Messages in this thread | | | Date | Sun, 7 Dec 2008 20:42:22 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] percpu_counter: Fix __percpu_counter_sum() |
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(cc stable)
On Sun, 7 Dec 2008 10:28:21 -0500 Theodore Tso <tytso@mit.edu> wrote:
> On Sat, Dec 06, 2008 at 08:22:33PM -0800, Andrew Morton wrote: > > > > 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. > > I've looked the two patches which you've queued in the -mm branch, and > they look correct to me. > > The bugs fixed by these patches can potentially lead to filesystem > corruption, since we ultimately use these fields to set the superblock > values. This in my mind makes them stable candidates at the very > least, and if we weren't so late in the 2.6.28 cycle, I'd be strongly > tempted to push them to Linus as a bugfix before the merge window. > > Andrew, any strong objections for me to grab them for the ext4 tree? > Or would you rather carry them? I would prefer that they get pushed > to Linus as soon as the merge window opens, which is one reason why > I'd prefer carry them, but we can do this either way. >
I'm planning on sending them off to Linus for 2.6.28 this week, assuming nobody can think of a plausible reason to not do that.
Now I didn't look _very_ closely at the chronology, but I think that revert-percpu-counter-clean-up-percpu_counter_sum_and_set.patch reverts a post-2.6.27 change, and is not needed in stable.
revert-percpu_counter-new-function-percpu_counter_sum_and_set.patch however reverts a pre-2.6.27 change, and should be merged into 2.6.27. This patch reverts the addition and use of percpu_counter_sum_and_set(), which is racy and can corrupt the counters.
However revert-percpu_counter-new-function-percpu_counter_sum_and_set.patch won't apply to 2.6.27 because the dirty_blocks stuff was added and generates rejects.
So if all the above is correct, I'd propose that if and when revert-percpu_counter-new-function-percpu_counter_sum_and_set.patch hits mainline, we should ask the -stable guys to directly revert
commit e8ced39d5e8911c662d4d69a342b9d053eaaac4e Author: Mingming Cao <cmm@us.ibm.com> Date: Fri Jul 11 19:27:31 2008 -0400
percpu_counter: new function percpu_counter_sum_and_set
which should be all that 2.6.27.x needs.
Agree? If so, can you please take care of getting that patch over to stable@kernel.org? (I added the cc:stable to the diff, so there's probably nothing which you need to do..)
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