On Mon, Nov 11, 2024 at 02:57:06PM +1030, Qu Wenruo wrote: > Hi, > > Recently I'm working on migrating btrfs_buffered_write() to utilize > write_begin() and write_end() callbacks. Why? They aren't exactly efficient, and it's just going to create more Churn for Goldwyn's iomap work. > Currently only the following filesystems really utilizing that pointer: > > - bcachefs > Which is a structure of 24 bytes without any extra pointer. And as pointed out last time willy and I did go through the users of write_begin/end this is just dead code that is never called. > Thus I'm wondering should we make perform_generic_write() to accept a > *fsdata pointer, other than making write_begin() to allocate one. > So that we only need to allocate the memory (or use the on-stack one) > once per write, other than once per folio. And that scheme was one of my suggestions back then, together with removing write_begin/end from address_space_operations because they aren't operations called by MM/pagecache code, but just callbacks provided by the file system to perform_generic_write.
