f2fs: introduce discard_io_aware_gran sysfs node

The current discard_io_aware_gran is a fixed value, change it to be
configurable through the sys node.
Signed-off-by: Yangtao Li <frank.li@vivo.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -708,3 +708,12 @@ Description:	Support configuring fault injection type, should be
 		FAULT_LOCK_OP            0x000020000
 		FAULT_BLKADDR            0x000040000
 		===================      ===========
+
+What:		/sys/fs/f2fs/<disk>/discard_io_aware_gran
+Date:		January 2023
+Contact:	"Yangtao Li" <frank.li@vivo.com>
+Description:	Controls background discard granularity of inner discard thread
+		when is not in idle. Inner thread will not issue discards with size that
+		is smaller than granularity. The unit size is one block(4KB), now only
+		support configuring in range of [0, 512].
+		Default: 512

fs/f2fs/f2fs.h

@@ -409,6 +409,7 @@ struct discard_cmd_control {
 	unsigned int min_discard_issue_time;	/* min. interval between discard issue */
 	unsigned int mid_discard_issue_time;	/* mid. interval between discard issue */
 	unsigned int max_discard_issue_time;	/* max. interval between discard issue */
+	unsigned int discard_io_aware_gran; /* minimum discard granularity not be aware of I/O */
 	unsigned int discard_urgent_util;	/* utilization which issue discard proactively */
 	unsigned int discard_granularity;	/* discard granularity */
 	unsigned int max_ordered_discard;	/* maximum discard granularity issued by lba order */

fs/f2fs/segment.c

@@ -1059,7 +1059,7 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi,
 	dpolicy->granularity = granularity;
 
 	dpolicy->max_requests = dcc->max_discard_request;
-	dpolicy->io_aware_gran = MAX_PLIST_NUM;
+	dpolicy->io_aware_gran = dcc->discard_io_aware_gran;
 	dpolicy->timeout = false;
 
 	if (discard_type == DPOLICY_BG) {
@@ -2063,6 +2063,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
 	if (!dcc)
 		return -ENOMEM;
 
+	dcc->discard_io_aware_gran = MAX_PLIST_NUM;
 	dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
 	dcc->max_ordered_discard = DEFAULT_MAX_ORDERED_DISCARD_GRANULARITY;
 	if (F2FS_OPTION(sbi).discard_unit == DISCARD_UNIT_SEGMENT)

fs/f2fs/sysfs.c

@@ -473,6 +473,17 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
 		return count;
 	}
 
+	if (!strcmp(a->attr.name, "discard_io_aware_gran")) {
+		if (t > MAX_PLIST_NUM)
+			return -EINVAL;
+		if (!f2fs_block_unit_discard(sbi))
+			return -EINVAL;
+		if (t == *ui)
+			return count;
+		*ui = t;
+		return count;
+	}
+
 	if (!strcmp(a->attr.name, "discard_granularity")) {
 		if (t == 0 || t > MAX_PLIST_NUM)
 			return -EINVAL;
@@ -825,6 +836,7 @@ F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_discard_request, max_discard_req
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, min_discard_issue_time, min_discard_issue_time);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, mid_discard_issue_time, mid_discard_issue_time);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_discard_issue_time, max_discard_issue_time);
+F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_io_aware_gran, discard_io_aware_gran);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_urgent_util, discard_urgent_util);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, discard_granularity);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_ordered_discard, max_ordered_discard);
@@ -960,6 +972,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(min_discard_issue_time),
 	ATTR_LIST(mid_discard_issue_time),
 	ATTR_LIST(max_discard_issue_time),
+	ATTR_LIST(discard_io_aware_gran),
 	ATTR_LIST(discard_urgent_util),
 	ATTR_LIST(discard_granularity),
 	ATTR_LIST(max_ordered_discard),