frontswap: simplify frontswap_register_ops

Given that frontswap_register_ops must be called from built-in code,
there is no need to handle the case of swapfiles coming online before or
during it, so delete the code that deals with that case.

Link: https://lkml.kernel.org/r/20211224062246.1258487-11-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/frontswap.c b/mm/frontswap.c
index f51159f0d75d50cc09980771d5c7351611fcdb95..35040fa4eba8389fb37a4455e3b4772e6b1d53a5 100644 (file)
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -99,25 +99,6 @@ static inline void inc_frontswap_invalidates(void) { }
  */
 void frontswap_register_ops(struct frontswap_ops *ops)
 {
-       DECLARE_BITMAP(a, MAX_SWAPFILES);
-       DECLARE_BITMAP(b, MAX_SWAPFILES);
-       struct swap_info_struct *si;
-       unsigned int i;
-
-       bitmap_zero(a, MAX_SWAPFILES);
-       bitmap_zero(b, MAX_SWAPFILES);
-
-       spin_lock(&swap_lock);
-       plist_for_each_entry(si, &swap_active_head, list) {
-               if (!WARN_ON(!si->frontswap_map))
-                       __set_bit(si->type, a);
-       }
-       spin_unlock(&swap_lock);
-
-       /* the new ops needs to know the currently active swap devices */
-       for_each_set_bit(i, a, MAX_SWAPFILES)
-               ops->init(i);
-
        /*
         * Setting frontswap_ops must happen after the ops->init() calls
         * above; cmpxchg implies smp_mb() which will ensure the init is
@@ -128,28 +109,6 @@ void frontswap_register_ops(struct frontswap_ops *ops)
        } while (cmpxchg(&frontswap_ops, ops->next, ops) != ops->next);
 
        static_branch_inc(&frontswap_enabled_key);
-
-       spin_lock(&swap_lock);
-       plist_for_each_entry(si, &swap_active_head, list) {
-               if (si->frontswap_map)
-                       __set_bit(si->type, b);
-       }
-       spin_unlock(&swap_lock);
-
-       /*
-        * On the very unlikely chance that a swap device was added or
-        * removed between setting the "a" list bits and the ops init
-        * calls, we re-check and do init or invalidate for any changed
-        * bits.
-        */
-       if (unlikely(!bitmap_equal(a, b, MAX_SWAPFILES))) {
-               for (i = 0; i < MAX_SWAPFILES; i++) {
-                       if (!test_bit(i, a) && test_bit(i, b))
-                               ops->init(i);
-                       else if (test_bit(i, a) && !test_bit(i, b))
-                               ops->invalidate_area(i);
-               }
-       }
 }
 
 /*