , , , , Subject: [PATCH v4 08/11] blksnap: difference storage Date: Fri, 9 Jun 2023 13:58:55 +0200 Message-ID: <20230609115858.4737-8-sergei.shtepa@veeam.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20230609115858.4737-1-sergei.shtepa@veeam.com> References: <20230609115858.4737-1-sergei.shtepa@veeam.com> MIME-Version: 1.0 X-Originating-IP: [172.24.10.107] X-ClientProxiedBy: prgmbx02.amust.local (172.24.128.103) To prgmbx01.amust.local (172.24.128.102) X-EsetResult: clean, is OK X-EsetId: 37303A2924031554627C6B X-Veeam-MMEX: True Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Provides management of difference blocks of block devices. Storing difference blocks, and reading them to get a snapshot images. Co-developed-by: Christoph Hellwig Signed-off-by: Christoph Hellwig Signed-off-by: Sergei Shtepa --- drivers/block/blksnap/diff_area.c | 554 +++++++++++++++++++++++++++ drivers/block/blksnap/diff_area.h | 144 +++++++ drivers/block/blksnap/diff_buffer.c | 127 ++++++ drivers/block/blksnap/diff_buffer.h | 37 ++ drivers/block/blksnap/diff_storage.c | 315 +++++++++++++++ drivers/block/blksnap/diff_storage.h | 111 ++++++ 6 files changed, 1288 insertions(+) create mode 100644 drivers/block/blksnap/diff_area.c create mode 100644 drivers/block/blksnap/diff_area.h create mode 100644 drivers/block/blksnap/diff_buffer.c create mode 100644 drivers/block/blksnap/diff_buffer.h create mode 100644 drivers/block/blksnap/diff_storage.c create mode 100644 drivers/block/blksnap/diff_storage.h -- 2.20.1 diff --git a/drivers/block/blksnap/diff_area.c b/drivers/block/blksnap/diff_area.c new file mode 100644 index 000000000000..831505689dfd --- /dev/null +++ b/drivers/block/blksnap/diff_area.c @@ -0,0 +1,554 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 2023 Veeam Software Group GmbH */ +#define pr_fmt(fmt) KBUILD_MODNAME "-diff-area: " fmt + +#include +#include +#include +#include +#include "chunk.h" +#include "diff_buffer.h" +#include "diff_storage.h" +#include "params.h" + +static inline sector_t diff_area_chunk_offset(struct diff_area *diff_area, + sector_t sector) +{ + return sector & ((1ull << (diff_area->chunk_shift - SECTOR_SHIFT)) - 1); +} + +static inline unsigned long diff_area_chunk_number(struct diff_area *diff_area, + sector_t sector) +{ + return (unsigned long)(sector >> + (diff_area->chunk_shift - SECTOR_SHIFT)); +} + +static inline sector_t chunk_sector(struct chunk *chunk) +{ + return (sector_t)(chunk->number) + << (chunk->diff_area->chunk_shift - SECTOR_SHIFT); +} + +static inline sector_t last_chunk_size(sector_t sector_count, sector_t capacity) +{ + sector_t capacity_rounded = round_down(capacity, sector_count); + + if (capacity > capacity_rounded) + sector_count = capacity - capacity_rounded; + + return sector_count; +} + +static inline unsigned long long count_by_shift(sector_t capacity, + unsigned long long shift) +{ + unsigned long long shift_sector = (shift - SECTOR_SHIFT); + + return round_up(capacity, (1ull << shift_sector)) >> shift_sector; +} + +static inline struct chunk *chunk_alloc(struct diff_area *diff_area, + unsigned long number) +{ + struct chunk *chunk; + + chunk = kzalloc(sizeof(struct chunk), GFP_NOIO); + if (!chunk) + return NULL; + + INIT_LIST_HEAD(&chunk->link); + sema_init(&chunk->lock, 1); + chunk->diff_area = NULL; + chunk->number = number; + chunk->state = CHUNK_ST_NEW; + + chunk->sector_count = diff_area_chunk_sectors(diff_area); + /* + * The last chunk has a special size. + */ + if (unlikely((number + 1) == diff_area->chunk_count)) { + chunk->sector_count = bdev_nr_sectors(diff_area->orig_bdev) - + (chunk->sector_count * number); + } + + return chunk; +} + +static inline void chunk_free(struct diff_area *diff_area, struct chunk *chunk) +{ + down(&chunk->lock); + if (chunk->diff_buffer) + diff_buffer_release(diff_area, chunk->diff_buffer); + diff_storage_free_region(chunk->diff_region); + up(&chunk->lock); + kfree(chunk); +} + +static void diff_area_calculate_chunk_size(struct diff_area *diff_area) +{ + unsigned long count; + unsigned long shift = get_chunk_minimum_shift(); + sector_t capacity; + sector_t min_io_sect; + + min_io_sect = (sector_t)(bdev_io_min(diff_area->orig_bdev) >> + SECTOR_SHIFT); + capacity = bdev_nr_sectors(diff_area->orig_bdev); + pr_debug("Minimal IO block %llu sectors\n", min_io_sect); + pr_debug("Device capacity %llu sectors\n", capacity); + + count = count_by_shift(capacity, shift); + pr_debug("Chunks count %lu\n", count); + while ((count > get_chunk_maximum_count()) || + ((1ul << (shift - SECTOR_SHIFT)) < min_io_sect)) { + shift++; + count = count_by_shift(capacity, shift); + pr_debug("Chunks count %lu\n", count); + } + + diff_area->chunk_shift = shift; + diff_area->chunk_count = (unsigned long)DIV_ROUND_UP_ULL(capacity, + (1ul << (shift - SECTOR_SHIFT))); +} + +void diff_area_free(struct kref *kref) +{ + unsigned long inx = 0; + struct chunk *chunk; + struct diff_area *diff_area = + container_of(kref, struct diff_area, kref); + + might_sleep(); + + flush_work(&diff_area->store_queue_work); + xa_for_each(&diff_area->chunk_map, inx, chunk) + if (chunk) + chunk_free(diff_area, chunk); + xa_destroy(&diff_area->chunk_map); + + if (diff_area->orig_bdev) { + blkdev_put(diff_area->orig_bdev, FMODE_READ | FMODE_WRITE); + diff_area->orig_bdev = NULL; + } + + /* Clean up free_diff_buffers */ + diff_buffer_cleanup(diff_area); + + kfree(diff_area); +} + +static inline bool diff_area_store_one(struct diff_area *diff_area) +{ + struct chunk *iter, *chunk = NULL; + + spin_lock(&diff_area->store_queue_lock); + list_for_each_entry(iter, &diff_area->store_queue, link) { + if (!down_trylock(&iter->lock)) { + chunk = iter; + atomic_dec(&diff_area->store_queue_count); + list_del_init(&chunk->link); + chunk->diff_area = diff_area_get(diff_area); + break; + } + /* + * If it is not possible to lock a chunk for writing, + * then it is currently in use, and we try to clean up the + * next chunk. + */ + } + spin_unlock(&diff_area->store_queue_lock); + if (!chunk) + return false; + + if (chunk->state != CHUNK_ST_IN_MEMORY) { + /* + * There cannot be a chunk in the store queue whose buffer has + * not been read into memory. + */ + chunk_up(chunk); + pr_warn("Cannot release empty buffer for chunk #%ld", + chunk->number); + return true; + } + + if (diff_area_is_corrupted(diff_area)) { + chunk_store_failed(chunk, 0); + return true; + } + + if (!chunk->diff_region) { + struct diff_region *diff_region; + + diff_region = diff_storage_new_region( + diff_area->diff_storage, + diff_area_chunk_sectors(diff_area), + diff_area->logical_blksz); + + if (IS_ERR(diff_region)) { + pr_debug("Cannot get store for chunk #%ld\n", + chunk->number); + chunk_store_failed(chunk, PTR_ERR(diff_region)); + return true; + } + chunk->diff_region = diff_region; + } + chunk_store(chunk); + return true; +} + +static void diff_area_store_queue_work(struct work_struct *work) +{ + struct diff_area *diff_area = container_of( + work, struct diff_area, store_queue_work); + + while (diff_area_store_one(diff_area)) + ; +} + +struct diff_area *diff_area_new(dev_t dev_id, struct diff_storage *diff_storage) +{ + int ret = 0; + struct diff_area *diff_area = NULL; + struct block_device *bdev; + + pr_debug("Open device [%u:%u]\n", MAJOR(dev_id), MINOR(dev_id)); + + bdev = blkdev_get_by_dev(dev_id, FMODE_READ | FMODE_WRITE, NULL); + if (IS_ERR(bdev)) { + int err = PTR_ERR(bdev); + + pr_err("Failed to open device. errno=%d\n", abs(err)); + return ERR_PTR(err); + } + + diff_area = kzalloc(sizeof(struct diff_area), GFP_KERNEL); + if (!diff_area) { + blkdev_put(bdev, FMODE_READ | FMODE_WRITE); + return ERR_PTR(-ENOMEM); + } + + kref_init(&diff_area->kref); + diff_area->orig_bdev = bdev; + diff_area->diff_storage = diff_storage; + + diff_area_calculate_chunk_size(diff_area); + if (diff_area->chunk_shift > get_chunk_maximum_shift()) { + pr_info("The maximum allowable chunk size has been reached.\n"); + return ERR_PTR(-EFAULT); + } + pr_debug("The optimal chunk size was calculated as %llu bytes for device [%d:%d]\n", + (1ull << diff_area->chunk_shift), + MAJOR(diff_area->orig_bdev->bd_dev), + MINOR(diff_area->orig_bdev->bd_dev)); + + xa_init(&diff_area->chunk_map); + + spin_lock_init(&diff_area->store_queue_lock); + INIT_LIST_HEAD(&diff_area->store_queue); + atomic_set(&diff_area->store_queue_count, 0); + INIT_WORK(&diff_area->store_queue_work, diff_area_store_queue_work); + + spin_lock_init(&diff_area->free_diff_buffers_lock); + INIT_LIST_HEAD(&diff_area->free_diff_buffers); + atomic_set(&diff_area->free_diff_buffers_count, 0); + + diff_area->physical_blksz = bdev->bd_queue->limits.physical_block_size; + diff_area->logical_blksz = bdev->bd_queue->limits.logical_block_size; + diff_area->corrupt_flag = 0; + + if (!diff_storage->capacity) { + pr_err("Difference storage is empty\n"); + pr_err("In-memory difference storage is not supported\n"); + ret = -EFAULT; + } + + if (ret) { + diff_area_put(diff_area); + return ERR_PTR(ret); + } + + return diff_area; +} + +static inline unsigned int chunk_limit(struct chunk *chunk, + struct bvec_iter *iter) +{ + sector_t chunk_ofs = iter->bi_sector - chunk_sector(chunk); + sector_t chunk_left = chunk->sector_count - chunk_ofs; + + return min(iter->bi_size, (unsigned int)(chunk_left << SECTOR_SHIFT)); +} + +/* + * Implements the copy-on-write mechanism. + */ +bool diff_area_cow(struct bio *bio, struct diff_area *diff_area, + struct bvec_iter *iter) +{ + bool nowait = bio->bi_opf & REQ_NOWAIT; + struct bio *chunk_bio = NULL; + LIST_HEAD(chunks); + int ret = 