On Thu, Jun 13, 2019 at 08:45:30PM -0300, Jason Gunthorpe wrote: > On Thu, Jun 13, 2019 at 02:13:21PM -0700, Ira Weiny wrote: > > On Thu, Jun 13, 2019 at 08:27:55AM -0700, Matthew Wilcox wrote: > > > On Thu, Jun 13, 2019 at 10:25:55AM +1000, Dave Chinner wrote: > > > > e.g. Process A has an exclusive layout lease on file F. It does an > > > > IO to file F. The filesystem IO path checks that Process A owns the > > > > lease on the file and so skips straight through layout breaking > > > > because it owns the lease and is allowed to modify the layout. It > > > > then takes the inode metadata locks to allocate new space and write > > > > new data. > > > > > > > > Process B now tries to write to file F. The FS checks whether > > > > Process B owns a layout lease on file F. It doesn't, so then it > > > > tries to break the layout lease so the IO can proceed. The layout > > > > breaking code sees that process A has an exclusive layout lease > > > > granted, and so returns -ETXTBSY to process B - it is not allowed to > > > > break the lease and so the IO fails with -ETXTBSY. > > > > > > This description doesn't match the behaviour that RDMA wants either. > > > Even if Process A has a lease on the file, an IO from Process A which > > > results in blocks being freed from the file is going to result in the > > > RDMA device being able to write to blocks which are now freed (and > > > potentially reallocated to another file). > > > > I don't understand why this would not work for RDMA? As long as the layout > > does not change the page pins can remain in place. > > Because process A had a layout lease (and presumably a MR) and the > layout was still modified in way that invalidates the RDMA MR. Oh sorry I miss read the above... (got Process A and B mixed up...) Right, but Process A still can't free those blocks because the gup pin exists on them... So yea it can't _just_ be a layout lease which controls this on the "file fd". Ira
