• Hugh Dickins's avatar
    mm: fix swapoff hang after page migration and fork · 2022b4d1
    Hugh Dickins authored
    I've been seeing swapoff hangs in recent testing: it's cycling around
    trying unsuccessfully to find an mm for some remaining pages of swap.
    
    I have been exercising swap and page migration more heavily recently,
    and now notice a long-standing error in copy_one_pte(): it's trying to
    add dst_mm to swapoff's mmlist when it finds a swap entry, but is doing
    so even when it's a migration entry or an hwpoison entry.
    
    Which wouldn't matter much, except it adds dst_mm next to src_mm,
    assuming src_mm is already on the mmlist: which may not be so.  Then if
    pages are later swapped out from dst_mm, swapoff won't be able to find
    where to replace them.
    
    There's already a !non_swap_entry() test for stats: move that up before
    the swap_duplicate() and the addition to mmlist.
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Cc: Kelley Nielsen <kelleynnn@gmail.com>
    Cc: <stable@vger.kernel.org>	[2.6.18+]
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    2022b4d1
memory.c 102 KB