Messages in this thread | | | Date | Mon, 14 Jan 2008 18:21:15 +0100 | From | Jens Axboe <> | Subject | Re: [patch] rewrite rd |
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On Mon, Jan 14 2008, Matthew Wilcox wrote: > On Tue, Dec 04, 2007 at 05:26:28AM +0100, Nick Piggin wrote: > > +static void copy_to_brd(struct brd_device *brd, const void *src, > > + sector_t sector, size_t n) > > +{ > > + struct page *page; > > + void *dst; > > + unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; > > + size_t copy; > > + > > + copy = min((unsigned long)n, PAGE_SIZE - offset); > > + page = brd_lookup_page(brd, sector); > > + BUG_ON(!page); > > + > > + dst = kmap_atomic(page, KM_USER1); > > + memcpy(dst + offset, src, copy); > > + kunmap_atomic(dst, KM_USER1); > > You're using kmap_atomic, but I see no reason you can't be preempted. > Don't you need to at least disable preemption while you have stuff > atomically kmapped?
kmap_atomic() disables preemption through pagefault_disable().
-- Jens Axboe
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