Messages in this thread Patch in this message | | | Subject | Re: [PATCH] Add notification of page becoming writable to VMA ops | From | Anton Altaparmakov <> | Date | Tue, 25 Oct 2005 08:59:19 +0100 |
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On Mon, 2005-10-24 at 20:11 +0100, Hugh Dickins wrote: > On Mon, 24 Oct 2005, David Howells wrote: > > > > The attached patch adds a new VMA operation to notify a filesystem or other > > driver about the MMU generating a fault because userspace attempted to write > > to a page mapped through a read-only PTE. > > > > This facility permits the filesystem or driver to: > > > > (*) Implement storage allocation/reservation on attempted write, and so to > > deal with problems such as ENOSPC more gracefully (perhaps by generating > > SIGBUS). > > > > (*) Delay making the page writable until the contents have been written to a > > backing cache. This is useful for NFS/AFS when using FS-Cache/CacheFS. > > It permits the filesystem to have some guarantee about the state of the > > cache. > > I've only given it a quick look, it looks pretty good, but too hastily > thrown together, without understanding of the intervening changes:
There really is quite a difference between mm/*.c in -mm and Linus kernel at present. Is all this planned to be merged as soon as 2.6.14 is out or is -mm just a playground for now with no mainline merge intentions?
Just asking so I know whether to work against stock kernels or -mm for the moment...
[snip some corrections I am in no position to comment on at the moment] > > @@ -1945,7 +1998,7 @@ static int do_file_page(struct mm_struct > > Drop all those changes to do_file_page (which I added), they're no > longer necessary. A case appeared which made it clear that we cannot > rely on resolving this issue for get_user_pages in a single call to > handle_mm_fault, and that's why the VM_FAULT_WRITE stuff got added. > > This complication of do_file_page was always ugly, and I'm delighted > to drop it. Whereas the call to do_wp_page from do_swap_page is less > obtrusive and may still be a worthwhile optimization, though I added > it for the same disgraced reason a year or more back.
Cool, that reduces the size of the patch. (-:
Best regards,
Anton -- Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/
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