From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:43474 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751714AbbGGIOK (ORCPT ); Tue, 7 Jul 2015 04:14:10 -0400 Date: Tue, 7 Jul 2015 16:13:55 +0800 From: Liu Bo To: Zhaolei Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH 6/9] btrfs: Fix NO_SPACE bug caused by delayed-iput Message-ID: <20150707081352.GA1967@localhost.localdomain> Reply-To: bo.li.liu@oracle.com References: <581e0ffa1ce1dd6345519e7953bf4e895bda35ae.1428554023.git.zhaolei@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <581e0ffa1ce1dd6345519e7953bf4e895bda35ae.1428554023.git.zhaolei@cn.fujitsu.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hi, On Thu, Apr 09, 2015 at 12:34:41PM +0800, Zhaolei wrote: > From: Zhao Lei > > Steps to reproduce: > while true; do > dd if=/dev/zero of=/btrfs_dir/file count=[fs_size * 75%] > rm /btrfs_dir/file > sync > done > > And we'll see dd failed because btrfs return NO_SPACE. > > Reason: > Normally, btrfs_commit_transaction() call btrfs_run_delayed_iputs() > in end to free fs space for next write, but sometimes it hadn't > done work on time, because btrfs-cleaner thread get delayed-iputs > from list before, but do iput() after next write. > > This is log: > [ 2569.050776] comm=btrfs-cleaner func=btrfs_evict_inode() begin > > [ 2569.084280] comm=sync func=btrfs_commit_transaction() call btrfs_run_delayed_iputs() > [ 2569.085418] comm=sync func=btrfs_commit_transaction() done btrfs_run_delayed_iputs() > [ 2569.087554] comm=sync func=btrfs_commit_transaction() end > > [ 2569.191081] comm=dd begin > [ 2569.790112] comm=dd func=__btrfs_buffered_write() ret=-28 > > [ 2569.847479] comm=btrfs-cleaner func=add_pinned_bytes() 0 + 32677888 = 32677888 > [ 2569.849530] comm=btrfs-cleaner func=add_pinned_bytes() 32677888 + 23834624 = 56512512 > ... > [ 2569.903893] comm=btrfs-cleaner func=add_pinned_bytes() 943976448 + 21762048 = 965738496 > [ 2569.908270] comm=btrfs-cleaner func=btrfs_evict_inode() end > > Fix: > Make btrfs_commit_transaction() wait current running btrfs-cleaner's > delayed-iputs() done in end. > > Test: > Use script similar to above(more complex), > before patch: > 7 failed in 100 * 20 loop. > after patch: > 0 failed in 100 * 20 loop. > > Signed-off-by: Zhao Lei > --- > fs/btrfs/ctree.h | 1 + > fs/btrfs/disk-io.c | 3 ++- > fs/btrfs/extent-tree.c | 6 ++++++ > fs/btrfs/inode.c | 4 ++++ > 4 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > index f9c89ca..54d4d78 100644 > --- a/fs/btrfs/ctree.h > +++ b/fs/btrfs/ctree.h > @@ -1513,6 +1513,7 @@ struct btrfs_fs_info { > > spinlock_t delayed_iput_lock; > struct list_head delayed_iputs; > + struct rw_semaphore delayed_iput_sem; > > /* this protects tree_mod_seq_list */ > spinlock_t tree_mod_seq_lock; > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index 639f266..6867471 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -2241,11 +2241,12 @@ int open_ctree(struct super_block *sb, > spin_lock_init(&fs_info->qgroup_op_lock); > spin_lock_init(&fs_info->buffer_lock); > spin_lock_init(&fs_info->unused_bgs_lock); > - mutex_init(&fs_info->unused_bg_unpin_mutex); > rwlock_init(&fs_info->tree_mod_log_lock); > + mutex_init(&fs_info->unused_bg_unpin_mutex); > mutex_init(&fs_info->reloc_mutex); > mutex_init(&fs_info->delalloc_root_mutex); > seqlock_init(&fs_info->profiles_lock); > + init_rwsem(&fs_info->delayed_iput_sem); > > init_completion(&fs_info->kobj_unregister); > INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots); > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index 203ac63..6fd7dca 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -3732,6 +3732,12 @@ commit_trans: > ret = btrfs_commit_transaction(trans, root); > if (ret) > return ret; > + /* > + * make sure that all running delayed iput are > + * done > + */ > + down_write(&root->fs_info->delayed_iput_sem); > + up_write(&root->fs_info->delayed_iput_sem); > goto