Questions about pynfs:testLargeData-WRT5

Questions about pynfs:testLargeData-WRT5

[Lu Xinyu]

Hi,Bruce

I ran pynfs on the RHEL7.4GA with different kernels(3.10.0-830.el7,4.15). The testLargeData:WRT5 failed with broken pipe. I investigated pynfs code and got the following questions.

1.The intent of WRT5
To check whether the server could handle a too-large value over NFSSVC_MAXBLKSIZE.

2.The expected procedure when test gets passed
The server could write down the oversize data successfully sent by client and return NFS4_OK.
Then, client could read back the data from server.
(Actually, the test failed with broken pipe and did not return packet information.)

3.The nfs server's standrd procedure of handling oversize data
It seems that the related error is not defined in the RFC3530. Whether the server should return any NFSERR before ceasing receving ?

Thanks for check the above questions.

Best regards!

--
Lu Xinyu 
--

Re: Questions about pynfs:testLargeData-WRT5

[J. Bruce Fields]

On Fri, Feb 09, 2018 at 09:27:00AM +0800, Lu Xinyu wrote:
> I ran pynfs on the RHEL7.4GA with different
> kernels(3.10.0-830.el7,4.15). The testLargeData:WRT5 failed with
> broken pipe. I investigated pynfs code and got the following
> questions.
> 
> 1.The intent of WRT5 To check whether the server could handle a
> too-large value over NFSSVC_MAXBLKSIZE.
> 
> 2.The expected procedure when test gets passed The server could write
> down the oversize data successfully sent by client and return NFS4_OK.
> Then, client could read back the data from server.

Yes, that test is definitely wrong.  It might happen to work on servers
that support larger IO size, but the Linux server doesn't.  And, anyway,
it's perfectly legal for a server to only support lower read/write size.

So, the test needs check the server's advertised maximum read and write
sizes, and then either:

	1) use that maximum size, and expect success, or
	2) use a larger size and expect some sort of error.

> (Actually, the test failed with broken pipe and did not return packet
> information.)
> 
> 3.The nfs server's standrd procedure of handling oversize data It
> seems that the related error is not defined in the RFC3530. Whether
> the server should return any NFSERR before ceasing receving ?

I'm not sure if the RFC's specify the behavior here.  I'll go do some
research.  I have a feeling they don't.  In that case I think the best
option will be 1) above.

--b.

Re: Questions about pynfs:testLargeData-WRT5

[Trond Myklebust]

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Re: Questions about pynfs:testLargeData-WRT5

[J. Bruce Fields]

On Fri, Feb 09, 2018 at 03:04:42PM +0000, Trond Myklebust wrote:
> For NFSv4, you would have the option of returning NFS4ERR_RESOURCE or
> possibly NFS4ERR_INVAL (personally, I'd prefer the latter, since
> NFS4ERR_RESOURCE is too wooly).
> 
> For NFSv4.1 or above, you probably have a choice of NFS4ERR_REQ_TOO_BIG
> (if the size is greater than ca_maxrequestsize) or NFS4ERR_INVAL.

I think this sort of problem is typically found early in the rpc code
(probably the check against sv_max_mesg in
net/sunrpc/svcsock.c:svc_tcp_recv_record()).  It drops the connection.
I'm not sure why.

Returning an NFS-level error does sound friendlier.  I guess I'd do that
by throwing away the rest of the request data and setting a flag on the
svc_rqst saying "this request was too long, don't trust the data" and
then making NFS check for that flag somewhere early on.

The only case I can recall seeing this in practice is when the limits
change across reboots.  Which is something to avoid.  But the choice of
failure mode might make this more or less easy to diagnose or recover
from....

--b.

Re: Questions about pynfs:testLargeData-WRT5

[Seiichi Ikarashi]

On Fri, 9 Feb 2018 13:31:12 -0500, J. Bruce Fields wrote:

>> For NFSv4, you would have the option of returning NFS4ERR_RESOURCE or
>> possibly NFS4ERR_INVAL (personally, I'd prefer the latter, since
>> NFS4ERR_RESOURCE is too wooly).
>>
>> For NFSv4.1 or above, you probably have a choice of NFS4ERR_REQ_TOO_BIG
>> (if the size is greater than ca_maxrequestsize) or NFS4ERR_INVAL.
> 
> I think this sort of problem is typically found early in the rpc code
> (probably the check against sv_max_mesg in
> net/sunrpc/svcsock.c:svc_tcp_recv_record()).  It drops the connection.
> I'm not sure why.

It looks implemented long time ago.

