[PATCH v2 0/5] lib: rework bitmap_parselist and tests

[PATCH v2 0/5] lib: rework bitmap_parselist and tests

[Yury Norov]

bitmap_parselist has been evolved from a pretty simple idea for long and
now lacks for refactoring. It is not structured, has nested loops and a
set of opaque-named variables. All this leads to extremely hard
understanding of the code. Once during the optimization of it I missed a
scenario which leads to kernel hangup. Tetsuo Handa spotted this and found
it simpler to rewrite the code instead fixing it. (Though, that attempt
had some flaws.)
https://lkml.org/lkml/2018/4/1/93 

Things are more complicated than they may be because bitmap_parselist()
is part of user interface, and its behavior should not change.

In this patchset 
 - __bitmap_parselist() is reworked (patches 2 and 3);
 - time measurement in test_bitmap_parselist switched to ktime_get
   (patch 4);
 - new tests introduced (patch 5), and
 - bitmap_parselist_user() testing enabled with the same testset as
   bitmap_parselist() (patch 6).

Patch 1 is a fix and may be applied separately.

V1: https://lkml.org/lkml/2018/12/23/50
v2: - use PTR_ERR() and ERR_PTR() where appropriate;
    - fix parser logic (last byte of string handling);
    - tests for bitmap_parselist_user() in patch 5.

Yury Norov (4):
  bitmap_parselist: don't calculate length of the input string
  bitmap_parselist: move non-parser logic to helpers
  bitmap_parselist: rework input string parser
  lib/test_bitmap: switch test_bitmap_parselist to ktime_get()
  lib/test_bitmap: add testcases for bitmap_parselist
  lib/test_bitmap: add tests for bitmap_parselist_user

 lib/bitmap.c      | 293 ++++++++++++++++++++++++++++++----------------
 lib/test_bitmap.c |  67 +++++++++--
 2 files changed, 245 insertions(+), 115 deletions(-)

-- 
2.17.1

[PATCH 1/6] bitmap_parselist: don't calculate length of the input string

[Yury Norov]

bitmap_parselist() calculates length of the input string before passing
it to the __bitmap_parselist(). But the end-of-line condition is checked
for every character in __bitmap_parselist() anyway. So doing it in wrapper
is a simple waste of time.

Signed-off-by: Yury Norov <ynorov@marvell.com>
---
 lib/bitmap.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 98872e9025da..ad1fb7e6ad0e 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -614,10 +614,7 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
 
 int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
 {
-	char *nl  = strchrnul(bp, '\n');
-	int len = nl - bp;
-
-	return __bitmap_parselist(bp, len, 0, maskp, nmaskbits);
+	return __bitmap_parselist(bp, UINT_MAX, 0, maskp, nmaskbits);
 }
 EXPORT_SYMBOL(bitmap_parselist);
 
-- 
2.17.1

[PATCH 2/6] bitmap_parselist: move non-parser logic to helpers

[Yury Norov]

Move region checking and setting functionality of __bitmap_parselist()
to helpers.

Signed-off-by: Yury Norov <ynorov@marvell.com>
---
 lib/bitmap.c | 64 +++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 53 insertions(+), 11 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index ad1fb7e6ad0e..307a1b20bead 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -477,6 +477,42 @@ int bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp,
 }
 EXPORT_SYMBOL(bitmap_print_to_pagebuf);
 
