Hello, We have a new Dell EMC Unity 300 acting as NAS Server that is presenting a NFSv4 NFS Share. Our clients are mostly Ubuntu 18.04.3 but issue is also present on CentOS 7.6 systems. We have been struggling with this issue for over a week now and not sure how to resolve it. We are having trouble with NFS Clients completing their writes to the Dell EMC Unity 300 NFS Server when Kerberos is enabled on the NFS Share. I created the NFS Share on the U300, associated it with our FreeIPA (Kerberos/LDAP server) and everything shows successful. I can mount the share without a problem on multiple Ubuntu/CentOS machines without issues. I can ls around and move around on the share without issue (seemingly). I can copy files as well and that seem to work (haven’t tested it extensively as I have been heavily focused on this issue). However, clients won't complete their writes to the NFS share randomly once the file gets to > 2GB or so in file size. _sometimes_ they do, but I would say anything > 3GB, the client locks up and won’t ever return 80% of the time I try it. For example, I can run dd and write ten 1MB files to the NFS share no issues, all back to back to back. However, when I try to do a single 3GB file, it _might_ or might not finish. If it doesn’t finish it just locks up the client. Sometimes it will finish though so its random. However, I would say 70-80% of the time it is reproducible with files > 3GB or so. Here is some information on the client and what I’m doing to reproduce the issue. I have tried krb5, and krb5p with the same results. Removing the requirement for krb5 in the NFS server and mounting with sec=none, I don’t seem to hit the issue. $uname -a 5.0.0-27-generic #28~18.04.1-Ubuntu SMP Thu Aug 22 03:00:32 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux $mount nfs-server.example.com:/ds1 on /data type nfs4 (rw,relatime,vers=4.1,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=krb5p,clientaddr=10.75.40.254,local_lock=none,addr=10.75.37.2) $ dd if=/dev/zero of=/data/test.img count=1000 bs=1000 1000+0 records in 1000+0 records out 1000000 bytes (1.0 MB, 977 KiB) copied, 0.00613671 s, 163 MB/s $ dd if=/dev/zero of=/data/test.img bs=1000M count=6 ---- HUNG ---- After it hangs it will NEVER return. The only way I've been able to get the client to return is to go into the U300 Control panel and change the "SP Owner:" from SPA to SPB (effectively restarting the NFS server). Once that happens the client returns. If I disable Kerberos on the NFS Share I have no problems writing larger files it seems. I did some straces of the dd and this is what I saw. This was a successful write…. $ strace dd if=/dev/zero of=/data/test3.img bs=100M count=1 execve("/bin/dd", ["dd", "if=/dev/zero", "of=/data/test3.img", "bs=100M", "count=1"], 0x7fff8c03c7f0 /* 21 vars */) = 0 brk(NULL) = 0x559b8b39a000 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=93482, ...}) = 0 mmap(NULL, 93482, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f62b6180000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260\34\2\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0755, st_size=2030544, ...}) = 0 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f62b617e000 mmap(NULL, 4131552, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f62b5b7f000 mprotect(0x7f62b5d66000, 2097152, PROT_NONE) = 0 mmap(0x7f62b5f66000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f62b5f66000 mmap(0x7f62b5f6c000, 15072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f62b5f6c000 close(3) = 0 arch_prctl(ARCH_SET_FS, 0x7f62b617f540) = 0 mprotect(0x7f62b5f66000, 16384, PROT_READ) = 0 mprotect(0x559b8978b000, 4096, PROT_READ) = 0 mprotect(0x7f62b6197000, 4096, PROT_READ) = 0 munmap(0x7f62b6180000, 93482) = 0 rt_sigaction(SIGINT, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0 rt_sigaction(SIGUSR1, {sa_handler=0x559b8957e0e0, sa_mask=[INT USR1], sa_flags=SA_RESTORER, sa_restorer=0x7f62b5bbdf20}, NULL, 8) = 0 rt_sigaction(SIGINT, {sa_handler=0x559b8957e0d0, sa_mask=[INT USR1], sa_flags=SA_RESTORER|SA_NODEFER|SA_RESETHAND, sa_restorer=0x7f62b5bbdf20}, NULL, 8) = 0 brk(NULL) = 0x559b8b39a000 brk(0x559b8b3bb000) = 0x559b8b3bb000 openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=4326016, ...