在 2025/1/27 1:27, Chuck Lever 写道:
On 1/26/25 4:50 AM, Li Lingfeng wrote:
We got -ELOOP from ext4, resulting in the following WARNING:
VFS: Lookup of 'dc' in ext4 sdd would have caused loop
------------[ cut here ]------------
nfsd: non-standard errno: -40
WARNING: CPU: 1 PID: 297024 at fs/nfsd/vfs.c:113 nfserrno+0xc8/0x128
Modules linked in:
CPU: 1 PID: 297024 Comm: nfsd Not tainted 6.6.0-gfa4c2159cd0d-dirty #21
Hardware name: linux,dummy-virt (DT)
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : nfserrno+0xc8/0x128
lr : nfserrno+0xc8/0x128
sp : ffff8000846475a0
x29: ffff8000846475a0 x28: 0000000000000130 x27: ffff0000d65a24e8
x26: ffff0000c7319134 x25: ffff0000d6de4240 x24: 0000000000000002
x23: ffffcda9eaac3080 x22: 00000000ffffffd8 x21: 0000000000000026
x20: ffffcda9ee055000 x19: 0000000000000000 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000001 x12: ffff60001b5ca39b
x11: 1fffe0001b5ca39a x10: ffff60001b5ca39a x9 : dfff800000000000
x8 : 00009fffe4a35c66 x7 : ffff0000dae51cd3 x6 : 0000000000000001
x5 : ffff0000dae51cd0 x4 : ffff60001b5ca39b x3 : dfff800000000000
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000ca5d8040
Call trace:
nfserrno+0xc8/0x128
nfsd4_encode_dirent_fattr+0x358/0x380
nfsd4_encode_dirent+0x164/0x3a8
nfsd_buffered_readdir+0x1a8/0x3a0
nfsd_readdir+0x14c/0x188
nfsd4_encode_readdir+0x1d4/0x370
nfsd4_encode_operation+0x130/0x518
nfsd4_proc_compound+0x394/0xec0
nfsd_dispatch+0x264/0x418
svc_process_common+0x584/0xc78
svc_process+0x1e8/0x2c0
svc_recv+0x194/0x2d0
nfsd+0x198/0x378
kthread+0x1d8/0x1f0
ret_from_fork+0x10/0x20
Kernel panic - not syncing: kernel: panic_on_warn set ...
The ELOOP error in Linux indicates that too many symbolic links were
encountered in resolving a path name. Mapping it to nfserr_symlink
may be
fine.
Signed-off-by: Li Lingfeng <lilingfeng3@xxxxxxxxxx>
---
fs/nfsd/vfs.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 29cb7b812d71..0f727010b8cb 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -100,6 +100,7 @@ nfserrno (int errno)
{ nfserr_perm, -ENOKEY },
{ nfserr_no_grace, -ENOGRACE},
{ nfserr_io, -EBADMSG },
+ { nfserr_symlink, -ELOOP },
};
int i;
Adding ELOOP -> SYMLINK as a generic mapping could be a problem.
RFC 8881 Section 15.2 does not list NFS4ERR_SYMLINK as a permissible
status code for NFSv4 READDIR. Further, Section 15.4 lists only the
following operations for NFS4ERR_SYMLINK:
COMMIT, LAYOUTCOMMIT, LINK, LOCK, LOCKT, LOOKUP, LOOKUPP, OPEN, READ,
WRITE
Which of lookup_positive_unlocked() or nfsd_cross_mnt() returned
ELOOP, and why? What were the export options? What was in the file
system that caused this? Can this scenario be reproduced on v6.13?
Hi,
I got a more detailed log with line numbers from our test team.
