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small changes for plan 9 in Truncate and GetFileInfo; NFS server now works on Plan 9 #142

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small changes for plan 9 in Truncate and GetFileInfo; NFS server now works on Plan 9 #142

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rminnich
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@rminnich rminnich commented Jul 2, 2025

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I don't understand either of these changes

  • first commit resubmits Add plan 9 support for osFileInfo #141 which you haven't justified
  • second commit does not apply to truncate, and I can't find any documentation for why the 'exclusive' bit in opening a file is an issue in plan 9

@rminnich
Truncate: do not use O_EXCL on Plan 9
dbb21cc 
Signed-off-by: Ronald G Minnich <rminnich@gmail.com>
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rminnich commented Jul 3, 2025

ah, file_other.go was not there when I wrote file_plan9.go

As for O_EXCL, I see the actual problem:
linux:
" In general, the behavior of O_EXCL is undefined if it is used without O_CREAT. There is one ex‐
ception: on Linux 2.6 and later, O_EXCL can be used without O_CREAT if pathname refers to a block
device. If the block device is in use by the system (e.g., mounted), open() fails with the error
EBUSY."

Plan 9: O_EXCL only makes sense for create.

The flags currently are: os.O_WRONLY|os.O_EXCL

I don't think it even makes sense to use O_EXCL at all here, but on Plan 9 you get an error, and on linux you don't.

I think just dropping O_EXCL completely may be the proper fix. But the combination of os.O_WRONLY|os.O_EXCL gets an error on Plan 9.

rminnich added 2 commits July 9, 2025 09:25
@rminnich
Lstat: do not Log.Errorf for os.ErrNotExist
2f2b5e4 
Lots of programs (including git) do an Lstat to test
file existence. This can produce a lot of not-very-useful
spew. Just return nil for this error.

This makes the package more usable.

Signed-off-by: Ronald G Minnich <rminnich@gmail.com>
@rminnich
Create: warn, but do not error, when Exclusive is requested
6cd629d 
Exclusive over NFS has always been a dicey situation,
and failing breaks lots of things for which it is
mainly best-effort (e.g. git); if it does not work,
that is ok.

Print a warning message, but continue with the operation.

Signed-off-by: Ronald G Minnich <rminnich@gmail.com>
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@rminnich @willscott