NFSv4: handle EINVAL from EXCHANGE_ID better.
Subsystems (2)
PATCH 1/1 NFSv4: handle EINVAL from EXCHANGE_ID better.
nfs4_proc_exchange_id() can return -EINVAL if the server reported NFS4INVAL (which I have seen in a packet trace), or nfs4_check_cl_exchange_flags() exchange flags detects a problem.
Each of these mean that NFSv4.1 later cannot be use, but they should not prevent fallback to NFSv4.0.
Currently this EINVAL error is returned by nfs4_proc_exchange_id() to nfs41_discover_server_trunking(), and thence to nfs4_discover_server_trunking(). nfs4_discover_server_trunking() doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.
It would be a more graceful failure if nfs4_discover_server_trunking() mapped -EINVAL to -EPROTONOSUPPORT - a failure to negotiate a client ID clearly shows that NFSv4.1 cannot be supported, but isn't as general a failure as EIO.
--- fs/nfs/nfs4state.c | 2 ++ 1 file changed, 2 insertions(+)
fs/nfs/nfs4state.c +2 -0
@@ -2219,6 +2219,8 @@ int nfs4_discover_server_trunking(struct nfs_client *clp, clnt = clp->cl_rpcclient; goto again; +case -NFS4INVAL : +/* Server confused - assume this minor isn't supported */ case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break ;
Signature · 1 line
2.14.0.rc0.dirty
PATCH v2 1/1 NFSv4: handle EINVAL from EXCHANGE_ID better.
nfs4_proc_exchange_id() can return -EINVAL if the server reported NFS4INVAL (which I have seen in a packet trace), or nfs4_check_cl_exchange_flags() exchange flags detects a problem.
Each of these mean that NFSv4.1 later cannot be use, but they should not prevent fallback to NFSv4.0.
Currently this EINVAL error is returned by nfs4_proc_exchange_id() to nfs41_discover_server_trunking(), and thence to nfs4_discover_server_trunking(). nfs4_discover_server_trunking() doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.
It would be a more graceful failure if nfs4_discover_server_trunking() mapped -EINVAL to -EPROTONOSUPPORT - a failure to negotiate a client ID clearly shows that NFSv4.1 cannot be supported, but isn't as general a failure as EIO.
---
Sorry - a bit too trigger-happy with that first version of the patch.
NeilBrown
fs/nfs/nfs4state.c | 2 ++ 1 file changed, 2 insertions(+)
fs/nfs/nfs4state.c +2 -0
@@ -2219,6 +2219,8 @@ int nfs4_discover_server_trunking(struct nfs_client *clp, clnt = clp->cl_rpcclient; goto again; +case -NFS4ERR_INVAL : +/* Server confused - assume this minor isn't supported */ case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break ;
Signature · 1 line
2.14.0.rc0.dirty
Hi Neil,
according to rfc5661, NFS4ERR_INVAL is returned by the server if it thinks that client sends an invalid request (e.g. points to a client bug) or server misinterpret it (broken server).
With your change instead of failing the mount, client will silently go for v4.0, even v4.1 mount was requested and produce undesirable behavior, e.g. proxy-io instead of pnfs. I fill prefer fail-fast instead of long debug sessions.
On the other hand, I understand, that it's not always possible to fix server or clients in production environment and time-to-time workarounds are necessary.
Tigran.
----- Original Message -----
Quoted 50 lines
From: "NeilBrown" <[email protected]>
To: "Trond Myklebust" <[email protected]>, "Anna Schumaker" <[email protected]>
Cc: "linux-nfs" <[email protected]>
Sent: Friday, March 16, 2018 12:44:23 AM
Subject: [PATCH - v2] NFSv4: handle EINVAL fromEXCHANGE_IDbetter.
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace), ornfs4_check_cl_exchange_flags()exchange flags detects a problem.
Each of these mean that NFSv4.1 later cannot be use, but they should not prevent fallback to NFSv4.0.Currently this EINVAL error is returned by
nfs4_proc_exchange_id()tonfs41_discover_server_trunking(), and thence tonfs4_discover_server_trunking().nfs4_discover_server_trunking()doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.It would be a more graceful failure if
nfs4_discover_server_trunking()mapped-EINVALto-EPROTONOSUPPORT- a failure to negotiate a client ID clearly shows that NFSv4.1 cannot be supported, but isn't as general a failure as EIO.Signed-off-by NeilBrown <[email protected]>---
Sorry - a bit too trigger-happy with that first version of the patch.
NeilBrown
fs/nfs/nfs4state.c| 2 ++1 file changed, 2 insertions(+)fs/nfs/nfs4state.c +2
-1@@ -2219,6 +2219,8 @@ int nfs4_discover_server_trunking(struct nfs_client *clp, clnt = clp->cl_rpcclient; goto again; +case -NFS4ERR_INVAL : +/* Server confused - assume this minor isn't supported */ case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break ; --2.14.0.rc0.dirty
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Quoted 23 lines · Trond Myklebust
Quoted 15 lines · Tigran
Hi Neil,
according to rfc5661,
NFS4ERR_INVALis returned by the server if it thinks that client sends an invalid request (e.g. points to a client bug)
or server misinterpret it (broken server).With your change instead of failing the mount, client will silently go for
v4.0, even v4.1 mount was requested and produce undesirable behavior, e.g.
proxy-io instead of pnfs. I fill prefer fail-fast instead of long debug
sessions.Quoted 6 lines
On the other hand, I understand, that it's not always possible to fix server
or clients in production environment and time-to-time workarounds are necessary.
Quoted 4 lines
I'd tend to agree with Tigran. Hiding server bugs, should not be a priority and particularly not in this case, where the workaround is
simple: either turn off version negotiation altogether, or edit/etc/nfsmount.confto negotiate a different set of versions.
Yes, it could be worked-around in nfsmount.conf, but manual
configuration should be seen as an optimization or a last resort. If
we can make things work without configuration, that provides the best experience.
In this case, the kernel has strong evidence that the server isn't responding as expected, but it gives an unhelpful error message.
At the very least, nfs4_discover_server_trunking() should not treat -NFS4ERR_INVAL as unexpect (because there is code in nfs4_check_cl_exchange_flags which explicitly generates it). If it just let this error through, instead of translating it to EIO, then the problem would go away.
Quoted 5 lines
What we might want to do, is make it easier to allow the user to detect that this is indeed a server bug and is not a problem with the arguments supplied to the "mount" utility. Perhaps we might have the kernel log something in the syslogs?
Yes, logging a message might be useful. Most of the messages logged about bad servers are currently going through dprintk(), so they won't often be seen. Is that what we want?? Don't know...
Anyway, you point that it "is not a problem with the arguments" is stop-on. If the client gets EINVAL from the server, then it shouldn't blindly report that back to the user as EINVAL means "Invalid argument" and the argements given to the server are probably not the argument given by the user.
Following that line of reasoning, I think nfs4_check_cl_exchange_flag() should *not* return -NFS4ERR_INVAL, and _nfs4_proc_exchange_id() shouldn't pass NFS4ERR_INVAL through unchanged.
So I propose the following version.
Thanks,
NeilBrown
------------------------8<---------------------------
From: NeilBrown <[email protected]>
Date: Tue, 20 Mar 2018 11:31:33 +1100
Subject: [PATCH] NFSv4: handle EINVAL from EXCHANGE_ID better.
nfs4_proc_exchange_id() can return -EINVAL if the server reported NFS4INVAL (which I have seen in a packet trace), or nfs4_check_cl_exchange_flags() exchange flags detects a problem.