}) = 0 mmap(NULL, 4326016, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f62b575e000 close(3) = 0 openat(AT_FDCWD, "/dev/zero", O_RDONLY) = 3 dup2(3, 0) = 0 close(3) = 0 lseek(0, 0, SEEK_CUR) = 0 openat(AT_FDCWD, "/data/test3.img", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3 dup2(3, 1) = 1 close(3) = 0 mmap(NULL, 104869888, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f62af35b000 read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 104857600) = 104857600 write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 104857600) = 104857600 close(0) = 0 close(1) = 0 openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 0 fstat(0, {st_mode=S_IFREG|0644, st_size=2995, ...}) = 0 read(0, "# Locale name alias data base.\n#"..., 4096) = 2995 read(0, "", 4096) = 0 close(0) = 0 openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale-langpack/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale-langpack/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale-langpack/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale-langpack/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale-langpack/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = 0 fstat(0, {st_mode=S_IFREG|0644, st_size=578, ...}) = 0 mmap(NULL, 578, PROT_READ, MAP_PRIVATE, 0, 0) = 0x7f62b6196000 close(0) = 0 write(2, "1+0 records in\n1+0 records out\n", 311+0 records in 1+0 records out ) = 31 write(2, "104857600 bytes (105 MB, 100 MiB"..., 61104857600 bytes (105 MB, 100 MiB) copied, 1.01552 s, 103 MB/s) = 61 write(2, "\n", 1 ) = 1 close(2) = 0 exit_group(0) = ? +++ exited with 0 +++ This one was unsuccessful write and hung until I restarted the NFS server. strace -f dd if=/dev/zero of=/data/test.img bs=1000M count=6 execve("/bin/dd", ["dd", "if=/dev/zero", "of=/data/test.img", "bs=1000M", "count=6"], 0x7ffc8ee7e8b8 /* 30 vars */) = 0 brk(NULL) = 0x5648bd26a000 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=125550, ...}) = 0 mmap(NULL, 125550, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f4f8dda1000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260\34\2\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0755, st_size=2030544, ...}) = 0 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f4f8dd9f000 mmap(NULL, 4131552, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f4f8d7a8000 mprotect(0x7f4f8d98f000, 2097152, PROT_NONE) = 0 mmap(0x7f4f8db8f000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f4f8db8f000 mmap(0x7f4f8db95000, 15072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f4f8db95000 close(3) = 0 arch_prctl(ARCH_SET_FS, 0x7f4f8dda0540) = 0 mprotect(0x7f4f8db8f000, 16384, PROT_READ) = 0 mprotect(0x5648bb739000, 4096, PROT_READ) = 0 mprotect(0x7f4f8ddc0000, 4096, PROT_READ) = 0 munmap(0x7f4f8dda1000, 125550) = 0 rt_sigaction(SIGINT, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0 rt_sigaction(SIGUSR1, {sa_handler=0x5648bb52c0e0, sa_mask=[INT USR1], sa_flags=SA_RESTORER, sa_restorer=0x7f4f8d7e6f20}, NULL, 8) = 0 rt_sigaction(SIGINT, {sa_handler=0x5648bb52c0d0, sa_mask=[INT USR1], sa_flags=SA_RESTORER|SA_NODEFER|SA_RESETHAND, sa_restorer=0x7f4f8d7e6f20}, NULL, 8) = 0 brk(NULL) = 0x5648bd26a000 brk(0x5648bd28b000) = 0x5648bd28b000 openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=11603728, ...}) = 0 mmap(NULL, 11603728, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f4f8cc97000 close(3) = 0 openat(AT_FDCWD, "/dev/zero", O_RDONLY) = 3 dup2(3, 0) = 0 close(3) = 0 lseek(0, 0, SEEK_CUR) = 0 openat(AT_FDCWD, "/data/test.img", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3 dup2(3, 1) = 1 close(3) = 0 mmap(NULL, 1048588288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f4f4e494000 read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 read(0, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 write(1, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1048576000) = 1048576000 close(0) = 0 close(1 I did some packet tracing and on the smaller writes, I would see a bunch of writes and replies to those writes, the client would COMMIT and then NFS server would reply with an ack COMMIT, client would then issue a CLOSE, and server would respond with a CLOSE. However, on