Messages in this thread | | | Date | Tue, 20 May 2014 21:32:47 -0700 (PDT) | From | Hugh Dickins <> | Subject | Re: remap_file_pages() use |
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On Tue, 20 May 2014, Kenny Simpson wrote:
> I might need a gentle nudge with a clue stick... > checking against latest git tree it looks as though most common > filesystem types do support remap_file_pages. > > I just wrote a simple test case and it worked on my 3.13-based ubuntu > 14.04 system on an ext4 filesystem.
It is all very confusing, yes.
When Kirill said disk-backed files don't support remap_file_pages since commit 3ee6dafc677a, he was meaning that that they do not support it with a special nonlinear vma; but the remap_file_pages syscall emulates the layout for them with separate linear vmas instead.
Confusingly, these filesystems opt in to this emulation by pointing their remap_pages method to generic_file_remap_pages - code which is then never used for them! tmpfs is the only filesystem (having no page_mkwrite) which actually passes through that code.
You can understand why there's some enthusiasm for cleaning this up :)
Hugh
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