Each of these mean that NFSv4.1 and later cannot be used, but they should not prevent fallback to NFSv4.0. Currently they do.
Currently this EINVAL error is returned by nfs4_proc_exchange_id() to nfs41_discover_server_trunking(), and thence to nfs4_discover_server_trunking(). nfs4_discover_server_trunking() doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.
EINVAL is never a sensible error code here. It means "Invalid argument", but is being used when the problem is "Invalid response from the server". If we change these two circumstances to report EPROTONOSUPPORT to the caller (which seems a reasonable assessment when the server gives confusing responses), and if we enhance nfs4_discover_server_trunking() to treat -EPROTONOSUPPORT as an expected error to pass through, then the error reported to user-space will be more representative of the actual fault.
A failure to negotiate a client ID clearly shows that NFSv4.1 cannot be supported, but isn't as general a failure as EIO.
--- fs/nfs/nfs4proc.c | 18 +++++++++++++++--- fs/nfs/nfs4state.c | 1 + 2 files changed, 16 insertions(+), 3 deletions(-)
fs/nfs/nfs4proc.c +15 -3
@@ -7364,7 +7364,8 @@ static int nfs4_check_cl_exchange_flags(u32 flags) goto out_inval;return NFS_OK ; out_inval: -return -NFS4ERR_INVAL ; +dprintk ("NFS: server returns invalid flags for EXCHANGE_ID\n" ); +return -EPROTONOSUPPORT ; } static bool
@@ -7741,8 +7742,19 @@ static int _nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred,int status; task =nfs4_run_exchange_id (clp, cred, sp4_how,NULL ); -if (IS_ERR (task)) -return PTR_ERR (task); +if (IS_ERR (task)) { + status =PTR_ERR (task); +if (status == -NFS4ERR_INVAL ) { +/* If the server think we did something invalid, it is certainly +* not the fault of our caller, so it would wrong to report +* this error back up. So in that case simply acknowledge that +* we don't seem able to support this protocol. +*/ +dprintk ("NFS: server return NFS4ERR_INVAL to EXCHANGE_ID\n" ); + status = -EPROTONOSUPPORT ; + } +return status; + } argp = task->tk_msg.rpc_argp; resp = task->tk_msg.rpc_resp;
fs/nfs/nfs4state.c +1 -0
@@ -2219,6 +2219,7 @@ int nfs4_discover_server_trunking(struct nfs_client *clp, clnt = clp->cl_rpcclient; goto again; +case -EPROTONOSUPPORT :case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break ;
Signature · 1 line
2.14.0.rc0.dirty
Quoted 36 lines · NeilBrown
Quoted 29 lines · Trond Myklebust
Quoted 19 lines · Tigran
Hi Neil,
according to rfc5661,
NFS4ERR_INVALis returned by the server if it
thinks that client sends an invalid request (e.g. points to a client
bug)
or server misinterpret it (broken server).With your change instead of failing the mount, client will silently
go for
v4.0, even v4.1 mount was requested and produce undesirable behavior,
e.g.
proxy-io instead of pnfs. I fill prefer fail-fast instead of long debug
sessions.Quoted 8 lines
On the other hand, I understand, that it's not always possible to fix
server
or clients in production environment and time-to-time workarounds are
necessary.Quoted 4 lines
I'd tend to agree with Tigran. Hiding server bugs, should not be a priority and particularly not in this case, where the workaround is
simple: either turn off version negotiation altogether, or edit/etc/nfsmount.confto negotiate a different set of versions.
Quoted 8 lines
Yes, it could be worked-around in nfsmount.conf, but manual configuration should be seen as an optimization or a last
resort. If
we can make things work without configuration, that provides the best experience.
In this case, the kernel has strong evidence that the server isn't responding as expected, but it gives an unhelpful error message.
Server do not spontaneously break their ability to process NFSv4 operations and so this is not an issue that we need to worry about in ordinary operation. It should only ever be an issue when
1) An insufficiently tested and broken upgrade is applied to an existing server, in which case the main workaround should be to revert the upgrade until it can be fixed.
2) A completely new broken server is introduced to the system.
Quoted 5 lines
At the very least,
nfs4_discover_server_trunking()should not treat -NFS4ERR_INVAL as unexpect (because there is code innfs4_check_cl_exchange_flagswhich explicitly generates it). If it just let this error through, instead of translating it to EIO, then the problem would go away.
The code in nfs4_check_cl_exchange_flags is there to check for explicit NFSv4.1 protocol violations. Is it broken?
Quoted 125 lines
Quoted 7 lines
What we might want to do, is make it easier to allow the user to detect
that this is indeed a server bug and is not a problem with the arguments supplied to the "mount" utility. Perhaps we might have the
kernel log something in the syslogs?Yes, logging a message might be useful. Most of the messages logged about bad servers are currently going through
dprintk(), so they won't
often be seen. Is that what we want?? Don't know...Anyway, you point that it "is not a problem with the arguments" is stop-on. If the client gets EINVAL from the server, then it shouldn't
blindly report that back to the user as EINVAL means "Invalid argument" and the argements given to the server are probably not the argument given by the user.Following that line of reasoning, I think
nfs4_check_cl_exchange_flag()
should *not* return -NFS4ERR_INVAL, and_nfs4_proc_exchange_id()shouldn't passNFS4ERR_INVALthrough unchanged.So I propose the following version.
Thanks,
NeilBrown------------------------8<---------------------------
From: NeilBrown <[email protected]>
Date: Tue, 20 Mar 2018 11:31:33 +1100
Subject: [PATCH] NFSv4: handle EINVAL fromEXCHANGE_IDbetter.
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace), ornfs4_check_cl_exchange_flags()exchange flags detects a problem.
Each of these mean that NFSv4.1 and later cannot be used, but they should not prevent fallback to NFSv4.0. Currently they do.Currently this EINVAL error is returned by
nfs4_proc_exchange_id()tonfs41_discover_server_trunking(), and thence tonfs4_discover_server_trunking().nfs4_discover_server_trunking()doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.EINVAL is never a sensible error code here. It means "Invalid argument", but is being used when the problem is "Invalid response from the server". If we change these two circumstances to report EPROTONOSUPPORT to the caller (which seems a reasonable assessment when the server gives confusing responses), and if we enhance
nfs4_discover_server_trunking()to treat-EPROTONOSUPPORTas an expected error to pass through, then the error reported to user-space will be more representative of the actual fault.A failure to negotiate a client ID clearly shows that NFSv4.1 cannot be supported, but isn't as general a failure as EIO.
