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 814bbf49dcd0 ("xen: remove tmem driver").

[akpm@linux-foundation.org: remove now-unreachable code]

Link: https://lkml.kernel.org/r/20211224062246.1258487-1-hch@lst.de
Link: https://lkml.kernel.org/r/20211224062246.1258487-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 2 insertions, 362 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index a99bd499ef51..430240289b02 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -444,28 +444,6 @@ config USE_PERCPU_NUMA_NODE_ID
 config HAVE_SETUP_PER_CPU_AREA
 	bool
 
-config CLEANCACHE
-	bool "Enable cleancache driver to cache clean pages if tmem is present"
-	help
-	  Cleancache can be thought of as a page-granularity victim cache
-	  for clean pages that the kernel's pageframe replacement algorithm
-	  (PFRA) would like to keep around, but can't since there isn't enough
-	  memory.  So when the PFRA "evicts" a page, it first attempts to use
-	  cleancache code to put the data contained in that page into
-	  "transcendent memory", memory that is not directly accessible or
-	  addressable by the kernel and is of unknown and possibly
-	  time-varying size.  And when a cleancache-enabled
-	  filesystem wishes to access a page in a file on disk, it first
-	  checks cleancache to see if it already contains it; if it does,
-	  the page is copied into the kernel and a disk access is avoided.
-	  When a transcendent memory driver is available (such as zcache or
-	  Xen transcendent memory), a significant I/O reduction
-	  may be achieved.  When none is available, all cleancache calls
-	  are reduced to a single pointer-compare-against-NULL resulting
-	  in a negligible performance hit.
-
-	  If unsure, say Y to enable cleancache
-
 config FRONTSWAP
 	bool "Enable frontswap to cache swap pages if tmem is present"
 	depends on SWAP
diff --git a/mm/Makefile b/mm/Makefile
index 588d3113f3b0..70d4309c9ce3 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -104,7 +104,6 @@ obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
 obj-$(CONFIG_DEBUG_RODATA_TEST) += rodata_test.o
 obj-$(CONFIG_DEBUG_VM_PGTABLE) += debug_vm_pgtable.o
 obj-$(CONFIG_PAGE_OWNER) += page_owner.o
-obj-$(CONFIG_CLEANCACHE) += cleancache.o
 obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
 obj-$(CONFIG_ZPOOL)	+= zpool.o
 obj-$(CONFIG_ZBUD)	+= zbud.o
diff --git a/mm/cleancache.c b/mm/cleancache.c
deleted file mode 100644
index db7eee9c0886..000000000000
--- a/mm/cleancache.c
+++ /dev/null
@@ -1,315 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * Cleancache frontend
- *
- * This code provides the generic "frontend" layer to call a matching
- * "backend" driver implementation of cleancache.  See
- * Documentation/vm/cleancache.rst for more information.
- *
- * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
- * Author: Dan Magenheimer
- */
-
-#include <linux/module.h>
-#include <linux/fs.h>
-#include <linux/exportfs.h>
-#include <linux/mm.h>
-#include <linux/debugfs.h>
-#include <linux/cleancache.h>
-
-/*
- * cleancache_ops is set by cleancache_register_ops to contain the pointers
- * to the cleancache "backend" implementation functions.
- */
-static const struct cleancache_ops *cleancache_ops __read_mostly;
-
-/*
- * Counters available via /sys/kernel/debug/cleancache (if debugfs is
- * properly configured.  These are for information only so are not protected
- * against increment races.
- */
-static u64 cleancache_succ_gets;
-static u64 cleancache_failed_gets;
-static u64 cleancache_puts;
-static u64 cleancache_invalidates;
-
-static void cleancache_register_ops_sb(struct super_block *sb, void *unused)
-{
-	switch (sb->cleancache_poolid) {
-	case CLEANCACHE_NO_BACKEND:
-		__cleancache_init_fs(sb);
-		break;
-	case CLEANCACHE_NO_BACKEND_SHARED:
-		__cleancache_init_shared_fs(sb);
-		break;
-	}
-}
-
-/*
- * Register operations for cleancache. Returns 0 on success.
- */
-int cleancache_register_ops(const struct cleancache_ops *ops)
-{
-	if (cmpxchg(&cleancache_ops, NULL, ops))
-		return -EBUSY;
-
-	/*
-	 * A cleancache backend can be built as a module and hence loaded after
-	 * a cleancache enabled filesystem has called cleancache_init_fs. To
-	 * handle such a scenario, here we call ->init_fs or ->init_shared_fs
-	 * for each active super block. To differentiate between local and
-	 * shared filesystems, we temporarily initialize sb->cleancache_poolid