0; + + while (iter->bi_size) { + unsigned long nr = diff_area_chunk_number(diff_area, + iter->bi_sector); + struct chunk *chunk = xa_load(&diff_area->chunk_map, nr); + unsigned int len; + + if (!chunk) { + chunk = chunk_alloc(diff_area, nr); + if (!chunk) { + diff_area_set_corrupted(diff_area, -EINVAL); + ret = -ENOMEM; + goto fail; + } + + ret = xa_insert(&diff_area->chunk_map, nr, chunk, + GFP_NOIO); + if (likely(!ret)) { + /* new chunk has been added */ + } else if (ret == -EBUSY) { + /* another chunk has just been created */ + chunk_free(diff_area, chunk); + chunk = xa_load(&diff_area->chunk_map, nr); + WARN_ON_ONCE(!chunk); + if (unlikely(!chunk)) { + ret = -EINVAL; + diff_area_set_corrupted(diff_area, ret); + goto fail; + } + } else if (ret) { + pr_err("Failed insert chunk to chunk map\n"); + chunk_free(diff_area, chunk); + diff_area_set_corrupted(diff_area, ret); + goto fail; + } + } + + if (nowait) { + if (down_trylock(&chunk->lock)) { + ret = -EAGAIN; + goto fail; + } + } else { + ret = down_killable(&chunk->lock); + if (unlikely(ret)) + goto fail; + } + chunk->diff_area = diff_area_get(diff_area); + + len = chunk_limit(chunk, iter); + if (chunk->state == CHUNK_ST_NEW) { + if (nowait) { + /* + * If the data of this chunk has not yet been + * copied to the difference storage, then it is + * impossible to process the I/O write unit with + * the NOWAIT flag. + */ + chunk_up(chunk); + ret = -EAGAIN; + goto fail; + } + + /* + * Load the chunk asynchronously. + */ + ret = chunk_load_and_postpone_io(chunk, &chunk_bio); + if (ret) { + chunk_up(chunk); + goto fail; + } + list_add_tail(&chunk->link, &chunks); + } else { + /* + * The chunk has already been: + * - failed, when the snapshot is corrupted + * - read into the buffer + * - stored into the diff storage + * In this case, we do not change the chunk. + */ + chunk_up(chunk); + } + bio_advance_iter_single(bio, iter, len); + } + + if (chunk_bio) { + /* Postpone bio processing in a callback. */ + chunk_load_and_postpone_io_finish(&chunks, chunk_bio, bio); + return true; + } + /* Pass bio to the low level */ + return false; + +fail: + if (chunk_bio) { + chunk_bio->bi_status = errno_to_blk_status(ret); + bio_endio(chunk_bio); + } + + if (ret == -EAGAIN) { + /* + * The -EAGAIN error code means that it is not possible to + * process a I/O unit with a flag REQ_NOWAIT. + * I/O unit processing is being completed with such error. + */ + bio->bi_status = BLK_STS_AGAIN; + bio_endio(bio); + return true; + } + /* In any other case, the processing of the I/O unit continues. */ + return false; +} + +static void orig_clone_endio(struct bio *bio) +{ + struct bio *orig_bio = bio->bi_private; + + if (unlikely(bio->bi_status != BLK_STS_OK)) + bio_io_error(orig_bio); + else + bio_endio(orig_bio); +} + +static void orig_clone_bio(struct diff_area *diff_area, struct bio *bio) +{ + struct bio *new_bio; + struct block_device *bdev = diff_area->orig_bdev; + sector_t chunk_limit; + + new_bio = chunk_alloc_clone(bdev, bio); + WARN_ON(!new_bio); + + chunk_limit = diff_area_chunk_sectors(diff_area) - + diff_area_chunk_offset(diff_area, bio->bi_iter.bi_sector); + + new_bio->bi_iter.bi_sector = bio->bi_iter.bi_sector; + new_bio->bi_iter.bi_size = min_t(unsigned int, + bio->bi_iter.bi_size, chunk_limit << SECTOR_SHIFT); + + bio_set_flag(new_bio, BIO_FILTERED); + new_bio->bi_end_io = orig_clone_endio; + new_bio->bi_private = bio; + + bio_advance(bio, new_bio->bi_iter.bi_size); + bio_inc_remaining(bio); + + submit_bio_noacct(new_bio); +} + +bool diff_area_submit_chunk(struct diff_area *diff_area, struct bio *bio) +{ + int ret; + struct chunk *chunk; + unsigned long nr = diff_area_chunk_number(diff_area, + bio->bi_iter.bi_sector); + + chunk = xa_load(&diff_area->chunk_map, nr); + /* + * If this chunk is not in the chunk map, then the COW algorithm did + * not access this part of the disk space, and writing to the snapshot + * in this part was also not performed. + */ + if (!chunk) { + if (op_is_write(bio_op(bio))) { + /* + * To process a write bio, we need to allocate a new + * chunk. + */ + chunk = chunk_alloc(diff_area, nr); + WARN_ON_ONCE(!chunk); + if (unlikely(!chunk)) + return false; + + ret = xa_insert(&diff_area->chunk_map, nr, chunk, + GFP_NOIO); + if (likely(!ret)) { + /* new chunk has been added */ + } else if (ret == -EBUSY) { + /* another chunk has just been created */ + chunk_free(diff_area, chunk); + chunk = xa_load(&diff_area->chunk_map, nr); + WARN_ON_ONCE(!chunk); + if (unlikely(!chunk)) + return false; + } else if (ret) { + pr_err("Failed insert chunk to chunk map\n"); + chunk_free(diff_area, chunk); + return false; + } + } else { + /* + * To read, we simply redirect the bio to the original + * block device. + */ + orig_clone_bio(diff_area, bio); + return