Page type

evictable

page dirty

clear_page_dirty_for_io  In the actual file system, there are a lot of , But it is all to support some special features of these file systems , such as f2fs The garbage collection of .

mm/page-writeback.c 2228 Row or so , Found calling the actual file system writeback Before writing back , Will cancel the dirty bit of the file , So to the real write_back Before ,

 Actually page Of dirty There are no more seats !

 meanwhile ,write_one_page Function , Calling precious writeback The dirty bit of the page will also be removed before the function !


Call trace:
[<ffffffc00008960c>] dump_backtrace+0x0/0x12c
[<ffffffc000089748>] show_stack+0x10/0x1c
[<ffffffc00034d97c>] do_write_data_page+0xa8/0x77c
[<ffffffc00034e44c>] f2fs_write_data_page+0x3fc/0x5dc
[<ffffffc00034761c>] __f2fs_writepage+0x18/0x60
[<ffffffc000180d70>] write_cache_pages+0x1f0/0x5b4  In this function page Of  dirty  sign  PG_dirty  eliminate .  Then enter write back  The process ,  Set before writing write back sign , And in bio After that ,  stay bio In the callback function of writeback The flag bit is cleared . 

[<ffffffc000348cbc>] f2fs_write_data_pages+0xf8/0x370
[<ffffffc000181bd4>] do_writepages+0x20/0x44
[<ffffffc000204e20>] __writeback_single_inode+0xac/0xbb0
[<ffffffc000205ba4>] writeback_sb_inodes+0x280/0x518
[<ffffffc000205ed4>] __writeback_inodes_wb+0x98/0xe0
[<ffffffc0002061d0>] wb_writeback+0x2b4/0x73c
[<ffffffc0002076c4>] wb_workfn+0x3d8/0x98c
[<ffffffc0000b505c>] process_one_work+0x218/0x7ec
[<ffffffc0000b5764>] worker_thread+0x134/0x458
[<ffffffc0000bc010>] kthread+0xd4/0xec

Reference material ：
https://www.cnblogs.com/honpey/p/4926605.html

page writeback