I've found that NFS access to an exported tmpfs file system hangs
indefinitely when the client first performs a GETATTR. The hanging
nfsd thread is waiting for the inode lock in shmem_getattr():
task:nfsd state:D stack:0 pid:1775 tgid:1775 ppid:2 flags:0x00004000
Call Trace:
<TASK>
__schedule+0x770/0x7b0
schedule+0x33/0x50
schedule_preempt_disabled+0x19/0x30
rwsem_down_read_slowpath+0x206/0x230
down_read+0x3f/0x60
shmem_getattr+0x84/0xf0
vfs_getattr_nosec+0x9e/0xc0
vfs_getattr+0x49/0x50
fh_getattr+0x43/0x50 [nfsd]
fh_fill_pre_attrs+0x4e/0xd0 [nfsd]
nfsd4_open+0x51f/0x910 [nfsd]
nfsd4_proc_compound+0x492/0x5d0 [nfsd]
nfsd_dispatch+0x117/0x1f0 [nfsd]
svc_process_common+0x3b2/0x5e0 [sunrpc]
? __pfx_nfsd_dispatch+0x10/0x10 [nfsd]
svc_process+0xcf/0x130 [sunrpc]
svc_recv+0x64e/0x750 [sunrpc]
? __wake_up_bit+0x4b/0x60
? __pfx_nfsd+0x10/0x10 [nfsd]
nfsd+0xc6/0xf0 [nfsd]
kthread+0xed/0x100
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2e/0x50
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
I bisected the problem to:
d949d1d14fa281ace388b1de978e8f2cd52875cf is the first bad commit
commit d949d1d14fa281ace388b1de978e8f2cd52875cf
Author: Jeongjun Park <aha310510@xxxxxxxxx>
AuthorDate: Mon Sep 9 21:35:58 2024 +0900
Commit: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CommitDate: Mon Oct 28 21:40:39 2024 -0700
mm: shmem: fix data-race in shmem_getattr()
...
Link: https://lkml.kernel.org/r/20240909123558.70229-1-aha310510@xxxxxxxxx
Fixes: 44a30220bc0a ("shmem: recalculate file inode when fstat")
Signed-off-by: Jeongjun Park <aha310510@xxxxxxxxx>
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
which first appeared in v6.12-rc6, and adds the line that is waiting
on the inode lock when my NFS server hangs.
I haven't yet found the process that is holding the inode lock for
this inode.
Because this commit addresses only a KCSAN splat that has been
present since v4.3, and does not address a reported behavioral
issue, I respectfully request that this commit be reverted
immediately so that it does not appear in v6.12 final.
Troubleshooting and testing should continue until a fix to the KCSAN
issue can be found that does not deadlock NFS exports of tmpfs.
--
Chuck Lever