true; + } + } + + if (down_killable(&chunk->lock)) + return false; + chunk->diff_area = diff_area_get(diff_area); + + if (unlikely(chunk->state == CHUNK_ST_FAILED)) { + pr_err("Chunk #%ld corrupted\n", chunk->number); + chunk_up(chunk); + return false; + } + if (chunk->state == CHUNK_ST_IN_MEMORY) { + /* + * Directly copy data from the in-memory chunk or + * copy to the in-memory chunk for write operation. + */ + chunk_copy_bio(chunk, bio, &bio->bi_iter); + chunk_up(chunk); + return true; + } + if ((chunk->state == CHUNK_ST_STORED) || !op_is_write(bio_op(bio))) { + /* + * Read data from the chunk on difference storage. + */ + chunk_clone_bio(chunk, bio); + chunk_up(chunk); + return true; + } + /* + * Starts asynchronous loading of a chunk from the original block device + * or difference storage and schedule copying data to (or from) the + * in-memory chunk. + */ + if (chunk_load_and_schedule_io(chunk, bio)) { + chunk_up(chunk); + return false; + } + return true; +} + +static inline void diff_area_event_corrupted(struct diff_area *diff_area) +{ + struct blksnap_event_corrupted data = { + .dev_id_mj = MAJOR(diff_area->orig_bdev->bd_dev), + .dev_id_mn = MINOR(diff_area->orig_bdev->bd_dev), + .err_code = abs(diff_area->error_code), + }; + + event_gen(&diff_area->diff_storage->event_queue, GFP_NOIO, + blksnap_event_code_corrupted, &data, + sizeof(struct blksnap_event_corrupted)); +} + +void diff_area_set_corrupted(struct diff_area *diff_area, int err_code) +{ + if (test_and_set_bit(0, &diff_area->corrupt_flag)) + return; + + diff_area->error_code = err_code; + diff_area_event_corrupted(diff_area); + + pr_err("Set snapshot device is corrupted for [%u:%u] with error code %d\n", + MAJOR(diff_area->orig_bdev->bd_dev), + MINOR(diff_area->orig_bdev->bd_dev), abs(err_code)); +} diff --git a/drivers/block/blksnap/diff_area.h b/drivers/block/blksnap/diff_area.h new file mode 100644 index 000000000000..6ecec9390282 --- /dev/null +++ b/drivers/block/blksnap/diff_area.h @@ -0,0 +1,144 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (C) 2023 Veeam Software Group GmbH */ +#ifndef __BLKSNAP_DIFF_AREA_H +#define __BLKSNAP_DIFF_AREA_H + +#include +#include +#include +#include +#include +#include +#include +#include "event_queue.h" + +struct diff_storage; +struct chunk; + +/** + * struct diff_area - Describes the difference area for one original device. + * + * @kref: + * The reference counter allows to manage the lifetime of an object. + * @orig_bdev: + * A pointer to the structure of an opened block device. + * @diff_storage: + * Pointer to difference storage for storing difference data. + * @chunk_shift: + * Power of 2 used to specify the chunk size. This allows to set different + * chunk sizes for huge and small block devices. + * @chunk_count: + * Count of chunks. The number of chunks into which the block device + * is divided. + * @chunk_map: + * A map of chunks. + * @store_queue_lock: + * This spinlock guarantees consistency of the linked lists of chunks + * queue. + * @store_queue: + * The queue of chunks waiting to be stored to the difference storage. + * @store_queue_count: + * The number of chunks in the store queue. + * @store_queue_work: + * The workqueue work item. This worker limits the number of chunks + * that store their data in RAM. + * @free_diff_buffers_lock: + * This spinlock guarantees consistency of the linked lists of + * free difference buffers. + * @free_diff_buffers: + * Linked list of free difference buffers allows to reduce the number + * of buffer allocation and release operations. + * @physical_blksz: + * The physical block size for the snapshot image is equal to the + * physical block size of the original device. + * @logical_blksz: + * The logical block size for the snapshot image is equal to the + * logical block size of the original device. + * @free_diff_buffers_count: + * The number of free difference buffers in the linked list. + * @corrupt_flag: + * The flag is set if an error occurred in the operation of the data + * saving mechanism in the diff area. In this case, an error will be + * generated when reading from the snapshot image. + * @error_code: + * The error code that caused the snapshot to be corrupted. + * + * The &struct diff_area is created for each block device in the snapshot. + * It is used to save the differences between the original block device and + * the snapshot image. That is, when writing data to the original device, + * the differences are copied as chunks to the difference storage. + * Reading and writing from the snapshot image is also performed using + * &struct diff_area. + * + * The xarray has a limit on the maximum size. This can be especially + * noticeable on 32-bit systems. This creates a limit in the size of + * supported disks. + * + * For