mm: kill frontswap

The only user of frontswap is zswap, and has been for a long time.  Have
swap call into zswap directly and remove the indirection.

[hannes@cmpxchg.org: remove obsolete comment, per Yosry]
  Link: https://lkml.kernel.org/r/20230719142832.GA932528@cmpxchg.org
[fengwei.yin@intel.com: don't warn if none swapcache folio is passed to zswap_load]
  Link: https://lkml.kernel.org/r/20230810095652.3905184-1-fengwei.yin@intel.com
Link: https://lkml.kernel.org/r/20230717160227.GA867137@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 0 insertions, 91 deletions

diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
deleted file mode 100644
index eaa0ac5f9003..000000000000
--- a/include/linux/frontswap.h
+++ /dev/null
@@ -1,91 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _LINUX_FRONTSWAP_H
-#define _LINUX_FRONTSWAP_H
-
-#include <linux/swap.h>
-#include <linux/mm.h>
-#include <linux/bitops.h>
-#include <linux/jump_label.h>
-
-struct frontswap_ops {
-	void (*init)(unsigned); /* this swap type was just swapon'ed */
-	int (*store)(unsigned, pgoff_t, struct page *); /* store a page */
-	int (*load)(unsigned, pgoff_t, struct page *, bool *); /* load a page */
-	void (*invalidate_page)(unsigned, pgoff_t); /* page no longer needed */
-	void (*invalidate_area)(unsigned); /* swap type just swapoff'ed */
-};
-
-int frontswap_register_ops(const struct frontswap_ops *ops);
-
-extern void frontswap_init(unsigned type, unsigned long *map);
-extern int __frontswap_store(struct page *page);
-extern int __frontswap_load(struct page *page);
-extern void __frontswap_invalidate_page(unsigned, pgoff_t);
-extern void __frontswap_invalidate_area(unsigned);
-
-#ifdef CONFIG_FRONTSWAP
-extern struct static_key_false frontswap_enabled_key;
-
-static inline bool frontswap_enabled(void)
-{
-	return static_branch_unlikely(&frontswap_enabled_key);
-}
-
-static inline void frontswap_map_set(struct swap_info_struct *p,
-				     unsigned long *map)
-{
-	p->frontswap_map = map;
-}
-
-static inline unsigned long *frontswap_map_get(struct swap_info_struct *p)
-{
-	return p->frontswap_map;
-}
-#else
-/* all inline routines become no-ops and all externs are ignored */
-
-static inline bool frontswap_enabled(void)
-{
-	return false;
-}
-
-static inline void frontswap_map_set(struct swap_info_struct *p,
-				     unsigned long *map)
-{
-}
-
-static inline unsigned long *frontswap_map_get(struct swap_info_struct *p)
-{
-	return NULL;
-}
-#endif
-
-static inline int frontswap_store(struct page *page)
-{
-	if (frontswap_enabled())
-		return __frontswap_store(page);
-
-	return -1;
-}
-
-static inline int frontswap_load(struct page *page)
-{
-	if (frontswap_enabled())
-		return __frontswap_load(page);
-
-	return -1;
-}
-
-static inline void frontswap_invalidate_page(unsigned type, pgoff_t offset)
-{
-	if (frontswap_enabled())
-		__frontswap_invalidate_page(type, offset);
-}
-
-static inline void frontswap_invalidate_area(unsigned type)
-{
-	if (frontswap_enabled())
-		__frontswap_invalidate_area(type);
-}
-
-#endif /* _LINUX_FRONTSWAP_H */