VFS: Lookup of 'dc' in ext4 sdd would have caused loop
------------[ cut here ]------------
nfsd: non-standard errno: -40
WARNING: CPU: 1 PID: 297024 at fs/nfsd/vfs.c:113 nfserrno
fs/nfsd/vfs.c:113 [inline]
WARNING: CPU: 1 PID: 297024 at fs/nfsd/vfs.c:113 nfserrno+0xc8/0x128
fs/nfsd/vfs.c:61
Modules linked in:
CPU: 1 PID: 297024 Comm: nfsd Not tainted 6.6.0-gfa4c2159cd0d-dirty #21
Hardware name: linux,dummy-virt (DT)
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : nfserrno fs/nfsd/vfs.c:113 [inline]
pc : nfserrno+0xc8/0x128 fs/nfsd/vfs.c:61
lr : nfserrno fs/nfsd/vfs.c:113 [inline]
lr : nfserrno+0xc8/0x128 fs/nfsd/vfs.c:61
sp : ffff8000846475a0
x29: ffff8000846475a0 x28: 0000000000000130 x27: ffff0000d65a24e8
x26: ffff0000c7319134 x25: ffff0000d6de4240 x24: 0000000000000002
x23: ffffcda9eaac3080 x22: 00000000ffffffd8 x21: 0000000000000026
x20: ffffcda9ee055000 x19: 0000000000000000 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000001 x12: ffff60001b5ca39b
x11: 1fffe0001b5ca39a x10: ffff60001b5ca39a x9 : dfff800000000000
x8 : 00009fffe4a35c66 x7 : ffff0000dae51cd3 x6 : 0000000000000001
x5 : ffff0000dae51cd0 x4 : ffff60001b5ca39b x3 : dfff800000000000
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000ca5d8040
Call trace:
nfserrno fs/nfsd/vfs.c:113 [inline]
nfserrno+0xc8/0x128 fs/nfsd/vfs.c:61
nfsd4_encode_dirent_fattr+0x358/0x380 fs/nfsd/nfs4xdr.c:3536
nfsd4_encode_dirent+0x164/0x3a8 fs/nfsd/nfs4xdr.c:3633
nfsd_buffered_readdir+0x1a8/0x3a0 fs/nfsd/vfs.c:2067
nfsd_readdir+0x14c/0x188 fs/nfsd/vfs.c:2123
nfsd4_encode_readdir+0x1d4/0x370 fs/nfsd/nfs4xdr.c:4273
nfsd4_encode_operation+0x130/0x518 fs/nfsd/nfs4xdr.c:5399
nfsd4_proc_compound+0x394/0xec0 fs/nfsd/nfs4proc.c:2753
nfsd_dispatch+0x264/0x418 fs/nfsd/nfssvc.c:1011
svc_process_common+0x584/0xc78 net/sunrpc/svc.c:1396
svc_process+0x1e8/0x2c0 net/sunrpc/svc.c:1542
svc_recv+0x194/0x2d0 net/sunrpc/svc_xprt.c:877
nfsd+0x198/0x378 fs/nfsd/nfssvc.c:955
kthread+0x1d8/0x1f0 kernel/kthread.c:388
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:861
Although I don't have a reproducer to reproduce this problem, I think
ELOOP should be returned by the following path:
v6.6
nfsd4_encode_readdir
nfsd_readdir
nfsd_buffered_readdir
nfsd4_encode_dirent // func
nfsd4_encode_dirent_fattr
nfsd4_encode_dirent_fattr
lookup_positive_unlocked
lookup_one_positive_unlocked
lookup_one_unlocked // ELOOP
lookup_slow
__lookup_slow
ext4_lookup // inode->i_op->lookup
d_splice_alias
// VFS: Lookup of 'dc' in ext4 sdd would have caused loop
This scenario may be reproduced on v6.13 like this:
nfsd4_encode_readdir
nfsd4_encode_dirlist4
nfsd_readdir
nfsd_buffered_readdir
nfsd4_encode_entry4 // func
nfsd4_encode_entry4_fattr
lookup_positive_unlocked
lookup_one_positive_unlocked
lookup_one_unlocked
lookup_slow
__lookup_slow
ext4_lookup // inode->i_op->lookup
d_splice_alias
According to the information provided by the test team, the export option
is "rw,no_root_squash", and I'll try to reproduce the problem.
By the way, could you suggest which NFS error code would be most
appropriate to map ELOOP to?
Thanks.