[PATCH] PATCH 11/16: NFSD: TCP: close bad connections
https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=84e9f22a623a

Regards,
Ikarashi

Re: Questions about pynfs:testLargeData-WRT5

[J. Bruce Fields]

On Tue, Feb 13, 2018 at 12:19:58PM +0900, Seiichi Ikarashi wrote:
> 
> On Fri, 9 Feb 2018 13:31:12 -0500, J. Bruce Fields wrote:
> 
> >> For NFSv4, you would have the option of returning NFS4ERR_RESOURCE or
> >> possibly NFS4ERR_INVAL (personally, I'd prefer the latter, since
> >> NFS4ERR_RESOURCE is too wooly).
> >>
> >> For NFSv4.1 or above, you probably have a choice of NFS4ERR_REQ_TOO_BIG
> >> (if the size is greater than ca_maxrequestsize) or NFS4ERR_INVAL.
> > 
> > I think this sort of problem is typically found early in the rpc code
> > (probably the check against sv_max_mesg in
> > net/sunrpc/svcsock.c:svc_tcp_recv_record()).  It drops the connection.
> > I'm not sure why.
> 
> It looks implemented long time ago.
> 
> [PATCH] PATCH 11/16: NFSD: TCP: close bad connections
> https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=84e9f22a623a

Thanks for tracking that down!

If the length is just ridiculous then closing is our best option, but if
it's within a few megabytes (as might happen if the maximum size changes
over reboot), then I think it might still be reasonable to receive the
whole thing, throw away the data, and return an error.

But, I'm not sure whether it's really an improvement.  The spec's
unlikely to provide much guidance, so it'd probably be a question of
figuring out what the likely client behavior is.

So, if somebody wanted to make a case for it I'd look at patches, but I
think it's not a priority.

WRT5 is wrong in any case, I'll fix it.

--b.

Re: Questions about pynfs:testLargeData-WRT5

[J. Bruce Fields]

On Tue, Feb 13, 2018 at 11:15:40AM -0500, J. Bruce Fields wrote:
> WRT5 is wrong in any case, I'll fix it.

How about this?

--b.

commit 30f1fff66da3
Author: J. Bruce Fields <bfields@redhat.com>
Date:   Tue Feb 13 16:30:27 2018 -0500

    4.0 server tests: replace WRT5 by better tests
    
    This test is sending a write that (at least in the knfsd case) is larger
    than the server's maximum write size, and expecting it to succeed.
    That's weird.
    
    Remove WRT5 and replace it by two tests.  Both first query the maximum
    write size.  One does a large (but not too large) write and checks that
    the data was written correctly.  The other does a too-large write and
    expects nothing.  (A wide variety of server behavior would be in spec;
    we do this just in case a buggy server might crash.)
    
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/nfs4.0/servertests/st_write.py b/nfs4.0/servertests/st_write.py
index 710452efa11d..004562d2f52b 100644
--- a/nfs4.0/servertests/st_write.py
+++ b/nfs4.0/servertests/st_write.py
@@ -120,17 +120,22 @@ def testNoData(t, env):
     if compareTimes(time_prior,time_after) != 0:
         t.fail("WRITE with no data affected time_modify")
 
+#WRT5 permanently retired
+
 def testLargeData(t, env):
-    """WRITE with a large amount of data
+    """WRITE with the maximum size, READ it back and compare
 
     FLAGS: write read all
     DEPEND: MKFILE
-    CODE: WRT5
+    CODE: WRT5a
     """
     c = env.c1
     c.init_connection()
+    maxread, maxwrite = _get_iosize(t, c, c.homedir)
+    maxio = min(maxread, maxwrite)
     fh, stateid = c.create_confirm(t.code)
-    data = "abcdefghijklmnopq" * 0x10000
+    pattern="abcdefghijklmnop"
+    data = pattern * (maxio / len(pattern)) + "q" * (maxio % len(pattern))
     # Write the data
     pos = 0
     while pos < len(data):
@@ -150,6 +155,27 @@ def testLargeData(t, env):
     if data != newdata:
         t.fail("READ did not correspond to WRITE with large dataset")
 
+def testTooLargeData(t, env):
+    """WRITE with more than the maximum size
+
+    FLAGS: write read all
+    DEPEND: MKFILE
+    CODE: WRT5b
+    """
+    c = env.c1
+    c.init_connection()
+    maxread, maxwrite = _get_iosize(t, c, c.homedir)
+    fh, stateid = c.create_confirm(t.code)
+    data = "a" * (maxwrite + 1000000)
+    try:
+        # We don't care much what the server does, this is just a check
+        # to make sure it doesn't crash.
+        res = c.write_file(fh, data, 0, stateid)
+    except IOError:
+        # Linux knfsd closes the socket when the write is too large.
+        # That's OK.
+        pass
+
 def testDir(t, env):
     """WRITE to a dir should return NFS4ERR_ISDIR
 

Re: Questions about pynfs:testLargeData-WRT5

[Daniel Gryniewicz]

This looks sane, and like a good improvement.

