fail(9) support:

Add support for kernel fault injection using KFAIL_POINT_* macros and
fail_point_* infrastructure. Add example fail point in vfs_bio.c to
simulate VM buf pressure.

Approved by:        dfr (mentor)

2 files changed, 588 insertions, 3 deletions

diff --git a/sys/kern/kern_fail.c b/sys/kern/kern_fail.c
new file mode 100644
index 0000000..06dfc38
--- /dev/null
+++ b/sys/kern/kern_fail.c
@@ -0,0 +1,575 @@
+/*-
+ * Copyright (c) 2009 Isilon Inc http://www.isilon.com/
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+/**
+ * @file
+ *
+ * fail(9) Facility.
+ *
+ * @ingroup failpoint_private
+ */
+/**
+ * @defgroup failpoint fail(9) Facility
+ *
+ * Failpoints allow for injecting fake errors into running code on the fly,
+ * without modifying code or recompiling with flags.  Failpoints are always
+ * present, and are very efficient when disabled.  Failpoints are described
+ * in man fail(9).
+ */
+/**
+ * @defgroup failpoint_private Private fail(9) Implementation functions
+ *
+ * Private implementations for the actual failpoint code.
+ *
+ * @ingroup failpoint
+ */
+/**
+ * @addtogroup failpoint_private
+ * @{
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/errno.h>
+#include <sys/fail.h>
+#include <sys/kernel.h>
+#include <sys/libkern.h>
+#include <sys/lock.h>
+#include <sys/malloc.h>
+#include <sys/mutex.h>
+#include <sys/sbuf.h>
+
+#include <machine/stdarg.h>
+
+#ifdef ILOG_DEFINE_FOR_FILE
+ILOG_DEFINE_FOR_FILE(L_ISI_FAIL_POINT, L_ILOG, fail_point);
+#endif
+
+MALLOC_DEFINE(M_FAIL_POINT, "Fail Points", "fail points system");
+#define fp_free(ptr) free(ptr, M_FAIL_POINT)
+#define fp_malloc(size, flags) malloc((size), M_FAIL_POINT, (flags))
+
+static struct mtx g_fp_mtx;
+MTX_SYSINIT(g_fp_mtx, &g_fp_mtx, "fail point mtx", MTX_DEF);
+#define FP_LOCK()	mtx_lock(&g_fp_mtx)
+#define FP_UNLOCK()	mtx_unlock(&g_fp_mtx)
+
+static inline void
+fail_point_sleep(struct fail_point *fp, struct fail_point_entry *ent,
+    int msecs, enum fail_point_return_code *pret)
+{
+	/* convert from millisecs to ticks, rounding up */
+	int timo = ((msecs * hz) + 999) / 1000;
+
+	if (timo) {
+		if (fp->fp_sleep_fn == NULL) {
+			msleep(fp, &g_fp_mtx, PWAIT, "failpt", timo);
+		} else {
+			timeout(fp->fp_sleep_fn, fp->fp_sleep_arg, timo);
+			*pret = FAIL_POINT_RC_QUEUED;
+		}
+	}
+}
+
+
+/**
+ * Defines stating the equivalent of probablilty one (100%)
+ */
+enum {
+	PROB_MAX = 1000000,	/* probability between zero and this number */
+	PROB_DIGITS = 6,        /* number of zero's in above number */
+};
+
+static const char *fail_type_strings[] = {
+	"off",
+	"panic",
+	"return",
+	"break",
+	"print",
+	"sleep",
+};
+
+static char *parse_fail_point(struct fail_point_entries *, char *);
+static char *parse_term(struct fail_point_entries *, char *);
+static char *parse_number(int *out_units, int *out_decimal, char *);
+static char *parse_type(struct fail_point_entry *, char *);
+static void free_entry(struct fail_point_entries *, struct fail_point_entry *);
+static void clear_entries(struct fail_point_entries *);
+
+/**
+ * Initialize a fail_point.  The name is formed in a printf-like fashion
+ * from "fmt" and subsequent arguments.  This function is generally used
+ * for custom failpoints located at odd places in the sysctl tree, and is
+ * not explicitly needed for standard in-line-declared failpoints.