+/*
+ * Region 9-38:4/10 describes the following bitmap structure:
+ * 0	   9  12    18			38
+ * .........****......****......****......
+ *	    ^  ^     ^			 ^
+ *      start  off   grlen	       end
+ */
+struct region {
+	unsigned int start;
+	unsigned int off;
+	unsigned int grlen;
+	unsigned int end;
+};
+
+static int bitmap_set_region(const struct region *r,
+				unsigned long *bitmap, int nbits)
+{
+	unsigned int start;
+
+	if (r->end >= nbits)
+		return -ERANGE;
+
+	for (start = r->start; start <= r->end; start += r->grlen)
+		bitmap_set(bitmap, start, min(r->end - start + 1, r->off));
+
+	return 0;
+}
+
+static int bitmap_check_region(const struct region *r)
+{
+	if (r->start > r->end || r->grlen == 0 || r->off > r->grlen)
+		return -EINVAL;
+
+	return 0;
+}
+
 /**
  * __bitmap_parselist - convert list format ASCII string to bitmap
  * @buf: read nul-terminated user string from this buffer
@@ -507,10 +543,11 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
 		int nmaskbits)
 {
 	unsigned int a, b, old_a, old_b;
-	unsigned int group_size, used_size, off;
+	unsigned int group_size, used_size;
 	int c, old_c, totaldigits, ndigits;
 	const char __user __force *ubuf = (const char __user __force *)buf;
-	int at_start, in_range, in_partial_range;
+	int at_start, in_range, in_partial_range, ret;
+	struct region r;
 
 	totaldigits = c = 0;
 	old_a = old_b = 0;
@@ -599,15 +636,20 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
 		/* if no digit is after '-', it's wrong*/
 		if (at_start && in_range)
 			return -EINVAL;
-		if (!(a <= b) || group_size == 0 || !(used_size <= group_size))
-			return -EINVAL;
-		if (b >= nmaskbits)
-			return -ERANGE;
-		while (a <= b) {
-			off = min(b - a + 1, used_size);
-			bitmap_set(maskp, a, off);
-			a += group_size;
-		}
+
+		r.start = a;
+		r.off = used_size;
+		r.grlen = group_size;
+		r.end = b;
+
+		ret = bitmap_check_region(&r);
+		if (ret)
+			return ret;
+
+		ret = bitmap_set_region(&r, maskp, nmaskbits);
+		if (ret)
+			return ret;
+
 	} while (buflen && c == ',');
 	return 0;
 }
-- 
2.17.1

[PATCH 3/6] bitmap_parselist: rework input string parser

[Yury Norov]

The requirement for this rework is to keep the __bitmap_parselist()
copy-less and single-pass but make it more readable and maintainable by
splitting into logical parts and removing explicit nested cycles and
opaque local variables.

__bitmap_parselist() can parse userspace inputs and therefore we cannot
use simple_strtoul() to parse numbers.

Signed-off-by: Yury Norov <ynorov@marvell.com>
---
 lib/bitmap.c | 246 +++++++++++++++++++++++++++++++--------------------
 1 file changed, 148 insertions(+), 98 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 307a1b20bead..f1c42ee8b8f2 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -513,6 +513,139 @@ static int bitmap_check_region(const struct region *r)
 	return 0;
 }
 
