From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.burntcomma.com (mail2.burntcomma.com [217.169.27.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C54E82E173E for ; Fri, 14 Nov 2025 18:48:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.169.27.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763146092; cv=none; b=cOL7yOrdvN/DsoaSUzQGdRoimcwIFJL6eZFar+WTZ/P5yo7B4l3nOjtesujG9MM5CzuzkxswAhiQHh0u5cAuLAv1Nl0B6jLK0s9WbcEmqEEdgiSKr3Du099/AYAeiCd2la3Ndf8Dh25mzHt0VvhB5AhNCT6mA/rVujMSB+V2wTY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763146092; c=relaxed/simple; bh=Sum2HiPvegbtx0cOQ1861Sg+rBK08jkslCk1aPZowPo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: Mime-Version; b=HuYVUIllka6SDJkJ4Z1MN3bc0s+rQiTEbdJtk2jESMP+DQEPSNsGy3zS2GK0l7UG4901e2rsKHvDgjq2wSWtpnn+HAcCTcY7CTEUqVPXpRKgC+EBm8BzX7KfkFLF6KWLSNvQKp5NcGA12Igm+ByswLLO3CzwgGtEPVi86EGMJGk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=harmstone.com; spf=pass smtp.mailfrom=harmstone.com; dkim=pass (1024-bit key) header.d=harmstone.com header.i=@harmstone.com header.b=HNl17v3Q; arc=none smtp.client-ip=217.169.27.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=harmstone.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=harmstone.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=harmstone.com header.i=@harmstone.com header.b="HNl17v3Q" Received: from beren (beren.burntcomma.com [IPv6:2a02:8012:8cf0:0:ce28:aaff:fe0d:6db2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by mail.burntcomma.com (Postfix) with ESMTPSA id 7C09A2DAB09; Fri, 14 Nov 2025 18:47:52 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=harmstone.com; s=mail; t=1763146072; bh=eAssuVGo83VUxRC0GXXkQAEmXI/5ALncPYIA8PGvC/Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=HNl17v3Q+/AydqmR+ReJlU3LaLPF8Y47riW2IZVj8GWlJfGWWdWuCNZxJtfuXq9yW 3ms5kVgAP7+VBzp/eGr3/fKFjcmXAtinPv96xRFT9BwTx4bOtzhGVlhDUroRuS6vIQ PBxI8tSrU3IzoRLrWc7R0H7Thp4XhZZFI+ABWZGo= From: Mark Harmstone To: linux-btrfs@vger.kernel.org Cc: Mark Harmstone , Boris Burkov Subject: [PATCH v6 11/16] btrfs: move existing remaps before relocating block group Date: Fri, 14 Nov 2025 18:47:16 +0000 Message-ID: <20251114184745.9304-12-mark@harmstone.com> In-Reply-To: <20251114184745.9304-1-mark@harmstone.com> References: <20251114184745.9304-1-mark@harmstone.com> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: 8bit If when relocating a block group we find that `remap_bytes` > 0 in its block group item, that means that it has been the destination block group for another that has been remapped. We need to seach the remap tree for any remap backrefs within this range, and move the data to a third block group. This is because otherwise btrfs_translate_remap() could end up following an unbounded chain of remaps, which would only get worse over time. We only relocate one block group at a time, so `remap_bytes` will only ever go down while we are doing this. Once we're finished we set the REMAPPED flag on the block group, which will permanently prevent any other data from being moved to within it. Signed-off-by: Mark Harmstone Reviewed-by: Boris Burkov --- fs/btrfs/bio.c | 3 +- fs/btrfs/bio.h | 3 + fs/btrfs/extent-tree.c | 6 +- fs/btrfs/relocation.c | 487 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 496 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c index 1b38e3ee0a33..1301c8c48ae2 100644 --- a/fs/btrfs/bio.c +++ b/fs/btrfs/bio.c @@ -817,7 +817,8 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num) */ if (!