+ *
+ * @ingroup failpoint
+ */
+void
+fail_point_init(struct fail_point *fp, const char *fmt, ...)
+{
+	va_list ap;
+	char *name;
+	int n;
+
+	TAILQ_INIT(&fp->fp_entries);
+	fp->fp_flags = 0;
+
+	/* Figure out the size of the name. */
+	va_start(ap, fmt);
+	n = vsnprintf(NULL, 0, fmt, ap);
+	va_end(ap);
+
+	/* Allocate the name and fill it in. */
+	name = fp_malloc(n + 1, M_WAITOK);
+	if (name != NULL) {
+		va_start(ap, fmt);
+		vsnprintf(name, n + 1, fmt, ap);
+		va_end(ap);
+	}
+	fp->fp_name = name;
+	fp->fp_flags |= FAIL_POINT_DYNAMIC_NAME;
+	fp->fp_sleep_fn = NULL;
+	fp->fp_sleep_arg = NULL;
+}
+
+/**
+ * Free the resources held by a fail_point.
+ *
+ * @ingroup failpoint
+ */
+void
+fail_point_destroy(struct fail_point *fp)
+{
+	struct fail_point_entry *ent;
+
+	if (fp->fp_flags & FAIL_POINT_DYNAMIC_NAME && fp->fp_name != NULL) {
+		fp_free((void *)(intptr_t)fp->fp_name);
+		fp->fp_name = NULL;
+	}
+	fp->fp_flags = 0;
+
+	while (!TAILQ_EMPTY(&fp->fp_entries)) {
+		ent = TAILQ_FIRST(&fp->fp_entries);
+		TAILQ_REMOVE(&fp->fp_entries, ent, fe_entries);
+		fp_free(ent);
+	}
+}
+
+/**
+ * This does the real work of evaluating a fail point. If the fail point tells
+ * us to return a value, this function returns 1 and fills in 'return_value'
+ * (return_value is allowed to be null). If the fail point tells us to panic,
+ * we never return. Otherwise we just return 0 after doing some work, which
+ * means "keep going".
+ */
+enum fail_point_return_code
+fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
+{
+	enum fail_point_return_code ret = FAIL_POINT_RC_CONTINUE;
+	struct fail_point_entry *ent, *next;
+	int msecs;
+
+	FP_LOCK();
+
+	ent = TAILQ_FIRST(&fp->fp_entries);
+	while (ent) {
+		int cont = 0; /* don't continue by default */
+		next = TAILQ_NEXT(ent, fe_entries);
+
+		if (ent->fe_prob < PROB_MAX &&
+		    ent->fe_prob < random() % PROB_MAX) {
+			cont = 1;
+			goto loop_end;
+		}
+
+		switch (ent->fe_type) {
+		case FAIL_POINT_PANIC:
+			panic("fail point %s panicking", fp->fp_name);
+			/* NOTREACHED */
+
+		case FAIL_POINT_RETURN:
+			if (return_value)
+				*return_value = ent->fe_arg;
+			ret = FAIL_POINT_RC_RETURN;
+			break;
+
+		case FAIL_POINT_BREAK:
+			printf("fail point %s breaking to debugger\n", fp->fp_name);
+			breakpoint();
+			break;
+
+		case FAIL_POINT_PRINT:
+			printf("fail point %s executing\n", fp->fp_name);
+			cont = ent->fe_arg;
+			break;
+
+		case FAIL_POINT_SLEEP:
+			/*
+			 * Free the entry now if necessary, since
+			 * we're about to drop the mutex and sleep.