+static long get_char(char *c, const char *str, int is_user)
+{
+	if (unlikely(is_user))
+		return __get_user(*c, (const char __force __user *)str);
+
+	*c = *str;
+	return 0;
+}
+
+static const char *bitmap_getnum(unsigned int *num, const char *str,
+			    const char *const end, int is_user)
+{
+	unsigned int n = 0;
+	const char *_str;
+	long ret;
+	char c;
+
+	for (_str = str, *num = 0; _str <= end; _str++) {
+		ret = get_char(&c, _str, is_user);
+		if (ret)
+			return ERR_PTR(ret);
+
+		if (!isdigit(c)) {
+			if (_str == str)
+				return ERR_PTR(-EINVAL);
+
+			return _str;
+		}
+
+		*num = *num * 10 + (c - '0');
+		if (*num < n)
+			return ERR_PTR(-EOVERFLOW);
+
+		n = *num;
+	}
+
+	return _str;
+}
+
+static const char *bitmap_find_region(const char *str,
+			const char *const end, int is_user)
+{
+	long ret;
+	char c;
+
+	for (; str <= end; str++) {
+		ret = get_char(&c, str, is_user);
+		if (ret)
+			return ERR_PTR(ret);
+
+		/* Unexpected end of line. */
+		if (c == 0 || c == '\n')
+			return NULL;
+
+		/*
+		 * The format allows commas and whitespases
+		 * at the beginning of the region, so skip it.
+		 */
+		if (!isspace(c) && c != ',')
+			break;
+	}
+
+	return str <= end ? str : NULL;
+}
+
+static const char *bitmap_parse_region(struct region *r, const char *str,
+				 const char *const end, int is_user)
+{
+	long ret;
+	char c;
+
+	str = bitmap_getnum(&r->start, str, end, is_user);
+	if (IS_ERR(str))
+		return str;
+
+	ret = get_char(&c, str, is_user);
+	if (ret)
+		return (char *)ret;
+
+	if (c == 0 || c == '\n') {
+		str = end + 1;
+		goto no_end;
+	}
+
+	if (isspace(c) || c == ',')
+		goto no_end;
+
+	if (c != '-')
+		return ERR_PTR(-EINVAL);
+
+	str = bitmap_getnum(&r->end, str + 1, end, is_user);
+	if (IS_ERR(str))
+		return str;
+
+	ret = get_char(&c, str, is_user);
+	if (ret)
+		return ERR_PTR(ret);
+
+	if (c == 0 || c == '\n') {
+		str = end + 1;
+		goto no_pattern;
+	}
+
+	if (isspace(c) || c == ',')
+		goto no_pattern;
+
+	if (c != ':')
+		return ERR_PTR(-EINVAL);
+
+	str = bitmap_getnum(&r->off, str + 1, end, is_user);
+	if (IS_ERR(str))
+		return str;
+
+	ret = get_char(&c, str, is_user);
+	if (ret)
+		return (char *)ret;
+
+	if (c != '/')
+		return ERR_PTR(-EINVAL);
+
+	str = bitmap_getnum(&r->grlen, str + 1, end, is_user);
+
+	return str;
+
+no_end:
+	r->end = r->start;
+no_pattern:
+	r->off = r->end + 1;
+	r->grlen = r->end + 1;
+
+	return str;
+}
+
 /**
  * __bitmap_parselist - convert list format ASCII string to bitmap
  * @buf: read nul-terminated user string from this buffer
@@ -534,113 +667,29 @@ static int bitmap_check_region(const struct region *r)
  *
  * Returns: 0 on success, -errno on invalid input strings. Error values:
  *
- *   - ``-EINVAL``: second number in range smaller than first
+ *   - ``-EINVAL``: wrong region format
  *   - ``-EINVAL``: invalid character in string
  *   - ``-ERANGE``: bit number specified too large for mask
+ *   - ``-EOVERFLOW``: integer overflow in the input parameters
  */
-static int __bitmap_parselist(const char *buf, unsigned int buflen,
+static int __bitmap_parselist(const char *buf, const char *const end,
 		int is_user, unsigned long *maskp,
 		int nmaskbits)
 {
-	unsigned int a, b, old_a, old_b;
-	unsigned int group_size, used_size;
-	int c, old_c, totaldigits, ndigits;
-	const char __user __force *ubuf = (const char __user __force *)buf;
-	int at_start, in_range, in_partial_range, ret;
 	struct region r;
+	long ret;
 
-	totaldigits = c = 0;
-	old_a = old_b = 0;
-	group_size = used_size = 0;
 	bitmap_zero(maskp, nmaskbits);
-	do {
-		at_start = 1;
-		in_range = 0;
-		in_partial_range = 0;
-		a = b = 0;
-		ndigits = totaldigits;
 
-		/* Get the next cpu# or a range of cpu#'s */
-		while (buflen) {
-			old_c = c;
-			if (is_user) {
-				if (__get_user(c, ubuf++))
-					return -EFAULT;
-			} else
-				c = *buf++;
-			buflen--;
-			if (isspace(c))
-				continue;
 
