f2fs: support synchronous gc in ioctl

This patch drops in batches gc triggered through ioctl, since user
can easily control the gc by designing the loop around the ->ioctl.

We support synchronous gc by forcing using FG_GC in f2fs_gc, so with
it, user can make sure that in this round all blocks gced were
persistent in the device until ioctl returned.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -1830,7 +1830,7 @@ int f2fs_release_page(struct page *, gfp_t);
 int start_gc_thread(struct f2fs_sb_info *);
 void stop_gc_thread(struct f2fs_sb_info *);
 block_t start_bidx_of_node(unsigned int, struct f2fs_inode_info *);
-int f2fs_gc(struct f2fs_sb_info *);
+int f2fs_gc(struct f2fs_sb_info *, bool);
 void build_gc_manager(struct f2fs_sb_info *);
 
 /*

fs/f2fs/file.c

@@ -1618,29 +1618,25 @@ static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
-	__u32 i, count;
+	__u32 sync;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	if (get_user(count, (__u32 __user *)arg))
+	if (get_user(sync, (__u32 __user *)arg))
 		return -EFAULT;
 
-	if (!count || count > F2FS_BATCH_GC_MAX_NUM)
-		return -EINVAL;
+	if (f2fs_readonly(sbi->sb))
+		return -EROFS;
 
-	for (i = 0; i < count; i++) {
+	if (!sync) {
 		if (!mutex_trylock(&sbi->gc_mutex))
-			break;
-
-		if (f2fs_gc(sbi))
-			break;
+			return -EBUSY;
+	} else {
+		mutex_lock(&sbi->gc_mutex);
 	}
 
-	if (put_user(i, (__u32 __user *)arg))
-		return -EFAULT;
-
-	return 0;
+	return f2fs_gc(sbi, sync);
 }
 
 long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)

fs/f2fs/gc.c

@@ -78,7 +78,7 @@ static int gc_thread_func(void *data)
 		stat_inc_bggc_count(sbi);
 
 		/* if return value is not zero, no victim was selected */
-		if (f2fs_gc(sbi))
+		if (f2fs_gc(sbi, false))
 			wait_ms = gc_th->no_gc_sleep_time;
 
 		/* balancing f2fs's metadata periodically */
@@ -803,12 +803,12 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 	return nfree;
 }
 
-int f2fs_gc(struct f2fs_sb_info *sbi)
+int f2fs_gc(struct f2fs_sb_info *sbi, bool sync)
 {
 	unsigned int segno, i;
-	int gc_type = BG_GC;
+	int gc_type = sync ? FG_GC : BG_GC;
 	int sec_freed = 0;
-	int ret = -1;
+	int ret = -EINVAL;
 	struct cp_control cpc;
 	struct gc_inode_list gc_list = {
 		.ilist = LIST_HEAD_INIT(gc_list.ilist),
@@ -855,15 +855,20 @@ int f2fs_gc(struct f2fs_sb_info *sbi)
 	if (gc_type == FG_GC)
 		sbi->cur_victim_sec = NULL_SEGNO;
 
-	if (has_not_enough_free_secs(sbi, sec_freed))
-		goto gc_more;
+	if (!sync) {
+		if (has_not_enough_free_secs(sbi, sec_freed))
+			goto gc_more;
 
-	if (gc_type == FG_GC)
-		write_checkpoint(sbi, &cpc);
+		if (gc_type == FG_GC)
+			write_checkpoint(sbi, &cpc);
+	}
 stop:
 	mutex_unlock(&sbi->gc_mutex);
 
 	put_gc_inode(&gc_list);
+
+	if (sync)
+		ret = sec_freed ? 0 : -EAGAIN;
 	return ret;
 }
 

fs/f2fs/gc.h

@@ -19,12 +19,6 @@
 #define LIMIT_INVALID_BLOCK	40 /* percentage over total user space */
 #define LIMIT_FREE_BLOCK	40 /* percentage over invalid + free space */
 
-/*
- * with this macro, we can control the max time we do garbage collection,
- * when user triggers batch mode gc by ioctl.
- */
-#define F2FS_BATCH_GC_MAX_NUM		16
-
 /* Search max. number of dirty segments to select a victim segment */
 #define DEF_MAX_VICTIM_SEARCH 4096 /* covers 8GB */
 

fs/f2fs/segment.c

@@ -295,7 +295,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi)
 	 */
 	if (has_not_enough_free_secs(sbi, 0)) {
 		mutex_lock(&sbi->gc_mutex);
-		f2fs_gc(sbi);
+		f2fs_gc(sbi, false);
 	}
 }