mm: add cond_resched() in swapin_walk_pmd_entry()

When handling MADV_WILLNEED in madvise(), a soflockup may occurr in
swapin_walk_pmd_entry() if swapping in lots of memory on a slow device.
Add a cond_resched() to avoid the possible softlockup.

Link: https://lkml.kernel.org/r/20221205140327.72304-1-wangkefeng.wang@huawei.com
Fixes: 1998cc048901 ("mm: make madvise(MADV_WILLNEED) support swap file prefetch")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Shaohua Li <shli@fusionio.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/madvise.c b/mm/madvise.c
index 2573ea3..b7d9b1a 100644 (file)
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -223,6 +223,7 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
                        put_page(page);
        }
        swap_read_unplug(splug);
+       cond_resched();
 
        return 0;
 }