-	 * to CLEANCACHE_NO_BACKEND or CLEANCACHE_NO_BACKEND_SHARED
-	 * respectively in case there is no backend registered at the time
-	 * cleancache_init_fs or cleancache_init_shared_fs is called.
-	 *
-	 * Since filesystems can be mounted concurrently with cleancache
-	 * backend registration, we have to be careful to guarantee that all
-	 * cleancache enabled filesystems that has been mounted by the time
-	 * cleancache_register_ops is called has got and all mounted later will
-	 * get cleancache_poolid. This is assured by the following statements
-	 * tied together:
-	 *
-	 * a) iterate_supers skips only those super blocks that has started
-	 *    ->kill_sb
-	 *
-	 * b) if iterate_supers encounters a super block that has not finished
-	 *    ->mount yet, it waits until it is finished
-	 *
-	 * c) cleancache_init_fs is called from ->mount and
-	 *    cleancache_invalidate_fs is called from ->kill_sb
-	 *
-	 * d) we call iterate_supers after cleancache_ops has been set
-	 *
-	 * From a) it follows that if iterate_supers skips a super block, then
-	 * either the super block is already dead, in which case we do not need
-	 * to bother initializing cleancache for it, or it was mounted after we
-	 * initiated iterate_supers. In the latter case, it must have seen
-	 * cleancache_ops set according to d) and initialized cleancache from
-	 * ->mount by itself according to c). This proves that we call
-	 * ->init_fs at least once for each active super block.
-	 *
-	 * From b) and c) it follows that if iterate_supers encounters a super
-	 * block that has already started ->init_fs, it will wait until ->mount
-	 * and hence ->init_fs has finished, then check cleancache_poolid, see
-	 * that it has already been set and therefore do nothing. This proves
-	 * that we call ->init_fs no more than once for each super block.
-	 *
-	 * Combined together, the last two paragraphs prove the function
-	 * correctness.
-	 *
-	 * Note that various cleancache callbacks may proceed before this
-	 * function is called or even concurrently with it, but since
-	 * CLEANCACHE_NO_BACKEND is negative, they will all result in a noop
-	 * until the corresponding ->init_fs has been actually called and
-	 * cleancache_ops has been set.
-	 */
-	iterate_supers(cleancache_register_ops_sb, NULL);
-	return 0;
-}
-EXPORT_SYMBOL(cleancache_register_ops);
-
-/* Called by a cleancache-enabled filesystem at time of mount */
-void __cleancache_init_fs(struct super_block *sb)
-{
-	int pool_id = CLEANCACHE_NO_BACKEND;
-
-	if (cleancache_ops) {
-		pool_id = cleancache_ops->init_fs(PAGE_SIZE);
-		if (pool_id < 0)
-			pool_id = CLEANCACHE_NO_POOL;
-	}
-	sb->cleancache_poolid = pool_id;
-}
-EXPORT_SYMBOL(__cleancache_init_fs);
-
-/* Called by a cleancache-enabled clustered filesystem at time of mount */
-void __cleancache_init_shared_fs(struct super_block *sb)
-{
-	int pool_id = CLEANCACHE_NO_BACKEND_SHARED;
-
-	if (cleancache_ops) {
-		pool_id = cleancache_ops->init_shared_fs(&sb->s_uuid, PAGE_SIZE);
-		if (pool_id < 0)
-			pool_id = CLEANCACHE_NO_POOL;
-	}
-	sb->cleancache_poolid = pool_id;
-}
-EXPORT_SYMBOL(__cleancache_init_shared_fs);
-
-/*
- * If the filesystem uses exportable filehandles, use the filehandle as
- * the key, else use the inode number.
- */
-static int cleancache_get_key(struct inode *inode,
-			      struct cleancache_filekey *key)
-{
-	int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
-	int len = 0, maxlen = CLEANCACHE_KEY_MAX;
-	struct super_block *sb = inode->i_sb;
-
-	key->u.ino = inode->i_ino;
-	if (sb->s_export_op != NULL) {
-		fhfn = sb->s_export_op->encode_fh;
-		if  (fhfn) {
-			len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
-			if (len <= FILEID_ROOT || len == FILEID_INVALID)
-				return -1;
-			if (maxlen > CLEANCACHE_KEY_MAX)
-				return -1;
-		}
-	}
-	return 0;
-}
-
-/*
- * "Get" data from cleancache associated with the poolid/inode/index
- * that were specified when the data was put to cleanache and, if
- * successful, use it to fill the specified page with data and return 0.
- * The pageframe is unchanged and returns -1 if the get fails.
- * Page must be locked by caller.
- *
- * The function has two checks before any action is taken - whether
- * a backend is registered and whether the sb->cleancache_poolid
- * is correct.
- */
-int __cleancache_get_page(struct page *page)
-{
-	int ret = -1;
-	int pool_id;
-	struct cleancache_filekey key = { .u.key = { 0 } };
-
-	if (!cleancache_ops) {