Daniel

On 02/14/2018 10:49 AM, J. Bruce Fields wrote:
> On Tue, Feb 13, 2018 at 11:15:40AM -0500, J. Bruce Fields wrote:
>> WRT5 is wrong in any case, I'll fix it.
> 
> How about this?
> 
> --b.
> 
> commit 30f1fff66da3
> Author: J. Bruce Fields <bfields@redhat.com>
> Date:   Tue Feb 13 16:30:27 2018 -0500
> 
>      4.0 server tests: replace WRT5 by better tests
>      
>      This test is sending a write that (at least in the knfsd case) is larger
>      than the server's maximum write size, and expecting it to succeed.
>      That's weird.
>      
>      Remove WRT5 and replace it by two tests.  Both first query the maximum
>      write size.  One does a large (but not too large) write and checks that
>      the data was written correctly.  The other does a too-large write and
>      expects nothing.  (A wide variety of server behavior would be in spec;
>      we do this just in case a buggy server might crash.)
>      
>      Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> diff --git a/nfs4.0/servertests/st_write.py b/nfs4.0/servertests/st_write.py
> index 710452efa11d..004562d2f52b 100644
> --- a/nfs4.0/servertests/st_write.py
> +++ b/nfs4.0/servertests/st_write.py
> @@ -120,17 +120,22 @@ def testNoData(t, env):
>       if compareTimes(time_prior,time_after) != 0:
>           t.fail("WRITE with no data affected time_modify")
>   
> +#WRT5 permanently retired
> +
>   def testLargeData(t, env):
> -    """WRITE with a large amount of data
> +    """WRITE with the maximum size, READ it back and compare
>   
>       FLAGS: write read all
>       DEPEND: MKFILE
> -    CODE: WRT5
> +    CODE: WRT5a
>       """
>       c = env.c1
>       c.init_connection()
> +    maxread, maxwrite = _get_iosize(t, c, c.homedir)
> +    maxio = min(maxread, maxwrite)
>       fh, stateid = c.create_confirm(t.code)
> -    data = "abcdefghijklmnopq" * 0x10000
> +    pattern="abcdefghijklmnop"
> +    data = pattern * (maxio / len(pattern)) + "q" * (maxio % len(pattern))
>       # Write the data
>       pos = 0
>       while pos < len(data):
> @@ -150,6 +155,27 @@ def testLargeData(t, env):
>       if data != newdata:
>           t.fail("READ did not correspond to WRITE with large dataset")
>   
> +def testTooLargeData(t, env):
> +    """WRITE with more than the maximum size
> +
> +    FLAGS: write read all
> +    DEPEND: MKFILE
> +    CODE: WRT5b
> +    """
> +    c = env.c1
> +    c.init_connection()
> +    maxread, maxwrite = _get_iosize(t, c, c.homedir)
> +    fh, stateid = c.create_confirm(t.code)
> +    data = "a" * (maxwrite + 1000000)
> +    try:
> +        # We don't care much what the server does, this is just a check
> +        # to make sure it doesn't crash.
> +        res = c.write_file(fh, data, 0, stateid)
> +    except IOError:
> +        # Linux knfsd closes the socket when the write is too large.
> +        # That's OK.
> +        pass
> +
>   def testDir(t, env):
>       """WRITE to a dir should return NFS4ERR_ISDIR
>   
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
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> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: Questions about pynfs:testLargeData-WRT5

[Seiichi Ikarashi]

On 2018-02-15 00:49, J. Bruce Fields wrote:
> On Tue, Feb 13, 2018 at 11:15:40AM -0500, J. Bruce Fields wrote:
>> WRT5 is wrong in any case, I'll fix it.
> 
> How about this?
> 
> --b.
> 
> commit 30f1fff66da3
> Author: J. Bruce Fields <bfields@redhat.com>
> Date:   Tue Feb 13 16:30:27 2018 -0500
> 
>     4.0 server tests: replace WRT5 by better tests
>     
>     This test is sending a write that (at least in the knfsd case) is larger
>     than the server's maximum write size, and expecting it to succeed.
>     That's weird.
>     
>     Remove WRT5 and replace it by two tests.  Both first query the maximum

Really good to split it into WRT5a and WRT5b!

