lib/test_bitmap: add tests for bitmap_{read,write}()

Add basic tests ensuring that values can be added at arbitrary positions
of the bitmap, including those spanning into the adjacent unsigned
longs.

Two new performance tests, test_bitmap_read_perf() and
test_bitmap_write_perf(), can be used to assess future performance
improvements of bitmap_read() and bitmap_write():

[    0.431119][    T1] test_bitmap: Time spent in test_bitmap_read_perf:	615253
[    0.433197][    T1] test_bitmap: Time spent in test_bitmap_write_perf:	916313

(numbers from a Intel(R) Xeon(R) Gold 6154 CPU @ 3.00GHz machine running
QEMU).

Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 6b2b33579f565bfb1326cb63db8bd165515aebe9..9198e93b798558ce723546594286535a978040d1 100644 (file)
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -60,18 +60,17 @@ static const unsigned long exp3_1_0[] __initconst = {
 };
 
 static bool __init
-__check_eq_uint(const char *srcfile, unsigned int line,
-               const unsigned int exp_uint, unsigned int x)
+__check_eq_ulong(const char *srcfile, unsigned int line,
+                const unsigned long exp_ulong, unsigned long x)
 {
-       if (exp_uint != x) {
-               pr_err("[%s:%u] expected %u, got %u\n",
-                       srcfile, line, exp_uint, x);
+       if (exp_ulong != x) {
+               pr_err("[%s:%u] expected %lu, got %lu\n",
+                       srcfile, line, exp_ulong, x);
                return false;
        }
        return true;
 }
 
-
 static bool __init
 __check_eq_bitmap(const char *srcfile, unsigned int line,
                  const unsigned long *exp_bmap, const unsigned long *bmap,
@@ -185,7 +184,8 @@ __check_eq_str(const char *srcfile, unsigned int line,
                result;                                                 \
        })
 
-#define expect_eq_uint(...)            __expect_eq(uint, ##__VA_ARGS__)
+#define expect_eq_ulong(...)           __expect_eq(ulong, ##__VA_ARGS__)
+#define expect_eq_uint(x, y)           expect_eq_ulong((unsigned int)(x), (unsigned int)(y))
 #define expect_eq_bitmap(...)          __expect_eq(bitmap, ##__VA_ARGS__)
 #define expect_eq_pbl(...)             __expect_eq(pbl, ##__VA_ARGS__)
 #define expect_eq_u32_array(...)       __expect_eq(u32_array, ##__VA_ARGS__)
@@ -1286,6 +1286,168 @@ static void __init test_bitmap_const_eval(void)
        BUILD_BUG_ON(~var != ~BIT(25));
 }
 