(inode->flags & BTRFS_INODE_NODATASUM) && !test_bit(BTRFS_FS_STATE_NO_DATA_CSUMS, &fs_info->fs_state) && - !btrfs_is_data_reloc_root(inode->root)) { + !btrfs_is_data_reloc_root(inode->root) && + !bbio->is_remap) { if (should_async_write(bbio) && btrfs_wq_submit_bio(bbio, bioc, &smap, mirror_num)) goto done; diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h index 035145909b00..0bfd7981fe1f 100644 --- a/fs/btrfs/bio.h +++ b/fs/btrfs/bio.h @@ -87,6 +87,9 @@ struct btrfs_bio { */ bool is_scrub; + /* Whether the bio is coming from copy_remapped_data_io(). */ + bool is_remap; + /* Whether the csum generation for data write is async. */ bool async_csum; diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index b8fed3246e1f..ab20f7fed4cf 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -4543,7 +4543,8 @@ static noinline int find_free_extent(struct btrfs_root *root, block_group->cached != BTRFS_CACHE_NO) { down_read(&space_info->groups_sem); if (list_empty(&block_group->list) || - block_group->ro) { + block_group->ro || + block_group->flags & BTRFS_BLOCK_GROUP_REMAPPED) { /* * someone is removing this block group, * we can't jump into the have_block_group @@ -4577,7 +4578,8 @@ static noinline int find_free_extent(struct btrfs_root *root, ffe_ctl->hinted = false; /* If the block group is read-only, we can skip it entirely. */ - if (unlikely(block_group->ro)) { + if (unlikely(block_group->ro) || + block_group->flags & BTRFS_BLOCK_GROUP_REMAPPED) { if (ffe_ctl->for_treelog) btrfs_clear_treelog_bg(block_group); if (ffe_ctl->for_data_reloc) diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 1f86c81678bb..a95899af811d 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -3977,6 +3977,487 @@ static void adjust_block_group_remap_bytes(struct btrfs_trans_handle *trans, btrfs_inc_delayed_refs_rsv_bg_updates(fs_info); } +struct reloc_io_private { + struct completion done; + refcount_t pending_refs; + blk_status_t status; +}; + +static void reloc_endio(struct btrfs_bio *bbio) +{ + struct reloc_io_private *priv = bbio->private; + + if (bbio->bio.bi_status) + WRITE_ONCE(priv->status, bbio->bio.bi_status); + + if (refcount_dec_and_test(&priv->pending_refs)) + complete(&priv->done); + + bio_put(&bbio->bio); +} + +static int copy_remapped_data_io(struct btrfs_fs_info *fs_info, + struct reloc_io_private *priv, + struct page **pages, u64 addr, u64 length, + bool do_write) +{ + struct btrfs_bio *bbio; + unsigned long i = 0; + blk_opf_t op = do_write ? REQ_OP_WRITE : REQ_OP_READ; + + init_completion(&priv->done); + refcount_set(&priv->pending_refs, 1); + priv->status = 0; + + bbio = btrfs_bio_alloc(BIO_MAX_VECS, op, BTRFS_I(fs_info->btree_inode), + addr, reloc_endio, priv); + bbio->bio.bi_iter.bi_sector = addr >> SECTOR_SHIFT; + bbio->is_remap = true; + + do { + size_t bytes = min_t(u64, length, PAGE_SIZE); + + if (bio_add_page(&bbio->bio, pages[i], bytes, 0) < bytes) { + refcount_inc(&priv->pending_refs); + btrfs_submit_bbio(bbio, 0); + + bbio = btrfs_bio_alloc(BIO_MAX_VECS, op, + BTRFS_I(fs_info->btree_inode), + addr, reloc_endio, priv); + bbio->bio.bi_iter.bi_sector = addr >> SECTOR_SHIFT; + bbio->is_remap = true; + continue; + } + + i++; + addr += bytes; + length -= bytes; + } while (length); + + refcount_inc(&priv->pending_refs); + btrfs_submit_bbio(bbio, 0); + + if (!refcount_dec_and_test(&priv->pending_refs)) + wait_for_completion_io(&priv->done); + + return blk_status_to_errno(READ_ONCE(priv->status)); +} + +static int copy_remapped_data(struct btrfs_fs_info *fs_info, u64 old_addr, + u64 new_addr, u64 length) +{ + int ret; + struct page **pages; + unsigned int nr_pages; + struct reloc_io_private priv; + + nr_pages = (length + PAGE_SIZE - 1) >> PAGE_SHIFT; + pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS); + if (!pages) + return -ENOMEM; + ret = btrfs_alloc_page_array(nr_pages, pages, 0); + if (ret) { + ret = -ENOMEM; + goto end; + } + + ret = copy_remapped_data_io(fs_info, &priv, pages, old_addr, length, + false); + if (ret) + goto end; + + ret = copy_remapped_data_io(fs_info, &priv, pages, new_addr, length, + true); + +end: + for (unsigned int i = 0; i < nr_pages; i++) { + if (pages[i]) + __free_page(pages[i]); + } + kfree(pages); + + return ret; +} + +static int do_copy(struct btrfs_fs_info *fs_info, u64 old_addr, u64 new_addr, + u64 length) +{ + int ret; + + /* Copy 1MB at a time, to avoid using too much memory. */ + + do { + u64 to_copy = min_t(u64, length, SZ_1M); + + /* Limit to one bio. */ + to_copy = min_t(u64, to_copy, BIO_MAX_VECS << PAGE_SHIFT); + + ret = copy_remapped_data(fs_info, old_addr, new_addr, + to_copy); + if (ret) + return ret; + + if (to_copy == length) + break; + + old_addr += to_copy; + new_addr += to_copy; + length -= to_copy; + } while (true); + + return 0; +} + +static int add_remap_item(struct btrfs_trans_handle *trans, + struct btrfs_path *path, u64 new_addr, u64 length, + u64 old_addr) +{ + struct btrfs_fs_info *fs_info = trans->fs_info; + struct btrfs_remap remap; + struct btrfs_key key; + struct extent_buffer *leaf; + int ret; + + key.objectid = old_addr; + key.type = BTRFS_REMAP_KEY; + key.offset = length; + + ret = btrfs_insert_empty_item(trans, fs_info->remap_root, path, + &key, sizeof(struct btrfs_remap)); + if (ret) + return ret; + + leaf = path->nodes[0]; + + btrfs_set_stack_remap_address(&remap, new_addr); + + write_extent_buffer(leaf, &remap, + btrfs_item_ptr_offset(leaf, path->slots[0]), + sizeof(struct btrfs_remap)); + + btrfs_release_path(path); + + return 0; +} + +static int add_remap_backref_item(struct btrfs_trans_handle *trans, + struct btrfs_path *path, u64 new_addr, + u64 length, u64 old_addr) +{ + struct btrfs_fs_info *fs_info = trans->fs_info; + struct btrfs_remap remap; + struct btrfs_key key; + struct extent_buffer *leaf; + int ret; + + key.objectid = new_addr; + key.type = BTRFS_REMAP_BACKREF_KEY; + key.offset = length; + + ret = btrfs_insert_empty_item(trans, fs_info->remap_root, + path, &key, sizeof(struct btrfs_remap)); + if (ret) + return ret; + + leaf = path->nodes[0]; + + btrfs_set_stack_remap_address(&remap, old_addr); + + write_extent_buffer(leaf, &remap, + btrfs_item_ptr_offset(leaf, path->slots[0]), + sizeof(struct btrfs_remap)); + + btrfs_release_path(path); + + return 0; +} + +static int move_existing_remap(struct btrfs_fs_info *fs_info, + struct btrfs_path *path, + struct btrfs_block_group *bg, u64 new_addr, + u64 length, u64 old_addr) +{ + struct btrfs_trans_handle *trans; + struct extent_buffer *leaf; + struct btrfs_remap *remap_ptr, remap; + struct btrfs_key key, ins; + u64 