value strings: pretty printers for flags and enums

This adds zfs_valstr, a collection of pretty printers for bitfields and
enums. These are useful in debugging, logging and other display contexts
where raw values are difficult for the untrained (or even trained!) eye
to decipher.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Signed-off-by: Rob Norris <[email protected]>

1 files changed, 277 insertions, 0 deletions

diff --git a/module/zcommon/zfs_valstr.c b/module/zcommon/zfs_valstr.c
new file mode 100644
index 000000000..e2d4d1aef
--- /dev/null
+++ b/module/zcommon/zfs_valstr.c
@@ -0,0 +1,277 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or https://opensource.org/licenses/CDDL-1.0.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2024, Klara Inc.
+ */
+
+#include <sys/fs/zfs.h>
+#include <sys/types.h>
+#include <sys/sysmacros.h>
+#include <sys/string.h>
+#include <sys/debug.h>
+#include "zfs_valstr.h"
+
+/*
+ * Each bit in a bitfield has three possible string representations:
+ * - single char
+ * - two-char pair
+ * - full name
+ */
+typedef struct {
+	const char	vb_bit;
+	const char	vb_pair[2];
+	const char	*vb_name;
+} valstr_bit_t;
+
+/*
+ * Emits a character for each bit in `bits`, up to the number of elements
+ * in the table. Set bits get the character in vb_bit, clear bits get a
+ * space. This results in all strings having the same width, for easier
+ * visual comparison.
+ */
+static size_t
+valstr_bitfield_bits(const valstr_bit_t *table, const size_t nelems,
+    uint64_t bits, char *out, size_t outlen)
+{
+	ASSERT(out);
+	size_t n = 0;
+	for (int b = 0; b < nelems; b++) {
+		if (n == outlen)
+			break;
+		uint64_t mask = (1ULL << b);
+		out[n++] = (bits & mask) ? table[b].vb_bit : ' ';
+	}
+	if (n < outlen)
+		out[n++] = '\0';
+	return (n);
+}
+
+/*
+ * Emits a two-char pair for each bit set in `bits`, taken from vb_pair, and
+ * separated by a `|` character. This gives a concise representation of the
+ * whole value.
+ */
+static size_t
+valstr_bitfield_pairs(const valstr_bit_t *table, const size_t nelems,
+    uint64_t bits, char *out, size_t outlen)
+{
+	ASSERT(out);
+	size_t n = 0;
+	for (int b = 0; b < nelems; b++) {
+		ASSERT3U(n, <=, outlen);
+		if (n == outlen)
+			break;
+		uint64_t mask = (1ULL << b);
+		if (bits & mask) {
+			size_t len = (n > 0) ? 3 : 2;
+			if (n > outlen-len)
+				break;
+			if (n > 0)
+				out[n++] = '|';
+			out[n++] = table[b].vb_pair[0];
+			out[n++] = table[b].vb_pair[1];
+		}
+	}
+	if (n < outlen)
+		out[n++] = '\0';
+	return (n);
+}
+
+/*
+ * Emits the full name for each bit set in `bits`, taken from vb_name, and
+ * separated by a space. This unambiguously shows the entire set of bits, but
+ * can get very long.
+ */
+static size_t
+valstr_bitfield_str(const valstr_bit_t *table, const size_t nelems,
+    uint64_t bits, char *out, size_t outlen)
+{
+	ASSERT(out);
+	size_t n = 0;
+	for (int b = 0; b < nelems; b++) {
+		ASSERT3U(n, <=, outlen);
+		if (n == outlen)
+			break;
+		uint64_t mask = (1ULL << b);
+		if (bits & mask) {
+			size_t len = strlen(table[b].vb_name);
+			if (n > 0)
+				len++;
+			if (n > outlen-len)
+				break;
+			if (n > 0) {
+				out[n++] = ' ';
+				len--;
+			}
+			memcpy(&out[n], table[b].vb_name, len);
+			n += len;
+		}
+	}
+	if (n < outlen)
+		out[n++] = '\0';
+	return (n);
+}
+
+/*
+ * Emits the name of the given enum value in the table.
+ */
+static size_t
+valstr_enum_str(const char **table, const size_t nelems,
+    int v, char *out, size_t outlen)
+{
+	ASSERT(out);
+	ASSERT3U(v, <, nelems);
+	if (v >= nelems)
+		return (0);
+	return (MIN(strlcpy(out, table[v], outlen), outlen));
+}
+
+/*
+ * These macros create the string tables for the given name, and implement