>     write size.  One does a large (but not too large) write and checks that
>     the data was written correctly.  The other does a too-large write and
>     expects nothing.  (A wide variety of server behavior would be in spec;
>     we do this just in case a buggy server might crash.)
>     
>     Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> diff --git a/nfs4.0/servertests/st_write.py b/nfs4.0/servertests/st_write.py
> index 710452efa11d..004562d2f52b 100644
> --- a/nfs4.0/servertests/st_write.py
> +++ b/nfs4.0/servertests/st_write.py
> @@ -120,17 +120,22 @@ def testNoData(t, env):
>      if compareTimes(time_prior,time_after) != 0:
>          t.fail("WRITE with no data affected time_modify")
>  
> +#WRT5 permanently retired
> +
>  def testLargeData(t, env):

How about the name "testMaximumData()" or something?
It's not just "Large".

> -    """WRITE with a large amount of data
> +    """WRITE with the maximum size, READ it back and compare
>  
>      FLAGS: write read all
>      DEPEND: MKFILE
> -    CODE: WRT5
> +    CODE: WRT5a
>      """
>      c = env.c1
>      c.init_connection()
> +    maxread, maxwrite = _get_iosize(t, c, c.homedir)
> +    maxio = min(maxread, maxwrite)
>      fh, stateid = c.create_confirm(t.code)
> -    data = "abcdefghijklmnopq" * 0x10000
> +    pattern="abcdefghijklmnop"
> +    data = pattern * (maxio / len(pattern)) + "q" * (maxio % len(pattern))
>      # Write the data
>      pos = 0
>      while pos < len(data):
> @@ -150,6 +155,27 @@ def testLargeData(t, env):
>      if data != newdata:
>          t.fail("READ did not correspond to WRITE with large dataset")
>  
> +def testTooLargeData(t, env):
> +    """WRITE with more than the maximum size

                with 10^6 bytes beyond the maximum size

Regards,
Ikarashi

> +
> +    FLAGS: write read all
> +    DEPEND: MKFILE
> +    CODE: WRT5b
> +    """
> +    c = env.c1
> +    c.init_connection()
> +    maxread, maxwrite = _get_iosize(t, c, c.homedir)
> +    fh, stateid = c.create_confirm(t.code)
> +    data = "a" * (maxwrite + 1000000)
> +    try:
> +        # We don't care much what the server does, this is just a check
> +        # to make sure it doesn't crash.
> +        res = c.write_file(fh, data, 0, stateid)
> +    except IOError:
> +        # Linux knfsd closes the socket when the write is too large.
> +        # That's OK.
> +        pass
> +
>  def testDir(t, env):
>      """WRITE to a dir should return NFS4ERR_ISDIR
>  
> 
> 
> .
> 

Re: Questions about pynfs:testLargeData-WRT5

[J. Bruce Fields]

On Thu, Feb 15, 2018 at 11:08:51AM +0900, Seiichi Ikarashi wrote:
> How about the name "testMaximumData()" or something?
> It's not just "Large".
...
> > +def testTooLargeData(t, env):
> > +    """WRITE with more than the maximum size
> 
>                 with 10^6 bytes beyond the maximum size

Both done, thanks.--b.

RE: Questions about pynfs:testLargeData-WRT5

[Frank Filz]

> On Fri, Feb 09, 2018 at 09:27:00AM +0800, Lu Xinyu wrote:
> > I ran pynfs on the RHEL7.4GA with different
> > kernels(3.10.0-830.el7,4.15). The testLargeData:WRT5 failed with
> > broken pipe. I investigated pynfs code and got the following
> > questions.
> >
> > 1.The intent of WRT5 To check whether the server could handle a
> > too-large value over NFSSVC_MAXBLKSIZE.
> >
> > 2.The expected procedure when test gets passed The server could write
> > down the oversize data successfully sent by client and return NFS4_OK.
> > Then, client could read back the data from server.
> 
> Yes, that test is definitely wrong.  It might happen to work on servers
that
> support larger IO size, but the Linux server doesn't.  And, anyway, it's
perfectly
> legal for a server to only support lower read/write size.

The test does happen to pass on Ganesha.

> So, the test needs check the server's advertised maximum read and write
sizes,
> and then either:
> 
> 	1) use that maximum size, and expect success, or
> 	2) use a larger size and expect some sort of error.
> 
> > (Actually, the test failed with broken pipe and did not return packet
> > information.)
> >
> > 3.The nfs server's standrd procedure of handling oversize data It
> > seems that the related error is not defined in the RFC3530. Whether
> > the server should return any NFSERR before ceasing receving ?
> 
> I'm not sure if the RFC's specify the behavior here.  I'll go do some
research.  I
> have a feeling they don't.  In that case I think the best option will be
1) above.

That's probably the right thing to do.

Frank


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