+			 */
+			msecs = ent->fe_arg;
+			if (ent->fe_count > 0 && --ent->fe_count == 0) {
+				free_entry(&fp->fp_entries, ent);
+				ent = NULL;
+			}
+
+			if (msecs)
+				fail_point_sleep(fp, ent, msecs, &ret);
+			break;
+
+		default:
+			break;
+		}
+
+		if (ent && ent->fe_count > 0 && --ent->fe_count == 0)
+			free_entry(&fp->fp_entries, ent);
+
+loop_end:
+		if (cont)
+			ent = next;
+		else
+			break;
+	}
+
+	/* Get rid of "off"s at the end. */
+	while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
+	       ent->fe_type == FAIL_POINT_OFF)
+		free_entry(&fp->fp_entries, ent);
+
+	FP_UNLOCK();
+
+	return ret;
+}
+
+/**
+ * Translate internal fail_point structure into human-readable text.
+ */
+static void
+fail_point_get(struct fail_point *fp, struct sbuf *sb)
+{
+	struct fail_point_entry *ent;
+
+	FP_LOCK();
+
+	TAILQ_FOREACH(ent, &fp->fp_entries, fe_entries) {
+		if (ent->fe_prob < PROB_MAX) {
+			int decimal = ent->fe_prob % (PROB_MAX / 100);
+			int units = ent->fe_prob / (PROB_MAX / 100);
+			sbuf_printf(sb, "%d", units);
+			if (decimal) {
+				int digits = PROB_DIGITS - 2;
+				while (!(decimal % 10)) {
+					digits--;
+					decimal /= 10;
+				}
+				sbuf_printf(sb, ".%0*d", digits, decimal);
+			}
+			sbuf_printf(sb, "%%");
+		}
+		if (ent->fe_count > 0)
+			sbuf_printf(sb, "%d*", ent->fe_count);
+		sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type]);
+		if (ent->fe_arg)
+			sbuf_printf(sb, "(%d)", ent->fe_arg);
+		if (TAILQ_NEXT(ent, fe_entries))
+			sbuf_printf(sb, "->");
+	}
+	if (TAILQ_EMPTY(&fp->fp_entries))
+		sbuf_printf(sb, "off");
+
+	FP_UNLOCK();
+}
+
+/**
+ * Set an internal fail_point structure from a human-readable failpoint string
+ * in a lock-safe manner.
+ */
+static int
+fail_point_set(struct fail_point *fp, char *buf)
+{
+	int error = 0;
+	struct fail_point_entry *ent, *ent_next;
+	struct fail_point_entries new_entries;
+
+	/* Parse new entries. */
+	TAILQ_INIT(&new_entries);
+	if (!parse_fail_point(&new_entries, buf)) {
+	        clear_entries(&new_entries);
+		error = EINVAL;
+		goto end;
+	}
+
+	FP_LOCK();
+
+	/* Move new entries in. */
+	TAILQ_SWAP(&fp->fp_entries, &new_entries, fail_point_entry, fe_entries);
+	clear_entries(&new_entries);
+
+	/* Get rid of useless zero probability entries. */
+	TAILQ_FOREACH_SAFE(ent, &fp->fp_entries, fe_entries, ent_next) {
+		if (ent->fe_prob == 0)
+			free_entry(&fp->fp_entries, ent);
+	}
+
+	/* Get rid of "off"s at the end. */
+	while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
+		ent->fe_type == FAIL_POINT_OFF)
+		free_entry(&fp->fp_entries, ent);
+
+	FP_UNLOCK();
+
+ end:
+#ifdef IWARNING
+	if (error)
+		IWARNING("Failed to set %s (%s) to %s",
+		    fp->fp_name, fp->fp_location, buf);
+	else
+		INOTICE("Set %s (%s) to %s",
+		    fp->fp_name, fp->fp_location, buf);
+#endif /* IWARNING */
+
+	return error;
+}
+
+#define MAX_FAIL_POINT_BUF	1023
+
+/**
+ * Handle kernel failpoint set/get.
