Add orphan_scan_delay_ms mount option

Add a mount option to set the delay betwen scanning of the orphan list.
The sysfs file for the option is writable so this option can be set at
run time.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/src/inode.c

@@ -1745,18 +1745,26 @@ void scoutfs_inode_queue_iput(struct inode *inode)
 /*
  * All mounts are performing this work concurrently.  We introduce
  * significant jitter between them to try and keep them from all
- * bunching up and working on the same inodes.
+ * bunching up and working on the same inodes.  We always try to delay
+ * for at least one jiffy if precision tricks us into calculating no
+ * delay.
  */
-static void schedule_orphan_dwork(struct inode_sb_info *inf)
+void scoutfs_inode_schedule_orphan_dwork(struct super_block *sb)
 {
-#define ORPHAN_SCAN_MIN_MS (10 * MSEC_PER_SEC)
-#define ORPHAN_SCAN_JITTER_MS (40 * MSEC_PER_SEC)
+	DECLARE_INODE_SB_INFO(sb, inf);
+	struct scoutfs_mount_options opts;
+	unsigned long low;
+	unsigned long high;
 	unsigned long delay;
 
 	if (!inf->stopped) {
-		delay = msecs_to_jiffies(ORPHAN_SCAN_MIN_MS +
-					 prandom_u32_max(ORPHAN_SCAN_JITTER_MS));
-		schedule_delayed_work(&inf->orphan_scan_dwork, delay);
+		scoutfs_options_read(sb, &opts);
+
+		low = (opts.orphan_scan_delay_ms * 80) / 100;
+		high = (opts.orphan_scan_delay_ms * 120) / 100;
+		delay = msecs_to_jiffies(low + prandom_u32_max(high - low)) ?: 1;
+
+		mod_delayed_work(system_wq, &inf->orphan_scan_dwork, delay);
 	}
 }
 
@@ -1885,7 +1893,7 @@ out:
 	if (ret < 0)
 		scoutfs_inc_counter(sb, orphan_scan_error);
 
-	schedule_orphan_dwork(inf);
+	scoutfs_inode_schedule_orphan_dwork(sb);
 }
 
 /*
@@ -2010,9 +2018,7 @@ int scoutfs_inode_setup(struct super_block *sb)
  */
 void scoutfs_inode_start(struct super_block *sb)
 {
-	DECLARE_INODE_SB_INFO(sb, inf);
-
-	schedule_orphan_dwork(inf);
+	scoutfs_inode_schedule_orphan_dwork(sb);
 }
 
 /*

kmod/src/inode.h

@@ -126,6 +126,7 @@ int scoutfs_setattr(struct dentry *dentry, struct iattr *attr);
 
 int scoutfs_inode_orphan_create(struct super_block *sb, u64 ino, struct scoutfs_lock *lock);
 int scoutfs_inode_orphan_delete(struct super_block *sb, u64 ino, struct scoutfs_lock *lock);
+void scoutfs_inode_schedule_orphan_dwork(struct super_block *sb);
 
 void scoutfs_inode_queue_writeback(struct inode *inode);
 int scoutfs_inode_walk_writeback(struct super_block *sb, bool write);

kmod/src/options.c

@@ -26,16 +26,19 @@
 #include "msg.h"
 #include "options.h"
 #include "super.h"
+#include "inode.h"
 
 enum {
-	Opt_quorum_slot_nr,
 	Opt_metadev_path,
+	Opt_orphan_scan_delay_ms,
+	Opt_quorum_slot_nr,
 	Opt_err,
 };
 
 static const match_table_t tokens = {
-	{Opt_quorum_slot_nr, "quorum_slot_nr=%s"},
 	{Opt_metadev_path, "metadev_path=%s"},
+	{Opt_orphan_scan_delay_ms, "orphan_scan_delay_ms=%s"},
+	{Opt_quorum_slot_nr, "quorum_slot_nr=%s"},
 	{Opt_err, NULL}
 };
 
@@ -99,10 +102,15 @@ static void free_options(struct scoutfs_mount_options *opts)
 	kfree(opts->metadev_path);
 }
 
+#define MIN_ORPHAN_SCAN_DELAY_MS	100UL
+#define DEFAULT_ORPHAN_SCAN_DELAY_MS	(10 * MSEC_PER_SEC)
+#define MAX_ORPHAN_SCAN_DELAY_MS	(60 * MSEC_PER_SEC)
+
 static void init_default_options(struct scoutfs_mount_options *opts)
 {
 	memset(opts, 0, sizeof(*opts));
 	opts->quorum_slot_nr = -1;
+	opts->orphan_scan_delay_ms = DEFAULT_ORPHAN_SCAN_DELAY_MS;
 }
 
 /*
@@ -126,6 +134,30 @@ static int parse_options(struct super_block *sb, char *options, struct scoutfs_m
 		token = match_token(p, tokens, args);
 		switch (token) {
 
+		case Opt_metadev_path:
+			ret = parse_bdev_path(sb, &args[0], &opts->metadev_path);
+			if (ret < 0)
+				return ret;
+			break;
+
+		case Opt_orphan_scan_delay_ms:
+			if (opts->orphan_scan_delay_ms != -1) {
+				scoutfs_err(sb, "multiple orphan_scan_delay_ms options provided, only provide one.");
+				return -EINVAL;
+			}
+
+			ret = match_int(args, &nr);
+			if (ret < 0 ||
+			    nr < MIN_ORPHAN_SCAN_DELAY_MS || nr > MAX_ORPHAN_SCAN_DELAY_MS) {
+				scoutfs_err(sb, "invalid orphan_scan_delay_ms option, must be between %lu and %lu",
+					    MIN_ORPHAN_SCAN_DELAY_MS, MAX_ORPHAN_SCAN_DELAY_MS);
+				if (ret == 0)
+					ret = -EINVAL;
+				return ret;
+			}
+			opts->orphan_scan_delay_ms = nr;
+			break;
+
 		case Opt_quorum_slot_nr:
 			if (opts->quorum_slot_nr != -1) {
 				scoutfs_err(sb, "multiple quorum_slot_nr options provided, only provide one.");
@@ -143,12 +175,6 @@ static int parse_options(struct super_block *sb, char *options, struct scoutfs_m
 			opts->quorum_slot_nr = nr;
 			break;
 