again; > } else { > btrfs_end_transaction(trans, root); > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index d2e732d..34d10be 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -3110,6 +3110,8 @@ void btrfs_run_delayed_iputs(struct btrfs_root *root) > if (empty) > return; > > + down_read(&fs_info->delayed_iput_sem); > + > spin_lock(&fs_info->delayed_iput_lock); > list_splice_init(&fs_info->delayed_iputs, &list); > spin_unlock(&fs_info->delayed_iput_lock); > @@ -3120,6 +3122,8 @@ void btrfs_run_delayed_iputs(struct btrfs_root *root) > iput(delayed->inode); > kfree(delayed); > } > + > + up_read(&root->fs_info->delayed_iput_sem); By introducing this "delayed_iput_sem", fstests's generic/241 cries about a possible deadlock, can we use a waitqueue to avoid this? [ 2061.345955] ============================================= [ 2061.346027] [ INFO: possible recursive locking detected ] [ 2061.346027] 4.1.0+ #268 Tainted: G W [ 2061.346027] --------------------------------------------- [ 2061.346027] btrfs-cleaner/3045 is trying to acquire lock: [ 2061.346027] (&fs_info->delayed_iput_sem){++++..}, at: [] btrfs_run_delayed_iputs+0x6b/0x100 [ 2061.346027] but task is already holding lock: [ 2061.346027] (&fs_info->delayed_iput_sem){++++..}, at: [] btrfs_run_delayed_iputs+0x6b/0x100 [ 2061.346027] other info that might help us debug this: [ 2061.346027] Possible unsafe locking scenario: [ 2061.346027] CPU0 [ 2061.346027] ---- [ 2061.346027] lock(&fs_info->delayed_iput_sem); [ 2061.346027] lock(&fs_info->delayed_iput_sem); [ 2061.346027] *** DEADLOCK *** [ 2061.346027] May be due to missing lock nesting notation [ 2061.346027] 2 locks held by btrfs-cleaner/3045: [ 2061.346027] #0: (&fs_info->cleaner_mutex){+.+.+.}, at: [] cleaner_kthread+0x64/0x1a0 [ 2061.346027] #1: (&fs_info->delayed_iput_sem){++++..}, at: [] btrfs_run_delayed_iputs+0x6b/0x100 [ 2061.346027] stack backtrace: [ 2061.346027] CPU: 0 PID: 3045 Comm: btrfs-cleaner Tainted: G W 4.1.0+ #268 [ 2061.346027] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140709_153950- 04/01/2014 [ 2061.346027] ffff88013760a700 ffff8800b4aff888 ffffffff818bb68e 0000000000000007 [ 2061.346027] ffffffff828fa0a0 ffff8800b4aff968 ffffffff810db18d ffff8800b4aff978 [ 2061.346027] ffffffff00000000 ffff88013760a750 ffffffff00000001 ffff88013760b470 [ 2061.346027] Call Trace: [ 2061.346027] [] dump_stack+0x4c/0x65 [ 2061.346027] [] __lock_acquire+0x214d/0x22f0 [ 2061.346027] [] ? trace_hardirqs_off+0xd/0x10 [ 2061.346027] [] ? __lock_is_held+0x4d/0x70 [ 2061.346027] [] lock_acquire+0xd0/0x280 [ 2061.346027] [] ? btrfs_run_delayed_iputs+0x6b/0x100 [ 2061.346027] [] down_read+0x4c/0x70 [ 2061.346027] [] ? btrfs_run_delayed_iputs+0x6b/0x100 [ 2061.346027] [] ? _raw_spin_unlock+0x2b/0x40 [ 2061.346027] [] btrfs_run_delayed_iputs+0x6b/0x100 [ 2061.346027] [] ? btrfs_commit_transaction+0xa1f/0xc50 [ 2061.346027] [] btrfs_commit_transaction+0xa44/0xc50 [ 2061.346027] [] ? wait_woken+0xa0/0xa0 [ 2061.346027] [] flush_space+0x97/0x4b0 [ 2061.346027] [] ? _raw_spin_unlock+0x2b/0x40 [ 2061.346027] [] ? reserve_metadata_bytes+0x20b/0x6d0 [ 2061.346027] [] reserve_metadata_bytes+0x222/0x6d0 [ 2061.346027] [] ? btrfs_block_rsv_refill+0x65/0x90 [ 2061.346027] [] btrfs_block_rsv_refill+0x77/0x90 [ 2061.346027] [] btrfs_evict_inode+0x473/0x700 [ 2061.346027] [] evict+0xab/0x170 [ 2061.346027] [] iput+0x1cd/0x350 [ 2061.346027] [] btrfs_run_delayed_iputs+0xc9/0x100 [ 2061.346027] [] ? cleaner_kthread+0x64/0x1a0 [ 2061.346027] [] cleaner_kthread+0x15a/0x1a0 [ 2061.346027] [] ? btree_invalidatepage+0x90/0x90 [ 2061.346027] [] kthread+0xef/0x110 [ 2061.346027] [] ? kthread_create_on_node+0x210/0x210 [ 2061.346027] [] ret_from_fork+0x3f/0x70 [ 2061.346027] [] ? kthread_create_on_node+0x210/0x210 Thanks, -liubo > } > > /* > -- > 1.8.5.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html