Messages in this thread | | | Date | Tue, 13 May 2003 15:06:26 -0700 | From | William Lee Irwin III <> | Subject | Re: [RFC][PATCH] Fix for latent bug in vmtruncate() |
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On Tue, May 13, 2003 at 01:58:07PM -0700, Paul E. McKenney wrote: > The vmtruncate() function shifts down by PAGE_CACHE_SHIFT, then > calls vmtruncate_list(), which deals in terms of PAGE_SHIFT > instead. Currently, no harm done, since PAGE_CACHE_SHIFT and > PAGE_SHIFT are identical. Some day they might not be, hence > this patch. > I also took the liberty of modifying a hand-coded "if" that > seems to optimize for files that are not mapped to instead > use unlikely().
pgoff describes a file offset in the same units used to map files with (the size of an area covered by a PTE), which is PAGE_SIZE (in mainline; elsewhere it's called MMUPAGE_SIZE and I had to fix this already for my tree). When they differ this would lose the offset into the PAGE_CACHE_SIZE-sized file page; hence, well-spotted.
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