From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0803C433F5 for ; Mon, 10 Oct 2022 00:57:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231180AbiJJA5T (ORCPT ); Sun, 9 Oct 2022 20:57:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57680 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230293AbiJJA5A (ORCPT ); Sun, 9 Oct 2022 20:57:00 -0400 Received: from out0.migadu.com (out0.migadu.com [IPv6:2001:41d0:2:267::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D50CA4BAB for ; Sun, 9 Oct 2022 17:40:49 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1665362401; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jdMoINWopUojLi7isqDQwSSMYLf8rxZoh8ltx/IKUhk=; b=RYPzBSaj1hvq7e1DuM1nr6WXL9rBml0+kEqkoRpUb8jkMP1NSZ4mTuiKy7zceqEzdb7NwF I2JNbR/g5+Tp+L3eHOkfqG+M1NEUiakV5TlpJtoFSVm7I7EYg7k8zHVVZLA/+vUHQix2ot rBNt9f3speIBFNaeqmZmkT7x9EO9Nz0= From: Guoqing Jiang Subject: Re: Memory leak when raid10 takeover raid0 To: Xiao Ni , linux-raid Cc: Song Liu References: Message-ID: <35f4a626-7f83-56c5-4cad-73ede197ccbf@linux.dev> Date: Mon, 10 Oct 2022 08:40:00 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org Hi Xiao, On 10/8/22 5:06 PM, Xiao Ni wrote: > Hi all > > Sometimes it will have a memory leak problem when raid10 takeover raid0. > And then panic. > > [ 6973.704097] BUG bio-176 (Not tainted): Objects remaining in bio-176 > on __kmem_cache_shutdown() > [ 6973.705627] ----------------------------------------------------------------------------- > [ 6973.705627] > [ 6973.707331] Slab 0x0000000067cd8c6c objects=21 used=1 > fp=0x000000005bf568c8 > flags=0xfffffc0000100(slab|node=0|zone=1|lastcpupid=0x1fffff) > [ 6973.709498] CPU: 0 PID: 735535 Comm: mdadm Kdump: loaded Not > tainted 4.18.0-423.el8.x86_64 #1 It is an old kernel, does it also happen to latest mainline version? Not sure mdadm test suite covers this case. > [ 6973.711027] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 > [ 6973.712068] Call Trace: > [ 6973.712550] dump_stack+0x41/0x60 > [ 6973.713185] slab_err.cold.117+0x53/0x67 > [ 6973.713878] ? __unfreeze_partials+0x1a0/0x1a0 > [ 6973.714659] ? cpumask_next+0x17/0x20 > [ 6973.715309] __kmem_cache_shutdown+0x16e/0x300 > [ 6973.716097] kmem_cache_destroy+0x4d/0x120 > [ 6973.716843] bioset_exit+0xb0/0x100 > [ 6973.717486] level_store+0x280/0x650 > [ 6973.718147] ? security_capable+0x38/0x60 > [ 6973.718856] md_attr_store+0x7c/0xc0 > [ 6973.719489] kernfs_fop_write+0x11e/0x1a0 > [ 6973.720200] vfs_write+0xa5/0x1b0 > [ 6973.720785] ksys_write+0x4f/0xb0 > [ 6973.721374] do_syscall_64+0x5b/0x1b0 > [ 6973.722028] entry_SYSCALL_64_after_hwframe+0x61/0xc6 > [ 6973.723005] RIP: 0033:0x7fb15d2b5bc8 > [ 6973.723660] Code: 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 > 00 00 f3 0f 1e fa 48 8d 05 55 4b 2a 00 8b 00 85 c0 75 17 b8 01 00 00 > 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 49 89 > d4 55 > [ 6973.726926] RSP: 002b:00007ffed8ebc8a8 EFLAGS: 00000246 ORIG_RAX: > 0000000000000001 > [ 6973.728278] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007fb15d2b5bc8 > [ 6973.729515] RDX: 0000000000000006 RSI: 0000560330046dd7 RDI: 0000000000000004 > [ 6973.730748] RBP: 0000560330046dd7 R08: 000056033003b927 R09: 00007fb15d315d40 > [ 6973.731986] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > [ 6973.733240] R13: 00007ffed8ebcc80 R14: 00007ffed8ebe8ee R15: 0000000000000000 > [ 6973.734520] Disabling lock debugging due to kernel taint > [ 6973.735452] Object 0x000000000923869f @offset=3264 > [ 6973.736317] kmem_cache_destroy bio-176: Slab cache still has objects > [ 6973.737479] CPU: 0 PID: 735535 Comm: mdadm Kdump: loaded Tainted: G > B --------- - - 