> IS_SWAPFILE isn't going way, as can't allow other writers to it. > Also asides from the that the layouts are fairly complex. > > The right way ahead for swap is to literally just treat it as a slightly > special case of direct I/o that is allowed to IS_SWAPFILE files. We > can safely do writeback to file backed folios under memory pressure, > so we can also go through the normal file system path. But that is prone to low-memory-deadlock because the filesystems allocate buffer memory when they are mapping logical blocks to physical blocks. You would need to have a mempool in the filesystems, so that they can make forward progress even if there is no memory free - and that would complicate them. GFP_NOIO won't help if the memory is completely exhausted. Only mempool would help in this situation. Mikulas
