f2fs: sysfs: support atgc_enabled

When we add "atgc" to the fstab table, ATGC is not immediately enabled.
There is a 7-day time threshold, and we can use "atgc_enabled" to
show whether ATGC is enabled.
Signed-off-by: liujinbao1 <liujinbao1@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -579,6 +579,12 @@ Description:	When ATGC is on, it controls age threshold to bypass GCing young
 		candidates whose age is not beyond the threshold, by default it was
 		initialized as 604800 seconds (equals to 7 days).
 
+What:		/sys/fs/f2fs/<disk>/atgc_enabled
+Date:		Feb 2024
+Contact:	"Jinbao Liu" <liujinbao1@xiaomi.com>
+Description:	It represents whether ATGC is on or off. The value is 1 which
+               indicates that ATGC is on, and 0 indicates that it is off.
+
 What:		/sys/fs/f2fs/<disk>/gc_reclaimed_segments
 Date:		July 2021
 Contact:	"Daeho Jeong" <daehojeong@google.com>

fs/f2fs/sysfs.c

@@ -170,6 +170,12 @@ static ssize_t undiscard_blks_show(struct f2fs_attr *a,
 				SM_I(sbi)->dcc_info->undiscard_blks);
 }
 
+static ssize_t atgc_enabled_show(struct f2fs_attr *a,
+		struct f2fs_sb_info *sbi, char *buf)
+{
+	return sysfs_emit(buf, "%d\n", sbi->am.atgc_enabled ? 1 : 0);
+}
+
 static ssize_t gc_mode_show(struct f2fs_attr *a,
 		struct f2fs_sb_info *sbi, char *buf)
 {
@@ -1082,6 +1088,7 @@ F2FS_GENERAL_RO_ATTR(encoding);
 F2FS_GENERAL_RO_ATTR(mounted_time_sec);
 F2FS_GENERAL_RO_ATTR(main_blkaddr);
 F2FS_GENERAL_RO_ATTR(pending_discard);
+F2FS_GENERAL_RO_ATTR(atgc_enabled);
 F2FS_GENERAL_RO_ATTR(gc_mode);
 #ifdef CONFIG_F2FS_STAT_FS
 F2FS_GENERAL_RO_ATTR(moved_blocks_background);
@@ -1211,6 +1218,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(atgc_candidate_count),
 	ATTR_LIST(atgc_age_weight),
 	ATTR_LIST(atgc_age_threshold),
+	ATTR_LIST(atgc_enabled),
 	ATTR_LIST(seq_file_ra_mul),
 	ATTR_LIST(gc_segment_mode),
 	ATTR_LIST(gc_reclaimed_segments),