Messages in this thread | | | Date | Thu, 11 Jan 2007 14:02:41 -0800 | From | Andrew Morton <> | Subject | Re: 2.6.20-rc4: known regressions with patches (v3) |
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On Fri, 12 Jan 2007 08:39:16 +1100 David Chinner <dgc@sgi.com> wrote:
> On Thu, Jan 11, 2007 at 06:13:29AM +0100, Adrian Bunk wrote: > > This email lists some known regressions in 2.6.20-rc4 compared to 2.6.19 > > with patches available. > > > > Subject : BUG: at mm/truncate.c:60 cancel_dirty_page() (XFS) > > References : http://lkml.org/lkml/2007/1/5/308 > > Submitter : Sami Farin <7atbggg02@sneakemail.com> > > Handled-By : David Chinner <dgc@sgi.com> > > Patch : http://lkml.org/lkml/2007/1/7/201 > > Status : patch available > > Patch is broken, do not merge. The original had an off-by-one bug in > it, and the fixed one I have has just shown a worse problem than > before - partial page truncation (i.e. filesystem block size less > than page size) is busted because invalidate_complete_page2_range() can > only handle complete pages. > > Andrew - looking at unmap_mapping_pages, it says it cannot handle > partial pages and must get rid of them whereas vmtrucate() handles > partial pages but changes file size so can't be used. I see that > vmtruncate handles this by not unmapping the first partial page. > > I can use the vmtruncate mechanism (unmap_mapping_pages, then > truncate_inode_pages) but that seems racy to me because we are not > actually truncating the file so a mmap could remap a page between > the unmap and the truncate and hence we still get the warning.
Yes, truncate relies upon there being nothing outside i_size, and that i_mutex is held.
> So the question is - is there any generic function that handles > this case (i.e. don't unmap first partial page, unmap the rest, > partial truncate of first page, complete truncate of the rest) > without racing? Or do I need to write a variation of > invalidate_inode_pages2_range() to do this?
umm, nothing I can immediately think of. Perhaps you can generalise vmtruncate_range() a bit? - 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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