f2fs: add an ioctl to disable GC for specific file

This patch gives a flag to disable GC on given file, which would be useful, when
user wants to keep its block map. It also conducts in-place-update for dontmove
file.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index d844dcb..33e7969 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -624,6 +624,11 @@ static void move_data_block(struct inode *inode, block_t bidx,
 	if (f2fs_is_atomic_file(inode))
 		goto out;
 
+	if (f2fs_is_pinned_file(inode)) {
+		f2fs_pin_file_control(inode, true);
+		goto out;
+	}
+
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
 	err = get_dnode_of_data(&dn, bidx, LOOKUP_NODE);
 	if (err)
@@ -720,6 +725,11 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
 
 	if (f2fs_is_atomic_file(inode))
 		goto out;
+	if (f2fs_is_pinned_file(inode)) {
+		if (gc_type == FG_GC)
+			f2fs_pin_file_control(inode, true);
+		goto out;
+	}
 
 	if (gc_type == BG_GC) {
 		if (PageWriteback(page))
@@ -1091,6 +1101,7 @@ void build_gc_manager(struct f2fs_sb_info *sbi)
 
 	sbi->fggc_threshold = div64_u64((main_count - ovp_count) *
 				BLKS_PER_SEC(sbi), (main_count - resv_count));
+	sbi->gc_pin_file_threshold = DEF_GC_FAILED_PINNED_FILES;
 
 	/* give warm/cold data area from slower device */
 	if (sbi->s_ndevs && sbi->segs_per_sec == 1)