Signed-off-by NeilBrown <[email protected]>--- fs/nfs/nfs4proc.c | 18 +++++++++++++++--- fs/nfs/nfs4state.c | 1 + 2 files changed, 16 insertions(+), 3 deletions(-)fs/nfs/nfs4proc.c +2
-1@@ -7364,7 +7364,8 @@ static int nfs4_check_cl_exchange_flags(u32 flags) goto out_inval;return NFS_OK ; out_inval: -return -NFS4ERR_INVAL ; +dprintk ("NFS: server returns invalid flags for EXCHANGE_ID\n"); +return -EPROTONOSUPPORT ; }static bool
fs/nfs/nfs4proc.c +4
-2@@ -7741,8 +7742,19 @@ static int _nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred, int status; task =nfs4_run_exchange_id (clp, cred, sp4_how,NULL ); -if (IS_ERR (task)) -return PTR_ERR (task); +if (IS_ERR (task)) { + status =PTR_ERR (task); +if (status == -NFS4ERR_INVAL ) { +/* If the server think we did something invalid, it is certainly
fs/nfs/nfs4proc.c +1
-0+* not the fault of our caller, so it would wrong to report
fs/nfs/nfs4proc.c +1
-0+* this error back up. So in that case simply acknowledge that
fs/nfs/nfs4proc.c +1
-0+* we don't seem able to support this protocol.
fs/nfs/nfs4proc.c +2
-0+*/ + dprintk("NFS: server return NFS4ERR_INVAL toEXCHANGE_ID\n");
fs/nfs/nfs4proc.c +4
-0+ status = -EPROTONOSUPPORT ; + } +return status; + } argp = task->tk_msg.rpc_argp; resp = task->tk_msg.rpc_resp;fs/nfs/nfs4state.c +1
-0@@ -2219,6 +2219,7 @@ int nfs4_discover_server_trunking(structnfs_client *clp, clnt = clp->cl_rpcclient; goto again; +case -EPROTONOSUPPORT :case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break;
Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]
Quoted 46 lines · Trond Myklebust
Quoted 36 lines · NeilBrown
Quoted 29 lines · Trond Myklebust
Quoted 19 lines · Tigran
Hi Neil,
according to rfc5661,
NFS4ERR_INVALis returned by the server if it
thinks that client sends an invalid request (e.g. points to a client
bug)
or server misinterpret it (broken server).With your change instead of failing the mount, client will silently
go for
v4.0, even v4.1 mount was requested and produce undesirable behavior,
e.g.
proxy-io instead of pnfs. I fill prefer fail-fast instead of long debug
sessions.Quoted 8 lines
On the other hand, I understand, that it's not always possible to fix
server
or clients in production environment and time-to-time workarounds are
necessary.Quoted 4 lines
I'd tend to agree with Tigran. Hiding server bugs, should not be a priority and particularly not in this case, where the workaround is
simple: either turn off version negotiation altogether, or edit/etc/nfsmount.confto negotiate a different set of versions.Quoted 8 lines
Yes, it could be worked-around in nfsmount.conf, but manual configuration should be seen as an optimization or a last
resort. If
we can make things work without configuration, that provides the best experience.
In this case, the kernel has strong evidence that the server isn't responding as expected, but it gives an unhelpful error message.
Quoted 8 lines
Server do not spontaneously break their ability to process NFSv4 operations and so this is not an issue that we need to worry about in ordinary operation. It should only ever be an issue when
1) An insufficiently tested and broken upgrade is applied to an existing server, in which case the main workaround should be to revert the upgrade until it can be fixed.
2) A completely new broken server is introduced to the system.
3) An upgrade to the client defaults to trying 4.2 first, then 4.1 and only then 4.0. Previous client defaulted to 4.0.
Quoted 9 lines
Quoted 6 lines
At the very least,
nfs4_discover_server_trunking()should not treat -NFS4ERR_INVAL as unexpect (because there is code innfs4_check_cl_exchange_flagswhich explicitly generates it). If it just let this error through, instead of translating it to EIO, then the problem would go away.The code in
nfs4_check_cl_exchange_flagsis there to check for explicit NFSv4.1 protocol violations. Is it broken?
It is broken in that it reports -EINVAL when no arguments were invalid. This gets translated to -EIO when there was no IO error.
Thanks,
NeilBrown
Quoted 130 lines
Quoted 126 lines
Quoted 8 lines
What we might want to do, is make it easier to allow the user to detect
that this is indeed a server bug and is not a problem with the arguments supplied to the "mount" utility. Perhaps we might have the
kernel log something in the syslogs?Yes, logging a message might be useful. Most of the messages logged about bad servers are currently going through
dprintk(), so they won't
often be seen. Is that what we want?? Don't know...Anyway, you point that it "is not a problem with the arguments" is stop-on. If the client gets EINVAL from the server, then it shouldn't
blindly report that back to the user as EINVAL means "Invalid argument" and the argements given to the server are probably not the argument given by the user.Following that line of reasoning, I think
nfs4_check_cl_exchange_flag()
should *not* return -NFS4ERR_INVAL, and_nfs4_proc_exchange_id()shouldn't passNFS4ERR_INVALthrough unchanged.So I propose the following version.
Thanks,
NeilBrown------------------------8<---------------------------
From: NeilBrown <[email protected]>
Date: Tue, 20 Mar 2018 11:31:33 +1100
Subject: [PATCH] NFSv4: handle EINVAL fromEXCHANGE_IDbetter.
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace), ornfs4_check_cl_exchange_flags()exchange flags detects a problem.
Each of these mean that NFSv4.1 and later cannot be used, but they should not prevent fallback to NFSv4.0. Currently they do.Currently this EINVAL error is returned by
nfs4_proc_exchange_id()tonfs41_discover_server_trunking(), and thence tonfs4_discover_server_trunking().nfs4_discover_server_trunking()doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.EINVAL is never a sensible error code here. It means "Invalid argument", but is being used when the problem is "Invalid response from the server". If we change these two circumstances to report EPROTONOSUPPORT to the caller (which seems a reasonable assessment when the server gives confusing responses), and if we enhance
nfs4_discover_server_trunking()to treat-EPROTONOSUPPORTas an expected error to pass through, then the error reported to user-space will be more representative of the actual fault.A failure to negotiate a client ID clearly shows that NFSv4.1 cannot be supported, but isn't as general a failure as EIO.
Signed-off-by NeilBrown <[email protected]>--- fs/nfs/nfs4proc.c | 18 +++++++++++++++--- fs/nfs/nfs4state.c | 1 + 2 files changed, 16 insertions(+), 3 deletions(-)fs/nfs/nfs4proc.c +2
-1@@ -7364,7 +7364,8 @@ static int nfs4_check_cl_exchange_flags(u32 flags) goto out_inval;return NFS_OK ; out_inval: -return -NFS4ERR_INVAL ; +dprintk ("NFS: server returns invalid flags for EXCHANGE_ID\n"); +return -EPROTONOSUPPORT ; }static bool
fs/nfs/nfs4proc.c +4
-2@@ -7741,8 +7742,19 @@ static int _nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred, int status; task =nfs4_run_exchange_id (clp, cred, sp4_how,NULL ); -if (IS_ERR (task)) -return PTR_ERR (task); +if (IS_ERR (task)) { + status =PTR_ERR (task); +if (status == -NFS4ERR_INVAL ) { +/* If the server think we did something invalid, it is certainly
fs/nfs/nfs4proc.c +1
-0+* not the fault of our caller, so it would wrong to report
fs/nfs/nfs4proc.c +1
-0+* this error back up. So in that case simply acknowledge that
fs/nfs/nfs4proc.c +1
-0+* we don't seem able to support this protocol.
fs/nfs/nfs4proc.c +2
-0+*/ + dprintk("NFS: server return NFS4ERR_INVAL toEXCHANGE_ID\n");
fs/nfs/nfs4proc.c +4
-0+ status = -EPROTONOSUPPORT ; + } +return status; + } argp = task->tk_msg.rpc_argp; resp = task->tk_msg.rpc_resp;fs/nfs/nfs4state.c +1
-0@@ -2219,6 +2219,7 @@ int nfs4_discover_server_trunking(structnfs_client *clp, clnt = clp->cl_rpcclient; goto again; +case -EPROTONOSUPPORT :case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break;
Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]
Quoted 66 lines · NeilBrown
Quoted 58 lines · Trond Myklebust
Quoted 42 lines · NeilBrown
Quoted 33 lines · Trond Myklebust
Quoted 21 lines · Tigran
Hi Neil,
according to rfc5661,
NFS4ERR_INVALis returned by the server if
it
thinks that client sends an invalid request (e.g. points to a client
bug)
or server misinterpret it (broken server).With your change instead of failing the mount, client will silently
go for
v4.0, even v4.1 mount was requested and produce undesirable behavior,
e.g.
proxy-io instead of pnfs. I fill prefer fail-fast instead of long
debug
sessions.Quoted 10 lines
On the other hand, I understand, that it's not always possible to
fix
server
or clients in production environment and time-to-time workarounds
are
necessary.Quoted 6 lines
I'd tend to agree with Tigran. Hiding server bugs, should not be a
priority and particularly not in this case, where the workaround is
simple: either turn off version negotiation altogether, or edit/etc/nfsmount.confto negotiate a different set of versions.Quoted 9 lines
Yes, it could be worked-around in nfsmount.conf, but manual configuration should be seen as an optimization or a last
resort. If
we can make things work without configuration, that provides the best
experience.
