From patchwork Wed Nov 18 19:18:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 11915665 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17727C83013 for ; Wed, 18 Nov 2020 19:19:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF4342220B for ; Wed, 18 Nov 2020 19:19:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20150623.gappssmtp.com header.i=@osandov-com.20150623.gappssmtp.com header.b="VGpv8eX7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727217AbgKRTS5 (ORCPT ); Wed, 18 Nov 2020 14:18:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55732 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727196AbgKRTS4 (ORCPT ); Wed, 18 Nov 2020 14:18:56 -0500 Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77304C0613D6 for ; Wed, 18 Nov 2020 11:18:56 -0800 (PST) Received: by mail-pg1-x542.google.com with SMTP id 62so1847494pgg.12 for ; Wed, 18 Nov 2020 11:18:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Cuq7YiBJBm1kUqmAArsOeQ+Ws5ns12VRJuznPdU2Ils=; b=VGpv8eX7C7GAGHSNR6gwBsW2F4SOxwPi9mwtYPkkDzRhfxetG/dmpU9kQVkE0DHAIE 1OPWAwuydwjM80L+IVFpDK+/hq+ahYpDLsM1gqikMpB+zVDRE47zA77d8LQsdxV1dI7N MICT91KGbpCbi9QX5CvjK1akJMkv80Juanx3T3JjQAJ37HfRNfaHffK9583aiX1Wf1aW Tsfuv2qn5c9IBK8sOxVM+SsmLYdv+o/9EBV452msmuqTOrZ/MSPJvxdUIxYUKktlDpBU 2DEJkMWuj8OqU5uHuXGuTuOr6YL3IG7gwxlDxkRqVxP7ciXNP2hEsZrBl6f7MsirUnjg Om/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Cuq7YiBJBm1kUqmAArsOeQ+Ws5ns12VRJuznPdU2Ils=; b=IaNd1VzQdoaWcxWnBcVpwI9ZGTIIOwOr/Hst6DnrjygfLJXtnDF37QDws1xd+e/YWF J5AN1CfAOfLrArlHYd6fJRfrArtc3yTDf8gZW8wJNqco2BCllYhg3Zy494q2jIPTNezG SuOC4FP+HTnBWVPuaAUQ82FTZQ4yw96CIzxH+M8BVgjNYP53Ya/wcuJ18aQ/2030Z3M0 YQvZAbmdKkooMJYjp37N5FCoh4SUb07D1EpQXWz4S9HeZ8pfiITVGUju324Kdylz4jSB NtjJGRyNabrxtoQFD1ALbFbQ4PDoEX01tSu5Y8Ec6uJWlX+IKdNLH09Hsar9iXCaEepR /gng== X-Gm-Message-State: AOAM533JntMutqfmrxEt5GDzHEmWLmNlkID0B0UdjNA+pM8dUSRIitP2 p1/lqSTA/2EmViwMevDtLbJUQA== X-Google-Smtp-Source: ABdhPJxwPH7G9AVO9VOB579w8Uo8tckiThM7w3L9yvTChcNFTiS2Tlw0QFtYsLDIkf+6pJO5YG5lZw== X-Received: by 2002:a17:90a:aa87:: with SMTP id l7mr451883pjq.167.1605727135831; Wed, 18 Nov 2020 11:18:55 -0800 (PST) Received: from relinquished.tfbnw.net ([2620:10d:c090:400::5:8b43]) by smtp.gmail.com with ESMTPSA id c22sm19491863pfo.211.2020.11.18.11.18.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Nov 2020 11:18:54 -0800 (PST) From: Omar Sandoval To: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Al Viro , Christoph Hellwig Cc: Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v6 10/11] btrfs: implement RWF_ENCODED reads Date: Wed, 18 Nov 2020 11:18:17 -0800 Message-Id: X-Mailer: git-send-email 2.29.2 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Omar Sandoval There are 4 main cases: 1. Inline extents: we copy the data straight out of the extent buffer. 2. Hole/preallocated extents: we fill in zeroes. 3. Regular, uncompressed extents: we read the sectors we need directly from disk. 4. Regular, compressed extents: we read the entire compressed extent from disk and indicate what subset of the decompressed extent is in the file. This initial implementation simplifies a few things that can be improved in the future: - We hold the inode lock during the operation. - Cases 1, 3, and 4 allocate temporary memory to read into before copying out to userspace. - We don't do read repair, because it turns out that read repair is currently broken for compressed data. Signed-off-by: Omar Sandoval Reviewed-by: Josef Bacik --- fs/btrfs/ctree.h | 2 + fs/btrfs/file.c | 5 + fs/btrfs/inode.c | 496 +++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 