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[174.109.172.136]) by smtp.gmail.com with ESMTPSA id i14sm3244701qtq.33.2020.08.20.08.46.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Aug 2020 08:46:27 -0700 (PDT) From: Josef Bacik To: linux-btrfs@vger.kernel.org, kernel-team@fb.com Subject: [PATCH 07/12] btrfs: introduce BTRFS_NESTING_SPLIT for split blocks Date: Thu, 20 Aug 2020 11:46:06 -0400 Message-Id: <873113d522b5b1183a4805e1140114b64174cf00.1597938191.git.josef@toxicpanda.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org If we are splitting a leaf/node, we could do something like the following lock(leaf) BTRFS_NESTING_NORMAL lock(left) BTRFS_NESTING_LEFT + BTRFS_NESTING_COW push from leaf -> left reset path to point to left split left allocate new block, lock block BTRFS_NESTING_SPLIT at the new block point we need to have a different nesting level, because we have already used either BTRFS_NESTING_LEFT or BTRFS_NESTING_RIGHT when pushing items from the original leaf into the adjacent leaves. Signed-off-by: Josef Bacik --- fs/btrfs/ctree.c | 4 ++-- fs/btrfs/locking.h | 9 +++++++++ 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index ae5e3f1056d8..4b62acac31b6 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -3473,7 +3473,7 @@ static noinline int split_node(struct btrfs_trans_handle *trans, btrfs_node_key(c, &disk_key, mid); split = alloc_tree_block_no_bg_flush(trans, root, 0, &disk_key, level, - c->start, 0, BTRFS_NESTING_NORMAL); + c->start, 0, BTRFS_NESTING_SPLIT); if (IS_ERR(split)) return PTR_ERR(split); @@ -4250,7 +4250,7 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans, btrfs_item_key(l, &disk_key, mid); right = alloc_tree_block_no_bg_flush(trans, root, 0, &disk_key, 0, - l->start, 0, BTRFS_NESTING_NORMAL); + l->start, 0, BTRFS_NESTING_SPLIT); if (IS_ERR(right)) return PTR_ERR(right); diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h index a88c6f59f616..3b5a948bf74f 100644 --- a/fs/btrfs/locking.h +++ b/fs/btrfs/locking.h @@ -47,6 +47,15 @@ enum btrfs_lock_nesting { BTRFS_NESTING_LEFT_COW, BTRFS_NESTING_RIGHT_COW, + /* + * When splitting we may push nodes to the left or right, but still use + * the subsequent nodes in our path, keeping our locks on those adjacent + * blocks. Thus when we go to allocate a new split block we've already + * used up all of our available subclasses, so this subclass exists to + * handle this case where we need to allocate a new split block. + */ + BTRFS_NESTING_SPLIT, + /* * We are limited to MAX_LOCKDEP_SUBLCLASSES number of subclasses, so * add this in here and add a static_assert to keep us from going over -- 2.24.1