mm: remove cleancache

Patch series "remove Xen tmem leftovers".

Since the removal of the Xen tmem driver in 2019, the cleancache hooks
are entirely unused, as are large parts of frontswap.  This series
against linux-next (with the folio changes included) removes
cleancaches, and cuts down frontswap to the bits actually used by zswap.

This patch (of 13):

The cleancache subsystem is unused since the removal of Xen tmem driver
in commit 814bbf4 ("xen: remove tmem driver").

[[email protected]: remove now-unreachable code]

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Seth Jennings <[email protected]>
Cc: Dan Streetman <[email protected]>
Cc: Vitaly Wool <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Christoph Hellwig

Documentation/vm/cleancache.rst

@@ -8,12 +8,6 @@ Frontswap provides a "transcendent memory" interface for swap pages.
 In some environments, dramatic performance savings may be obtained because
 swapped pages are saved in RAM (or a RAM-like device) instead of a swap disk.
 
-(Note, frontswap -- and :ref:`cleancache` (merged at 3.0) -- are the "frontends"
-and the only necessary changes to the core kernel for transcendent memory;
-all other supporting code -- the "backends" -- is implemented as drivers.
-See the LWN.net article `Transcendent memory in a nutshell`_
-for a detailed overview of frontswap and related kernel parts)
-
 .. _Transcendent memory in a nutshell: https://lwn.net/Articles/454795/
 
 Frontswap is so named because it can be thought of as the opposite of
@@ -87,11 +81,9 @@ This interface is ideal when data is transformed to a different form
 and size (such as with compression) or secretly moved (as might be
 useful for write-balancing for some RAM-like devices).  Swap pages (and
 evicted page-cache pages) are a great use for this kind of slower-than-RAM-
-but-much-faster-than-disk "pseudo-RAM device" and the frontswap (and
-cleancache) interface to transcendent memory provides a nice way to read
-and write -- and indirectly "name" -- the pages.
+but-much-faster-than-disk "pseudo-RAM device".
 
-Frontswap -- and cleancache -- with a fairly small impact on the kernel,
+Frontswap with a fairly small impact on the kernel,
 provides a huge amount of flexibility for more dynamic, flexible RAM
 utilization in various system configurations:
 

Documentation/vm/frontswap.rst

@@ -15,7 +15,6 @@ algorithms.  If you are looking for advice on simply allocating memory, see the
    active_mm
    arch_pgtable_helpers
    balance
-   cleancache
    damon/index
    free_page_reporting
    frontswap

Documentation/vm/index.rst

@@ -4705,13 +4705,6 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/cla
 F:	include/linux/cfi.h
 F:	kernel/cfi.c
 
-CLEANCACHE API
-M:	Konrad Rzeszutek Wilk <[email protected]>
-L:	[email protected]
-S:	Maintained
-F:	include/linux/cleancache.h
-F:	mm/cleancache.c
-
 CLK API
 M:	Russell King <[email protected]>
 L:	[email protected]

MAINTAINERS

@@ -31,7 +31,6 @@ CONFIG_ARCH_BCM2835=y
 CONFIG_PREEMPT_VOLUNTARY=y
 CONFIG_AEABI=y
 CONFIG_KSM=y
-CONFIG_CLEANCACHE=y
 CONFIG_CMA=y
 CONFIG_SECCOMP=y
 CONFIG_KEXEC=y

arch/arm/configs/bcm2835_defconfig

@@ -27,7 +27,6 @@ CONFIG_PCIE_QCOM=y
 CONFIG_SMP=y
 CONFIG_PREEMPT=y
 CONFIG_HIGHMEM=y
-CONFIG_CLEANCACHE=y
 CONFIG_ARM_APPENDED_DTB=y
 CONFIG_ARM_ATAG_DTB_COMPAT=y
 CONFIG_CPU_IDLE=y

arch/arm/configs/qcom_defconfig

@@ -45,7 +45,6 @@ CONFIG_IOSCHED_BFQ=m
 CONFIG_BINFMT_AOUT=m
 CONFIG_BINFMT_MISC=m
 # CONFIG_COMPACTION is not set
-CONFIG_CLEANCACHE=y
 CONFIG_ZPOOL=m
 CONFIG_NET=y
 CONFIG_PACKET=y

arch/m68k/configs/amiga_defconfig

@@ -41,7 +41,6 @@ CONFIG_IOSCHED_BFQ=m
 CONFIG_BINFMT_AOUT=m
 CONFIG_BINFMT_MISC=m
 # CONFIG_COMPACTION is not set
-CONFIG_CLEANCACHE=y
 CONFIG_ZPOOL=m
 CONFIG_NET=y
 CONFIG_PACKET=y

arch/m68k/configs/apollo_defconfig

@@ -48,7 +48,6 @@ CONFIG_IOSCHED_BFQ=m
 CONFIG_BINFMT_AOUT=m
 CONFIG_BINFMT_MISC=m
 # CONFIG_COMPACTION is not set
-CONFIG_CLEANCACHE=y
 CONFIG_ZPOOL=m
 CONFIG_NET=y
 CONFIG_PACKET=y

arch/m68k/configs/atari_defconfig

@@ -38,7 +38,6 @@ CONFIG_IOSCHED_BFQ=m
 CONFIG_BINFMT_AOUT=m
 CONFIG_BINFMT_MISC=m
 # CONFIG_COMPACTION is not set
-CONFIG_CLEANCACHE=y
 CONFIG_ZPOOL=m
 CONFIG_NET=y
 CONFIG_PACKET=y