-			/* A '\0' or a ',' signal the end of a cpu# or range */
-			if (c == '\0' || c == ',')
-				break;
-			/*
-			* whitespaces between digits are not allowed,
-			* but it's ok if whitespaces are on head or tail.
-			* when old_c is whilespace,
-			* if totaldigits == ndigits, whitespace is on head.
-			* if whitespace is on tail, it should not run here.
-			* as c was ',' or '\0',
-			* the last code line has broken the current loop.
-			*/
-			if ((totaldigits != ndigits) && isspace(old_c))
-				return -EINVAL;
-
-			if (c == '/') {
-				used_size = a;
-				at_start = 1;
-				in_range = 0;
-				a = b = 0;
-				continue;
-			}
-
-			if (c == ':') {
-				old_a = a;
-				old_b = b;
-				at_start = 1;
-				in_range = 0;
-				in_partial_range = 1;
-				a = b = 0;
-				continue;
-			}
-
-			if (c == '-') {
-				if (at_start || in_range)
-					return -EINVAL;
-				b = 0;
-				in_range = 1;
-				at_start = 1;
-				continue;
-			}
-
-			if (!isdigit(c))
-				return -EINVAL;
-
-			b = b * 10 + (c - '0');
-			if (!in_range)
-				a = b;
-			at_start = 0;
-			totaldigits++;
-		}
-		if (ndigits == totaldigits)
-			continue;
-		if (in_partial_range) {
-			group_size = a;
-			a = old_a;
-			b = old_b;
-			old_a = old_b = 0;
-		} else {
-			used_size = group_size = b - a + 1;
-		}
-		/* if no digit is after '-', it's wrong*/
-		if (at_start && in_range)
-			return -EINVAL;
+	while (buf && buf <= end) {
+		buf = bitmap_find_region(buf, end, is_user);
+		if (buf == NULL)
+			return 0;
 
-		r.start = a;
-		r.off = used_size;
-		r.grlen = group_size;
-		r.end = b;
+		buf = bitmap_parse_region(&r, buf, end, is_user);
+		if (IS_ERR(buf))
+			return PTR_ERR(buf);
 
 		ret = bitmap_check_region(&r);
 		if (ret)
@@ -649,14 +698,14 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
 		ret = bitmap_set_region(&r, maskp, nmaskbits);
 		if (ret)
 			return ret;
+	}
 
-	} while (buflen && c == ',');
 	return 0;
 }
 
 int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
 {
-	return __bitmap_parselist(bp, UINT_MAX, 0, maskp, nmaskbits);
+	return __bitmap_parselist(bp, (char *)SIZE_MAX, 0, maskp, nmaskbits);
 }
 EXPORT_SYMBOL(bitmap_parselist);
 
@@ -683,7 +732,8 @@ int bitmap_parselist_user(const char __user *ubuf,
 	if (!access_ok(ubuf, ulen))
 		return -EFAULT;
 	return __bitmap_parselist((const char __force *)ubuf,
-					ulen, 1, maskp, nmaskbits);
+				  (const char __force *)ubuf + ulen - 1,
+				  1, maskp, nmaskbits);
 }
 EXPORT_SYMBOL(bitmap_parselist_user);
 
-- 
2.17.1

[PATCH 4/6] lib/test_bitmap: switch test_bitmap_parselist to ktime_get()

[Yury Norov]

test_bitmap_parselist currently uses get_cycles which is not
implemented on some platforms, so use ktime_get() instead.

Signed-off-by: Yury Norov <ynorov@marvell.com>
---
 lib/test_bitmap.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 6cd7d0740005..b06e0fd3811b 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -266,15 +266,15 @@ static void __init test_bitmap_parselist(void)
 {
 	int i;
 	int err;
-	cycles_t cycles;
+	ktime_t time;
 	DECLARE_BITMAP(bmap, 2048);
 
 	for (i = 0; i < ARRAY_SIZE(parselist_tests); i++) {
 #define ptest parselist_tests[i]
 
-		cycles = get_cycles();
+		time = ktime_get();
 		err = bitmap_parselist(ptest.in, bmap, ptest.nbits);
-		cycles = get_cycles() - cycles;
+		time = ktime_get() - time;
 
 		if (err != ptest.errno) {
 			pr_err("test %d: input is %s, errno is %d, expected %d\n",
@@ -291,8 +291,7 @@ static void __init test_bitmap_parselist(void)
 
 		if (ptest.flags & PARSE_TIME)
 			pr_err("test %d: input is '%s' OK, Time: %llu\n",
-					i, ptest.in,
-					(unsigned long long)cycles);
+					i, ptest.in, time);
 	}
 }
 
-- 
2.17.1

[PATCH 5/6] lib/test_bitmap: add testcases for bitmap_parselist

[Yury Norov]

Add tests for non-number character, empty regions, integer overflow.