+ */
+int
+fail_point_sysctl(SYSCTL_HANDLER_ARGS)
+{
+	struct fail_point *fp = arg1;
+	char *buf = NULL;
+	struct sbuf sb;
+	int error;
+
+	/* Retrieving */
+	sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND);
+	fail_point_get(fp, &sb);
+	sbuf_trim(&sb);
+	sbuf_finish(&sb);
+	error = SYSCTL_OUT(req, sbuf_data(&sb), sbuf_len(&sb));
+	sbuf_delete(&sb);
+
+	/* Setting */
+	if (!error && req->newptr) {
+		if (req->newlen > MAX_FAIL_POINT_BUF) {
+			error = EINVAL;
+			goto out;
+		}
+
+		buf = fp_malloc(req->newlen + 1, M_WAITOK);
+
+		error = SYSCTL_IN(req, buf, req->newlen);
+		if (error)
+			goto out;
+		buf[req->newlen] = '\0';
+
+		error = fail_point_set(fp, buf);
+        }
+
+out:
+	if (buf)
+		fp_free(buf);
+	return error;
+}
+
+/**
+ * Internal helper function to translate a human-readable failpoint string
+ * into a internally-parsable fail_point structure.
+ */
+static char *
+parse_fail_point(struct fail_point_entries *ents, char *p)
+{
+	/*  <fail_point> ::
+	 *      <term> ( "->" <term> )*
+	 */
+	if (!(p = parse_term(ents, p)))
+		return 0;
+	while (*p)
+		if (p[0] != '-' || p[1] != '>' || !(p = parse_term(ents, p+2)))
+			return 0;
+	return p;
+}
+
+/**
+ * Internal helper function to parse an individual term from a failpoint.
+ */
+static char *
+parse_term(struct fail_point_entries *ents, char *p)
+{
+	struct fail_point_entry *ent;
+
+	ent = fp_malloc(sizeof *ent, M_WAITOK | M_ZERO);
+	ent->fe_prob = PROB_MAX;
+	TAILQ_INSERT_TAIL(ents, ent, fe_entries);
+
+	/*
+	 * <term> ::
+	 *     ( (<float> "%") | (<integer> "*" ) )*
+	 *     <type>
+	 *     [ "(" <integer> ")" ]
+	 */
+
+	/* ( (<float> "%") | (<integer> "*" ) )* */
+	while (('0' <= *p && *p <= '9') || *p == '.') {
+		int units, decimal;
+
+		if (!(p = parse_number(&units, &decimal, p)))
+			return 0;
+
+		if (*p == '%') {
+			if (units > 100) /* prevent overflow early */
+				units = 100;
+			ent->fe_prob = units * (PROB_MAX / 100) + decimal;
+			if (ent->fe_prob > PROB_MAX)
+				ent->fe_prob = PROB_MAX;
+
+		} else if (*p == '*') {
+			if (!units || decimal)
+				return 0;
+			ent->fe_count = units;;
+
+		} else {
+			return 0;
+		}
+
+		p++;
+	}
+
+	/* <type> */
+	if (!(p = parse_type(ent, p)))
+		return 0;
+	if (*p == '\0')
+		return p;
+
+	/* [ "(" <integer> ")" ] */
+	if (*p != '(')
+		return p;
+	p++;
+	if (('0' <= *p && *p <= '9') || *p == '-')
+		ent->fe_arg = strtol(p, &p, 0);
+	else
+		return 0;
+	if (*p++ != ')')
+		return 0;
+
+	return p;
+}
+
+/**
+ * Internal helper function to parse a numeric for a failpoint term.
+ */
+static char *
+parse_number(int *out_units, int *out_decimal, char *p)
+{
+	char *old_p;
+
+	/*
+	 *  <number> ::
+	 *      <integer> [ "." <integer> ] |
+	 *      "." <integer>
+	 */
+
+	/* whole part */
+	old_p = p;
+	*out_units = strtol(p, &p, 10);;
+	if (p == old_p && *p != '.')