larger writes where it would hang it would do…client would do a bunch of writes packets, NFS server would respond to the write packets, client would issue a COMMIT command, server would respond with a COMMIT, and then nothing else would happen. No CLOSE would seemingly be sent from the client, so I don’t know if the client was waiting on the server to send back some type of message saying that the system could issue a CLOSE or the client was never sending a CLOSE. Once it is in the locked state, if I restart the NFS server as I mentioned above the close(1…will continue and finish the write and exit normally. I did a kernel Stack Traceback on the NFS client (the light weight version of just printing out /proc/*/wchan) while the dd command was stuck in the “close(1” and the process for the dd command just says. Process /proc/32161/wchan ep_poll I also enabled the NFS debugging and while its stuck it just keep repeating the bottom section. Sep 19 06:25:19 examplehost kernel: [772614.270750] NFS: commit (0:52/9439 4096@4609744896) OK Sep 19 06:25:19 examplehost kernel: [772614.270751] NFS: commit (0:52/9439 4096@4609748992) OK Sep 19 06:25:19 examplehost kernel: [772614.270754] NFS: commit (0:52/9439 4096@4609753088) OK Sep 19 06:25:19 examplehost kernel: [772614.270757] NFS: commit (0:52/9439 4096@4609757184) OK Sep 19 06:25:19 examplehost kernel: [772614.270759] NFS: commit (0:52/9439 4096@4609761280) OK Sep 19 06:25:19 examplehost kernel: [772614.270761] NFS: commit (0:52/9439 4096@4609765376) OK Sep 19 06:25:19 examplehost kernel: [772614.270763] NFS: commit (0:52/9439 4096@4609769472) OK Sep 19 06:25:19 examplehost kernel: [772614.270767] NFS: commit (0:52/9439 4096@4609773568) OK Sep 19 06:25:19 examplehost kernel: [772614.270769] NFS: commit (0:52/9439 4096@4609777664) OK Sep 19 06:25:19 examplehost kernel: [772614.270772] NFS: commit (0:52/9439 4096@4609781760) OK Sep 19 06:25:19 examplehost kernel: [772614.270773] NFS: commit (0:52/9439 4096@4609785856) OK Sep 19 06:25:19 examplehost kernel: [772614.270775] NFS: commit (0:52/9439 4096@4609789952) OK Sep 19 06:25:19 examplehost kernel: [772614.270777] NFS: commit (0:52/9439 4096@4609794048) OK Sep 19 06:25:19 examplehost kernel: [772614.270781] NFS: commit (0:52/9439 4096@4609798144) OK Sep 19 06:25:31 examplehost kernel: [772626.175927] <-- nfs41_proc_async_sequence status=0 Sep 19 06:25:31 examplehost kernel: [772626.176018] encode_sequence: sessionid=61:1568410703:305419896:61 seqid=2907 slotid=0 max_slotid=35 cache_this=0 Sep 19 06:25:31 examplehost kernel: [772626.176572] nfs41_sequence_process: Error 0 free the slot Sep 19 06:25:31 examplehost kernel: [772626.176576] nfs41_sequence_call_done rpc_cred 000000004b01718a Sep 19 06:25:31 examplehost kernel: [772626.176577] <-- nfs41_sequence_call_done Sep 19 06:25:43 examplehost kernel: [772638.207976] <-- nfs41_proc_async_sequence status=0 Sep 19 06:25:43 examplehost kernel: [772638.208074] encode_sequence: sessionid=61:1568410703:305419896:61 seqid=2908 slotid=0 max_slotid=35 cache_this=0 Sep 19 06:25:43 examplehost kernel: [772638.208642] nfs41_sequence_process: Error 0 free the slot Sep 19 06:25:43 examplehost kernel: [772638.208646] nfs41_sequence_call_done rpc_cred 000000004b01718a Sep 19 06:25:43 examplehost kernel: [772638.208648] <-- nfs41_sequence_call_done Sep 19 06:25:55 examplehost kernel: [772650.240046] <-- nfs41_proc_async_sequence status=0 Sep 19 06:25:55 examplehost kernel: [772650.240129] encode_sequence: sessionid=61:1568410703:305419896:61 seqid=2909 slotid=0 max_slotid=35 cache_this=0 Sep 19 06:25:55 examplehost kernel: [772650.240904] nfs41_sequence_process: Error 0 free the slot Sep 19 06:25:55 examplehost kernel: [772650.240908] nfs41_sequence_call_done rpc_cred 000000004b01718a Sep 19 06:25:55 examplehost kernel: [772650.240909] <-- nfs41_sequence_call_done On a small file that actually completes it looks like this… Sep 19 06:13:29 examplehost kernel: [771904.532059] NFS: commit (0:52/9439 4096@7409315840) OK Sep 19 06:13:29 examplehost kernel: [771904.532061] NFS: commit (0:52/9439 4096@7409319936) OK Sep 19 06:13:29 examplehost kernel: [771904.532064] NFS: commit (0:52/9439 4096@7409324032) OK Sep 19 06:13:29 