Issue opening file on NFS read-only mount

[Bob Apodaca]

On 10/31/2013 02:19 AM, N.M. Maclaren wrote:
> On Oct 30 2013, Janne Blomqvist wrote:
>>
>> I don't think it's a bug in gfortran; as you can see from the traces,
>> the exact same open() call is made in both cases.
>>
>> My guess it's a bug in the kernel.   Googling for "Linux NFS ENOTDIR"
>> turns up a number of suspicious bugs that might be related to the
>> problem you're seeing.
>
> Or possibly one in the NFS server (or an incompatibility between it and
> the client), though I don't know the NFS protocol well enough to more
> than guess and haven't looked (as you have).
>
> But this class of failure is ancient (pre-Unix!) and ubiquitous, and
> is inherent in the conflict between Fortran's file model and almost
> every file system interface.  I would dearly like to see not providing
> ACTION on OPEN deprecated, but have tried and failed with that one :-(
>
> Thinks:  Hmm.  That's a possible candidate for -Wextra!
>
>
> Regards,
> Nick Maclaren.
I am still investigating this issue and am not sure which direction to 
go. Things I have tried:
1. ACTION='READ' and got the same failure.
2. Changed the server to export the NFS share as read-write and the 
client to mount it as read-write. This fixed the problem but 
unfortunately is not a workable solution.

Next, I wrote a small C program that I hoped with make similar system 
calls I was seeing in the original FORTRAN code:

int main(void) {
   const char * path = "/mnt/nfs/stuff/stuff/more_stuff/file";
   FILE *fp;

   fp = fopen(path, "r+");
   if(fp == NULL) {
     printf("fopen() failed for %s with mode 'r+'\n", path);
   }

   fp = fopen(path, "r");
   if(fp == NULL) {
     printf("fopen() failed for %s with mode 'r'\n", path);
   } else {
     fclose(fp);
   }
   return(0);
}

This works as expected and gives an strace output similar to:

open("/mnt/nfs/stuff/stuff/more_stuff/file", O_RDWR) = -1 EROFS 
(Read-only file system)
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 
0) = 0xb77a7000
write(1, "fopen() failed for /mnt/nfs"..., 91fopen() failed for 
/mnt/nfs/stuff/stuff/more_stuff/file with mode 'rw'
) = 91
open("/mnt/nfs/stuff/stuff/more_stuff/file", O_RDONLY) = 3
close(3)                                = 0
exit_group(0)                           = ?

If you recall from my previous post, the FORTRAN strace was:

stat64("/mnt/nfs/stuff/stuff/more_stuff/file", {st_mode=S_IFREG|0664, 
st_size=15533, ...}) = 0
open("/mnt/nfs/stuff/stuff/more_stuff/file", O_RDWR|O_CREAT|O_LARGEFILE, 
0666) = -1 EROFS (Read-only file system)
open("/mnt/nfs/stuff/stuff/more_stuff/file", 
O_RDONLY|O_CREAT|O_LARGEFILE, 0666) = -1 ENOTDIR (Not a directory)
write(2, "At line 10 of file file_open.f ("..., 53At line 10 of file 
file_open.f (unit = 7, file = '')
) = 53
write(2, "Fortran runtime error: ", 23Fortran runtime error: ) = 23
write(2, "Not a directory", 15Not a directory)         = 15
write(2, "\n", 1
)                       = 1
exit_group(2)                           = ?

Could the O_CREAT in the second open() call be causing the problem? 
Would this be in the gfortran library?