From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> PageWaiters is used by PageWriteback and PageLocked (and no other page flags), so it makes sense to use the same codepaths that have already been optimised for PageLocked, even if there's probably no real performance benefit to be had. Unfortunately, clear_bit_unlock_is_negative_byte() isn't present on every architecture, and the default implementation is only available in filemap.c while I want to use it in page-writeback.c. Rather than move the default implementation to a header file, I've done optimised implementations for alpha and ia64. I can't figure out optimised implementations for m68k, mips, riscv and s390, so I've just replicated the effect of the generic implementation in them. I leave it to the experts to fix that (... or convert over to using asm-generic/bitops/lock.h ...) v3: - Added implementations of clear_bit_unlock_is_negative_byte() to architectures which need it v2: Rebased to 5.7-rc1 - Split up patches better - Moved the BUG() from end_page_writeback() to __clear_page_writeback() as requested by Jan Kara. - Converted the BUG() to WARN_ON() - Removed TestClearPageWriteback Matthew Wilcox (Oracle) (11): alpha: Add clear_bit_unlock_is_negative_byte implementation ia64: Add clear_bit_unlock_is_negative_byte implementation m68k: Add clear_bit_unlock_is_negative_byte implementation mips: Add clear_bit_unlock_is_negative_byte implementation riscv: Add clear_bit_unlock_is_negative_byte implementation s390: Add clear_bit_unlock_is_negative_byte implementation mm: Remove definition of clear_bit_unlock_is_negative_byte mm: Move PG_writeback into the bottom byte mm: Convert writeback BUG to WARN_ON mm: Use clear_bit_unlock_is_negative_byte for PageWriteback mm: Remove TestClearPageWriteback arch/alpha/include/asm/bitops.h | 23 ++++++++++++++++++ arch/ia64/include/asm/bitops.h | 20 ++++++++++++++++ arch/m68k/include/asm/bitops.h | 7 ++++++ arch/mips/include/asm/bitops.h | 7 ++++++ arch/riscv/include/asm/bitops.h | 7 ++++++ arch/s390/include/asm/bitops.h | 9 +++++++ include/linux/page-flags.h | 8 +++---- mm/filemap.c | 41 ++++---------------------------- mm/page-writeback.c | 42 ++++++++++++++++++++------------- 9 files changed, 107 insertions(+), 57 deletions(-) -- 2.25.1