Signed-off-by: Yury Norov <ynorov@marvell.com>
---
 lib/test_bitmap.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index b06e0fd3811b..709424a788ee 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -224,7 +224,8 @@ static const unsigned long exp[] __initconst = {
 	BITMAP_FROM_U64(0xffffffff),
 	BITMAP_FROM_U64(0xfffffffe),
 	BITMAP_FROM_U64(0x3333333311111111ULL),
-	BITMAP_FROM_U64(0xffffffff77777777ULL)
+	BITMAP_FROM_U64(0xffffffff77777777ULL),
+	BITMAP_FROM_U64(0),
 };
 
 static const unsigned long exp2[] __initconst = {
@@ -247,19 +248,34 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
 	{0, "1-31:4/4",			&exp[9 * step], 32, 0},
 	{0, "0-31:1/4,32-63:2/4",	&exp[10 * step], 64, 0},
 	{0, "0-31:3/4,32-63:4/4",	&exp[11 * step], 64, 0},
+	{0, "  ,,  0-31:3/4  ,, 32-63:4/4  ,,  ",	&exp[11 * step], 64, 0},
 
 	{0, "0-31:1/4,32-63:2/4,64-95:3/4,96-127:4/4",	exp2, 128, 0},
 
 	{0, "0-2047:128/256", NULL, 2048, PARSE_TIME},
 
+	{0, "",				&exp[12], 8, 0},
+	{0, "\n",			&exp[12], 8, 0},
+	{0, ",,  ,,  , ,  ,",		&exp[12], 8, 0},
+	{0, " ,  ,,  , ,   ",		&exp[12], 8, 0},
+	{0, " ,  ,,  , ,   \n",		&exp[12], 8, 0},
+
 	{-EINVAL, "-1",	NULL, 8, 0},
 	{-EINVAL, "-0",	NULL, 8, 0},
 	{-EINVAL, "10-1", NULL, 8, 0},
 	{-EINVAL, "0-31:", NULL, 8, 0},
 	{-EINVAL, "0-31:0", NULL, 8, 0},
+	{-EINVAL, "0-31:0/", NULL, 8, 0},
 	{-EINVAL, "0-31:0/0", NULL, 8, 0},
 	{-EINVAL, "0-31:1/0", NULL, 8, 0},
 	{-EINVAL, "0-31:10/1", NULL, 8, 0},
+	{-EOVERFLOW, "0-98765432123456789:10/1", NULL, 8, 0},
+
+	{-EINVAL, "a-31", NULL, 8, 0},
+	{-EINVAL, "0-a1", NULL, 8, 0},
+	{-EINVAL, "a-31:10/1", NULL, 8, 0},
+	{-EINVAL, "0-31:a/1", NULL, 8, 0},
+	{-EINVAL, "0-\n", NULL, 8, 0},
 };
 
 static void __init test_bitmap_parselist(void)
-- 
2.17.1

[PATCH 6/6] lib/test_bitmap: add tests for bitmap_parselist_user

[Yury Norov]

Propagate existing bitmap_parselist() tests to bitmap_parselist_user().

