mm/madvise: deduplicate madvise_do_behavior() skip case handlings

The logic for checking if a given madvise() request for a single memory
range can skip real work, namely madvise_do_behavior(), is duplicated in
do_madvise() and vector_madvise().  Split out the logic to a function and
reuse it.

Link: https://lkml.kernel.org/r/20250312164750.59215-4-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 611db868ae382e03c6e8aa72888acaed59bde4b8..ba006d05c7ea6ec5ecc7ba635f916e3163a3d75d 100644 (file)
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1640,6 +1640,31 @@ static bool is_valid_madvise(unsigned long start, size_t len_in, int behavior)
        return true;
 }
 
+/*
+ * madvise_should_skip() - Return if the request is invalid or nothing.
+ * @start:     Start address of madvise-requested address range.
+ * @len_in:    Length of madvise-requested address range.
+ * @behavior:  Requested madvise behavor.
+ * @err:       Pointer to store an error code from the check.
+ *
+ * If the specified behaviour is invalid or nothing would occur, we skip the
+ * operation.  This function returns true in the cases, otherwise false.  In
+ * the former case we store an error on @err.
+ */
+static bool madvise_should_skip(unsigned long start, size_t len_in,
+               int behavior, int *err)
+{
+       if (!is_valid_madvise(start, len_in, behavior)) {
+               *err = -EINVAL;
+               return true;
+       }
+       if (start + PAGE_ALIGN(len_in) == start) {
+               *err = 0;
+               return true;
+       }
+       return false;
+}
+
 static bool is_madvise_populate(int behavior)
 {
        switch (behavior) {
@@ -1747,23 +1772,15 @@ static int madvise_do_behavior(struct mm_struct *mm,
  */
 int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior)
 {
-       unsigned long end;
        int error;
-       size_t len;
-
-       if (!is_valid_madvise(start, len_in, behavior))
-               return -EINVAL;
-
-       len = PAGE_ALIGN(len_in);
-       end = start + len;
-
-       if (end == start)
-               return 0;
 
+       if (madvise_should_skip(start, len_in, behavior, &error))
+               return error;
        error = madvise_lock(mm, behavior);
        if (error)
                return error;
-       error = madvise_do_behavior(mm, start, len_in, len, behavior);
+       error = madvise_do_behavior(mm, start, len_in, PAGE_ALIGN(len_in),
+                       behavior);
        madvise_unlock(mm, behavior);
 
        return error;
@@ -1790,19 +1807,13 @@ static ssize_t vector_madvise(struct mm_struct *mm, struct iov_iter *iter,
        while (iov_iter_count(iter)) {
                unsigned long start = (unsigned long)iter_iov_addr(iter);
                size_t len_in = iter_iov_len(iter);
-               size_t len;
-
-               if (!is_valid_madvise(start, len_in, behavior)) {
-                       ret = -EINVAL;
-                       break;
-               }
+               int error;
 
-               len = PAGE_ALIGN(len_in);
-               if (start + len == start)
-                       ret = 0;
+               if (madvise_should_skip(start, len_in, behavior, &error))
+                       ret = error;
                else
-                       ret = madvise_do_behavior(mm, start, len_in, len,
-                                       behavior);
+                       ret = madvise_do_behavior(mm, start, len_in,
+                                       PAGE_ALIGN(len_in), behavior);
                /*
                 * An madvise operation is attempting to restart the syscall,
                 * but we cannot proceed as it would not be correct to repeat