fabrics: fix incorrect access filename check

[martin-gpy]

Config JSON file handling is currently broken due to an incorrect access filename check. Fix it.

[igaw]

Can you elaborate what you are doing. I am pretty sure I added this on purpose during my testing. So what did I miss?

[martin-gpy]

Can you elaborate what you are doing. I am pretty sure I added this on purpose during my testing. So what did I miss?

Well, I was just passing the JSON config file using the -J option to the nvme connect-all command, which ended up failing:

nvme connect-all -J <filename>

Turns out access returns a zero if the filename exists & non-zero if otherwise. So this current check actually returns an ENOENT if the JSON file exists:

if (!access(filename, F_OK)) return -ENOENT;

So all one needs to do is switch the check to make this work, and that's what this patch does:

if (access(filename, F_OK)) return -ENOENT;

[igaw]

Ah, I think I figured out why I didn't see any problem during my testing. I only tested with connect which doesn't use this function for checking if there is config. So this one makes sense.

We might also return errno; I'll update the patch accordingly.