Signed-off-by: Yury Norov <ynorov@marvell.com>
---
 lib/test_bitmap.c | 46 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 36 insertions(+), 10 deletions(-)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 709424a788ee..d4ecac0da160 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -11,6 +11,7 @@
 #include <linux/printk.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/uaccess.h>
 
 static unsigned total_tests __initdata;
 static unsigned failed_tests __initdata;
@@ -278,39 +279,63 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
 	{-EINVAL, "0-\n", NULL, 8, 0},
 };
 
-static void __init test_bitmap_parselist(void)
+static void __init __test_bitmap_parselist(int is_user)
 {
 	int i;
 	int err;
 	ktime_t time;
 	DECLARE_BITMAP(bmap, 2048);
+	char *mode = is_user ? "_user"  : "";
 
 	for (i = 0; i < ARRAY_SIZE(parselist_tests); i++) {
 #define ptest parselist_tests[i]
 
-		time = ktime_get();
-		err = bitmap_parselist(ptest.in, bmap, ptest.nbits);
-		time = ktime_get() - time;
+		if (is_user) {
+			mm_segment_t orig_fs = get_fs();
+			size_t len = strlen(ptest.in);
+
+			set_fs(KERNEL_DS);
+			time = ktime_get();
+			err = bitmap_parselist_user(ptest.in, len,
+						    bmap, ptest.nbits);
+			time = ktime_get() - time;
+			set_fs(orig_fs);
+		} else {
+			time = ktime_get();
+			err = bitmap_parselist(ptest.in, bmap, ptest.nbits);
+			time = ktime_get() - time;
+		}
 
 		if (err != ptest.errno) {
-			pr_err("test %d: input is %s, errno is %d, expected %d\n",
-					i, ptest.in, err, ptest.errno);
+			pr_err("parselist%s: %d: input is %s, errno is %d, expected %d\n",
+					mode, i, ptest.in, err, ptest.errno);
 			continue;
 		}
 
 		if (!err && ptest.expected
 			 && !__bitmap_equal(bmap, ptest.expected, ptest.nbits)) {
-			pr_err("test %d: input is %s, result is 0x%lx, expected 0x%lx\n",
-					i, ptest.in, bmap[0], *ptest.expected);
+			pr_err("parselist%s: %d: input is %s, result is 0x%lx, expected 0x%lx\n",
+					mode, i, ptest.in, bmap[0],
+					*ptest.expected);
 			continue;
 		}
 
 		if (ptest.flags & PARSE_TIME)
-			pr_err("test %d: input is '%s' OK, Time: %llu\n",
-					i, ptest.in, time);
+			pr_err("parselist%s: %d: input is '%s' OK, Time: %llu\n",
+					mode, i, ptest.in, time);
 	}
 }
 
+static void __init test_bitmap_parselist(void)
+{
+	__test_bitmap_parselist(0);
+}
+
+static void __init test_bitmap_parselist_user(void)
+{
+	__test_bitmap_parselist(1);
+}
+
 #define EXP_BYTES	(sizeof(exp) * 8)
 
 static void __init test_bitmap_arr32(void)
@@ -383,6 +408,7 @@ static int __init test_bitmap_init(void)
 	test_copy();
 	test_bitmap_arr32();
 	test_bitmap_parselist();
+	test_bitmap_parselist_user();
 	test_mem_optimisations();
 
 	if (failed_tests == 0)
-- 
2.17.1

Re: [PATCH 4/6] lib/test_bitmap: switch test_bitmap_parselist to ktime_get()

[Andy Shevchenko]

On Wed, Feb 20, 2019 at 11:37:03AM +0300, Yury Norov wrote:
> test_bitmap_parselist currently uses get_cycles which is not
> implemented on some platforms, so use ktime_get() instead.

This sounds like a fix that should go first in the series.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 4/6] lib/test_bitmap: switch test_bitmap_parselist to ktime_get()

[Andy Shevchenko]

On Wed, Feb 20, 2019 at 03:51:01PM +0200, Andy Shevchenko wrote:
> On Wed, Feb 20, 2019 at 11:37:03AM +0300, Yury Norov wrote:
> > test_bitmap_parselist currently uses get_cycles which is not
> > implemented on some platforms, so use ktime_get() instead.
> 
> This sounds like a fix that should go first in the series.

