On Sun, Feb 04, 2007 at 05:40:35PM +0000, Anton Altaparmakov wrote: > On Sun, 4 Feb 2007, Andrew Morton wrote: > > truncate's OK: we're holding i_mutex. > > How about excluding readpage() (in addition to truncate if Nick is right > and some cases of truncate do not hold i_mutex) with an extra page flag as > I proposed for truncate exclusion? Then it would not matter that > prepare_write might have allocated blocks and might expose stale data. > It would go to sleep and wait on the bit to be cleared instead of trying > to bring the page uptodate. It can then lock the page and either find it > uptodate (because commit_write did it) or not and then bring it uptodate. > > Then we could safely fault in the page, copy from it into a temporary > page, then lock the destination page again and copy into it. > > This is getting more involved as a patch again... )-: But at least it > does not affect the common case except for having to check the new page > flag in every readpage() and truncate() call. But at least the checks > could be with an "if (unlikely(newpageflag()))" so should not be too bad. > > Have I missed anything this time? Yes. If you have a flag to exclude readpage(), then you must also exclude filemap_nopage, in which case it is still deadlocky. - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