4.18.0-423.el8.x86_64 #1 > [ 6973.739438] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 > [ 6973.740437] Call Trace: > [ 6973.740877] dump_stack+0x41/0x60 > [ 6973.741473] kmem_cache_destroy+0x116/0x120 > [ 6973.742209] bioset_exit+0xb0/0x100 > [ 6973.742824] level_store+0x280/0x650 > [ 6973.743463] ? security_capable+0x38/0x60 > [ 6973.744177] md_attr_store+0x7c/0xc0 > [ 6973.744807] kernfs_fop_write+0x11e/0x1a0 > [ 6973.745516] vfs_write+0xa5/0x1b0 > [ 6973.746112] ksys_write+0x4f/0xb0 > [ 6973.746695] do_syscall_64+0x5b/0x1b0 > [ 6973.747373] entry_SYSCALL_64_after_hwframe+0x61/0xc6 > [ 6973.748293] RIP: 0033:0x7fb15d2b5bc8 > [ 6973.748929] Code: 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 > 00 00 f3 0f 1e fa 48 8d 05 55 4b 2a 00 8b 00 85 c0 75 17 b8 01 00 00 > 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 49 89 > d4 55 > [ 6973.752255] RSP: 002b:00007ffed8ebc8a8 EFLAGS: 00000246 ORIG_RAX: > 0000000000000001 > [ 6973.753628] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007fb15d2b5bc8 > [ 6973.754900] RDX: 0000000000000006 RSI: 0000560330046dd7 RDI: 0000000000000004 > [ 6973.756142] RBP: 0000560330046dd7 R08: 000056033003b927 R09: 00007fb15d315d40 > [ 6973.757420] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > [ 6973.758702] R13: 00007ffed8ebcc80 R14: 00007ffed8ebe8ee R15: 0000000000000000 > [ 6973.762429] BUG: unable to handle kernel NULL pointer dereference > at 0000000000000000 > [ 6973.763818] PGD 0 P4D 0 > [ 6973.764277] Oops: 0002 [#1] SMP PTI > [ 6973.764896] CPU: 0 PID: 12 Comm: ksoftirqd/0 Kdump: loaded Tainted: > G B --------- - - 4.18.0-423.el8.x86_64 #1 > [ 69 it73.766944] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 > [ 6973.767999] RIP: 0010:mempool_free+0x52/0x80 > [ 6973.768779] Code: e4 6f 96 00 e9 0f 72 96 00 48 89 f7 e8 a7 5e 75 > 00 48 63 53 08 3b 53 04 7d 30 48 8b 4b 10 8d 72 01 48 89 df 89 73 08 > 48 89 c6 <48> 89 2c d1 e8 f5 5e 75 00 48 8d 7b 30 31 c9 5b ba 01 00 00 > 00 be > [ 6973.772088] RSP: 0018:ffffbc6c4068fdf8 EFLAGS: 00010093 > [ 6973.773026] RAX: 0000000000000293 RBX: ffff9b5844fed7d8 RCX: 0000000000000000 > [ 6973.774318] RDX: 0000000000000000 RSI: 0000000000000293 RDI: ffff9b5844fed7d8 > [ 6973.775560] RBP: ffff9b5759046cc0 R08: 000000000000003d R09: ffff9b57420e62a0 > [ 6973.776794] R10: 0000000000000008 R11: ffff9b574a602a00 R12: ffff9b5845004ed0 > [ 6973.778096] R13: 0000000000001000 R14: 0000000000000000 R15: 0000000000000000 > [ 6973.779357] FS: 0000000000000000(0000) GS:ffff9b5870000000(0000) > knlGS:0000000000000000 > [ 6973.780757] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 6973.781806] CR2: 0000000000000000 CR3: 0000000043410002 CR4: 00000000007706f0 > [ 6973.783076] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 6973.784313] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 6973.785593] PKRU: 55555554 > [ 6973.786098] Call Trace: > [ 6973.786549] md_end_io_acct+0x31/0x40 > [ 6973.787227] blk_update_request+0x224/0x380 > [ 6973.787994] blk_mq_end_request+0x1a/0x130 > [ 6973.788739] blk_complete_reqs+0x35/0x50 > [ 6973.789456] __do_softirq+0xd7/0x2c8 > [ 6973.790114] ? sort_range+0x20/0x20 > [ 6973.790763] run_ksoftirqd+0x2a/0x40 > [ 6973.791400] smpboot_thread_fn+0xb5/0x150 > [ 6973.792114] kthread+0x10b/0x130 > [ 6973.792724] ? set_kthread_struct+0x50/0x50 > [ 6973.793491] ret_from_fork+0x1f/0x40 > > The reason is that raid0 doesn't do anything in raid0_quiesce. During > the level change in level_store, it needs > to make sure all inflight bios to finish. We can add a count to do > this in raid0. Is it a good way? > > There is a count mddev->active_io in mddev. But it's decreased in > md_handle_request rather than in the callback > endio function. Is it right to decrease active_io in callbcak endio function? > I think it is a race between ios and takeover action, since mddev_suspend called by level_store should ensure no io is submitted to array at that time by below.     