Error codes for VFS calls

Shyam Prasad N nspmangalore at
Thu Oct 1 10:59:38 UTC 2020

Hi developers,

I seek your opinions about the error codes returned by the Linux
filesystem for the I/Os triggered by users. In general, each VFS
system call (open, read, write, close, stat) man page defines a
limited set of error codes returned by the call, and the meaning of
the error, in the context of that call.

But in many cases, especially in network based filesystems, this
limited set of error codes may not be sufficient to indicate the exact
problem to the user. For example, in case of SMB3, where things like
authentication or actual mount of the filesystem may be delayed to the
point of first I/O by the specific user on the mount point, having a
limited set of error codes could end up confusing the user, and not
indicate the actual error to the user.

So my questions here:
1. Should the error codes be specific to the filesystem in question,
and not just specific to the VFS system call?
2. Do we have any other mechanism of returning a custom error message
to the user (the one that tells the user about the exact problem in
more detail), other than to print this in the logs?


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