Messages in this thread | | | Date | Tue, 22 Oct 2002 12:23:41 -0700 | From | Andrew Morton <> | Subject | Re: [patch] generic nonlinear mappings, 2.5.44-mm2-D0 |
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Christoph Hellwig wrote: > > On Tue, Oct 22, 2002 at 07:57:00PM +0200, Ingo Molnar wrote: > > the attached patch (ontop of 2.5.44-mm2) implements generic (swappable!) > > nonlinear mappings and sys_remap_file_pages() support. Ie. no more > > MAP_LOCKED restrictions and strange pagefault semantics. > > > > to implement this i added a new pte concept: "file pte's". This means that > > upon swapout, shared-named mappings do not get cleared but get converted > > into file pte's, which can then be decoded by the pagefault path and can > > be looked up in the pagecache. > > > > the normal linear pagefault path from now on does not assume linearity and > > decodes the offset in the pte. This also tests pte encoding/decoding in > > the pagecache case, and the ->populate functions. > > Ingo, > > what is the reason for that interface? It looks like a gross performance > hack for misdesigned applications to me, kindof windowsish.. >
So that evicted pages in non-linear mappings can be reestablished at fault time by the kernel, rather than by delegation to userspace via SIGBUS.
We seem to have lost a pte_page_unlock() from fremap.c:zap_pte()? I fixed up the ifdef tangle in there within the shpte-ng patch and then put the pte_page_unlock() back.
I also added a page_cache_release() to the error path in filemap_populate(), if install_page() failed.
The 2TB file size limit for mmap on non-PAE is a little worrisome. I wonder if we can only instantiate the pte_file() bit if the mapping is using MAP_POPULATE? Seems hard to do. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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