Andrew Morton a écrit : > On Sun, 07 Dec 2008 14:28:00 +0100 Eric Dumazet <dada1@xxxxxxxxxxxxx> wrote: > >> Andrew Morton a __crit : >>> On Wed, 03 Dec 2008 21:24:36 +0100 Eric Dumazet <dada1@xxxxxxxxxxxxx> wrote: >>> >>>> Eric Dumazet a __crit : >>>> >>>> 1) __percpu_counter_sum() is buggy, it should not write >>>> on per_cpu_ptr(fbc->counters, cpu), or another cpu >>>> could get its changes lost. >>>> >>>> __percpu_counter_sum should be read only (const struct percpu_counter *fbc), >>>> and no locking needed. >>> No, we can't do this - it will break ext4. >>> >>> Take a closer look at 1f7c14c62ce63805f9574664a6c6de3633d4a354 and at >>> e8ced39d5e8911c662d4d69a342b9d053eaaac4e. >>> >>> I suggest that what we do is to revert both those changes. We can >>> worry about the possibly-unneeded spin_lock later, in a separate patch. >>> >>> It should have been a separate patch anyway. It's conceptually >>> unrelated and is not a bugfix, but it was mixed in with a bugfix. >>> >>> Mingming, this needs urgent consideration, please. Note that I had to >>> make additional changes to ext4 due to the subsequent introduction of >>> the dirty_blocks counter. >>> >>> >>> Please read the below changelogs carefully and check that I have got my >>> head around this correctly - I may not have done. >>> >> >> Hum... e8ced39d5e8911c662d4d69a342b9d053eaaac4e is probably following >> the wrong path, but I see the intent. Even in the 'nr_files' case, it could >> help to reduce excessive calls to percpu_counter_sum() >> > > We should fix this in 2.6.28 - right now percpu_counter_sum() is subtly > corrupting the counter's value. > > I sent two revert patches which I hope to merge into 2.6.28. Could you > guys please read/review/maybe-test them? Your revert patches have the same effect than my first patch : No writes in percpu_counter_sum() I am lost here Andrew... -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html