+/*
+ * Test bitmap should be big enough to include the cases when start is not in
+ * the first word, and start+nbits lands in the following word.
+ */
+#define TEST_BIT_LEN (1000)
+
+/*
+ * Helper function to test bitmap_write() overwriting the chosen byte pattern.
+ */
+static void __init test_bitmap_write_helper(const char *pattern)
+{
+       DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
+       DECLARE_BITMAP(exp_bitmap, TEST_BIT_LEN);
+       DECLARE_BITMAP(pat_bitmap, TEST_BIT_LEN);
+       unsigned long w, r, bit;
+       int i, n, nbits;
+
+       /*
+        * Only parse the pattern once and store the result in the intermediate
+        * bitmap.
+        */
+       bitmap_parselist(pattern, pat_bitmap, TEST_BIT_LEN);
+
+       /*
+        * Check that writing a single bit does not accidentally touch the
+        * adjacent bits.
+        */
+       for (i = 0; i < TEST_BIT_LEN; i++) {
+               bitmap_copy(bitmap, pat_bitmap, TEST_BIT_LEN);
+               bitmap_copy(exp_bitmap, pat_bitmap, TEST_BIT_LEN);
+               for (bit = 0; bit <= 1; bit++) {
+                       bitmap_write(bitmap, bit, i, 1);
+                       __assign_bit(i, exp_bitmap, bit);
+                       expect_eq_bitmap(exp_bitmap, bitmap,
+                                        TEST_BIT_LEN);
+               }
+       }
+
+       /* Ensure writing 0 bits does not change anything. */
+       bitmap_copy(bitmap, pat_bitmap, TEST_BIT_LEN);
+       bitmap_copy(exp_bitmap, pat_bitmap, TEST_BIT_LEN);
+       for (i = 0; i < TEST_BIT_LEN; i++) {
+               bitmap_write(bitmap, ~0UL, i, 0);
+               expect_eq_bitmap(exp_bitmap, bitmap, TEST_BIT_LEN);
+       }
+
+       for (nbits = BITS_PER_LONG; nbits >= 1; nbits--) {
+               w = IS_ENABLED(CONFIG_64BIT) ? 0xdeadbeefdeadbeefUL
+                                            : 0xdeadbeefUL;
+               w >>= (BITS_PER_LONG - nbits);
+               for (i = 0; i <= TEST_BIT_LEN - nbits; i++) {
+                       bitmap_copy(bitmap, pat_bitmap, TEST_BIT_LEN);
+                       bitmap_copy(exp_bitmap, pat_bitmap, TEST_BIT_LEN);
+                       for (n = 0; n < nbits; n++)
+                               __assign_bit(i + n, exp_bitmap, w & BIT(n));
+                       bitmap_write(bitmap, w, i, nbits);
+                       expect_eq_bitmap(exp_bitmap, bitmap, TEST_BIT_LEN);
+                       r = bitmap_read(bitmap, i, nbits);
+                       expect_eq_ulong(r, w);
+               }
+       }
+}
+
+static void __init test_bitmap_read_write(void)
+{
+       unsigned char *pattern[3] = {"", "all:1/2", "all"};
+       DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
+       unsigned long zero_bits = 0, bits_per_long = BITS_PER_LONG;
+       unsigned long val;
+       int i, pi;
+
+       /*
+        * Reading/writing zero bits should not crash the kernel.
+        * READ_ONCE() prevents constant folding.
+        */
+       bitmap_write(NULL, 0, 0, READ_ONCE(zero_bits));
+       /* Return value of bitmap_read() is undefined here. */
+       bitmap_read(NULL, 0, READ_ONCE(zero_bits));
+
+       /*
+        * Reading/writing more than BITS_PER_LONG bits should not crash the
+        * kernel. READ_ONCE() prevents constant folding.
+        */
+       bitmap_write(NULL, 0, 0, READ_ONCE(bits_per_long) + 1);
+       /* Return value of bitmap_read() is undefined here. */
+       bitmap_read(NULL, 0, READ_ONCE(bits_per_long) + 1);
+
+       /*
+        * Ensure that bitmap_read() reads the same value that was previously
+        * written, and two consequent values are correctly merged.
+        * The resulting bit pattern is asymmetric to rule out possible issues
+        * with bit numeration order.
+        */
+       for (i = 0; i < TEST_BIT_LEN - 7; i++) {
+               bitmap_zero(bitmap, TEST_BIT_LEN);
+
+               bitmap_write(bitmap, 0b10101UL, i, 5);
+               val = bitmap_read(bitmap, i, 5);
+               expect_eq_ulong(0b10101UL, val);
+
+               bitmap_write(bitmap, 0b101UL, i + 5, 3);
+               val = bitmap_read(bitmap, i + 5, 3);
+               expect_eq_ulong(0b101UL, val);
+
+               val = bitmap_read(bitmap, i, 8);
+               expect_eq_ulong(0b10110101UL, val);
+       }
+
+       for (pi = 0; pi < ARRAY_SIZE(pattern); pi++)
+               test_bitmap_write_helper(pattern[pi]);
+}
+
+static void __init test_bitmap_read_perf(void)
+{
+       DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
+       unsigned int cnt, nbits, i;
+       unsigned long val;
+       ktime_t time;
+
+       bitmap_fill(bitmap, TEST_BIT_LEN);
+       time = ktime_get();
+       for (cnt = 0; cnt < 5; cnt++) {
+               for (nbits = 1; nbits <= BITS_PER_LONG; nbits++) {
+                       for (i = 0; i < TEST_BIT_LEN; i++) {
+                               if (i + nbits > TEST_BIT_LEN)
+                                       break;
+                               /*
+                                * Prevent the compiler from optimizing away the
+                                * bitmap_read() by using its value.
+                                */
+                               WRITE_ONCE(val, bitmap_read(bitmap, i, nbits));
+                       }
+               }
+       }
+       time = ktime_get() - time;
+       pr_err("Time spent in %s:\t%llu\n", __func__, time);
+}
+
+static void __init test_bitmap_write_perf(void)
+{
+       DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
+       unsigned int cnt, nbits, i;
+       unsigned long val = 0xfeedface;
+       ktime_t time;
+
+       bitmap_zero(bitmap, TEST_BIT_LEN);
+       time = ktime_get();
+       for (cnt = 0; cnt < 5; cnt++) {
+               for (nbits = 1; nbits <= BITS_PER_LONG; nbits++) {
+                       for (i = 0; i < TEST_BIT_LEN; i++) {
+                               if (i + nbits > TEST_BIT_LEN)
+                                       break;
+                               bitmap_write(bitmap, val, i, nbits);
+                       }
+               }
+       }
+       time = ktime_get() - time;
+       pr_err("Time spent in %s:\t%llu\n", __func__, time);
+}
+
+#undef TEST_BIT_LEN
+
 static void __init selftest(void)
 {
        test_zero_clear();
@@ -1303,6 +1465,9 @@ static void __init selftest(void)
        test_bitmap_cut();
        test_bitmap_print_buf();
        test_bitmap_const_eval();
+       test_bitmap_read_write();
+       test_bitmap_read_perf();
+       test_bitmap_write_perf();
 
        test_find_nth_bit();
        test_for_each_set_bit();