wait_event(mddev->sb_wait, atomic_read(&mddev->active_io) == 0) However it can't guarantee new io comes after mddev_suspend because the empty raid0 quiesce.  Maybe we can do something like this. diff --git a/drivers/md/md.c b/drivers/md/md.c index afaf36b2f6ab..0fdc07008bcf 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -3891,6 +3891,7 @@ level_store(struct mddev *mddev, const char *buf, size_t len)         if (rv)                 return rv; +       set_bit(MD_TAKENOVER, &mddev->flags);         if (mddev->pers == NULL) {                 strncpy(mddev->clevel, buf, slen);                 if (mddev->clevel[slen-1] == '\n') @@ -4074,6 +4075,7 @@ level_store(struct mddev *mddev, const char *buf, size_t len)         rv = len;  out_unlock:         mddev_unlock(mddev); +       clear_bit(MD_TAKENOVER, &mddev->flags);         return rv;  } diff --git a/drivers/md/md.h b/drivers/md/md.h index b4e2d8b87b61..e77da3bc6a72 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -255,6 +255,7 @@ struct md_cluster_info;   *                array is ready yet.   * @MD_BROKEN: This is used to stop writes and mark array as failed.   * @MD_DELETED: This device is being deleted + * @MD_TAKENOVER: This device is being taken over to another personality.   *   * change UNSUPPORTED_MDDEV_FLAGS for each array type if new flag is added   */ @@ -272,6 +273,7 @@ enum mddev_flags {         MD_NOT_READY,         MD_BROKEN,         MD_DELETED, +       MD_TAKENOVER,  };  enum mddev_sb_flags { diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c index 78addfe4a0c9..b00ae87c42d3 100644 --- a/drivers/md/raid0.c +++ b/drivers/md/raid0.c @@ -523,6 +523,9 @@ static bool raid0_make_request(struct mddev *mddev, struct bio *bio)         unsigned chunk_sects;         unsigned sectors; +       if (test_bit(MD_TAKENOVER, &mddev->flags)) +               return true; +         if (unlikely(bio->bi_opf & REQ_PREFLUSH)             && md_flush_request(mddev, bio))                 return true; Another way is set mddev->pers to NULL before mddev_suspend in level_store, then move "mddev->pers = pers" after mddev_resume, this way makes md_submit_bio returns earlier. I guess this way is more simple and straightforward. diff --git a/drivers/md/md.c b/drivers/md/md.c index afaf36b2f6ab..5a7134e3c182 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -3979,6 +3979,9 @@ level_store(struct mddev *mddev, const char *buf, size_t len)                 goto out_unlock;         } +       /* Only accept IO after takeover is done */ +       mddev->pers = NULL; +         /* Looks like we have a winner */         mddev_suspend(mddev);         mddev_detach(mddev); @@ -3986,7 +3989,6 @@ level_store(struct mddev *mddev, const char *buf, size_t len)         spin_lock(&mddev->lock);         oldpers = mddev->pers;         oldpriv = mddev->private; -       mddev->pers = pers;         mddev->private = priv;         strscpy(mddev->clevel, pers->name, sizeof(mddev->clevel));         mddev->level = mddev->new_level; @@ -4067,6 +4069,7 @@ level_store(struct mddev *mddev, const char *buf, size_t len)         pers->run(mddev);         set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);         mddev_resume(mddev); +       mddev->pers = pers;         if (!mddev->thread)                 md_update_sb(mddev, 1);         sysfs_notify_dirent_safe(mddev->sysfs_level); Thanks, Guoqing