-		cleancache_failed_gets++;
-		goto out;
-	}
-
-	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	pool_id = page->mapping->host->i_sb->cleancache_poolid;
-	if (pool_id < 0)
-		goto out;
-
-	if (cleancache_get_key(page->mapping->host, &key) < 0)
-		goto out;
-
-	ret = cleancache_ops->get_page(pool_id, key, page->index, page);
-	if (ret == 0)
-		cleancache_succ_gets++;
-	else
-		cleancache_failed_gets++;
-out:
-	return ret;
-}
-EXPORT_SYMBOL(__cleancache_get_page);
-
-/*
- * "Put" data from a page to cleancache and associate it with the
- * (previously-obtained per-filesystem) poolid and the page's,
- * inode and page index.  Page must be locked.  Note that a put_page
- * always "succeeds", though a subsequent get_page may succeed or fail.
- *
- * The function has two checks before any action is taken - whether
- * a backend is registered and whether the sb->cleancache_poolid
- * is correct.
- */
-void __cleancache_put_page(struct page *page)
-{
-	int pool_id;
-	struct cleancache_filekey key = { .u.key = { 0 } };
-
-	if (!cleancache_ops) {
-		cleancache_puts++;
-		return;
-	}
-
-	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	pool_id = page->mapping->host->i_sb->cleancache_poolid;
-	if (pool_id >= 0 &&
-		cleancache_get_key(page->mapping->host, &key) >= 0) {
-		cleancache_ops->put_page(pool_id, key, page->index, page);
-		cleancache_puts++;
-	}
-}
-EXPORT_SYMBOL(__cleancache_put_page);
-
-/*
- * Invalidate any data from cleancache associated with the poolid and the
- * page's inode and page index so that a subsequent "get" will fail.
- *
- * The function has two checks before any action is taken - whether
- * a backend is registered and whether the sb->cleancache_poolid
- * is correct.
- */
-void __cleancache_invalidate_page(struct address_space *mapping,
-					struct page *page)
-{
-	/* careful... page->mapping is NULL sometimes when this is called */
-	int pool_id = mapping->host->i_sb->cleancache_poolid;
-	struct cleancache_filekey key = { .u.key = { 0 } };
-
-	if (!cleancache_ops)
-		return;
-
-	if (pool_id >= 0) {
-		VM_BUG_ON_PAGE(!PageLocked(page), page);
-		if (cleancache_get_key(mapping->host, &key) >= 0) {
-			cleancache_ops->invalidate_page(pool_id,
-					key, page->index);
-			cleancache_invalidates++;
-		}
-	}
-}
-EXPORT_SYMBOL(__cleancache_invalidate_page);
-
-/*
- * Invalidate all data from cleancache associated with the poolid and the
- * mappings's inode so that all subsequent gets to this poolid/inode
- * will fail.
- *
- * The function has two checks before any action is taken - whether
- * a backend is registered and whether the sb->cleancache_poolid
- * is correct.
- */
-void __cleancache_invalidate_inode(struct address_space *mapping)
-{
-	int pool_id = mapping->host->i_sb->cleancache_poolid;
-	struct cleancache_filekey key = { .u.key = { 0 } };
-
-	if (!cleancache_ops)
-		return;
-
-	if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
-		cleancache_ops->invalidate_inode(pool_id, key);
-}
-EXPORT_SYMBOL(__cleancache_invalidate_inode);
-
-/*
- * Called by any cleancache-enabled filesystem at time of unmount;
- * note that pool_id is surrendered and may be returned by a subsequent
- * cleancache_init_fs or cleancache_init_shared_fs.
- */
-void __cleancache_invalidate_fs(struct super_block *sb)
-{
-	int pool_id;
-
-	pool_id = sb->cleancache_poolid;
-	sb->cleancache_poolid = CLEANCACHE_NO_POOL;
-
-	if (cleancache_ops && pool_id >= 0)
-		cleancache_ops->invalidate_fs(pool_id);
-}
-EXPORT_SYMBOL(__cleancache_invalidate_fs);
-
-static int __init init_cleancache(void)
-{
-#ifdef CONFIG_DEBUG_FS
-	struct dentry *root = debugfs_create_dir("cleancache", NULL);
-
-	debugfs_create_u64("succ_gets", 0444, root, &cleancache_succ_gets);
-	debugfs_create_u64("failed_gets", 0444, root, &cleancache_failed_gets);
-	debugfs_create_u64("puts", 0444, root, &cleancache_puts);
-	debugfs_create_u64("invalidates", 0444, root, &cleancache_invalidates);
-#endif
-	return 0;
-}
-module_init(init_cleancache)
diff --git a/mm/filemap.c b/mm/filemap.c
index 60866ae711e2..b50910ac2c88 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -35,7 +35,6 @@
 #include <linux/cpuset.h>
 #include <linux/hugetlb.h>
 #include <linux/memcontrol.h>
-#include <linux/cleancache.h>
 #include <linux/shmem_fs.h>
 #include <linux/rmap.h>
 #include <linux/delayacct.h>
@@ -151,16 +150,6 @@ static void filemap_unaccount_folio(struct address_space *mapping,
 {
 	long nr;
 