Ah, okay, it's already first for test module.
Perhaps Fixes tag and actually one or more examples of such architectures?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 4/6] lib/test_bitmap: switch test_bitmap_parselist to ktime_get()

[Yury Norov]

On Wed, Feb 20, 2019 at 03:52:36PM +0200, Andy Shevchenko wrote:
> On Wed, Feb 20, 2019 at 03:51:01PM +0200, Andy Shevchenko wrote:
> > On Wed, Feb 20, 2019 at 11:37:03AM +0300, Yury Norov wrote:
> > > test_bitmap_parselist currently uses get_cycles which is not
> > > implemented on some platforms, so use ktime_get() instead.
> > 
> > This sounds like a fix that should go first in the series.
> 
> Ah, okay, it's already first for test module.
> Perhaps Fixes tag and actually one or more examples of such architectures?

Hi Andy, thanks for your time on it.

Only arm, arm64, openrisc, riscv and sparc64 #define get_cycles.
So IIUC, others take stub from include/asm-generic/timex.h.

sparc32, xtensa, m68k, um, and in some cases x86, mips and nios2
provide zero-stubs explicitly.

Yury

> -- 
> With Best Regards,
> Andy Shevchenko
> 

Re: [PATCH 4/6] lib/test_bitmap: switch test_bitmap_parselist to ktime_get()

[Palmer Dabbelt]

On Wed, 20 Feb 2019 06:20:48 PST (-0800), yury.norov@gmail.com wrote:
> On Wed, Feb 20, 2019 at 03:52:36PM +0200, Andy Shevchenko wrote:
>> On Wed, Feb 20, 2019 at 03:51:01PM +0200, Andy Shevchenko wrote:
>> > On Wed, Feb 20, 2019 at 11:37:03AM +0300, Yury Norov wrote:
>> > > test_bitmap_parselist currently uses get_cycles which is not
>> > > implemented on some platforms, so use ktime_get() instead.
>> >
>> > This sounds like a fix that should go first in the series.
>>
>> Ah, okay, it's already first for test module.
>> Perhaps Fixes tag and actually one or more examples of such architectures?
>
> Hi Andy, thanks for your time on it.
>
> Only arm, arm64, openrisc, riscv and sparc64 #define get_cycles.
> So IIUC, others take stub from include/asm-generic/timex.h.

Should we (RISC-V) be doing something else?  It seems odd to be in such a 
minority here, but we do have a ISA-mandated timer so the get_cycles() 
implementation is super easy.

> sparc32, xtensa, m68k, um, and in some cases x86, mips and nios2
> provide zero-stubs explicitly.
>
> Yury
>
>> --
>> With Best Regards,
>> Andy Shevchenko
>>

Re: [PATCH 4/6] lib/test_bitmap: switch test_bitmap_parselist to ktime_get()

[Yury Norov]

On Wed, Feb 20, 2019 at 03:10:44PM -0800, Palmer Dabbelt wrote:
> On Wed, 20 Feb 2019 06:20:48 PST (-0800), yury.norov@gmail.com wrote:
> > On Wed, Feb 20, 2019 at 03:52:36PM +0200, Andy Shevchenko wrote:
> > > On Wed, Feb 20, 2019 at 03:51:01PM +0200, Andy Shevchenko wrote:
> > > > On Wed, Feb 20, 2019 at 11:37:03AM +0300, Yury Norov wrote:
> > > > > test_bitmap_parselist currently uses get_cycles which is not
> > > > > implemented on some platforms, so use ktime_get() instead.
> > > >
> > > > This sounds like a fix that should go first in the series.
> > > 
> > > Ah, okay, it's already first for test module.
> > > Perhaps Fixes tag and actually one or more examples of such architectures?
> > 
> > Hi Andy, thanks for your time on it.
> > 
> > Only arm, arm64, openrisc, riscv and sparc64 #define get_cycles.
> > So IIUC, others take stub from include/asm-generic/timex.h.
> 
> Should we (RISC-V) be doing something else?  It seems odd to be in such a
> minority here, but we do have a ISA-mandated timer so the get_cycles()
> implementation is super easy.

I think you are completely fine because you are one of those who
implement get_cycles().

get_cycles() is the problem for those who use it in generic code
because their code surprisingly gets broken on some machines while
works OK on others. This is not a problem of any specific arch.