In this case, the kernel has strong evidence that the server isn't responding as expected, but it gives an unhelpful error message.Server do not spontaneously break their ability to process NFSv4 operations and so this is not an issue that we need to worry about in
ordinary operation. It should only ever be an issue whenQuoted 5 lines
1) An insufficiently tested and broken upgrade is applied to an existing server, in which case the main workaround should be to revert
the upgrade until it can be fixed.
2) A completely new broken server is introduced to the system.
Quoted 3 lines
3) An upgrade to the client defaults to trying 4.2 first, then 4.1 and
only then 4.0. Previous client defaulted to 4.0.
I'm sorry, but this still does not sounds like a good case for "fix the kernel client". The kernel has no opinion on which NFS version you should try first in a mount attempt: that decision is made in userspace.
If you upgraded the nfs-utils to something that now tries 4.2 first, then that is a user space policy issue.
Quoted 9 lines
Quoted 9 lines
Quoted 8 lines
At the very least,
nfs4_discover_server_trunking()should not treat
-NFS4ERR_INVAL as unexpect (because there is code innfs4_check_cl_exchange_flagswhich explicitly generates it). If it just let this error through, instead of translating it to EIO,
then the problem would go away.
Quoted 6 lines
Quoted 2 lines
The code in
nfs4_check_cl_exchange_flagsis there to check for explicit NFSv4.1 protocol violations. Is it broken?It is broken in that it reports
-EINVALwhen no arguments were invalid.
This gets translated to-EIOwhen there was no IO error.
The purpose of that function is to ensure that the server is advertising itself as a bona fide NFSv4.1 or newer server, and to ensure that it is not replying to our EXCHANGE_ID request with some flag or service that we did not expect and that might cause us to break.
IOW: it is there to check protocol compliance. As far as I can tell, it is doing that, and doing so correctly.
Quoted 146 lines
Thanks,
NeilBrownQuoted 142 lines
Quoted 137 lines
Quoted 10 lines
What we might want to do, is make it easier to allow the user to
detect
that this is indeed a server bug and is not a problem with the arguments supplied to the "mount" utility. Perhaps we might have
the
kernel log something in the syslogs?Yes, logging a message might be useful. Most of the messages logged
about bad servers are currently going throughdprintk(), so they won't
often be seen. Is that what we want?? Don't know...Anyway, you point that it "is not a problem with the arguments" is
stop-on. If the client gets EINVAL from the server, then it shouldn't
blindly report that back to the user as EINVAL means "Invalid argument" and the argements given to the server are probably not the
argument given by the user.Following that line of reasoning, I think
nfs4_check_cl_exchange_flag()
should *not* return -NFS4ERR_INVAL, and_nfs4_proc_exchange_id()shouldn't passNFS4ERR_INVALthrough unchanged.So I propose the following version.
Thanks,
NeilBrown------------------------8<---------------------------
From: NeilBrown <[email protected]>
Date: Tue, 20 Mar 2018 11:31:33 +1100
Subject: [PATCH] NFSv4: handle EINVAL fromEXCHANGE_IDbetter.
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace), ornfs4_check_cl_exchange_flags()exchange flags detects a problem.
Each of these mean that NFSv4.1 and later cannot be used, but they should not prevent fallback to NFSv4.0. Currently they do.Currently this EINVAL error is returned by
nfs4_proc_exchange_id()tonfs41_discover_server_trunking(), and thence tonfs4_discover_server_trunking().nfs4_discover_server_trunking()doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.EINVAL is never a sensible error code here. It means "Invalid argument", but is being used when the problem is "Invalid response
from the server". If we change these two circumstances to report EPROTONOSUPPORT to the caller (which seems a reasonable assessment
when the server gives confusing responses), and if we enhancenfs4_discover_server_trunking()to treat-EPROTONOSUPPORTas an expected error to pass through, then the error reported to user- space
will be more representative of the actual fault.A failure to negotiate a client ID clearly shows that NFSv4.1 cannot
be supported, but isn't as general a failure as EIO.Signed-off-by NeilBrown <[email protected]>--- fs/nfs/nfs4proc.c | 18 +++++++++++++++--- fs/nfs/nfs4state.c | 1 + 2 files changed, 16 insertions(+), 3 deletions(-)fs/nfs/nfs4proc.c +2
-1@@ -7364,7 +7364,8 @@ static int nfs4_check_cl_exchange_flags(u32 flags) goto out_inval;return NFS_OK ; out_inval: -return -NFS4ERR_INVAL ; +dprintk ("NFS: server returns invalid flags for EXCHANGE_ID\n"); +return -EPROTONOSUPPORT ; }static bool
fs/nfs/nfs4proc.c +4
-2@@ -7741,8 +7742,19 @@ static int _nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred, int status; task =nfs4_run_exchange_id (clp, cred, sp4_how,NULL ); -if (IS_ERR (task)) -return PTR_ERR (task); +if (IS_ERR (task)) { + status =PTR_ERR (task); +if (status == -NFS4ERR_INVAL ) { +/* If the server think we did something invalid, it is certainly
fs/nfs/nfs4proc.c +1
-0+* not the fault of our caller, so it would
wrong to reportfs/nfs/nfs4proc.c +1
-0+* this error back up. So in that case simply acknowledge that
fs/nfs/nfs4proc.c +1
-0+* we don't seem able to support this protocol.
fs/nfs/nfs4proc.c +2
-0+*/ + dprintk("NFS: server return
NFS4ERR_INVALto
EXCHANGE_ID\n");fs/nfs/nfs4proc.c +4
-0+ status = -EPROTONOSUPPORT ; + } +return status; + } argp = task->tk_msg.rpc_argp; resp = task->tk_msg.rpc_resp;fs/nfs/nfs4state.c +1
-0@@ -2219,6 +2219,7 @@ int nfs4_discover_server_trunking(structnfs_client *clp, clnt = clp->cl_rpcclient; goto again; +case -EPROTONOSUPPORT :case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break;
Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]
Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]
Quoted 67 lines · Trond Myklebust
Quoted 66 lines · NeilBrown
Quoted 63 lines · Trond Myklebust
Quoted 42 lines · NeilBrown
Quoted 33 lines · Trond Myklebust
Quoted 21 lines · Tigran
Hi Neil,
according to rfc5661,
NFS4ERR_INVALis returned by the server if
it
thinks that client sends an invalid request (e.g. points to a client
bug)
or server misinterpret it (broken server).With your change instead of failing the mount, client will silently
go for
v4.0, even v4.1 mount was requested and produce undesirable behavior,
e.g.
proxy-io instead of pnfs. I fill prefer fail-fast instead of long
debug
sessions.Quoted 10 lines
On the other hand, I understand, that it's not always possible to
fix
server
or clients in production environment and time-to-time workarounds
are
necessary.Quoted 6 lines
I'd tend to agree with Tigran. Hiding server bugs, should not be a
priority and particularly not in this case, where the workaround is
simple: either turn off version negotiation altogether, or edit/etc/nfsmount.confto negotiate a different set of versions.Quoted 9 lines
Yes, it could be worked-around in nfsmount.conf, but manual configuration should be seen as an optimization or a last
resort. If
we can make things work without configuration, that provides the best
experience.
