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X-MS-Exchange-CrossTenant-Id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: d5C3k8MgiOA8DVX9mRFtZporNfsP9nsQuuQiKXkXH21SjYnw96XV4kWSYIDQihhcNDFxYDuBdpNBg4GK9kADW9EDmSWFV3OsTXuFP4g4qMk= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR04MB8291 On Aug 25, 2026 / 16:27, Eric Dumazet wrote: > On Tue, Aug 25, 2026 at 3:53 PM Eric Dumazet wrote: > > > > On Tue, Aug 25, 2026 at 3:26 PM Shin'ichiro Kawasaki > > wrote: > > > > > > On Aug 25, 2026 / 14:45, Hillf Danton wrote: > > > > On Tue, 25 Aug 2026 14:44:35 +0900 Shin'ichiro Kawasaki wrote: > > > > > On Aug 25, 2026 / 03:50, Eric Dumazet wrote: > > > > > > > > > > > > I think 19bdb70c77d3 should be reverted. > > > > > > > > > > Just reverting the commit will reintroduce the other lockdep WARN that the > > > > > commit addressed. I hope to have another fix to avoid the WARN. > > > > > > > > > I do not think you know the root cause of that lockdep warn, so reverting > > > > 19bdb70c77d3 is the right thing to do because of [11, 12]. > > > > > > > > [11] ffa1e7ada456 ("block: Make request_queue lockdep splats show up earlier") > > > > [12] Subject: Re: [PATCH] nbd: don't warn when reclassifying a busy socket lock > > > > https://lore.kernel.org/lkml/20260816014906.1149-1-hdanton@sina.com/ > > > > > > I took a look in the commit [11] and the discussion [12], but couldn't follow > > > why the commit 19bdb70c77d3 should be reverted. Could you elaborate a bit more > > > about the reason you suggest the revert? > > > > I think you missed one problem in lib/once.c > > > > Revert commit e8eef69a99f1 (or restore once_disable_jump(once_key, > > mod) inside __do_once_sleepable_done()) > > so static_branch_disable() is never called synchronously under caller locks. > > > > Previously, once_disable_jump() deferred static_branch_disable() to a > > worker thread via schedule_work(). > > > > Commit e8eef69a99f1 made it run synchronously in the caller's context. > > Because __inet_hash_connect() is called under lock_sock(sk), calling > > static_branch_disable() directly inside DO_ONCE_SLEEPABLE() takes > > cpus_read_lock() (cpu_hotplug_lock) while holding lock_sock(sk). > > > > This created the bogus lock dependency sk_lock -> cpu_hotplug_lock. > > > > Every other storage/networking client (sunrpc, nbd, cifs, iscsi_tcp, > > rxe, siw) uses static lockdep keys (static struct lock_class_key > > ...[2]) without issue. > > I sent the revert request for review : > https://lore.kernel.org/lkml/20260825142515.1965654-1-edumazet@google.com/T/#u Thank you for the clarification. Now I have better understanding. When I looked at the lock dependency chain among six locks below, I assumed that any of the dependencies could not be cut. set->srcu -> sk_lock -> cpu_hotplug_lock -> fs_reclaim -> q_usage_counter -> elevator_lock -> set->srcu So I thought that the idea to introduce the dynamic lockdep key for nvme-tcp sk_lock instances would be the only one solution. But you pointed out that the dependency sk_lock -> cpu_hotplug_lock can be cut by reverting the commit e8eef69a99f1. I did trial and confirmed that your suggestion works. With the kerenl v7.2 + revert 19bdb70c77d3 + revert e8eef69a99f1, I confirmed the blktests test case nvme/005 passed with tcp transport. The lockdep WARN due to the six locks goes away. Great :) Assuming e8eef69a99f1 will be reverted, I agree to revert 19bdb70c77d3 also. > > > > > Use my pending TCP patch, which is a no brainer : > > https://lore.kernel.org/netdev/20260825023614.1228551-1-edumazet@google.com/ IIUC, this patch uses GFP_ATOMIC to cut the dependency sk_lock -> fs_reclaim. I did another trial: using the kerenl v7.2 + revert 19bdb70c77d3 + the TCP patch "tcp: use GFP_ATOMIC in tcp_send_active_reset()", I still observed the blktests test case nvme/005 failed with the lockdep WARN due to the six locks. Hmm. The TCP patch cuts the direct dependency sk_lock -> fs_reclaim, but the depdency chain I face has indirect dependency between sk_lock and fs_reclaim: ... sk_lock -> cpu_hotplug_lock -> fs_reclaim ... I think this explains why the TCP patch does not fix the lockdep WARN due to the six locks. > > > > Revert 19bdb70c77d3 in drivers/nvme/host/tcp.c : Restore static > > lockdep keys nvme_tcp_sk_key[2] and nvme_tcp_slock_key[2]. > > > > And we should be good. > > > > If you think each nvme-tcp socket MUST have its own LOCKDEP class, > > please elaborate, because I have no idea > > why this would be needed. As I noted above, if e8eef69a99f1 will be reverted, I do not have reason to make nvme-tcp socket have its owy dynamic lockdep key and class. Let me wait and see how the e8eef69a99f1 revert patch will go. If it goes well, I will send out the patch to revert 19bdb70c77d3.