On Fri, 2022-09-09 at 16:47 +0000, Trond Myklebust wrote: > This looks like it might be the root cause issue. It looks like > you're using pNFS: > > /proc/3278822/stack: > [<0>] pnfs_update_layout+0x603/0xed0 [nfsv4] > [<0>] fl_pnfs_update_layout.constprop.18+0x23/0x1e0 > [nfs_layout_nfsv41_files] > [<0>] filelayout_pg_init_write+0x3a/0x70 [nfs_layout_nfsv41_files] > [<0>] __nfs_pageio_add_request+0x294/0x470 [nfs] > [<0>] nfs_pageio_add_request_mirror+0x2f/0x40 [nfs] > [<0>] nfs_pageio_add_request+0x200/0x2d0 [nfs] > [<0>] nfs_page_async_flush+0x120/0x310 [nfs] > [<0>] nfs_writepages_callback+0x5b/0xc0 [nfs] > [<0>] write_cache_pages+0x187/0x4d0 > [<0>] nfs_writepages+0xe1/0x200 [nfs] > [<0>] do_writepages+0xd2/0x1b0 > [<0>] __writeback_single_inode+0x41/0x360 > [<0>] writeback_sb_inodes+0x1f0/0x460 > [<0>] __writeback_inodes_wb+0x5f/0xd0 > [<0>] wb_writeback+0x235/0x2d0 > [<0>] wb_workfn+0x312/0x4a0 > [<0>] process_one_work+0x1c5/0x390 > [<0>] worker_thread+0x30/0x360 > [<0>] kthread+0xd7/0x100 > [<0>] ret_from_fork+0x1f/0x30 > > What is the pNFS server you are running against? I see you're using > the files pNFS layout type, so is this a NetApp? > Sorry for the HTML spam... Resending with all that crap stripped out. > From: Igor Raits <igor@xxxxxxxxxxxx> > Sent: Friday, September 9, 2022 11:09 > To: Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> > Cc: anna@xxxxxxxxxx <anna@xxxxxxxxxx>; linux-nfs@xxxxxxxxxxxxxxx > <linux-nfs@xxxxxxxxxxxxxxx> > Subject: Re: Regression: deadlock in io_schedule / > nfs_writepage_locked > > Hello Trond, > > On Mon, Aug 22, 2022 at 5:01 PM Trond Myklebust > <trondmy@xxxxxxxxxxxxxxx> wrote: > > > > On Mon, 2022-08-22 at 16:43 +0200, Igor Raits wrote: > > > [You don't often get email from igor@xxxxxxxxxxxx. Learn why this > > > is > > > important at https://aka.ms/LearnAboutSenderIdentification ] > > > > > > Hello Trond, > > > > > > On Mon, Aug 22, 2022 at 4:02 PM Trond Myklebust > > > <trondmy@xxxxxxxxxxxxxxx> wrote: > > > > > > > > On Mon, 2022-08-22 at 10:16 +0200, Igor Raits wrote: > > > > > [You don't often get email from igor@xxxxxxxxxxxx. Learn why > > > > > this > > > > > is > > > > > important at https://aka.ms/LearnAboutSenderIdentification ] > > > > > > > > > > Hello everyone, > > > > > > > > > > Hopefully I'm sending this to the right place… > > > > > We recently started to see the following stacktrace quite > > > > > often > > > > > on > > > > > our > > > > > VMs that are using NFS extensively (I think after upgrading > > > > > to > > > > > 5.18.11+, but not sure when exactly. For sure it happens on > > > > > 5.18.15): > > > > > > > > > > INFO: task kworker/u36:10:377691 blocked for more than 122 > > > > > seconds. > > > > > Tainted: G E 5.18.15-1.gdc.el8.x86_64 #1 > > > > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables > > > > > this > > > > > message. > > > > > task:kworker/u36:10 state:D stack: 0 pid:377691 ppid: > > > > > 2 > > > > > flags:0x00004000 > > > > > Workqueue: writeback wb_workfn (flush-0:308) > > > > > Call Trace: > > > > > <TASK> > > > > > __schedule+0x38c/0x7d0 > > > > > schedule+0x41/0xb0 > > > > > io_schedule+0x12/0x40 > > > > > __folio_lock+0x110/0x260 > > > > > ? filemap_alloc_folio+0x90/0x90 > > > > > write_cache_pages+0x1e3/0x4d0 > > > > > ? nfs_writepage_locked+0x1d0/0x1d0 [nfs] > > > > > nfs_writepages+0xe1/0x200 [nfs] > > > > > do_writepages+0xd2/0x1b0 > > > > > ? check_preempt_curr+0x47/0x70 > > > > > ? ttwu_do_wakeup+0x17/0x180 > > > > > __writeback_single_inode+0x41/0x360 > > > > > writeback_sb_inodes+0x1f0/0x460 > > > > > __writeback_inodes_wb+0x5f/0xd0 > > > > > wb_writeback+0x235/0x2d0 > > > > > wb_workfn+0x348/0x4a0 > > > > > ? put_prev_task_fair+0x1b/0x30 > > > > > ? pick_next_task+0x84/0x940 > > > > > ? __update_idle_core+0x1b/0xb0 > > > > > process_one_work+0x1c5/0x390 > > > > > worker_thread+0x30/0x360 > > > > > ? process_one_work+0x390/0x390 > > > > > kthread+0xd7/0x100 > > > > > ? kthread_complete_and_exit+0x20/0x20 > > > > > ret_from_fork+0x1f/0x30 > > > > > </TASK> > > > > > > > > > > I see that something very similar was fixed in btrfs > > > > > ( > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commi > > > > > t/?h=linux- > > > > > 5.18.y&id=9535ec371d741fa037e37eddc0a5b25ba82d0027) > > > > > but I could not find anything similar for NFS. > > > > > > > > > > Do you happen to know if this is already fixed? If so, would > > > > > you > > > > > mind > > > > > sharing some commits? If not, could you help getting this > > > > > addressed? > > > > > > > > > > > > > The stack trace you show above isn't particularly helpful for > > > > diagnosing what the problem is. > > > > > > > > All it is saying is that 'thread A' is waiting to take a page > > > > lock > > > > that > > > > is being held by a different 'thread B'. Without information on > > > > what > > > > 'thread B' is doing, and why it isn't releasing the lock, there > > > > is > > > > nothing we can conclude. > > > > > > Do you have some hint how to debug this issue further (when it > > > happens > > > again)? Would `virsh dump` to get a memory dump and then some > > > kind of > > > "bt all" via crash help to get more information? > > > Or something else? > > > > > > Thanks in advance! > > > -- > > > Igor Raits > > > > Please try running the following two lines of 'bash' script as > > root: > > > > (for tt in $(grep -l 'nfs[^d]' /proc/*/stack); do echo "${tt}:"; > > cat ${tt}; echo; done) >/tmp/nfs_threads.txt > > > > cat /sys/kernel/debug/sunrpc/rpc_clnt/*/tasks > /tmp/rpc_tasks.txt > > > > and then send us the output from the two files /tmp/nfs_threads.txt > > and > > /tmp/rpc_tasks.txt. > > > > The file nfs_threads.txt gives us a full set of stack traces from > > all > > processes that are currently in the NFS client code. So it should > > contain both the stack trace from your 'thread A' above, and the > > traces > > from all candidates for the 'thread B' process that is causing the > > blockage. > > The file rpc_tasks.txt gives us the status of any RPC calls that > > might > > be outstanding and might help diagnose any issues with the TCP > > connection. > > > > That should therefore give us a better starting point for root > > causing > > the problem. > > The rpc_tasks is empty but I got nfs_threads from the moment it is > stuck (see attached file). > > It still happens with 5.19.3, 5.19.6. -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@xxxxxxxxxxxxxxx