-	/*
-	 * if we're uptodate, flush out into the cleancache, otherwise
-	 * invalidate any existing cleancache entries.  We can't leave
-	 * stale data around in the cleancache once our page is gone
-	 */
-	if (folio_test_uptodate(folio) && folio_test_mappedtodisk(folio))
-		cleancache_put_page(&folio->page);
-	else
-		cleancache_invalidate_page(mapping, &folio->page);
-
 	VM_BUG_ON_FOLIO(folio_mapped(folio), folio);
 	if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) {
 		int mapcount;
diff --git a/mm/truncate.c b/mm/truncate.c
index 5e243d7269c0..9dbf0b75da5d 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -22,7 +22,6 @@
 #include <linux/buffer_head.h>	/* grr. try_to_release_page,
 				   do_invalidatepage */
 #include <linux/shmem_fs.h>
-#include <linux/cleancache.h>
 #include <linux/rmap.h>
 #include "internal.h"
 
@@ -264,7 +263,6 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end)
 	 */
 	folio_zero_range(folio, offset, length);
 
-	cleancache_invalidate_page(folio->mapping, &folio->page);
 	if (folio_has_private(folio))
 		do_invalidatepage(&folio->page, offset, length);
 	if (!folio_test_large(folio))
@@ -351,7 +349,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
 	bool		same_folio;
 
 	if (mapping_empty(mapping))
-		goto out;
+		return;
 
 	/*
 	 * 'start' and 'end' always covers the range of pages to be fully
@@ -442,9 +440,6 @@ void truncate_inode_pages_range(struct address_space *mapping,
 		folio_batch_release(&fbatch);
 		index++;
 	}
-
-out:
-	cleancache_invalidate_inode(mapping);
 }
 EXPORT_SYMBOL(truncate_inode_pages_range);
 
@@ -498,10 +493,6 @@ void truncate_inode_pages_final(struct address_space *mapping)
 		xa_unlock_irq(&mapping->i_pages);
 	}
 
-	/*
-	 * Cleancache needs notification even if there are no pages or shadow
-	 * entries.
-	 */
 	truncate_inode_pages(mapping, 0);
 }
 EXPORT_SYMBOL(truncate_inode_pages_final);
@@ -661,7 +652,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 	int did_range_unmap = 0;
 
 	if (mapping_empty(mapping))
-		goto out;
+		return 0;
 
 	folio_batch_init(&fbatch);
 	index = start;
@@ -725,8 +716,6 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 	if (dax_mapping(mapping)) {
 		unmap_mapping_pages(mapping, start, end - start + 1, false);
 	}
-out:
-	cleancache_invalidate_inode(mapping);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);