On Thu 19-11-20 22:36:00, Theodore Y. Ts'o wrote: > On Tue, Aug 25, 2020 at 10:41:37AM +0200, Jan Kara wrote: > > On Tue 25-08-20 10:11:29, yebin wrote: > > > Your patch certainly can fix the problem with my testcases, but I don't > > > think it's a good way. There are other paths that can call > > > do_invalidatepage , for instance block ioctl to discard and zero_range. > > > > OK, good point! So my patch is a cleanup that stands on its own and we > > should do it regardless. But I agree we need more to completely fix this. > > I don't quite like the callback you've added just for this special case > > (furthermore it grows size of every buffer_head and there can be lots of > > those). But I agree with the general idea that we shouldn't discard buffers > > that the filesystem is working with. > > > > In fact I believe that fallocate(2) and zeroout/discard ioctls should > > return EBUSY if they are run against a mounted device because with 99% > > probability something went wrong and you're accidentally discarding the > > wrong device. But maybe I'm wrong. I'll run this idea through other fs > > developers. > > I'm going through old patches, and I'm trying to figure out where did > we end up on this issue? Did we come to a conclusion on this? Yes, it is fixed by 384d87ef2c95 ("block: Do not discard buffers under a mounted filesystem"). Also the block_write_full_page() got fixed up by 6dbf7bb555981 ("fs: Don't invalidate page buffers in block_write_full_page()"). So we should be all set. > One other thing which I noticed when looking at the original patch was > shouldn't lvreduce not be allowed to run on a LV which has a mounted > file system on its block device? No, that is IMO working by design. The expectation is you can online-shrink the fs and then lvreduce the device... Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR