From: Hugh Dickins <hughd@xxxxxxxxxx> Subject: 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: b56a2d8af914 ("mm: rid swapoff of quadratic complexity") Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> Cc: "Alex Xu (Hello71)" <alex_y_xu@xxxxxxxx> Cc: Huang Ying <ying.huang@xxxxxxxxx> Cc: Kelley Nielsen <kelleynnn@xxxxxxxxx> Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxxx> Cc: Vineeth Pillai <vpillai@xxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/swapfile.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) --- a/mm/swapfile.c~mm-swapoff-take-notice-of-completion-sooner +++ a/mm/swapfile.c @@ -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) - goto retry; + if (si->inuse_pages) { + if (!signal_pending(current)) + goto retry; + retval = -EINTR; + } out: return (retval == FRONTSWAP_PAGES_UNUSED) ? 0 : retval; } _
