Commit 64165b1a authored Apr 18, 2019 by Hugh Dickins Committed by Linus Torvalds Apr 19, 2019

mm: swapoff: take notice of completion sooner

The old try_to_unuse() implementation was driven by find_next_to_unuse(),
which terminated as soon as all the swap had been freed.

Add inuse_pages checks now (alongside signal_pending()) to stop scanning
mms and swap_map once finished.

The same ought to be done in shmem_unuse() too, but never was before,
and needs a different interface: so leave it as is for now.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1904081258200.1523@eggly.anvils


Fixes: b56a2d8a ("mm: rid swapoff of quadratic complexity")
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Kelley Nielsen <kelleynnn@gmail.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vineeth Pillai <vpillai@digitalocean.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent dd862deb

mm/swapfile.c

+11 −8

Original line number	Diff line number	Diff line
		@@ -2051,11 +2051,9 @@ retry:

		spin_lock(&mmlist_lock);
		p = &init_mm.mmlist;
		while ((p = p->next) != &init_mm.mmlist) {
		if (signal_pending(current)) {
		retval = -EINTR;
		break;
		}
		while (si->inuse_pages &&
		!signal_pending(current) &&
		(p = p->next) != &init_mm.mmlist) {

		mm = list_entry(p, struct mm_struct, mmlist);
		if (!mmget_not_zero(mm))
		@@ -2082,7 +2080,9 @@ retry:
		mmput(prev_mm);

		i = 0;
		while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
		while (si->inuse_pages &&
		!signal_pending(current) &&
		(i = find_next_to_unuse(si, i, frontswap)) != 0) {

		entry = swp_entry(type, i);
		page = find_get_page(swap_address_space(entry), i);
		@@ -2123,8 +2123,11 @@ retry:
		* separate lists, and wait for those lists to be emptied; but it's
		* easier and more robust (though cpu-intensive) just to keep retrying.
		*/
		if (si->inuse_pages)
		if (si->inuse_pages) {
		if (!signal_pending(current))
		goto retry;
		retval = -EINTR;
		}
		out:
		return (retval == FRONTSWAP_PAGES_UNUSED) ? 0 : retval;
		}

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