mm/madvise: split out populate behavior check logic

madvise_do_behavior() has a long open-coded 'behavior' check for
MADV_POPULATE_{READ,WRITE}.  It adds multiple layers[1] and make the code
arguably take longer time to read.  Like is_memory_failure(), split out
the check to a separate function.  This is not technically removing the
additional layer but discourage further extending the switch-case.  Also
it makes madvise_do_behavior() code shorter and therefore easier to read.

[1] https://lore.kernel.org/bd6d0bf1-c79e-46bd-a810-9791efb9ad73@lucifer.local

Link: https://lkml.kernel.org/r/20250312164750.59215-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Liam R. Howlett <howlett@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/madvise.c b/mm/madvise.c
index c3ab1f283b181a441e1d5ea3c9b6eff2e756648c..611db868ae382e03c6e8aa72888acaed59bde4b8 100644 (file)
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1640,6 +1640,17 @@ static bool is_valid_madvise(unsigned long start, size_t len_in, int behavior)
        return true;
 }
 
+static bool is_madvise_populate(int behavior)
+{
+       switch (behavior) {
+       case MADV_POPULATE_READ:
+       case MADV_POPULATE_WRITE:
+               return true;
+       default:
+               return false;
+       }
+}
+
 static int madvise_do_behavior(struct mm_struct *mm,
                unsigned long start, size_t len_in, size_t len, int behavior)
 {
@@ -1653,16 +1664,11 @@ static int madvise_do_behavior(struct mm_struct *mm,
        end = start + len;
 
        blk_start_plug(&plug);
-       switch (behavior) {
-       case MADV_POPULATE_READ:
-       case MADV_POPULATE_WRITE:
+       if (is_madvise_populate(behavior))
                error = madvise_populate(mm, start, end, behavior);
-               break;
-       default:
+       else
                error = madvise_walk_vmas(mm, start, end, behavior,
                                          madvise_vma_behavior);
-               break;
-       }
        blk_finish_plug(&plug);
        return error;
 }