examplehost kernel: [771904.532066] NFS: commit (0:52/9439 4096@7409328128) OK Sep 19 06:13:29 examplehost kernel: [771904.532069] NFS: commit (0:52/9439 4096@7409332224) OK Sep 19 06:13:29 examplehost kernel: [771904.532071] NFS: commit (0:52/9439 4096@7409336320) OK Sep 19 06:13:29 examplehost kernel: [771904.532073] NFS: commit (0:52/9439 4096@7409340416) OK Sep 19 06:13:29 examplehost kernel: [771904.532076] NFS: commit (0:52/9439 4096@7409344512) OK Sep 19 06:13:29 examplehost kernel: [771904.532078] NFS: commit (0:52/9439 4096@7409348608) OK Sep 19 06:13:29 examplehost kernel: [771904.532081] NFS: commit (0:52/9439 4096@7409352704) OK Sep 19 06:13:29 examplehost kernel: [771904.532083] NFS: commit (0:52/9439 4096@7409356800) OK Sep 19 06:13:29 examplehost kernel: [771904.532086] NFS: commit (0:52/9439 4096@7409360896) OK Sep 19 06:13:29 examplehost kernel: [771904.532088] NFS: commit (0:52/9439 4096@7409364992) OK Sep 19 06:13:29 examplehost kernel: [771904.532090] NFS: commit (0:52/9439 4096@7409369088) OK Sep 19 06:13:29 examplehost kernel: [771904.532093] NFS: commit (0:52/9439 4096@7409373184) OK Sep 19 06:13:29 examplehost kernel: [771904.532171] NFS: release(/test.img) Sep 19 06:13:29 examplehost kernel: [771904.532193] nfs4_close_prepare: begin! Sep 19 06:13:29 examplehost kernel: [771904.532197] nfs4_close_prepare: done! Sep 19 06:13:29 examplehost kernel: [771904.532235] encode_sequence: sessionid=61:1568410703:305419896:61 seqid=6 slotid=0 max_slotid=0 cache_this=1 Sep 19 06:13:29 examplehost kernel: [771904.532525] nfs4_close_done: begin! Sep 19 06:13:29 examplehost kernel: [771904.532528] nfs41_sequence_process: Error 0 free the slot Sep 19 06:13:29 examplehost kernel: [771904.532531] nfs4_close_done: done, ret = 0! Sep 19 06:13:29 examplehost kernel: [771904.532555] NFS: dentry_delete(/test.img, 48084c) Sep 19 06:13:41 examplehost kernel: [771916.540491] <-- nfs41_proc_async_sequence status=0 Sep 19 06:13:41 examplehost kernel: [771916.540586] encode_sequence: sessionid=61:1568410703:305419896:61 seqid=7 slotid=0 max_slotid=0 cache_this=0 Sep 19 06:13:41 examplehost kernel: [771916.541182] nfs41_sequence_process: Error 0 free the slot Sep 19 06:13:41 examplehost kernel: [771916.541186] nfs41_sequence_call_done rpc_cred 000000004b01718a Sep 19 06:13:41 examplehost kernel: [771916.541187] <-- nfs41_sequence_call_done Sep 19 06:13:53 examplehost kernel: [771928.572599] <-- nfs41_proc_async_sequence status=0 Sep 19 06:13:53 examplehost kernel: [771928.572675] encode_sequence: sessionid=61:1568410703:305419896:61 seqid=8 slotid=0 max_slotid=0 cache_this=0 Sep 19 06:13:53 examplehost kernel: [771928.572895] encode_sequence: sessionid=61:1568410703:305419896:61 seqid=2 slotid=1 max_slotid=1 cache_this=1 Sep 19 06:13:53 examplehost kernel: [771928.573163] nfs41_sequence_process: Error 0 free the slot Sep 19 06:13:53 examplehost kernel: [771928.573166] nfs41_sequence_call_done rpc_cred 000000004b01718a Sep 19 06:13:53 examplehost kernel: [771928.573167] <-- nfs41_sequence_call_done Sep 19 06:13:53 examplehost kernel: [771928.573236] decode_attr_type: type=00 Sep 19 06:13:53 examplehost kernel: [771928.573238] decode_attr_change: change attribute=6738121685800950864 Sep 19 06:13:53 examplehost kernel: [771928.573240] decode_attr_size: file size=8388608000 Sep 19 06:13:53 examplehost kernel: [771928.573242] decode_attr_fsid: fsid=(0x0/0x0) Sep 19 06:13:53 examplehost kernel: [771928.573243] decode_attr_fileid: fileid=0 Sep 19 06:13:53 examplehost kernel: [771928.573245] decode_attr_fs_locations: fs_locations done, error = 0 Sep 19 06:13:53 examplehost kernel: [771928.573246] decode_attr_mode: file mode=00 As you can see the NFS: release(/test.img) is immediately after all of the writes on the successful version. In the version that gets stuck it never responds with that “release”. It’s hard for me to do any debugging on the NFS Server sinces its more of a “managed” box (e.g I don’t have root and only have access to certain debugging utilities). I do have a ticket open with Dell and their engineering team is looking at this but I’m trying anything I can do to figure this out as soon as I can. Any help on this matter would be appreciated.