For long term, we should inspect the non-arch code and replace 
get_cycles() with ktime_get() where appropriate, and avoid
introducing new get_cycles() uses.
 
> > sparc32, xtensa, m68k, um, and in some cases x86, mips and nios2
> > provide zero-stubs explicitly.
> > 
> > Yury
> > 
> > > --
> > > With Best Regards,
> > > Andy Shevchenko
> > > 

Re: [PATCH 4/6] lib/test_bitmap: switch test_bitmap_parselist to ktime_get()

[Yury Norov]

On Wed, Feb 20, 2019 at 05:20:48PM +0300, Yury Norov wrote:
> On Wed, Feb 20, 2019 at 03:52:36PM +0200, Andy Shevchenko wrote:
> > On Wed, Feb 20, 2019 at 03:51:01PM +0200, Andy Shevchenko wrote:
> > > On Wed, Feb 20, 2019 at 11:37:03AM +0300, Yury Norov wrote:
> > > > test_bitmap_parselist currently uses get_cycles which is not
> > > > implemented on some platforms, so use ktime_get() instead.
> > > 
> > > This sounds like a fix that should go first in the series.
> > 
> > Ah, okay, it's already first for test module.
> > Perhaps Fixes tag and actually one or more examples of such architectures?
> 
> Hi Andy, thanks for your time on it.
> 
> Only arm, arm64, openrisc, riscv and sparc64 #define get_cycles.
> So IIUC, others take stub from include/asm-generic/timex.h.
> 
> sparc32, xtensa, m68k, um, and in some cases x86, mips and nios2
> provide zero-stubs explicitly.

I forgot about Fixes tag:
Fixes: 6df0d464dbcc1a5 ("lib/test_bitmap.c: add test for bitmap_parselist()")

If it comes to v3, I'll add the tag and explanations above to the
patch message.

Re: [PATCH v2 0/5] lib: rework bitmap_parselist and tests

[Yury Norov]

Ping?

On Wed, Feb 20, 2019 at 11:36:59AM +0300, Yury Norov wrote:
> bitmap_parselist has been evolved from a pretty simple idea for long and
> now lacks for refactoring. It is not structured, has nested loops and a
> set of opaque-named variables. All this leads to extremely hard
> understanding of the code. Once during the optimization of it I missed a
> scenario which leads to kernel hangup. Tetsuo Handa spotted this and found
> it simpler to rewrite the code instead fixing it. (Though, that attempt
> had some flaws.)
> https://lkml.org/lkml/2018/4/1/93 
> 
> Things are more complicated than they may be because bitmap_parselist()
> is part of user interface, and its behavior should not change.
> 
> In this patchset 
>  - __bitmap_parselist() is reworked (patches 2 and 3);
>  - time measurement in test_bitmap_parselist switched to ktime_get
>    (patch 4);
>  - new tests introduced (patch 5), and
>  - bitmap_parselist_user() testing enabled with the same testset as
>    bitmap_parselist() (patch 6).
> 
> Patch 1 is a fix and may be applied separately.
> 
> V1: https://lkml.org/lkml/2018/12/23/50
> v2: - use PTR_ERR() and ERR_PTR() where appropriate;
>     - fix parser logic (last byte of string handling);
>     - tests for bitmap_parselist_user() in patch 5.
> 
> Yury Norov (4):
>   bitmap_parselist: don't calculate length of the input string
>   bitmap_parselist: move non-parser logic to helpers
>   bitmap_parselist: rework input string parser
>   lib/test_bitmap: switch test_bitmap_parselist to ktime_get()
>   lib/test_bitmap: add testcases for bitmap_parselist
>   lib/test_bitmap: add tests for bitmap_parselist_user
> 
>  lib/bitmap.c      | 293 ++++++++++++++++++++++++++++++----------------
>  lib/test_bitmap.c |  67 +++++++++--
>  2 files changed, 245 insertions(+), 115 deletions(-)
> 
> -- 
> 2.17.1