+		return 0;
+
+	/* fractional part */
+	*out_decimal = 0;
+	if (*p == '.') {
+		int digits = 0;
+		p++;
+		while ('0' <= *p && *p <= '9') {
+			int digit = *p - '0';
+			if (digits < PROB_DIGITS - 2)
+				*out_decimal = *out_decimal * 10 + digit;
+			else if (digits == PROB_DIGITS - 2 && digit >= 5)
+				(*out_decimal)++;
+			digits++;
+			p++;
+		}
+		if (!digits) /* need at least one digit after '.' */
+			return 0;
+		while (digits++ < PROB_DIGITS - 2) /* add implicit zeros */
+			*out_decimal *= 10;
+	}
+
+	return p; /* success */
+}
+
+/**
+ * Internal helper function to parse an individual type for a failpoint term.
+ */
+static char *
+parse_type(struct fail_point_entry *ent, char *beg)
+{
+	enum fail_point_t type;
+	char *end = beg;
+	while ('a' <= *end && *end <= 'z')
+		end++;
+	if (beg == end)
+		return 0;
+	for (type = FAIL_POINT_OFF; type != FAIL_POINT_INVALID; type++) {
+		const char *p = fail_type_strings[type];
+		const char *q = beg;
+		while (q < end && *p++ == *q++);
+		if (q == end && *p == '\0') {
+			ent->fe_type = type;
+			return end;
+		}
+	}
+	return 0;
+}
+
+/**
+ * Internal helper function to free an individual failpoint term.
+ */
+static void
+free_entry(struct fail_point_entries *ents, struct fail_point_entry *ent)
+{
+	TAILQ_REMOVE(ents, ent, fe_entries);
+	fp_free(ent);
+}
+
+/**
+ * Internal helper function to clear out all failpoint terms for a single
+ * failpoint.
+ */
+static void
+clear_entries(struct fail_point_entries *ents)
+{
+	struct fail_point_entry *ent, *ent_next;
+	TAILQ_FOREACH_SAFE(ent, ents, fe_entries, ent_next)
+		fp_free(ent);
+	TAILQ_INIT(ents);
+}
+
+/* The fail point sysctl tree. */
+SYSCTL_NODE(_debug, OID_AUTO, fail_point, CTLFLAG_RW, 0, "fail points");
diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index a3c3e97..0817c7f 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -48,6 +48,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/buf.h>
 #include <sys/devicestat.h>
 #include <sys/eventhandler.h>
+#include <sys/fail.h>
 #include <sys/limits.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
@@ -1167,6 +1168,15 @@ buf_dirty_count_severe(void)
 	return(numdirtybuffers >= hidirtybuffers);
 }
 
+static __noinline int
+buf_vm_page_count_severe(void)
+{
+
+	KFAIL_POINT_CODE(DEBUG_FP, buf_pressure, return 1);
+
+	return vm_page_count_severe();
+}
+
 /*
  *	brelse:
  *
@@ -1233,7 +1243,7 @@ brelse(struct buf *bp)
 	 */
 	if (bp->b_flags & B_DELWRI)
 		bp->b_flags &= ~B_RELBUF;
-	else if (vm_page_count_severe()) {
+	else if (buf_vm_page_count_severe()) {
 		/*
 		 * The locking of the BO_LOCK is not necessary since
 		 * BKGRDINPROG cannot be set while we hold the buf
@@ -1502,7 +1512,7 @@ bqrelse(struct buf *bp)
 		 * lock, it can only be cleared if it is already
 		 * pending.
 		 */
-		if (!vm_page_count_severe() || (bp->b_vflags & BV_BKGRDINPROG)) {
+		if (!buf_vm_page_count_severe() || (bp->b_vflags & BV_BKGRDINPROG)) {
 			bp->b_qindex = QUEUE_CLEAN;
 			TAILQ_INSERT_TAIL(&bufqueues[QUEUE_CLEAN], bp,
 			    b_freelist);
@@ -1571,7 +1581,7 @@ vfs_vmio_release(struct buf *bp)
 				vm_page_free(m);
 			} else if (bp->b_flags & B_DIRECT) {
 				vm_page_try_to_free(m);
-			} else if (vm_page_count_severe()) {
+			} else if (buf_vm_page_count_severe()) {
 				vm_page_try_to_cache(m);
 			}
 		}