Re: [RFD] readonly/read-write semantics

Alexander Viro (viro@math.psu.edu)
Sat, 1 Sep 2001 00:23:05 -0400 (EDT)


On Fri, 31 Aug 2001, Bryan Henderson wrote:

>
> 1) I want to see files open for write have nothing to do with it. Unix
> open/close is not a transaction, it's just a connection. Some applications
> manage to use open/close as a transaction, but we're seeing less and less
> of that as more sophisticated facilities for transactions become available.
>
> How many times have we all been frustrated trying to remount read only when
> some log file that hasn't been written to for hours is open for write?
>
> A file write is in progress when a write() system call hasn't returned, not
> when the file is open for write.

Uh-oh... How about shared mappings?

> 2) I'd like to see a readonly mount state defined as "the filesystem will
> not change. Period." Not for system calls in progress, not for cache
> synchronization, not to set an "unmounted" flag, not for writes that are
> queued in the device driver or device. (That last one may stretch
> feasability, but it's a worthy goal anyway).

It doesn't work. Think of r/o mounting of remote filesystem. Do you
suggest that it should make it impossible to change from other clients?

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