frontswap: remove frontswap_shrink

frontswap_shrink is never called, so remove it.

Link: https://lkml.kernel.org/r/20211224062246.1258487-5-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/Documentation/vm/frontswap.rst b/Documentation/vm/frontswap.rst
index 2ab660651d04e9d9f5264f7053f2f7b57018c079..feecc5e2447780c2edb7e5c28cf7f5178ff925c2 100644 (file)
--- a/Documentation/vm/frontswap.rst
+++ b/Documentation/vm/frontswap.rst
@@ -255,19 +255,6 @@ the old data and ensure that it is no longer accessible.  Since the
 swap subsystem then writes the new data to the read swap device,
 this is the correct course of action to ensure coherency.
 
-* What is frontswap_shrink for?
-
-When the (non-frontswap) swap subsystem swaps out a page to a real
-swap device, that page is only taking up low-value pre-allocated disk
-space.  But if frontswap has placed a page in transcendent memory, that
-page may be taking up valuable real estate.  The frontswap_shrink
-routine allows code outside of the swap subsystem to force pages out
-of the memory managed by frontswap and back into kernel-addressable memory.
-For example, in RAMster, a "suction driver" thread will attempt
-to "repatriate" pages sent to a remote machine back to the local machine;
-this is driven using the frontswap_shrink mechanism when memory pressure
-subsides.
-
 * Why does the frontswap patch create the new include file swapfile.h?
 
 The frontswap code depends on some swap-subsystem-internal data

diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index 83a56392cc7f67e46ca704b3638f3d2e85e9772d..d268d7bb65134b701e953a128591acb5822be98c 100644 (file)
--- a/include/linux/frontswap.h
+++ b/include/linux/frontswap.h
@@ -24,7 +24,6 @@ struct frontswap_ops {
 };
 
 extern void frontswap_register_ops(struct frontswap_ops *ops);
-extern void frontswap_shrink(unsigned long);
 extern unsigned long frontswap_curr_pages(void);
 
 extern bool __frontswap_test(struct swap_info_struct *, pgoff_t);

diff --git a/mm/frontswap.c b/mm/frontswap.c
index dba7f087ee862e116cf46fcdf5a1a755d7586400..a77ebba6101bddaec6a25aa35b5bb6bd79b14157 100644 (file)
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -341,89 +341,6 @@ static unsigned long __frontswap_curr_pages(void)
        return totalpages;
 }
 
-static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
-                                       int *swapid)
-{
-       int ret = -EINVAL;
-       struct swap_info_struct *si = NULL;
-       int si_frontswap_pages;
-       unsigned long total_pages_to_unuse = total;
-       unsigned long pages = 0, pages_to_unuse = 0;
-
-       assert_spin_locked(&swap_lock);
-       plist_for_each_entry(si, &swap_active_head, list) {
-               si_frontswap_pages = atomic_read(&si->frontswap_pages);
-               if (total_pages_to_unuse < si_frontswap_pages) {
-                       pages = pages_to_unuse = total_pages_to_unuse;
-               } else {
-                       pages = si_frontswap_pages;
-                       pages_to_unuse = 0; /* unuse all */
-               }
-               /* ensure there is enough RAM to fetch pages from frontswap */
-               if (security_vm_enough_memory_mm(current->mm, pages)) {
-                       ret = -ENOMEM;
-                       continue;
-               }
-               vm_unacct_memory(pages);
-               *unused = pages_to_unuse;
-               *swapid = si->type;
-               ret = 0;
-               break;
-       }
-
-       return ret;
-}
-
-/*
- * Used to check if it's necessary and feasible to unuse pages.
- * Return 1 when nothing to do, 0 when need to shrink pages,
- * error code when there is an error.
- */
-static int __frontswap_shrink(unsigned long target_pages,
-                               unsigned long *pages_to_unuse,
-                               int *type)
-{
-       unsigned long total_pages = 0, total_pages_to_unuse;
-
-       assert_spin_locked(&swap_lock);
-
-       total_pages = __frontswap_curr_pages();
-       if (total_pages <= target_pages) {
-               /* Nothing to do */
-               *pages_to_unuse = 0;
-               return 1;
-       }
-       total_pages_to_unuse = total_pages - target_pages;
-       return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type);
-}
-
-/*
- * Frontswap, like a true swap device, may unnecessarily retain pages
- * under certain circumstances; "shrink" frontswap is essentially a
- * "partial swapoff" and works by calling try_to_unuse to attempt to
- * unuse enough frontswap pages to attempt to -- subject to memory
- * constraints -- reduce the number of pages in frontswap to the
- * number given in the parameter target_pages.
- */
-void frontswap_shrink(unsigned long target_pages)
-{
-       unsigned long pages_to_unuse = 0;
-       int type, ret;
-
-       /*
-        * we don't want to hold swap_lock while doing a very
-        * lengthy try_to_unuse, but swap_list may change
-        * so restart scan from swap_active_head each time
-        */
-       spin_lock(&swap_lock);
-       ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type);
-       spin_unlock(&swap_lock);
-       if (ret == 0)
-               try_to_unuse(type, true, pages_to_unuse);
-       return;
-}
-EXPORT_SYMBOL(frontswap_shrink);
-
 /*
  * Count and return the number of frontswap pages across all
  * swap devices.  This is exported so that backend drivers can