Re: Memory mapped files question

["H. Peter Anvin" <hpa@zytor.com>]

Followup to:  <11640000.1050332688@[10.10.2.4]>
By author:    "Martin J. Bligh" <mbligh@aracnet.com>
In newsgroup: linux.dev.kernel
>
> > Martin, something which was not mentioned last week (I've just checked).
> > 
> > It's OK if we never write to disk unless explicitely told, but will we writeback
> > when we munmap?
> 
> Don't know for sure - you'd have to read the code (do_munmap) ... I couldn't
> see anything there at a quick glance. However, I'd guess we don't write it, 
> as multiple people could have the file mapped, or we could remap it
> again from somewhere. Presumably the standard LRU will just flush it out.
> 

munmap() and fsync() or msync() will flush it to disk; there is no
reason munmap() should unless perhaps the file was opened O_SYNC.

	-hpa

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