-		case Opt_metadev_path:
-			ret = parse_bdev_path(sb, &args[0], &opts->metadev_path);
-			if (ret < 0)
-				return ret;
-			break;
-
 		default:
 			scoutfs_err(sb, "Unknown or malformed option, \"%s\"", p);
 			return -EINVAL;
@@ -227,9 +253,10 @@ int scoutfs_options_show(struct seq_file *seq, struct dentry *root)
 
 	scoutfs_options_read(sb, &opts);
 
+	seq_printf(seq, ",metadev_path=%s", opts.metadev_path);
+	seq_printf(seq, ",orphan_scan_delay_ms=%u", opts.orphan_scan_delay_ms);
 	if (opts.quorum_slot_nr >= 0)
 		seq_printf(seq, ",quorum_slot_nr=%d", opts.quorum_slot_nr);
-	seq_printf(seq, ",metadev_path=%s", opts.metadev_path);
 
 	return 0;
 }
@@ -245,6 +272,47 @@ static ssize_t metadev_path_show(struct kobject *kobj, struct kobj_attribute *at
 }
 SCOUTFS_ATTR_RO(metadev_path);
 
+static ssize_t orphan_scan_delay_ms_show(struct kobject *kobj, struct kobj_attribute *attr,
+					 char *buf)
+{
+	struct super_block *sb = SCOUTFS_SYSFS_ATTRS_SB(kobj);
+	struct scoutfs_mount_options opts;
+
+	scoutfs_options_read(sb, &opts);
+
+	return snprintf(buf, PAGE_SIZE, "%u", opts.orphan_scan_delay_ms);
+}
+static ssize_t orphan_scan_delay_ms_store(struct kobject *kobj, struct kobj_attribute *attr,
+					  const char *buf, size_t count)
+{
+	struct super_block *sb = SCOUTFS_SYSFS_ATTRS_SB(kobj);
+	DECLARE_OPTIONS_INFO(sb, optinf);
+	char nullterm[20]; /* more than enough for octal -U32_MAX */
+	long val;
+	int len;
+	int ret;
+
+	len = min(count, sizeof(nullterm) - 1);
+	memcpy(nullterm, buf, len);
+	nullterm[len] = '\0';
+
+	ret = kstrtol(nullterm, 0, &val);
+	if (ret < 0 || val < MIN_ORPHAN_SCAN_DELAY_MS || val > MAX_ORPHAN_SCAN_DELAY_MS) {
+		scoutfs_err(sb, "invalid orphan_scan_delay_ms value written to options sysfs file, must be between %lu and %lu",
+			    MIN_ORPHAN_SCAN_DELAY_MS, MAX_ORPHAN_SCAN_DELAY_MS);
+		return -EINVAL;
+	}
+
+	write_seqlock(&optinf->seqlock);
+	optinf->opts.orphan_scan_delay_ms = val;
+	write_sequnlock(&optinf->seqlock);
+
+	scoutfs_inode_schedule_orphan_dwork(sb);
+
+	return count;
+}
+SCOUTFS_ATTR_RW(orphan_scan_delay_ms);
+
 static ssize_t quorum_slot_nr_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 {
 	struct super_block *sb = SCOUTFS_SYSFS_ATTRS_SB(kobj);
@@ -258,6 +326,7 @@ SCOUTFS_ATTR_RO(quorum_slot_nr);
 
 static struct attribute *options_attrs[] = {
 	SCOUTFS_ATTR_PTR(metadev_path),
+	SCOUTFS_ATTR_PTR(orphan_scan_delay_ms),
 	SCOUTFS_ATTR_PTR(quorum_slot_nr),
 	NULL,
 };

kmod/src/options.h

@@ -6,8 +6,10 @@
 #include "format.h"
 
 struct scoutfs_mount_options {
-	int quorum_slot_nr;
 	char *metadev_path;
+	unsigned int orphan_scan_delay_ms;
+	int quorum_slot_nr;
+
 };
 
 void scoutfs_options_read(struct super_block *sb, struct scoutfs_mount_options *opts);

utils/man/scoutfs.5

@@ -21,6 +21,21 @@ contains the filesystem's metadata.
 .sp
 This option is required.
 .TP
+.B orphan_scan_delay_ms=<number>
+This option sets the average expected delay, in milliseconds, between
+each mount's scan of the global orphaned inode list.  Jitter is added to
+avoid contention so each individual delay between scans is a random
+value up to 20% less than or greater than this average expected delay.
+.sp
+The minimum value for this option is 100ms which is very short and is
+only reasonable for testing or experiments.   The default is 10000ms (10
+seconds) and the maximum is 60000ms (1 minute).
+.sp
+This option can be changed in an active mount by writing to its file in
+the options directory in the mount's sysfs directory.  Writing a new
+value will cause the next pending orphan scan to be rescheduled
+with the newly written delay time.
+.TP
 .B quorum_slot_nr=<number>
 The quorum_slot_nr option assigns a quorum member slot to the mount.
 The mount will use the slot assignment to claim exclusive ownership of