On Thu, Mar 04, 2021 at 06:47:41PM +0100, David Sterba wrote: > On Wed, Feb 10, 2021 at 05:14:32PM -0500, Josef Bacik wrote: > > v1->v2: > > - Rebase against misc-next. > > - Add Filipe's reviewed-bys. > > > > --- Original email --- > > > > Hello, > > > > Both Filipe and I have found different issues that result in the same > > thing, we > > need to be able to exclude mmap from happening in certain scenarios. The > > specifics are well described in the commit logs, but generally there's 2 > > issues > > > > 1) dedupe needs to validate that pages match, and since the validation is > > done > > outside of the extent lock we can race with mmap and dedupe pages that > > do not > > match. > > 2) We can deadlock in certain low metadata scenarios where we need to flush > > an ordered extent, but can't because mmap is holding the page lock. > > > > These issues exist for remap and fallocate, so add an i_mmap_sem to allow > > us to > > disallow mmap in these cases. I'm still waiting on xfstests to finish with > > this, but 2 hours in and no lockdep or deadlocks. Thanks, > > > > Josef Bacik (4): > > btrfs: add a i_mmap_lock to our inode > > btrfs: cleanup inode_lock/inode_unlock uses > > btrfs: exclude mmaps while doing remap > > btrfs: exclude mmap from happening during all fallocate operations > > Added as a topic branch to for-next.
Moved to misc-next. The added semaphore is not exactly cheap in terms of in memory inode, but the dio_sem got removed recently so it's not that bad. Regarding performance, there's probably some hit but in this case correctness must come first so we can't do much about that. Thanks.