example, for a 256 TiB disk with a block size of 65536 bytes, the + * number of elements in the chunk map will be equal to 2 with a power of 32. + * Therefore, the number of chunks into which the block device is divided is + * limited. + * + * The store queue allows to postpone the operation of storing a chunks data + * to the difference storage and perform it later in the worker thread. + * + * The linked list of difference buffers allows to have a certain number of + * "hot" buffers. This allows to reduce the number of allocations and releases + * of memory. + * + * + */ +struct diff_area { + struct kref kref; + struct block_device *orig_bdev; + struct diff_storage *diff_storage; + + unsigned long chunk_shift; + unsigned long chunk_count; + struct xarray chunk_map; + + spinlock_t store_queue_lock; + struct list_head store_queue; + atomic_t store_queue_count; + struct work_struct store_queue_work; + + spinlock_t free_diff_buffers_lock; + struct list_head free_diff_buffers; + atomic_t free_diff_buffers_count; + + unsigned int physical_blksz; + unsigned int logical_blksz; + + unsigned long corrupt_flag; + int error_code; +}; + +struct diff_area *diff_area_new(dev_t dev_id, + struct diff_storage *diff_storage); +void diff_area_free(struct kref *kref); +static inline struct diff_area *diff_area_get(struct diff_area *diff_area) +{ + kref_get(&diff_area->kref); + return diff_area; +}; +static inline void diff_area_put(struct diff_area *diff_area) +{ + kref_put(&diff_area->kref, diff_area_free); +}; + +void diff_area_set_corrupted(struct diff_area *diff_area, int err_code); +static inline bool diff_area_is_corrupted(struct diff_area *diff_area) +{ + return !!diff_area->corrupt_flag; +}; +static inline sector_t diff_area_chunk_sectors(struct diff_area *diff_area) +{ + return (sector_t)(1ull << (diff_area->chunk_shift - SECTOR_SHIFT)); +}; +bool diff_area_cow(struct bio *bio, struct diff_area *diff_area, + struct bvec_iter *iter); + +bool diff_area_submit_chunk(struct diff_area *diff_area, struct bio *bio); +void diff_area_rw_chunk(struct kref *kref); + +#endif /* __BLKSNAP_DIFF_AREA_H */ diff --git a/drivers/block/blksnap/diff_buffer.c b/drivers/block/blksnap/diff_buffer.c new file mode 100644 index 000000000000..77ad59cc46b3 --- /dev/null +++ b/drivers/block/blksnap/diff_buffer.c @@ -0,0 +1,127 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 2023 Veeam Software Group GmbH */ +#define pr_fmt(fmt) KBUILD_MODNAME "-diff-buffer: " fmt + +#include "diff_buffer.h" +#include "diff_area.h" +#include "params.h" + +static void diff_buffer_free(struct diff_buffer *diff_buffer) +{ + size_t inx = 0; + + if (unlikely(!diff_buffer)) + return; + + for (inx = 0; inx < diff_buffer->page_count; inx++) { + struct page *page = diff_buffer->pages[inx]; + + if (page) + __free_page(page); + } + + kfree(diff_buffer); +} + +static struct diff_buffer * +diff_buffer_new(size_t page_count, size_t buffer_size, gfp_t gfp_mask) +{ + struct diff_buffer *diff_buffer; + size_t inx = 0; + struct page *page; + + if (unlikely(page_count <= 0)) + return NULL; + + /* + * In case of overflow, it is better to get a null pointer + * than a pointer to some memory area. Therefore + 1. + */ + diff_buffer = kzalloc(sizeof(struct diff_buffer) + + (page_count + 1) * sizeof(struct page *), + gfp_mask); + if (!diff_buffer) + return NULL; + + INIT_LIST_HEAD(&diff_buffer->link); + diff_buffer->size = buffer_size; + diff_buffer->page_count = page_count; + + for (inx = 0; inx < page_count; inx++) { + page = alloc_page(gfp_mask); + if (!page) + goto fail; + + diff_buffer->pages[inx] = page; + } + return diff_buffer; +fail: + diff_buffer_free(diff_buffer); + return NULL; +} + +struct diff_buffer *diff_buffer_take(struct diff_area *diff_area) +{ + struct diff_buffer *diff_buffer = NULL; + sector_t chunk_sectors; + size_t page_count; + size_t buffer_size; + + spin_lock(&diff_area->free_diff_buffers_lock); + diff_buffer = list_first_entry_or_null(&diff_area->free_diff_buffers, + struct diff_buffer, link); + if (diff_buffer) { + list_del(&diff_buffer->link); + atomic_dec(&diff_area->free_diff_buffers_count); + } + spin_unlock(&diff_area->free_diff_buffers_lock); + + /* Return free buffer if it was found in a pool */ + if (diff_buffer) + return diff_buffer; + + /* Allocate new buffer */ + chunk_sectors = diff_area_chunk_sectors(diff_area); + page_count = round_up(chunk_sectors, PAGE_SECTORS) / PAGE_SECTORS; + buffer_size = chunk_sectors << SECTOR_SHIFT; + + diff_buffer = + diff_buffer_new(page_count, buffer_size, GFP_NOIO); + if (unlikely(!diff_buffer)) + return ERR_PTR(-ENOMEM); + return diff_buffer; +} + +void diff_buffer_release(struct diff_area *diff_area, + struct diff_buffer *diff_buffer) +{ + if (atomic_read(&diff_area->free_diff_buffers_count) > + get_free_diff_buffer_pool_size()) { + diff_buffer_free(diff_buffer); + return; + } + spin_lock(&diff_area->free_diff_buffers_lock); + list_add_tail(&diff_buffer->link, &diff_area->free_diff_buffers); + atomic_inc(&diff_area->free_diff_buffers_count); + spin_unlock(&diff_area->free_diff_buffers_lock); +} + +void diff_buffer_cleanup(struct diff_area *diff_area) +{ + struct diff_buffer *diff_buffer = NULL; + + do { + spin_lock(&diff_area->free_diff_buffers_lock); + diff_buffer = + list_first_entry_or_null(&diff_area->free_diff_buffers, + struct diff_buffer, link); + if (diff_buffer) { + list_del(&diff_buffer->link); + atomic_dec(&diff_area->free_diff_buffers_count); + } + spin_unlock(&diff_area->free_diff_buffers_lock); + + if (diff_buffer) + diff_buffer_free(diff_buffer); + } while (diff_buffer); +} diff --git a/drivers/block/blksnap/diff_buffer.h b/drivers/block/blksnap/diff_buffer.h new file mode 100644 index 000000000000..f81e56cf4b9a --- /dev/null +++ b/drivers/block/blksnap/diff_buffer.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (C) 2023 Veeam Software Group GmbH */ +#ifndef __BLKSNAP_DIFF_BUFFER_H +#define __BLKSNAP_DIFF_BUFFER_H + +#include +#include +#include +#include + +struct diff_area; + +/** + * struct diff_buffer - Difference buffer. + * @link: + * The list header allows to create a pool of the diff_buffer structures. + * @size: + * Count of bytes in the buffer. + * @page_count: + * The number of pages reserved for the buffer. + * @pages: + * An array of pointers to pages. + * + * Describes the memory buffer for a chunk in the memory. + */ +struct diff_buffer { + struct list_head link; + size_t size; + size_t page_count; + struct page *pages[0]; +}; + +struct diff_buffer *diff_buffer_take(struct diff_area *diff_area); +void diff_buffer_release(struct diff_area *diff_area, + struct diff_buffer *diff_buffer); +void diff_buffer_cleanup(struct diff_area *diff_area); +#endif /* __BLKSNAP_DIFF_BUFFER_H */ diff --git a/drivers/block/blksnap/diff_storage.c b/drivers/block/blksnap/diff_storage.c new file mode 100644 index 000000000000..47690bea2e6e --- /dev/null +++ b/drivers/block/blksnap/diff_storage.c @@ -0,0 +1,315 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 2023 Veeam Software Group GmbH */ +#define pr_fmt(fmt) KBUILD_MODNAME "-diff-storage: " fmt + +#include +#include +#include +#include +#include +#include +#include "chunk.h" +#include "diff_buffer.h" +#include "diff_storage.h" +#include "params.h" + +/** + * struct storage_bdev - Information about the opened block device. + * + * @link: + * Allows to combine structures into a linked list. + * @bdev: + * A pointer to an open block device. + */ +struct storage_bdev { + struct list_head link; + struct block_device *bdev; +}; + +/** + * struct storage_block - A storage unit reserved for storing differences. + * + * @link: + * Allows to combine structures into a linked list. + * @bdev: + * A pointer to a block device. + * @sector: + * The number of the first sector of the range of allocated space for + * storing the difference. + * @count: + * The count of sectors in the range of allocated space for storing the + * difference. + * @used: + * The count of used sectors in the range of allocated space for storing + * the difference. + */ +struct storage_block { + struct list_head link; + struct block_device *bdev; + sector_t sector; + sector_t count; + sector_t used; +}; + +static inline void diff_storage_event_low(struct diff_storage *diff_storage) +{ + struct blksnap_event_low_free_space data = { + .requested_nr_sect = get_diff_storage_minimum(), + }; + + diff_storage->requested += data.requested_nr_sect; + pr_debug("Diff storage low free space. Portion: %llu sectors, requested: %llu\n", + data.requested_nr_sect, diff_storage->requested); + event_gen(&diff_storage->event_queue, GFP_NOIO, + blksnap_event_code_low_free_space, &data, sizeof(data)); +} + +struct diff_storage *diff_storage_new(void) +{ + struct diff_storage *diff_storage; + + diff_storage = kzalloc(sizeof(struct diff_storage), GFP_KERNEL); + if (!diff_storage) + return NULL; + + kref_init(&diff_storage->kref); + spin_lock_init(&diff_storage->lock); + INIT_LIST_HEAD(&diff_storage->storage_bdevs); + INIT_LIST_HEAD(&diff_storage->empty_blocks); + INIT_LIST_HEAD(&diff_storage->filled_blocks); + + event_queue_init(&diff_storage->event_queue); + diff_storage_event_low(diff_storage); + + return diff_storage; +} + +static inline struct storage_block * +first_empty_storage_block(struct diff_storage *diff_storage) +{ + return list_first_entry_or_null(&diff_storage->empty_blocks, + struct storage_block, link); +}; + +static inline struct storage_block * +first_filled_storage_block(struct diff_storage *diff_storage) +{ + return