In this case, the kernel has strong evidence that the server isn't responding as expected, but it gives an unhelpful error message.Server do not spontaneously break their ability to process NFSv4 operations and so this is not an issue that we need to worry about in
ordinary operation. It should only ever be an issue when1) An insufficiently tested and broken upgrade is applied to an existing server, in which case the main workaround should be to revert
the upgrade until it can be fixed.
2) A completely new broken server is introduced to the system.
Quoted 8 lines
Quoted 3 lines
3) An upgrade to the client defaults to trying 4.2 first, then 4.1 and
only then 4.0. Previous client defaulted to 4.0.I'm sorry, but this still does not sounds like a good case for "fix the kernel client". The kernel has no opinion on which NFS version you should try first in a mount attempt: that decision is made in userspace.
Of course. But the kernel should still accurately report what it found. If it found that it cannot use that protocol, it should report "I cannot use that protocol". It shouldn't report "IO error".
This allows user space to know what the status is and to make a correctly informed decision.
Quoted 19 lines
If you upgraded the nfs-utils to something that now tries 4.2 first, then that is a user space policy issue.
Quoted 9 lines
Quoted 9 lines
Quoted 8 lines
At the very least,
nfs4_discover_server_trunking()should not treat
-NFS4ERR_INVAL as unexpect (because there is code innfs4_check_cl_exchange_flagswhich explicitly generates it). If it just let this error through, instead of translating it to EIO,
then the problem would go away.Quoted 6 lines
Quoted 2 lines
The code in
nfs4_check_cl_exchange_flagsis there to check for explicit NFSv4.1 protocol violations. Is it broken?It is broken in that it reports
-EINVALwhen no arguments were invalid.
This gets translated to-EIOwhen there was no IO error.
Quoted 8 lines
The purpose of that function is to ensure that the server is advertising itself as a bona fide NFSv4.1 or newer server, and to ensure that it is not replying to our
EXCHANGE_IDrequest with some flag or service that we did not expect and that might cause us to break.IOW: it is there to check protocol compliance. As far as I can tell, it is doing that, and doing so correctly.
It is checking correctly, but it is not reporting "the protocol is not compliant". It is reporting "invalid argument".
Thanks,
NeilBrown
Quoted 152 lines
Quoted 148 lines
Thanks,
NeilBrownQuoted 142 lines
Quoted 137 lines
Quoted 10 lines
What we might want to do, is make it easier to allow the user to
detect
that this is indeed a server bug and is not a problem with the arguments supplied to the "mount" utility. Perhaps we might have
the
kernel log something in the syslogs?Yes, logging a message might be useful. Most of the messages logged
about bad servers are currently going throughdprintk(), so they won't
often be seen. Is that what we want?? Don't know...Anyway, you point that it "is not a problem with the arguments" is
stop-on. If the client gets EINVAL from the server, then it shouldn't
blindly report that back to the user as EINVAL means "Invalid argument" and the argements given to the server are probably not the
argument given by the user.Following that line of reasoning, I think
nfs4_check_cl_exchange_flag()
should *not* return -NFS4ERR_INVAL, and_nfs4_proc_exchange_id()shouldn't passNFS4ERR_INVALthrough unchanged.So I propose the following version.
Thanks,
NeilBrown------------------------8<---------------------------
From: NeilBrown <[email protected]>
Date: Tue, 20 Mar 2018 11:31:33 +1100
Subject: [PATCH] NFSv4: handle EINVAL fromEXCHANGE_IDbetter.
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace), ornfs4_check_cl_exchange_flags()exchange flags detects a problem.
Each of these mean that NFSv4.1 and later cannot be used, but they should not prevent fallback to NFSv4.0. Currently they do.Currently this EINVAL error is returned by
nfs4_proc_exchange_id()tonfs41_discover_server_trunking(), and thence tonfs4_discover_server_trunking().nfs4_discover_server_trunking()doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.EINVAL is never a sensible error code here. It means "Invalid argument", but is being used when the problem is "Invalid response
from the server". If we change these two circumstances to report EPROTONOSUPPORT to the caller (which seems a reasonable assessment
when the server gives confusing responses), and if we enhancenfs4_discover_server_trunking()to treat-EPROTONOSUPPORTas an expected error to pass through, then the error reported to user- space
will be more representative of the actual fault.A failure to negotiate a client ID clearly shows that NFSv4.1 cannot
be supported, but isn't as general a failure as EIO.Signed-off-by NeilBrown <[email protected]>--- fs/nfs/nfs4proc.c | 18 +++++++++++++++--- fs/nfs/nfs4state.c | 1 + 2 files changed, 16 insertions(+), 3 deletions(-)fs/nfs/nfs4proc.c +2
-1@@ -7364,7 +7364,8 @@ static int nfs4_check_cl_exchange_flags(u32 flags) goto out_inval;return NFS_OK ; out_inval: -return -NFS4ERR_INVAL ; +dprintk ("NFS: server returns invalid flags for EXCHANGE_ID\n"); +return -EPROTONOSUPPORT ; }static bool
fs/nfs/nfs4proc.c +4
-2@@ -7741,8 +7742,19 @@ static int _nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred, int status; task =nfs4_run_exchange_id (clp, cred, sp4_how,NULL ); -if (IS_ERR (task)) -return PTR_ERR (task); +if (IS_ERR (task)) { + status =PTR_ERR (task); +if (status == -NFS4ERR_INVAL ) { +/* If the server think we did something invalid, it is certainly
fs/nfs/nfs4proc.c +1
-0+* not the fault of our caller, so it would
wrong to reportfs/nfs/nfs4proc.c +1
-0+* this error back up. So in that case simply acknowledge that
fs/nfs/nfs4proc.c +1
-0+* we don't seem able to support this protocol.
fs/nfs/nfs4proc.c +2
-0+*/ + dprintk("NFS: server return
NFS4ERR_INVALto
EXCHANGE_ID\n");fs/nfs/nfs4proc.c +4
-0+ status = -EPROTONOSUPPORT ; + } +return status; + } argp = task->tk_msg.rpc_argp; resp = task->tk_msg.rpc_resp;fs/nfs/nfs4state.c +1
-0@@ -2219,6 +2219,7 @@ int nfs4_discover_server_trunking(structnfs_client *clp, clnt = clp->cl_rpcclient; goto again; +case -EPROTONOSUPPORT :case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break;
Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]
Quoted 91 lines · NeilBrown
Quoted 83 lines · Trond Myklebust
Quoted 77 lines · NeilBrown
Quoted 69 lines · Trond Myklebust
Quoted 50 lines · NeilBrown
Quoted 38 lines · Trond Myklebust
Quoted 26 lines · Tigran
Hi Neil,
according to rfc5661,
NFS4ERR_INVALis returned by the server
if
it
thinks that client sends an invalid request (e.g. points to a
client
bug)
or server misinterpret it (broken server).With your change instead of failing the mount, client will
silently
go for
v4.0, even v4.1 mount was requested and produce undesirable
behavior,
e.g.
proxy-io instead of pnfs. I fill prefer fail-fast instead of
long
debug
sessions.Quoted 10 lines
On the other hand, I understand, that it's not always possible to
fix
server
or clients in production environment and time-to-time workarounds
are
necessary.Quoted 9 lines
I'd tend to agree with Tigran. Hiding server bugs, should not
be a
priority and particularly not in this case, where the workaround is
simple: either turn off version negotiation altogether, or edit/etc/nfsmount.confto negotiate a different set of versions.Quoted 10 lines
Yes, it could be worked-around in nfsmount.conf, but manual configuration should be seen as an optimization or a last
resort. If
we can make things work without configuration, that provides the
best
experience.