+ * the public functions described in zfs_valstr.h.
+ */
+#define	_VALSTR_BITFIELD_IMPL(name, ...)				\
+static const valstr_bit_t valstr_ ## name ## _table[] = { __VA_ARGS__ };\
+size_t									\
+zfs_valstr_ ## name ## _bits(uint64_t bits, char *out, size_t outlen)	\
+{									\
+	return (valstr_bitfield_bits(valstr_ ## name ## _table,		\
+	    ARRAY_SIZE(valstr_ ## name ## _table), bits, out, outlen));	\
+}									\
+									\
+size_t									\
+zfs_valstr_ ## name ## _pairs(uint64_t bits, char *out, size_t outlen)	\
+{									\
+	return (valstr_bitfield_pairs(valstr_ ## name ## _table,	\
+	    ARRAY_SIZE(valstr_ ## name ## _table), bits, out, outlen));	\
+}									\
+									\
+size_t									\
+zfs_valstr_ ## name(uint64_t bits, char *out, size_t outlen)		\
+{									\
+	return (valstr_bitfield_str(valstr_ ## name ## _table,		\
+	    ARRAY_SIZE(valstr_ ## name ## _table), bits, out, outlen));	\
+}									\
+
+#define	_VALSTR_ENUM_IMPL(name, ...)					\
+static const char *valstr_ ## name ## _table[] = { __VA_ARGS__ };	\
+size_t									\
+zfs_valstr_ ## name(int v, char *out, size_t outlen)			\
+{									\
+	return (valstr_enum_str(valstr_ ## name ## _table,		\
+	    ARRAY_SIZE(valstr_ ## name ## _table), v, out, outlen));	\
+}									\
+
+
+/* String tables */
+
+/* ZIO flags: zio_flag_t, typically zio->io_flags */
+/* BEGIN CSTYLED */
+_VALSTR_BITFIELD_IMPL(zio_flag,
+	{ '.', "DA", "DONT_AGGREGATE" },
+	{ '.', "RP", "IO_REPAIR" },
+	{ '.', "SH", "SELF_HEAL" },
+	{ '.', "RS", "RESILVER" },
+	{ '.', "SC", "SCRUB" },
+	{ '.', "ST", "SCAN_THREAD" },
+	{ '.', "PH", "PHYSICAL" },
+	{ '.', "CF", "CANFAIL" },
+	{ '.', "SP", "SPECULATIVE" },
+	{ '.', "CW", "CONFIG_WRITER" },
+	{ '.', "DR", "DONT_RETRY" },
+	{ '?', "??", "[UNUSED 11]" },
+	{ '.', "ND", "NODATA" },
+	{ '.', "ID", "INDUCE_DAMAGE" },
+	{ '.', "AL", "IO_ALLOCATING" },
+	{ '.', "RE", "IO_RETRY" },
+	{ '.', "PR", "PROBE" },
+	{ '.', "TH", "TRYHARD" },
+	{ '.', "OP", "OPTIONAL" },
+	{ '.', "DQ", "DONT_QUEUE" },
+	{ '.', "DP", "DONT_PROPAGATE" },
+	{ '.', "BY", "IO_BYPASS" },
+	{ '.', "RW", "IO_REWRITE" },
+	{ '.', "CM", "RAW_COMPRESS" },
+	{ '.', "EN", "RAW_ENCRYPT" },
+	{ '.', "GG", "GANG_CHILD" },
+	{ '.', "DD", "DDT_CHILD" },
+	{ '.', "GF", "GODFATHER" },
+	{ '.', "NP", "NOPWRITE" },
+	{ '.', "EX", "REEXECUTED" },
+	{ '.', "DG", "DELEGATED" },
+)
+/* END CSTYLED */
+
+/*
+ * ZIO pipeline stage(s): enum zio_stage, typically zio->io_stage or
+ *                        zio->io_pipeline.
+ */
+/* BEGIN CSTYLED */
+_VALSTR_BITFIELD_IMPL(zio_stage,
+	{ 'O', "O ", "OPEN" },
+	{ 'I', "RI", "READ_BP_INIT" },
+	{ 'I', "WI", "WRITE_BP_INIT" },
+	{ 'I', "FI", "FREE_BP_INIT" },
+	{ 'A', "IA", "ISSUE_ASYNC" },
+	{ 'W', "WC", "WRITE_COMPRESS" },
+	{ 'E', "EN", "ENCRYPT" },
+	{ 'C', "CG", "CHECKSUM_GENERATE" },
+	{ 'N', "NW", "NOP_WRITE" },
+	{ 'B', "BF", "BRT_FREE" },
+	{ 'd', "dS", "DDT_READ_START" },
+	{ 'd', "dD", "DDT_READ_DONE" },
+	{ 'd', "dW", "DDT_WRITE" },
+	{ 'd', "dF", "DDT_FREE" },
+	{ 'G', "GA", "GANG_ASSEMBLE" },
+	{ 'G', "GI", "GANG_ISSUE" },
+	{ 'D', "DT", "DVA_THROTTLE" },
+	{ 'D', "DA", "DVA_ALLOCATE" },
+	{ 'D', "DF", "DVA_FREE" },
+	{ 'D', "DC", "DVA_CLAIM" },
+	{ 'R', "R ", "READY" },
+	{ 'V', "VS", "VDEV_IO_START" },
+	{ 'V', "VD", "VDEV_IO_DONE" },
+	{ 'V', "VA", "VDEV_IO_ASSESS" },
+	{ 'C', "CV", "CHECKSUM_VERIFY" },
+	{ 'X', "X ", "DONE" },
+)
+/* END CSTYLED */
+
+/* ZIO priority: zio_priority_t, typically zio->io_priority */
+/* BEGIN CSTYLED */
+_VALSTR_ENUM_IMPL(zio_priority,
+	"SYNC_READ",
+	"SYNC_WRITE",
+	"ASYNC_READ",
+	"ASYNC_WRITE",
+	"SCRUB",
+	"REMOVAL",
+	"INITIALIZING",
+	"TRIM",
+	"REBUILD",
+	"[NUM_QUEUEABLE]",
+	"NOW",
+)
+/* END CSTYLED */
+
+#undef _VALSTR_BITFIELD_IMPL
+#undef _VALSTR_ENUM_IMPL