f2fs-for-4.17-rc1 In this round, we've mainly focused on performance tuning and critical bug fixes occurred in low-end devices. Sheng Yong introduced lost_found feature to keep missing files during recovery instead of thrashing them. We're preparing coming fsverity implementation. And, we've got more features to communicate with users for better performance. In low-end devices, some memory-related issues were fixed, and subtle race condtions and corner cases were addressed as well. Enhancement: - large nat bitmaps for more free node ids - add three block allocation policies to pass down write hints given by user - expose extension list to user and introduce hot file extension - tune small devices seamlessly for low-end devices - set readdir_ra by default - give more resources under gc_urgent mode regarding to discard and cleaning - introduce fsync_mode to enforce posix or not - nowait aio support - add lost_found feature to keep dangling inodes - reserve bits for future fsverity feature - add test_dummy_encryption for FBE Bug fix: - don't use highmem for dentry pages - align memory boundary for bitops - truncate preallocated blocks in write errors - guarantee i_times on fsync call - clear CP_TRIMMED_FLAG correctly - prevent node chain loop during recovery - avoid data race between atomic write and background cleaning - avoid unnecessary selinux violation warnings on resgid option - GFP_NOFS to avoid deadlock in quota and read paths - fix f2fs_skip_inode_update to allow i_size recovery In addition to them, there are several minor bug fixes and clean-ups.