In this case, the kernel has strong evidence that the server isn't responding as expected, but it gives an unhelpful error message.Server do not spontaneously break their ability to process NFSv4
operations and so this is not an issue that we need to worry about
in
ordinary operation. It should only ever be an issue whenQuoted 5 lines
1) An insufficiently tested and broken upgrade is applied to an existing server, in which case the main workaround should be to revert
the upgrade until it can be fixed.
2) A completely new broken server is introduced to the system.Quoted 4 lines
3) An upgrade to the client defaults to trying 4.2 first, then 4.1
and
only then 4.0. Previous client defaulted to 4.0.Quoted 5 lines
I'm sorry, but this still does not sounds like a good case for "fix the
kernel client". The kernel has no opinion on which NFS version you should try first in a mount attempt: that decision is made in userspace.
Quoted 4 lines
Of course. But the kernel should still accurately report what it found. If it found that it cannot use that protocol, it should report
"I cannot use that protocol". It shouldn't report "IO error".
EPROTONOSUPPORT means "that protocol is not supported". In the case you are arguing, the protocol is reported as being supported by both the client and the server, so that is not the issue. The existence of a server bug in the protocol implementation _is_ the issue.
As I said, I have no problems changing what we report so that it is easier to debug. I do have a problem with a change that makes the failure silent, and thus makes the problem harder to debug.
Bottom line: if the sysadmin has enabled NFSv4.2 on the server, and the userspace mount program is asking for NFSv4.2, then we should NOT be telling it to fail over silently to NFSv4.0.
Quoted 214 lines
This allows user space to know what the status is and to make a correctly informed decision.
Quoted 27 lines
If you upgraded the nfs-utils to something that now tries 4.2 first,
then that is a user space policy issue.Quoted 10 lines
Quoted 10 lines
Quoted 9 lines
At the very least,
nfs4_discover_server_trunking()should not treat
-NFS4ERR_INVAL as unexpect (because there is code innfs4_check_cl_exchange_flagswhich explicitly generates it). If it just let this error through, instead of translating it to
EIO,
then the problem would go away.Quoted 6 lines
Quoted 2 lines
The code in
nfs4_check_cl_exchange_flagsis there to check for explicit NFSv4.1 protocol violations. Is it broken?It is broken in that it reports
-EINVALwhen no arguments were invalid.
This gets translated to-EIOwhen there was no IO error.The purpose of that function is to ensure that the server is advertising itself as a bona fide NFSv4.1 or newer server, and to ensure that it is not replying to our
EXCHANGE_IDrequest with some flag or service that we did not expect and that might cause us to break.Quoted 3 lines
IOW: it is there to check protocol compliance. As far as I can tell, it
is doing that, and doing so correctly.It is checking correctly, but it is not reporting "the protocol is not
compliant". It is reporting "invalid argument".Thanks,
NeilBrownQuoted 172 lines
Quoted 167 lines
Thanks,
NeilBrownQuoted 161 lines
Quoted 156 lines
Quoted 12 lines
What we might want to do, is make it easier to allow the user
to
detect
that this is indeed a server bug and is not a problem with the
arguments supplied to the "mount" utility. Perhaps we might have
the
kernel log something in the syslogs?Yes, logging a message might be useful. Most of the messages logged
about bad servers are currently going throughdprintk(), so they
won't
often be seen. Is that what we want?? Don't know...Anyway, you point that it "is not a problem with the arguments"
is
stop-on. If the client gets EINVAL from the server, then it shouldn't
blindly report that back to the user as EINVAL means "Invalid argument" and the argements given to the server are probably not
the
argument given by the user.Following that line of reasoning, I think
nfs4_check_cl_exchange_flag()
should *not* return -NFS4ERR_INVAL, and_nfs4_proc_exchange_id()
shouldn't passNFS4ERR_INVALthrough unchanged.So I propose the following version.
Thanks,
NeilBrown------------------------8<---------------------------
From: NeilBrown <[email protected]>
Date: Tue, 20 Mar 2018 11:31:33 +1100
Subject: [PATCH] NFSv4: handle EINVAL fromEXCHANGE_IDbetter.
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace), ornfs4_check_cl_exchange_flags()exchange flags detects a problem.
Each of these mean that NFSv4.1 and later cannot be used, but they should not prevent fallback to NFSv4.0. Currently they do.Currently this EINVAL error is returned by
nfs4_proc_exchange_id()tonfs41_discover_server_trunking(), and thence tonfs4_discover_server_trunking().nfs4_discover_server_trunking()doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.EINVAL is never a sensible error code here. It means "Invalid
argument", but is being used when the problem is "Invalid response
from the server". If we change these two circumstances to report
EPROTONOSUPPORT to the caller (which seems a reasonable assessment
when the server gives confusing responses), and if we enhancenfs4_discover_server_trunking()to treat-EPROTONOSUPPORTas an
expected error to pass through, then the error reported to user-
space
will be more representative of the actual fault.A failure to negotiate a client ID clearly shows that NFSv4.1 cannot
be supported, but isn't as general a failure as EIO.Signed-off-by NeilBrown <[email protected]>--- fs/nfs/nfs4proc.c | 18 +++++++++++++++--- fs/nfs/nfs4state.c | 1 + 2 files changed, 16 insertions(+), 3 deletions(-)fs/nfs/nfs4proc.c +0
-0@@ -7364,7 +7364,8 @@ static intnfs4_check_cl_exchange_flags(u32
flags)fs/nfs/nfs4proc.c +1
-1goto out_inval;return NFS_OK ; out_inval: -return -NFS4ERR_INVAL ; + dprintk("NFS: server returns invalid flags forEXCHANGE_ID\n");
fs/nfs/nfs4proc.c +1
-0+return -EPROTONOSUPPORT ; } static bool@@ -7741,8 +7742,19 @@ static int_nfs4_proc_exchange_id(struct
nfs_client*clp, structrpc_cred*cred,fs/nfs/nfs4proc.c +0
-0int status; task = nfs4_run_exchange_id(clp, cred, sp4_how,NULL);
fs/nfs/nfs4proc.c +4
-2-if (IS_ERR (task)) -return PTR_ERR (task); +if (IS_ERR (task)) { + status =PTR_ERR (task); +if (status == -NFS4ERR_INVAL ) { +/* If the server think we did something
invalid, it is certainlyfs/nfs/nfs4proc.c +1
-0+* not the fault of our caller, so it
would
wrong to reportfs/nfs/nfs4proc.c +1
-0+* this error back up. So in that case
simply acknowledge thatfs/nfs/nfs4proc.c +1
-0+* we don't seem able to support this
protocol.fs/nfs/nfs4proc.c +2
-0+*/ + dprintk("NFS: server return
NFS4ERR_INVALto
EXCHANGE_ID\n");fs/nfs/nfs4proc.c +4
-0+ status = -EPROTONOSUPPORT ; + } +return status; + } argp = task->tk_msg.rpc_argp; resp = task->tk_msg.rpc_resp;fs/nfs/nfs4state.c +0
-0@@ -2219,6 +2219,7 @@ intnfs4_discover_server_trunking(struct
nfs_client*clp,fs/nfs/nfs4state.c +1
-0clnt = clp->cl_rpcclient; goto again; +case -EPROTONOSUPPORT :case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break ;Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]
Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]
Quoted 97 lines · Trond Myklebust
Quoted 91 lines · NeilBrown
Quoted 83 lines · Trond Myklebust
Quoted 77 lines · NeilBrown
Quoted 69 lines · Trond Myklebust
Quoted 50 lines · NeilBrown
Quoted 38 lines · Trond Myklebust
Quoted 26 lines · Tigran
Hi Neil,
according to rfc5661,
NFS4ERR_INVALis returned by the server
if
it
thinks that client sends an invalid request (e.g. points to a
client
bug)
or server misinterpret it (broken server).With your change instead of failing the mount, client will
silently
go for
v4.0, even v4.1 mount was requested and produce undesirable
behavior,
e.g.
