On Sun, 2007-09-02 at 15:20 +0200, Nick Piggin wrote: > OK, but then hasn't the patch just made the deadlock harder to hit, > or is there some invariant that says that readpage() will never be > invoked if gc was invoked on the same page as we're commit_write()ing?
> The Q/A comments aren't very sure about this. I guess from the look > of it, prepare_write/commit_write make sure the page will be uptodate > by the start of commit_write, That's the intention, yes. > and you avoid GCing the page in > prepare_write because your new page won't have any nodes allocated > yet that can possibly be GCed? We _might_ GC the page -- it might not be a new page; we might be overwriting it. But it's fine if we do. Actually it's slightly suboptimal because we'll write out the same data twice -- once in GC and then immediately afterward in the write which we were making space for. But that's not the end of the world, and it's not very common. > BTW. with write_begin/write_end, you get to control the page lock, > so for example if the readpage in prepare_write for partial writes > is *only* for the purpose of avoiding this deadlock later, you > could possibly avoid the RMW with the new aops. Maybe it would > help you with data nodes crossing page boundaries too... I'll look at that; thanks. > OK, thanks for looking at it. If you'd care to pass it on to Linus > before he releases 2.6.23 in random() % X days time... ;) Not before the Kernel Summit now, I suspect. But yes, I'll do that later today or in the morning (the linuxconf.eu conference has already started). -- dwmw2 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/