mm/mincore: handle non-swap entries before !CONFIG_SWAP guard

mincore_swap() also fields migration/hwpoison entries (and shmem
swapin-error entries), which can exist on !CONFIG_SWAP builds when
CONFIG_MIGRATION or CONFIG_MEMORY_FAILURE is enabled.  The
!IS_ENABLED(CONFIG_SWAP) guard ran before the non-swap-entry early return,
so mincore_pte_range() can spuriously WARN and report these pages
nonresident on !CONFIG_SWAP kernels.

Move the guard below the non-swap-entry check so only true swap entries
trip the WARN, and migration/hwpoison entries take the existing "uptodate
/ non-shmem" path.

Link: https://lore.kernel.org/20260602172247.279421-1-usama.arif@linux.dev
Fixes: 1f2052755c15 ("mm/mincore: use a helper for checking the swap cache")
Signed-off-by: Usama Arif <usama.arif@linux.dev>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/mincore.c b/mm/mincore.c
index e5d13eea92347d3cad8cbf6cf0e4a4f3edc92e88..296f2e3922b5f48eb66a2c54ca0e69cc2e91c1a1 100644 (file)
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -64,11 +64,6 @@ static unsigned char mincore_swap(swp_entry_t entry, bool shmem)
        struct folio *folio = NULL;
        unsigned char present = 0;
 
-       if (!IS_ENABLED(CONFIG_SWAP)) {
-               WARN_ON(1);
-               return 0;
-       }
-
        /*
         * Shmem mapping may contain swapin error entries, which are
         * absent. Page table may contain migration or hwpoison
@@ -77,6 +72,11 @@ static unsigned char mincore_swap(swp_entry_t entry, bool shmem)
        if (!softleaf_is_swap(entry))
                return !shmem;
 
+       if (!IS_ENABLED(CONFIG_SWAP)) {
+               WARN_ON(1);
+               return 0;
+       }
+
        /*
         * Shmem mapping lookup is lockless, so we need to grab the swap
         * device. mincore page table walk locks the PTL, and the swap