proxy-io instead of pnfs. I fill prefer fail-fast instead of
long
debug
sessions.Quoted 10 lines
On the other hand, I understand, that it's not always possible to
fix
server
or clients in production environment and time-to-time workarounds
are
necessary.Quoted 9 lines
I'd tend to agree with Tigran. Hiding server bugs, should not
be a
priority and particularly not in this case, where the workaround is
simple: either turn off version negotiation altogether, or edit/etc/nfsmount.confto negotiate a different set of versions.Quoted 10 lines
Yes, it could be worked-around in nfsmount.conf, but manual configuration should be seen as an optimization or a last
resort. If
we can make things work without configuration, that provides the
best
experience.
In this case, the kernel has strong evidence that the server isn't responding as expected, but it gives an unhelpful error message.Server do not spontaneously break their ability to process NFSv4
operations and so this is not an issue that we need to worry about
in
ordinary operation. It should only ever be an issue whenQuoted 5 lines
1) An insufficiently tested and broken upgrade is applied to an existing server, in which case the main workaround should be to revert
the upgrade until it can be fixed.
2) A completely new broken server is introduced to the system.Quoted 4 lines
3) An upgrade to the client defaults to trying 4.2 first, then 4.1
and
only then 4.0. Previous client defaulted to 4.0.Quoted 5 lines
I'm sorry, but this still does not sounds like a good case for "fix the
kernel client". The kernel has no opinion on which NFS version you should try first in a mount attempt: that decision is made in userspace.Quoted 4 lines
Of course. But the kernel should still accurately report what it found. If it found that it cannot use that protocol, it should report
"I cannot use that protocol". It shouldn't report "IO error".
Quoted 4 lines
EPROTONOSUPPORT means "that protocol is not supported". In the case you are arguing, the protocol is reported as being supported by both the client and the server, so that is not the issue. The existence of a server bug in the protocol implementation _is_ the issue.
I don't see how a server that fails the first transaction of a protocol can be said to "support" that protocol.
Quoted 8 lines
As I said, I have no problems changing what we report so that it is easier to debug. I do have a problem with a change that makes the failure silent, and thus makes the problem harder to debug.
Bottom line: if the sysadmin has enabled NFSv4.2 on the server, and the userspace mount program is asking for NFSv4.2, then we should NOT be telling it to fail over silently to NFSv4.0.
It is NOT telling it to fail over. It is tell it that v4.2 doesn't work.
How mount.nfs responds to that information is not the kernel's problem. Providing meaningful information is.
But I can see that we aren't going anywhere so let's just not bother. It isn't that much cost for me to carry a tiny patch that you don't want.
Thanks,
NeilBrown
Quoted 219 lines
Quoted 215 lines
This allows user space to know what the status is and to make a correctly informed decision.
Quoted 27 lines
If you upgraded the nfs-utils to something that now tries 4.2 first,
then that is a user space policy issue.Quoted 10 lines
Quoted 10 lines
Quoted 9 lines
At the very least,
nfs4_discover_server_trunking()should not treat
-NFS4ERR_INVAL as unexpect (because there is code innfs4_check_cl_exchange_flagswhich explicitly generates it). If it just let this error through, instead of translating it to
EIO,
then the problem would go away.Quoted 6 lines
Quoted 2 lines
The code in
nfs4_check_cl_exchange_flagsis there to check for explicit NFSv4.1 protocol violations. Is it broken?It is broken in that it reports
-EINVALwhen no arguments were invalid.
This gets translated to-EIOwhen there was no IO error.The purpose of that function is to ensure that the server is advertising itself as a bona fide NFSv4.1 or newer server, and to ensure that it is not replying to our
EXCHANGE_IDrequest with some flag or service that we did not expect and that might cause us to break.Quoted 3 lines
IOW: it is there to check protocol compliance. As far as I can tell, it
is doing that, and doing so correctly.It is checking correctly, but it is not reporting "the protocol is not
compliant". It is reporting "invalid argument".Thanks,
NeilBrownQuoted 172 lines
Quoted 167 lines
Thanks,
NeilBrownQuoted 161 lines
Quoted 156 lines
Quoted 12 lines
What we might want to do, is make it easier to allow the user
to
detect
that this is indeed a server bug and is not a problem with the
arguments supplied to the "mount" utility. Perhaps we might have
the
kernel log something in the syslogs?Yes, logging a message might be useful. Most of the messages logged
about bad servers are currently going throughdprintk(), so they
won't
often be seen. Is that what we want?? Don't know...Anyway, you point that it "is not a problem with the arguments"
is
stop-on. If the client gets EINVAL from the server, then it shouldn't
blindly report that back to the user as EINVAL means "Invalid argument" and the argements given to the server are probably not
the
argument given by the user.Following that line of reasoning, I think
nfs4_check_cl_exchange_flag()
should *not* return -NFS4ERR_INVAL, and_nfs4_proc_exchange_id()
shouldn't passNFS4ERR_INVALthrough unchanged.So I propose the following version.
Thanks,
NeilBrown------------------------8<---------------------------
From: NeilBrown <[email protected]>
Date: Tue, 20 Mar 2018 11:31:33 +1100
Subject: [PATCH] NFSv4: handle EINVAL fromEXCHANGE_IDbetter.
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace), ornfs4_check_cl_exchange_flags()exchange flags detects a problem.