list_first_entry_or_null(&diff_storage->filled_blocks, + struct storage_block, link); +}; + +static inline struct storage_bdev * +first_storage_bdev(struct diff_storage *diff_storage) +{ + return list_first_entry_or_null(&diff_storage->storage_bdevs, + struct storage_bdev, link); +}; + +void diff_storage_free(struct kref *kref) +{ + struct diff_storage *diff_storage = + container_of(kref, struct diff_storage, kref); + struct storage_block *blk; + struct storage_bdev *storage_bdev; + + while ((blk = first_empty_storage_block(diff_storage))) { + list_del(&blk->link); + kfree(blk); + } + + while ((blk = first_filled_storage_block(diff_storage))) { + list_del(&blk->link); + kfree(blk); + } + + while ((storage_bdev = first_storage_bdev(diff_storage))) { + blkdev_put(storage_bdev->bdev, FMODE_READ | FMODE_WRITE); + list_del(&storage_bdev->link); + kfree(storage_bdev); + } + event_queue_done(&diff_storage->event_queue); + + kfree(diff_storage); +} + +static struct block_device *diff_storage_add_storage_bdev( + struct diff_storage *diff_storage, const char *bdev_path) +{ + struct storage_bdev *storage_bdev, *existing_bdev = NULL; + struct block_device *bdev; + + bdev = blkdev_get_by_path(bdev_path, FMODE_READ | FMODE_WRITE, NULL); + if (IS_ERR(bdev)) { + pr_err("Failed to open device. errno=%ld\n", PTR_ERR(bdev)); + return bdev; + } + + spin_lock(&diff_storage->lock); + list_for_each_entry(existing_bdev, &diff_storage->storage_bdevs, link) { + if (existing_bdev->bdev == bdev) + break; + } + spin_unlock(&diff_storage->lock); + + if (existing_bdev->bdev == bdev) { + blkdev_put(bdev, FMODE_READ | FMODE_WRITE); + return existing_bdev->bdev; + } + + storage_bdev = kzalloc(sizeof(struct storage_bdev) + + strlen(bdev_path) + 1, GFP_KERNEL); + if (!storage_bdev) { + blkdev_put(bdev, FMODE_READ | FMODE_WRITE); + return ERR_PTR(-ENOMEM); + } + + INIT_LIST_HEAD(&storage_bdev->link); + storage_bdev->bdev = bdev; + + spin_lock(&diff_storage->lock); + list_add_tail(&storage_bdev->link, &diff_storage->storage_bdevs); + spin_unlock(&diff_storage->lock); + + return bdev; +} + +static inline int diff_storage_add_range(struct diff_storage *diff_storage, + struct block_device *bdev, + sector_t sector, sector_t count) +{ + struct storage_block *storage_block; + + pr_debug("Add range to diff storage: [%u:%u] %llu:%llu\n", + MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev), sector, count); + + storage_block = kzalloc(sizeof(struct storage_block), GFP_KERNEL); + if (!storage_block) + return -ENOMEM; + + INIT_LIST_HEAD(&storage_block->link); + storage_block->bdev = bdev; + storage_block->sector = sector; + storage_block->count = count; + + spin_lock(&diff_storage->lock); + list_add_tail(&storage_block->link, &diff_storage->empty_blocks); + diff_storage->capacity += count; + spin_unlock(&diff_storage->lock); + + return 0; +} + +int diff_storage_append_block(struct diff_storage *diff_storage, + const char *bdev_path, + struct blksnap_sectors __user *ranges, + unsigned int range_count) +{ + int ret; + int inx; + struct block_device *bdev; + struct blksnap_sectors range; + + pr_debug("Append %u blocks\n", range_count); + + bdev = diff_storage_add_storage_bdev(diff_storage, bdev_path); + if (IS_ERR(bdev)) + return PTR_ERR(bdev); + + for (inx = 0; inx < range_count; inx++) { + if (unlikely(copy_from_user(&range, ranges+inx, sizeof(range)))) + return -EINVAL; + + ret = diff_storage_add_range(diff_storage, bdev, + range.offset, + range.count); + if (unlikely(ret)) + return ret; + } + + if (atomic_read(&diff_storage->low_space_flag) && + (diff_storage->capacity >= diff_storage->requested)) + atomic_set(&diff_storage->low_space_flag, 0); + + return 0; +} + +static inline bool is_halffull(const sector_t sectors_left) +{ + return sectors_left <= + ((get_diff_storage_minimum() >> 1) & ~(PAGE_SECTORS - 1)); +} + +struct diff_region *diff_storage_new_region(struct diff_storage *diff_storage, + sector_t count, + unsigned int logical_blksz) +{ + int ret = 0; + struct diff_region *diff_region; + sector_t sectors_left; + + if (atomic_read(&diff_storage->overflow_flag)) + return ERR_PTR(-ENOSPC); + + diff_region = kzalloc(sizeof(struct diff_region), GFP_NOIO); + if (!diff_region) + return ERR_PTR(-ENOMEM); + + spin_lock(&diff_storage->lock); + do { + struct storage_block *storage_block; + sector_t available; + struct request_queue *q; + + storage_block = first_empty_storage_block(diff_storage); + if (unlikely(!storage_block)) { + atomic_inc(&diff_storage->overflow_flag); + ret = -ENOSPC; + break; + } + + q = storage_block->bdev->bd_queue; + if (logical_blksz < q->limits.logical_block_size) { + pr_err("Incompatibility of block sizes was detected."); + ret = -ENOTBLK; + break; + } + + available = storage_block->count - storage_block->used; + if (likely(available >= count)) { + diff_region->bdev = storage_block->bdev; + diff_region->sector = + storage_block->sector + storage_block->used; + diff_region->count = count; + + storage_block->used += count; + diff_storage->filled += count; + break; + } + + list_del(&storage_block->link); + list_add_tail(&storage_block->link, + &diff_storage->filled_blocks); + /* + * If there is still free space in the storage block, but + * it is not enough to store a piece, then such a block is + * considered used. + * We believe that the storage blocks are large enough + * to accommodate several pieces entirely. + */ + diff_storage->filled += available; + } while (1); + sectors_left = diff_storage->requested - diff_storage->filled; + spin_unlock(&diff_storage->lock); + + if (ret) { + pr_err("Cannot get empty storage block\n"); + diff_storage_free_region(diff_region); + return ERR_PTR(ret); + } + + if (is_halffull(sectors_left) && + (atomic_inc_return(&diff_storage->low_space_flag) == 1)) + diff_storage_event_low(diff_storage); + + return diff_region; +} diff --git a/drivers/block/blksnap/diff_storage.h b/drivers/block/blksnap/diff_storage.h new file mode 100644 index 000000000000..0913a0114ac0 --- /dev/null +++ b/drivers/block/blksnap/diff_storage.h @@ -0,0 +1,111 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (C) 2023 Veeam Software Group GmbH */ +#ifndef __BLKSNAP_DIFF_STORAGE_H +#define __BLKSNAP_DIFF_STORAGE_H + +#include "event_queue.h" + +struct blksnap_sectors; + +/** + * struct diff_region - Describes the location of the chunks data on + * difference storage. + * @bdev: + * The target block device. + * @sector: + * The sector offset of the region's first sector. + * @count: + * The count of sectors in the region. + */ +struct diff_region { + struct block_device *bdev; + sector_t sector; + sector_t count; +}; + +/** + * struct diff_storage - Difference storage. + * + * @kref: + * The reference counter. + * @lock: + * Spinlock allows to guarantee the safety of linked lists. + * @storage_bdevs: + * List of opened block devices. Blocks for storing snapshot data can be + * located on different block devices. So, all opened block devices are + * located in this list. Blocks on opened block devices are allocated for + * storing the chunks data. + * @empty_blocks: + * List of empty blocks on storage. This list can be updated while + * holding a snapshot. This allows us to dynamically increase the + * storage size for these snapshots. + * @filled_blocks: + * List of filled blocks. When the blocks from the list of empty blocks are filled, + * we move them to the list of filled blocks. + * @capacity: + * Total amount of available storage space. + * @filled: + * The number of sectors already filled in. + * @requested: + * The number of sectors already requested from user space. + * @low_space_flag: + * The flag is set if the number of free regions available in the + * difference storage is less than the allowed minimum. + * @overflow_flag: + * The request for a free region failed due to the absence of free + * regions in the difference storage. + * @event_queue: + * A queue of events to pass events to user space. Diff storage and its + * owner can notify its snapshot about events like snapshot overflow, + * low free space and snapshot terminated. + * + * The difference storage manages the regions of block devices that are used + * to store the data of the original block devices in the snapshot. + * The difference storage is created one per snapshot and is used to store + * data from all the original snapshot block devices. At the same time, the + * difference storage itself can contain regions on various block devices. + */ +struct diff_storage { + struct kref kref; + spinlock_t lock; + + struct list_head storage_bdevs; + struct list_head empty_blocks; + struct list_head filled_blocks; + + sector_t capacity; + sector_t filled; + sector_t requested; + + atomic_t low_space_flag; + atomic_t overflow_flag; + + struct event_queue event_queue; +}; + +struct diff_storage *diff_storage_new(void); +void diff_storage_free(struct kref *kref); + +static inline void diff_storage_get(struct diff_storage *diff_storage) +{ + kref_get(&diff_storage->kref); +}; +static inline void diff_storage_put(struct diff_storage *diff_storage) +{ + if (likely(diff_storage)) + kref_put(&diff_storage->kref, diff_storage_free); +}; + +int diff_storage_append_block(struct diff_storage *diff_storage, + const char *bdev_path, + struct blksnap_sectors __user *ranges, + unsigned int range_count); +struct diff_region *diff_storage_new_region(struct diff_storage *diff_storage, + sector_t count, + unsigned int logical_blksz); + +static inline void diff_storage_free_region(struct diff_region *region) +{ + kfree(region); +} +#endif /* __BLKSNAP_DIFF_STORAGE_H */