503 insertions(+) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 6ab2ab002bf6..ce78424f1d98 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -3133,6 +3133,8 @@ int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct page *locked_page int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end); void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start, u64 end, int uptodate); +ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter); + extern const struct dentry_operations btrfs_dentry_operations; extern const struct iomap_ops btrfs_dio_iomap_ops; extern const struct iomap_dio_ops btrfs_dio_ops; diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 224295f8f1e1..193477565200 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -3629,6 +3629,11 @@ static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to) { ssize_t ret = 0; + if (iocb->ki_flags & IOCB_ENCODED) { + if (iocb->ki_flags & IOCB_NOWAIT) + return -EOPNOTSUPP; + return btrfs_encoded_read(iocb, to); + } if (iocb->ki_flags & IOCB_DIRECT) { ret = btrfs_direct_read(iocb, to); if (ret < 0 || !iov_iter_count(to) || diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 1ff903f5c5a4..b0e800897b3b 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -9936,6 +9936,502 @@ void btrfs_set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end) } } +static int encoded_iov_compression_from_btrfs(unsigned int compress_type) +{ + switch (compress_type) { + case BTRFS_COMPRESS_NONE: + return ENCODED_IOV_COMPRESSION_NONE; + case BTRFS_COMPRESS_ZLIB: + return ENCODED_IOV_COMPRESSION_BTRFS_ZLIB; + case BTRFS_COMPRESS_LZO: + /* + * The LZO format depends on the page size. 64k is the maximum + * sectorsize (and thus page size) that we support. + */ + if (PAGE_SIZE < SZ_4K || PAGE_SIZE > SZ_64K) + return -EINVAL; + return ENCODED_IOV_COMPRESSION_BTRFS_LZO_4K + (PAGE_SHIFT - 12); + case BTRFS_COMPRESS_ZSTD: + return ENCODED_IOV_COMPRESSION_BTRFS_ZSTD; + default: + return -EUCLEAN; + } +} + +static ssize_t btrfs_encoded_read_inline(struct kiocb *iocb, + struct iov_iter *iter, u64 start, + u64 lockend, + struct extent_state **cached_state, + u64 extent_start, size_t count, + struct encoded_iov *encoded, + bool *unlocked) +{ + struct inode *inode = file_inode(iocb->ki_filp); + struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; + struct btrfs_path *path; + struct extent_buffer *leaf; + struct btrfs_file_extent_item *item; + u64 ram_bytes; + unsigned long ptr; + void *tmp; + ssize_t ret; + + path = btrfs_alloc_path(); + if (!path) { + ret = -ENOMEM; + goto out; + } + ret = btrfs_lookup_file_extent(NULL, BTRFS_I(inode)->root, path, + btrfs_ino(BTRFS_I(inode)), extent_start, + 0); + if (ret) { + if (ret > 0) { + /* The extent item disappeared? */ + ret = -EIO; + } + goto out; + } + leaf = path->nodes[0]; + item = btrfs_item_ptr(leaf, path->slots[0], + struct btrfs_file_extent_item); + + ram_bytes = btrfs_file_extent_ram_bytes(leaf, item); + ptr = btrfs_file_extent_inline_start(item); + + encoded->len = (min_t(u64, extent_start + ram_bytes, inode->i_size) - + iocb->ki_pos); + ret = encoded_iov_compression_from_btrfs( + btrfs_file_extent_compression(leaf, item)); + if (ret < 0) + goto out; + encoded->compression = ret; + if (encoded->compression) { + size_t inline_size; + + inline_size = btrfs_file_extent_inline_item_len(leaf, + btrfs_item_nr(path->slots[0])); + if (inline_size > count) { + ret = -ENOBUFS; + goto out; + } + count = inline_size; + encoded->unencoded_len = ram_bytes; + encoded->unencoded_offset = iocb->ki_pos - extent_start; + } else { + encoded->len = encoded->unencoded_len = count = + min_t(u64, count, encoded->len); + ptr += iocb->ki_pos - extent_start; + } + + tmp = kmalloc(count, GFP_NOFS); + if (!tmp) { + ret = -ENOMEM; + goto out; + } + read_extent_buffer(leaf, tmp, ptr, count); + btrfs_release_path(path); + unlock_extent_cached(io_tree, start, lockend, cached_state); + inode_unlock_shared(inode); + *unlocked = true; + + ret = copy_encoded_iov_to_iter(encoded, iter); + if (ret) + goto out_free; + ret = copy_to_iter(tmp, count, iter); + if (ret != count) + ret = -EFAULT; +out_free: + kfree(tmp); +out: + btrfs_free_path(path); + return ret; +} + +struct btrfs_encoded_read_private { + struct inode *inode; + wait_queue_head_t wait; + atomic_t pending; + blk_status_t status; + bool skip_csum; +}; + +static blk_status_t submit_encoded_read_bio(struct inode *inode, + struct bio *bio, int mirror_num, + unsigned long bio_flags) +{ + struct btrfs_encoded_read_private *priv = bio->bi_private; + struct btrfs_io_bio *io_bio = btrfs_io_bio(bio); + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + blk_status_t ret; + + if (!priv->skip_csum) { + ret = btrfs_lookup_bio_sums(inode, bio, io_bio->logical, NULL); + if (ret) + return ret; + } + + ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA); + if (ret) { + btrfs_io_bio_free_csum(io_bio); + return ret; + } + + atomic_inc(&priv->pending); + ret = btrfs_map_bio(fs_info, bio, mirror_num); + if (ret) { + atomic_dec(&priv->pending); + btrfs_io_bio_free_csum(io_bio); + } + return ret; +} + +static blk_status_t btrfs_encoded_read_check_bio(struct btrfs_io_bio *io_bio) +{ + const bool uptodate = io_bio->bio.bi_status == BLK_STS_OK; + struct btrfs_encoded_read_private *priv = io_bio->bio.bi_private; + struct inode *inode = priv->inode; + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + u32 sectorsize = fs_info->sectorsize; + struct bio_vec *bvec; + struct bvec_iter_all iter_all; + u64 start = io_bio->logical; + int icsum = 0; + + if (priv->skip_csum || !uptodate) + return io_bio->bio.bi_status; + + bio_for_each_segment_all(bvec, &io_bio->bio, iter_all) { + unsigned int i, nr_sectors, pgoff; + + nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec->bv_len); + pgoff = bvec->bv_offset; + for (i = 0; i < nr_sectors; i++) { + ASSERT(pgoff < PAGE_SIZE); + if (check_data_csum(inode, io_bio, icsum, bvec->bv_page, + pgoff, start)) + return BLK_STS_IOERR; + start += sectorsize; + icsum++; + pgoff += sectorsize; + } + } + return BLK_STS_OK; +} + +static void btrfs_encoded_read_endio(struct bio *bio) +{ + struct btrfs_encoded_read_private *priv = bio->bi_private; + struct btrfs_io_bio *io_bio = btrfs_io_bio(bio); + blk_status_t status; + + status = btrfs_encoded_read_check_bio(io_bio); + if (status) { + /* + * The memory barrier implied by the atomic_dec_return() here + * pairs with the memory barrier implied by the + * atomic_dec_return() or io_wait_event() in + * btrfs_encoded_read_regular_fill_pages() to ensure that this + * write is observed before the load of status in + * btrfs_encoded_read_regular_fill_pages(). + */ + WRITE_ONCE(priv->status, status); + } + if (!atomic_dec_return(&priv->pending)) + wake_up(&priv->wait); + btrfs_io_bio_free_csum(io_bio); + bio_put(bio); +} + +static int btrfs_encoded_read_regular_fill_pages(struct inode *inode, u64 offset, + u64 disk_io_size, struct page **pages) +{ + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + struct btrfs_encoded_read_private priv = { + .inode = inode, + .pending = ATOMIC_INIT(1), + .skip_csum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM, + }; + unsigned long i = 0; + u64 cur = 0; + int ret; + + init_waitqueue_head(&priv.wait); + /* + * Submit bios for the extent, splitting due to bio or stripe limits as + * necessary. + */ + while (cur < disk_io_size) { + struct btrfs_io_geometry geom; + struct bio *bio = NULL; + u64 remaining; + + ret = btrfs_get_io_geometry(fs_info, BTRFS_MAP_READ, + offset + cur, disk_io_size - cur, + &geom); + if (ret) { + WRITE_ONCE(priv.status, errno_to_blk_status(ret)); + break; + } + remaining = min(geom.len, disk_io_size - cur); + while (bio || remaining) { + size_t bytes = min_t(u64, remaining, PAGE_SIZE); + + if (!bio) { + bio = btrfs_bio_alloc(offset + cur); + bio->bi_end_io = btrfs_encoded_read_endio; + bio->bi_private = &priv; + bio->bi_opf = REQ_OP_READ; + } + + if (!bytes || + bio_add_page(bio, pages[i], bytes, 0) < bytes) { + blk_status_t status; + + status = submit_encoded_read_bio(inode, bio, 0, + 0); + if (status) { + WRITE_ONCE(priv.status, status); + bio_put(bio); + goto out; + } + bio = NULL; + continue; + } + + i++; + cur += bytes; + remaining -= bytes; + } + } + +out: + if (atomic_dec_return(&priv.pending)) + io_wait_event(priv.wait, !atomic_read(&priv.pending)); + /* See btrfs_encoded_read_endio() for ordering. */ + return blk_status_to_errno(READ_ONCE(priv.status)); +} + +static ssize_t btrfs_encoded_read_regular(struct kiocb *iocb, + struct iov_iter *iter, + u64 start, u64 lockend, + struct extent_state **cached_state, + u64 offset, u64 disk_io_size, + size_t count, + const struct encoded_iov *encoded, + bool *unlocked) +{ + struct inode *inode = file_inode(iocb->ki_filp); + struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; + struct page **pages; + unsigned long nr_pages, i; + u64 cur; + size_t page_offset; + ssize_t ret; + + nr_pages = DIV_ROUND_UP(disk_io_size, PAGE_SIZE); + pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS); + if (!pages) + return -ENOMEM; + for (i = 0; i < nr_pages; i++) { + pages[i] = alloc_page(GFP_NOFS | __GFP_HIGHMEM); + if (!pages[i]) { + ret = -ENOMEM; + goto out; + } + } + + ret = btrfs_encoded_read_regular_fill_pages(inode, offset, disk_io_size, + pages); + if (ret) + goto out; + + unlock_extent_cached(io_tree, start, lockend, cached_state); + inode_unlock_shared(inode); + *unlocked = true; + + ret = copy_encoded_iov_to_iter(encoded, iter); + if (ret) + goto out; + if (encoded->compression) { + i = 0; + page_offset = 0; + } else { + i = (iocb->ki_pos - start) >> PAGE_SHIFT; + page_offset = (iocb->ki_pos - start) & (PAGE_SIZE - 1); + } + cur = 0; + while (cur < count) { + size_t bytes = min_t(size_t, count - cur, + PAGE_SIZE - page_offset); + + if (copy_page_to_iter(pages[i], page_offset, bytes, + iter) != bytes) { + ret = -EFAULT; + goto out; + } + i++; + cur += bytes; + page_offset = 0; + } + ret = count; +out: + for (i = 0; i < nr_pages; i++) { + if (pages[i]) + __free_page(pages[i]); + } + kfree(pages); + return ret; +} + +ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter) +{ + struct inode *inode = file_inode(iocb->ki_filp); + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; + ssize_t ret; + size_t count; + u64 start, lockend, offset, disk_io_size; + struct extent_state *cached_state = NULL; + struct extent_map *em; + struct encoded_iov encoded = {}; + bool unlocked = false; + + ret = generic_encoded_read_checks(iocb, iter); + if (ret < 0) + return ret; + if (ret == 0) + return copy_encoded_iov_to_iter(&encoded, iter); + count = ret; + + file_accessed(iocb->ki_filp); + + inode_lock_shared(inode); + + if (iocb->ki_pos >= inode->i_size) { + inode_unlock_shared(inode); + return copy_encoded_iov_to_iter(&encoded, iter); + } + start = ALIGN_DOWN(iocb->ki_pos, fs_info->sectorsize); + /* + * We don't know how long the extent containing iocb->ki_pos is, but if + * it's compressed we know that it won't be longer than this. + */ + lockend = start + BTRFS_MAX_UNCOMPRESSED - 1; + + for (;;) { + struct btrfs_ordered_extent *ordered; + + ret = btrfs_wait_ordered_range(inode, start, + lockend - start + 1); + if (ret) + goto out_unlock_inode; + lock_extent_bits(io_tree, start, lockend, &cached_state); + ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), start, + lockend - start + 1); + if (!ordered) + break; + btrfs_put_ordered_extent(ordered); + unlock_extent_cached(io_tree, start, lockend, &cached_state); + cond_resched(); + } + + em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, + lockend - start + 1); + if (IS_ERR(em)) { + ret = PTR_ERR(em); + goto out_unlock_extent; + } + + if (em->block_start == EXTENT_MAP_INLINE) { + u64 extent_start = em->start; + + /* + * For inline extents we get everything we need out of the + * extent item. + */ + free_extent_map(em); + em = NULL; + ret = btrfs_encoded_read_inline(iocb, iter, start, lockend, + &cached_state, extent_start, + count, &encoded, &unlocked); + goto out; + } + + /* + * We only want to return up to EOF even if the extent extends beyond + * that. + */ + encoded.len = (min_t(u64, extent_map_end(em), inode->i_size) - + iocb->ki_pos); + if (em->block_start == EXTENT_MAP_HOLE || + test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) { + offset = EXTENT_MAP_HOLE; + encoded.len = encoded.unencoded_len = count = + min_t(u64, count, encoded.len); + } else if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) { + offset = em->block_start; + /* + * Bail if the buffer isn't large enough to return the whole + * compressed extent. + */ + if (em->block_len > count) { + ret = -ENOBUFS; + goto out_em; + } + disk_io_size = count = em->block_len; + encoded.unencoded_len = em->ram_bytes; + encoded.unencoded_offset = iocb->ki_pos - em->orig_start; + ret = encoded_iov_compression_from_btrfs(em->compress_type); + if (ret < 0) + goto out_em; + encoded.compression = ret; + } else { + offset = em->block_start + (start - em->start); + if (encoded.len > count) + encoded.len = count; + /* + * Don't read beyond what we locked. This also limits the page + * allocations that we'll do. + */ + disk_io_size = min(lockend + 1, iocb->ki_pos + encoded.len) - start; + encoded.len = encoded.unencoded_len = count = + start + disk_io_size - iocb->ki_pos; + disk_io_size = ALIGN(disk_io_size, fs_info->sectorsize); + } + free_extent_map(em); + em = NULL; + + if (offset == EXTENT_MAP_HOLE) { + unlock_extent_cached(io_tree, start, lockend, &cached_state); + inode_unlock_shared(inode); + unlocked = true; + ret = copy_encoded_iov_to_iter(&encoded, iter); + if (ret) + goto out; + ret = iov_iter_zero(count, iter); + if (ret != count) + ret = -EFAULT; + } else { + ret = btrfs_encoded_read_regular(iocb, iter, start, lockend, + &cached_state, offset, + disk_io_size, count, &encoded, + &unlocked); + } + +out: + if (ret >= 0) + iocb->ki_pos += encoded.len; +out_em: + free_extent_map(em); +out_unlock_extent: + if (!unlocked) + unlock_extent_cached(io_tree, start, lockend, &cached_state); +out_unlock_inode: + if (!unlocked) + inode_unlock_shared(inode); + return ret; +} + #ifdef CONFIG_SWAP /* * Add an entry indicating a block group or device which is pinned by a