Each of these mean that NFSv4.1 and later cannot be used, but they should not prevent fallback to NFSv4.0. Currently they do.Currently this EINVAL error is returned by
nfs4_proc_exchange_id()tonfs41_discover_server_trunking(), and thence tonfs4_discover_server_trunking().nfs4_discover_server_trunking()doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.EINVAL is never a sensible error code here. It means "Invalid
argument", but is being used when the problem is "Invalid response
from the server". If we change these two circumstances to report
EPROTONOSUPPORT to the caller (which seems a reasonable assessment
when the server gives confusing responses), and if we enhancenfs4_discover_server_trunking()to treat-EPROTONOSUPPORTas an
expected error to pass through, then the error reported to user-
space
will be more representative of the actual fault.A failure to negotiate a client ID clearly shows that NFSv4.1 cannot
be supported, but isn't as general a failure as EIO.Signed-off-by NeilBrown <[email protected]>--- fs/nfs/nfs4proc.c | 18 +++++++++++++++--- fs/nfs/nfs4state.c | 1 + 2 files changed, 16 insertions(+), 3 deletions(-)fs/nfs/nfs4proc.c +0
-0@@ -7364,7 +7364,8 @@ static intnfs4_check_cl_exchange_flags(u32
flags)fs/nfs/nfs4proc.c +1
-1goto out_inval;return NFS_OK ; out_inval: -return -NFS4ERR_INVAL ; + dprintk("NFS: server returns invalid flags forEXCHANGE_ID\n");
fs/nfs/nfs4proc.c +1
-0+return -EPROTONOSUPPORT ; } static bool@@ -7741,8 +7742,19 @@ static int_nfs4_proc_exchange_id(struct
nfs_client*clp, structrpc_cred*cred,fs/nfs/nfs4proc.c +0
-0int status; task = nfs4_run_exchange_id(clp, cred, sp4_how,NULL);
fs/nfs/nfs4proc.c +4
-2-if (IS_ERR (task)) -return PTR_ERR (task); +if (IS_ERR (task)) { + status =PTR_ERR (task); +if (status == -NFS4ERR_INVAL ) { +/* If the server think we did something
invalid, it is certainlyfs/nfs/nfs4proc.c +1
-0+* not the fault of our caller, so it
would
wrong to reportfs/nfs/nfs4proc.c +1
-0+* this error back up. So in that case
simply acknowledge thatfs/nfs/nfs4proc.c +1
-0+* we don't seem able to support this
protocol.fs/nfs/nfs4proc.c +2
-0+*/ + dprintk("NFS: server return
NFS4ERR_INVALto
EXCHANGE_ID\n");fs/nfs/nfs4proc.c +4
-0+ status = -EPROTONOSUPPORT ; + } +return status; + } argp = task->tk_msg.rpc_argp; resp = task->tk_msg.rpc_resp;fs/nfs/nfs4state.c +0
-0@@ -2219,6 +2219,7 @@ intnfs4_discover_server_trunking(struct
nfs_client*clp,fs/nfs/nfs4state.c +1
-0clnt = clp->cl_rpcclient; goto again; +case -EPROTONOSUPPORT :case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break ;Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]Signature · 3 lines
Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]
Quoted 5 lines · Tigran
Hi Neil,
according to rfc5661,
NFS4ERR_INVALis returned by the server if it thinks that client sends an invalid request (e.g. points to a client bug) or server misinterpret it (broken server).
Agreed.
Quoted 5 lines
With your change instead of failing the mount, client will silently go for v4.0, even v4.1 mount was requested and produce undesirable behavior, e.g. proxy-io instead of pnfs. I fill prefer fail-fast instead of long debug sessions.
I don't quite agree. With my change, the client will behave exactly the same way as if the server explicitly didn't support v4.1
So if you explicitly ask for v4.1, you will get a fail-fast. If you ask for "mount with whatever protocol seems to work" (the default), then you will get a protocol that works - not 4.1 in this case.
Quoted 4 lines
On the other hand, I understand, that it's not always possible to fix server or clients in production environment and time-to-time workarounds are necessary.
Yes. We are not overly eager to work-around broken implementations, but my memory is that we do it when it brings measurable benefits without unreasonable compromises.
In this can I am suggesting that change that results in a user-visible error of EPROTONOSUPPORT instead of EIO - in a case where the server doesn't respond to out v4.1 in the way we think it should. I don't think there is any compromise there.
Thanks,
NeilBrown
Quoted 56 lines
Tigran.
----- Original Message -----
Quoted 50 lines
From: "NeilBrown" <[email protected]>
To: "Trond Myklebust" <[email protected]>, "Anna Schumaker" <[email protected]>
Cc: "linux-nfs" <[email protected]>
Sent: Friday, March 16, 2018 12:44:23 AM
Subject: [PATCH - v2] NFSv4: handle EINVAL fromEXCHANGE_IDbetter.
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace), ornfs4_check_cl_exchange_flags()exchange flags detects a problem.
Each of these mean that NFSv4.1 later cannot be use, but they should not prevent fallback to NFSv4.0.Currently this EINVAL error is returned by
nfs4_proc_exchange_id()tonfs41_discover_server_trunking(), and thence tonfs4_discover_server_trunking().nfs4_discover_server_trunking()doesn't understand EINVAL, so converts it to EIO which causes mount.nfs to think something is horribly wrong and to give up.It would be a more graceful failure if
nfs4_discover_server_trunking()mapped-EINVALto-EPROTONOSUPPORT- a failure to negotiate a client ID clearly shows that NFSv4.1 cannot be supported, but isn't as general a failure as EIO.Signed-off-by NeilBrown <[email protected]>---
Sorry - a bit too trigger-happy with that first version of the patch.
NeilBrown
fs/nfs/nfs4state.c| 2 ++1 file changed, 2 insertions(+)fs/nfs/nfs4state.c +2
-1@@ -2219,6 +2219,8 @@ int nfs4_discover_server_trunking(struct nfs_client *clp, clnt = clp->cl_rpcclient; goto again; +case -NFS4ERR_INVAL : +/* Server confused - assume this minor isn't supported */ case -NFS4ERR_MINOR_VERS_MISMATCH : status = -EPROTONOSUPPORT ;break ; --2.14.0.rc0.dirty
Quoted 3 lines · NeilBrown
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace),
Can you say which server this was? (One we can fix?)
--b.
Quoted 6 lines · J. Bruce Fields
Quoted 3 lines · NeilBrown
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace),Can you say which server this was? (One we can fix?)
Unfortunately not - all I know is that it is a bit old and isn't SUSE (which doen't really narrow it down at all).
I've asked for more details and will pass on anything I discover.
Thanks,
NeilBrown
Quoted 6 lines · J. Bruce Fields
Quoted 3 lines · NeilBrown
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace),Can you say which server this was? (One we can fix?)
It was Linux 2.6.32 (on armv5), and presumably anything before
Commit: 357f54d6b382 ("NFS fix the setting of exchange id flag") which landed in 2.6.38.
These servers return NFS4ERR_INVAL when EXCHGID4_FLAG_BIND_PRINC_STATEID is set in the exchange_id flags, which Linux has done since
Commit: 4f0b429df104 ("NFSv4.1: Enable state protection")
in 3.11.
Maybe NFS should retry without that flag if it gets EINVAL?? Or it could just say that NFSv4.1 isn't supported. I still don't think EIO is justified.
Thanks,
NeilBrown
Quoted 4 lines · NeilBrown
Quoted 2 lines · J. Bruce Fields
Quoted 1 line · NeilBrown
Quoted 8 lines
Quoted 4 lines
Quoted 2 lines
nfs4_proc_exchange_id()can return-EINVALif the server reported NFS4INVAL (which I have seen in a packet trace),Can you say which server this was? (One we can fix?)
It was Linux 2.6.32 (on armv5), and presumably anything before
Commit:357f54d6b382("NFS fix the setting of exchange id flag") which landed in 2.6.38.
The kernel defaulted to keeping 4.1 off at that point, probably for good reason--that default didn't change for another 4 or 5 years. I suspect this is only the first of multiple 4.1 bugs you'd run into in a server of that vintage. So the solution is probably just to keep 4.1 off.
--b.
Quoted 11 lines
These servers return
NFS4ERR_INVALwhenEXCHGID4_FLAG_BIND_PRINC_STATEIDis set in theexchange_idflags, which Linux has done since
Commit:4f0b429df104("NFSv4.1: Enable state protection")
in 3.11.Maybe NFS should retry without that flag if it gets EINVAL?? Or it could just say that NFSv4.1 isn't supported. I still don't think EIO is justified.
Thanks,
NeilBrown