dest_addr, dest_length, min_size; + struct btrfs_block_group *dest_bg; + int ret; + bool is_data = bg->flags & BTRFS_BLOCK_GROUP_DATA; + struct btrfs_space_info *sinfo = bg->space_info; + bool mutex_taken = false, bg_needs_free_space; + + spin_lock(&sinfo->lock); + btrfs_space_info_update_bytes_may_use(sinfo, length); + spin_unlock(&sinfo->lock); + + if (is_data) + min_size = fs_info->sectorsize; + else + min_size = fs_info->nodesize; + + ret = btrfs_reserve_extent(fs_info->fs_root, length, length, min_size, + 0, 0, &ins, is_data, false); + if (ret) { + spin_lock(&sinfo->lock); + btrfs_space_info_update_bytes_may_use(sinfo, -length); + spin_unlock(&sinfo->lock); + return ret; + } + + dest_addr = ins.objectid; + dest_length = ins.offset; + + if (!is_data && !IS_ALIGNED(dest_length, fs_info->nodesize)) { + u64 new_length = ALIGN_DOWN(dest_length, fs_info->nodesize); + + btrfs_free_reserved_extent(fs_info, dest_addr + new_length, + dest_length - new_length, 0); + + dest_length = new_length; + } + + trans = btrfs_join_transaction(fs_info->remap_root); + if (IS_ERR(trans)) { + ret = PTR_ERR(trans); + trans = NULL; + goto end; + } + + mutex_lock(&fs_info->remap_mutex); + mutex_taken = true; + + /* Find old remap entry. */ + + key.objectid = old_addr; + key.type = BTRFS_REMAP_KEY; + key.offset = length; + + ret = btrfs_search_slot(trans, fs_info->remap_root, &key, + path, 0, 1); + if (ret == 1) { + /* + * Not a problem if the remap entry wasn't found: that means + * that another transaction has deallocated the data. + * move_existing_remaps() loops until the BG contains no + * remaps, so we can just return 0 in this case. + */ + btrfs_release_path(path); + ret = 0; + goto end; + } else if (ret) { + goto end; + } + + ret = do_copy(fs_info, new_addr, dest_addr, dest_length); + if (ret) + goto end; + + /* Change data of old remap entry. */ + + leaf = path->nodes[0]; + + remap_ptr = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_remap); + btrfs_set_remap_address(leaf, remap_ptr, dest_addr); + + btrfs_mark_buffer_dirty(trans, leaf); + + if (dest_length != length) { + key.offset = dest_length; + btrfs_set_item_key_safe(trans, path, &key); + } + + btrfs_release_path(path); + + if (dest_length != length) { + /* Add remap item for remainder. */ + + ret = add_remap_item(trans, path, new_addr + dest_length, + length - dest_length, + old_addr + dest_length); + if (ret) + goto end; + } + + /* Change or remove old backref. */ + + key.objectid = new_addr; + key.type = BTRFS_REMAP_BACKREF_KEY; + key.offset = length; + + ret = btrfs_search_slot(trans, fs_info->remap_root, &key, + path, -1, 1); + if (ret) { + if (ret == 1) { + btrfs_release_path(path); + ret = -ENOENT; + } + goto end; + } + + leaf = path->nodes[0]; + + if (dest_length == length) { + ret = btrfs_del_item(trans, fs_info->remap_root, path); + if (ret) { + btrfs_release_path(path); + goto end; + } + } else { + key.objectid += dest_length; + key.offset -= dest_length; + btrfs_set_item_key_safe(trans, path, &key); + + btrfs_set_stack_remap_address(&remap, old_addr + dest_length); + + write_extent_buffer(leaf, &remap, + btrfs_item_ptr_offset(leaf, path->slots[0]), + sizeof(struct btrfs_remap)); + } + + btrfs_release_path(path); + + /* Add new backref. */ + + ret = add_remap_backref_item(trans, path, dest_addr, dest_length, + old_addr); + if (ret) + goto