From patchwork Thu Oct 6 02:51:38 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiaoguang Wang X-Patchwork-Id: 9363625 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 6DDE4600C8 for ; Thu, 6 Oct 2016 02:57:33 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5F0ED28CF1 for ; Thu, 6 Oct 2016 02:57:33 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 536FB28DB1; Thu, 6 Oct 2016 02:57:33 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 76C0228CF1 for ; Thu, 6 Oct 2016 02:57:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751635AbcJFC52 (ORCPT ); Wed, 5 Oct 2016 22:57:28 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:22071 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751311AbcJFC51 (ORCPT ); Wed, 5 Oct 2016 22:57:27 -0400 X-IronPort-AV: E=Sophos;i="5.20,367,1444665600"; d="scan'208";a="881937" Received: from unknown (HELO cn.fujitsu.com) ([10.167.250.3]) by song.cn.fujitsu.com with ESMTP; 06 Oct 2016 10:57:22 +0800 Received: from localhost.localdomain (unknown [10.167.226.107]) by cn.fujitsu.com (Postfix) with ESMTP id 132794010CF4; Thu, 6 Oct 2016 10:57:20 +0800 (CST) From: Wang Xiaoguang To: linux-btrfs@vger.kernel.org Cc: jbacik@fb.com, dsterba@suse.com, s.priebe@profihost.ag Subject: [PATCH 1/2] btrfs: improve inode's outstanding_extents computation Date: Thu, 6 Oct 2016 10:51:38 +0800 Message-Id: <20161006025139.22776-1-wangxg.fnst@cn.fujitsu.com> X-Mailer: git-send-email 2.9.0 MIME-Version: 1.0 X-yoursite-MailScanner-ID: 132794010CF4.A02A6 X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: wangxg.fnst@cn.fujitsu.com Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This issue was revealed by modifying BTRFS_MAX_EXTENT_SIZE(128MB) to 64KB, When modifying BTRFS_MAX_EXTENT_SIZE(128MB) to 64KB, fsstress test often gets these warnings from btrfs_destroy_inode(): WARN_ON(BTRFS_I(inode)->outstanding_extents); WARN_ON(BTRFS_I(inode)->reserved_extents); Simple test program below can reproduce this issue steadily. Note: you need to modify BTRFS_MAX_EXTENT_SIZE to 64KB to have test, otherwise there won't be such WARNING. #include #include #include #include #include int main(void) { int fd; char buf[68 *1024]; memset(buf, 0, 68 * 1024); fd = open("testfile", O_CREAT | O_EXCL | O_RDWR); pwrite(fd, buf, 68 * 1024, 64 * 1024); return; } When BTRFS_MAX_EXTENT_SIZE is 64KB, and buffered data range is: 64KB 128K 132KB |-----------------------------------------------|---------------| 64 + 4KB 1) for above data range, btrfs_delalloc_reserve_metadata() will reserve metadata and set BTRFS_I(inode)->outstanding_extents to 2. (68KB + 64KB - 1) / 64KB == 2 Outstanding_extents: 2 2) then btrfs_dirty_page() will be called to dirty pages and set EXTENT_DELALLOC flag. In this case, btrfs_set_bit_hook() will be called twice. The 1st set_bit_hook() call will set DEALLOC flag for the first 64K. 64KB 128KB |-----------------------------------------------| 64KB DELALLOC Outstanding_extents: 2 Set_bit_hooks() uses FIRST_DELALLOC flag to avoid re-increase outstanding_extents counter. So for 1st set_bit_hooks() call, it won't modify outstanding_extents, it's still 2. Then FIRST_DELALLOC flag is *CLEARED*. 3) 2nd btrfs_set_bit_hook() call. Because FIRST_DELALLOC have been cleared by previous set_bit_hook(), btrfs_set_bit_hook() will increase BTRFS_I(inode)->outstanding_extents by one, so now BTRFS_I(inode)->outstanding_extents is 3. 64KB 128KB 132KB |-----------------------------------------------|----------------| 64K DELALLOC 4K DELALLOC Outstanding_extents: 3 But the correct outstanding_extents number should be 2, not 3. The 2nd btrfs_set_bit_hook() call just screwed up this, and leads to the WARN_ON(). Normally, we can solve it by only increasing outstanding_extents in set_bit_hook(). But the problem is for delalloc_reserve/release_metadata(), we only have a 'length' parameter, and calculate in-accurate outstanding_extents. If we only rely on set_bit_hook() release_metadata() will crew things up as it will decrease inaccurate number. So the fix we use is: 1) Increase *INACCURATE* outstanding_extents at delalloc_reserve_meta Just as a place holder. 2) Increase *accurate* outstanding_extents at set_bit_hooks() This is the real increaser. 3) Decrease *INACCURATE* outstanding_extents before returning This makes outstanding_extents to correct value. For 128M BTRFS_MAX_EXTENT_SIZE, due to limitation of __btrfs_buffered_write(), each iteration will only handle about 2MB data. So btrfs_dirty_pages() won't need to handle cases cross 2 extents. Signed-off-by: Wang Xiaoguang Tested-by: Stefan Priebe --- fs/btrfs/ctree.h | 2 ++ fs/btrfs/inode.