f2fs: Don't create discard thread when device doesn't support realtime discard

Don't create discard thread when device doesn't support realtime discard
or user specifies nodiscard mount option.
Signed-off-by: Fengnan Chang <changfengnan@vivo.com>
Signed-off-by: Yangtao Li <frank.li@vivo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -3448,6 +3448,7 @@ int f2fs_flush_device_cache(struct f2fs_sb_info *sbi);
 void f2fs_destroy_flush_cmd_control(struct f2fs_sb_info *sbi, bool free);
 void f2fs_invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr);
 bool f2fs_is_checkpointed_data(struct f2fs_sb_info *sbi, block_t blkaddr);
+int f2fs_start_discard_thread(struct f2fs_sb_info *sbi);
 void f2fs_drop_discard_cmd(struct f2fs_sb_info *sbi);
 void f2fs_stop_discard_thread(struct f2fs_sb_info *sbi);
 bool f2fs_issue_discard_timeout(struct f2fs_sb_info *sbi);

fs/f2fs/segment.c

@@ -2115,9 +2115,25 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi,
 	wake_up_discard_thread(sbi, false);
 }
 
-static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
+int f2fs_start_discard_thread(struct f2fs_sb_info *sbi)
 {
 	dev_t dev = sbi->sb->s_bdev->bd_dev;
+	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+	int err = 0;
+
+	if (!f2fs_realtime_discard_enable(sbi))
+		return 0;
+
+	dcc->f2fs_issue_discard = kthread_run(issue_discard_thread, sbi,
+				"f2fs_discard-%u:%u", MAJOR(dev), MINOR(dev));
+	if (IS_ERR(dcc->f2fs_issue_discard))
+		err = PTR_ERR(dcc->f2fs_issue_discard);
+
+	return err;
+}
+
+static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
+{
 	struct discard_cmd_control *dcc;
 	int err = 0, i;
 
@@ -2155,13 +2171,10 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
 	init_waitqueue_head(&dcc->discard_wait_queue);
 	SM_I(sbi)->dcc_info = dcc;
 init_thread:
-	dcc->f2fs_issue_discard = kthread_run(issue_discard_thread, sbi,
-				"f2fs_discard-%u:%u", MAJOR(dev), MINOR(dev));
-	if (IS_ERR(dcc->f2fs_issue_discard)) {
-		err = PTR_ERR(dcc->f2fs_issue_discard);
+	err = f2fs_start_discard_thread(sbi);
+	if (err) {
 		kfree(dcc);
 		SM_I(sbi)->dcc_info = NULL;
-		return err;
 	}
 
 	return err;

fs/f2fs/super.c

@@ -2105,12 +2105,15 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	bool need_restart_gc = false, need_stop_gc = false;
 	bool need_restart_ckpt = false, need_stop_ckpt = false;
 	bool need_restart_flush = false, need_stop_flush = false;
+	bool need_restart_discard = false, need_stop_discard = false;
 	bool no_extent_cache = !test_opt(sbi, EXTENT_CACHE);
 	bool enable_checkpoint = !test_opt(sbi, DISABLE_CHECKPOINT);
 	bool no_io_align = !F2FS_IO_ALIGNED(sbi);
 	bool no_atgc = !test_opt(sbi, ATGC);
+	bool no_discard = !test_opt(sbi, DISCARD);
 	bool no_compress_cache = !test_opt(sbi, COMPRESS_CACHE);
 	bool block_unit_discard = f2fs_block_unit_discard(sbi);
+	struct discard_cmd_control *dcc;
 #ifdef CONFIG_QUOTA
 	int i, j;
 #endif
@@ -2282,11 +2285,26 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 		need_stop_flush = true;
 	}
 
+	if (no_discard == !!test_opt(sbi, DISCARD)) {
+		if (test_opt(sbi, DISCARD)) {
+			err = f2fs_start_discard_thread(sbi);
+			if (err)
+				goto restore_flush;
+			need_stop_discard = true;
+		} else {
+			dcc = SM_I(sbi)->dcc_info;
+			f2fs_stop_discard_thread(sbi);
+			if (atomic_read(&dcc->discard_cmd_cnt))
+				f2fs_issue_discard_timeout(sbi);
+			need_restart_discard = true;
+		}
+	}
+
 	if (enable_checkpoint == !!test_opt(sbi, DISABLE_CHECKPOINT)) {
 		if (test_opt(sbi, DISABLE_CHECKPOINT)) {
 			err = f2fs_disable_checkpoint(sbi);
 			if (err)
-				goto restore_flush;
+				goto restore_discard;
 		} else {
 			f2fs_enable_checkpoint(sbi);
 		}
@@ -2306,6 +2324,13 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	adjust_unusable_cap_perc(sbi);
 	*flags = (*flags & ~SB_LAZYTIME) | (sb->s_flags & SB_LAZYTIME);
 	return 0;
+restore_discard:
+	if (need_restart_discard) {
+		if (f2fs_start_discard_thread(sbi))
+			f2fs_warn(sbi, "discard has been stopped");
+	} else if (need_stop_discard) {
+		f2fs_stop_discard_thread(sbi);
+	}
 restore_flush:
 	if (need_restart_flush) {
 		if (f2fs_create_flush_cmd_control(sbi))