end; + + adjust_block_group_remap_bytes(trans, bg, -dest_length); + + ret = btrfs_add_to_free_space_tree(trans, new_addr, dest_length); + if (ret) + goto end; + + dest_bg = btrfs_lookup_block_group(fs_info, dest_addr); + + adjust_block_group_remap_bytes(trans, dest_bg, dest_length); + + mutex_lock(&dest_bg->free_space_lock); + bg_needs_free_space = test_bit(BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE, + &dest_bg->runtime_flags); + mutex_unlock(&dest_bg->free_space_lock); + btrfs_put_block_group(dest_bg); + + if (bg_needs_free_space) { + ret = btrfs_add_block_group_free_space(trans, dest_bg); + if (ret) + goto end; + } + + ret = btrfs_remove_from_free_space_tree(trans, dest_addr, dest_length); + if (ret) { + btrfs_remove_from_free_space_tree(trans, new_addr, + dest_length); + goto end; + } + + ret = 0; + +end: + if (mutex_taken) + mutex_unlock(&fs_info->remap_mutex); + + btrfs_dec_block_group_reservations(fs_info, dest_addr); + + if (ret) { + btrfs_free_reserved_extent(fs_info, dest_addr, dest_length, 0); + + if (trans) { + btrfs_abort_transaction(trans, ret); + btrfs_end_transaction(trans); + } + } else { + dest_bg = btrfs_lookup_block_group(fs_info, dest_addr); + btrfs_free_reserved_bytes(dest_bg, dest_length, 0); + btrfs_put_block_group(dest_bg); + + ret = btrfs_commit_transaction(trans); + } + + return ret; +} + +static int move_existing_remaps(struct btrfs_fs_info *fs_info, + struct btrfs_block_group *bg, + struct btrfs_path *path) +{ + int ret; + struct btrfs_key key; + struct extent_buffer *leaf; + struct btrfs_remap *remap; + u64 old_addr; + + /* Look for backrefs in remap tree. */ + + while (bg->remap_bytes > 0) { + key.objectid = bg->start; + key.type = BTRFS_REMAP_BACKREF_KEY; + key.offset = 0; + + ret = btrfs_search_slot(NULL, fs_info->remap_root, &key, path, + 0, 0); + if (ret < 0) + return ret; + + leaf = path->nodes[0]; + + if (path->slots[0] >= btrfs_header_nritems(leaf)) { + ret = btrfs_next_leaf(fs_info->remap_root, path); + if (ret < 0) { + btrfs_release_path(path); + return ret; + } + + if (ret) { + btrfs_release_path(path); + break; + } + + leaf = path->nodes[0]; + } + + btrfs_item_key_to_cpu(leaf, &key, path->slots[0]); + + if (key.type != BTRFS_REMAP_BACKREF_KEY) { + path->slots[0]++; + + if (path->slots[0] >= btrfs_header_nritems(leaf)) { + ret = btrfs_next_leaf(fs_info->remap_root, path); + if (ret < 0) { + btrfs_release_path(path); + return ret; + } + + if (ret) { + btrfs_release_path(path); + break; + } + + leaf = path->nodes[0]; + } + } + + remap = btrfs_item_ptr(leaf, path->slots[0], + struct btrfs_remap); + + old_addr = btrfs_remap_address(leaf, remap); + + btrfs_release_path(path); + + ret = move_existing_remap(fs_info, path, bg, key.objectid, + key.offset, old_addr); + if (ret) + return ret; + } + + BUG_ON(bg->remap_bytes > 0); + + return 0; +} + static int create_remap_tree_entries(struct btrfs_trans_handle *trans, struct btrfs_path *path, struct btrfs_block_group *bg) @@ -4635,6 +5116,12 @@ int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start, WARN_ON(ret && ret != -EAGAIN); if (should_relocate_using_remap_tree(bg)) { + if (bg->remap_bytes != 0) { + ret = move_existing_remaps(fs_info, bg, path); + if (ret) + goto out; + } + ret = start_block_group_remapping(fs_info, path, bg); } else { ret = do_nonremap_reloc(fs_info, verbose, rc); -- 2.51.0