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++------ fs/btrfs/ioctl.c | 6 ++---- 3 files changed, 62 insertions(+), 11 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 33fe035..16885f6 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -3119,6 +3119,8 @@ int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, int delay_iput, int nr); int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end, struct extent_state **cached_state); +int btrfs_set_extent_defrag(struct inode *inode, u64 start, u64 end, + struct extent_state **cached_state); int btrfs_create_subvol_root(struct btrfs_trans_handle *trans, struct btrfs_root *new_root, struct btrfs_root *parent_root, diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index e6811c4..a7193b1 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1590,6 +1590,9 @@ static void btrfs_split_extent_hook(struct inode *inode, if (!(orig->state & EXTENT_DELALLOC)) return; + if (btrfs_is_free_space_inode(inode)) + return; + size = orig->end - orig->start + 1; if (size > BTRFS_MAX_EXTENT_SIZE) { u64 num_extents; @@ -1632,6 +1635,9 @@ static void btrfs_merge_extent_hook(struct inode *inode, if (!(other->state & EXTENT_DELALLOC)) return; + if (btrfs_is_free_space_inode(inode)) + return; + if (new->start > other->start) new_size = new->end - other->start + 1; else @@ -1727,7 +1733,6 @@ static void btrfs_del_delalloc_inode(struct btrfs_root *root, static void btrfs_set_bit_hook(struct inode *inode, struct extent_state *state, unsigned *bits) { - if ((*bits & EXTENT_DEFRAG) && !(*bits & EXTENT_DELALLOC)) WARN_ON(1); /* @@ -1738,13 +1743,16 @@ static void btrfs_set_bit_hook(struct inode *inode, if (!(state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) { struct btrfs_root *root = BTRFS_I(inode)->root; u64 len = state->end + 1 - state->start; + u64 num_extents = div64_u64(len + BTRFS_MAX_EXTENT_SIZE - 1, + BTRFS_MAX_EXTENT_SIZE); bool do_list = !btrfs_is_free_space_inode(inode); - if (*bits & EXTENT_FIRST_DELALLOC) { + if (*bits & EXTENT_FIRST_DELALLOC) *bits &= ~EXTENT_FIRST_DELALLOC; - } else { + + if (do_list) { spin_lock(&BTRFS_I(inode)->lock); - BTRFS_I(inode)->outstanding_extents++; + BTRFS_I(inode)->outstanding_extents += num_extents; spin_unlock(&BTRFS_I(inode)->lock); } @@ -1792,7 +1800,7 @@ static void btrfs_clear_bit_hook(struct inode *inode, if (*bits & EXTENT_FIRST_DELALLOC) { *bits &= ~EXTENT_FIRST_DELALLOC; - } else if (!(*bits & EXTENT_DO_ACCOUNTING)) { + } else if (!(*bits & EXTENT_DO_ACCOUNTING) && do_list) { spin_lock(&BTRFS_I(inode)->lock); BTRFS_I(inode)->outstanding_extents -= num_extents; spin_unlock(&BTRFS_I(inode)->lock); @@ -1990,9 +1998,52 @@ static noinline int add_pending_csums(struct btrfs_trans_handle *trans, int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end, struct extent_state **cached_state) { + int ret; + u64 num_extents = div64_u64(end - start + BTRFS_MAX_EXTENT_SIZE, + BTRFS_MAX_EXTENT_SIZE); + + WARN_ON((end & (PAGE_SIZE - 1)) == 0); + ret = set_extent_delalloc(&BTRFS_I(inode)->io_tree, start, end, + cached_state); + + /* + * btrfs_delalloc_reserve_metadata() will first add number of + * outstanding extents according to data length, which is inaccurate + * for case like dirtying already dirty pages. + * so here we will decrease such inaccurate numbers, to make + * outstanding_extents only rely on the correct values added by + * set_bit_hook() + * + * Also, we skipped the metadata space reserve for space cache inodes, + * so don't modify the outstanding_extents value. + */ + if (ret == 0 && !btrfs_is_free_space_inode(inode)) { + spin_lock(&BTRFS_I(inode)->lock); + BTRFS_I(inode)->outstanding_extents -= num_extents; + spin_unlock(&BTRFS_I(inode)->lock); + } + + return ret; +} + +int btrfs_set_extent_defrag(struct inode *inode, u64 start, u64 end, + struct extent_state **cached_state) +{ + int ret; + u64 num_extents = div64_u64(end - start + BTRFS_MAX_EXTENT_SIZE, + BTRFS_MAX_EXTENT_SIZE); + WARN_ON((end & (PAGE_SIZE - 1)) == 0); - return set_extent_delalloc(&BTRFS_I(inode)->io_tree, start, end, - cached_state); + ret = set_extent_defrag(&BTRFS_I(inode)->io_tree, start, end, + cached_state); + + if (ret == 0 && !btrfs_is_free_space_inode(inode)) { + spin_lock(&BTRFS_I(inode)->lock); + BTRFS_I(inode)->outstanding_extents -= num_extents; + spin_unlock(&BTRFS_I(inode)->lock); + } + + return ret; } /* see btrfs_writepage_start_hook for details on why this is required */ diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 7fd939b..6a19bea 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1235,10 +1235,8 @@ again: (page_cnt - i_done) << PAGE_SHIFT); } - - set_extent_defrag(&BTRFS_I(inode)->io_tree, page_start, page_end - 1, - &cached_state); - + btrfs_set_extent_defrag(inode, page_start, + page_end - 1, &cached_state); unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start, page_end - 1, &cached_state, GFP_NOFS);