nilfs2: fix regression of garbage collection ioctl

On 2.6.37-rc1, garbage collection ioctl of nilfs was broken due to the
commit 263d90ce ("nilfs2: remove own inode hash used for GC"),
and leading to filesystem corruption.

The patch doesn't queue gc-inodes for log writer if they are reused
through the vfs inode cache.  Here, gc-inode is the inode which
buffers blocks to be relocated on GC.  That patch queues gc-inodes in
nilfs_init_gcinode() function, but this function is not called when
they don't have I_NEW flag.  Thus, some of live blocks are wrongly
overrode without being moved to new logs.

This resolves the problem by moving the gc-inode queueing to an outer
function to ensure it's done right.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

fs/nilfs2/gcinode.c

@@ -176,7 +176,6 @@ int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *bh)
 int nilfs_init_gcinode(struct inode *inode)
 {
 	struct nilfs_inode_info *ii = NILFS_I(inode);
-	struct the_nilfs *nilfs = NILFS_SB(inode->i_sb)->s_nilfs;
 
 	inode->i_mode = S_IFREG;
 	mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
@@ -186,14 +185,6 @@ int nilfs_init_gcinode(struct inode *inode)
 	ii->i_flags = 0;
 	nilfs_bmap_init_gc(ii->i_bmap);
 
-	/*
-	 * Add the inode to GC inode list. Garbage Collection
-	 * is serialized and no two processes manipulate the
-	 * list simultaneously.
-	 */
-	igrab(inode);
-	list_add(&NILFS_I(inode)->i_dirty, &nilfs->ns_gc_inodes);
-
 	return 0;
 }
 

fs/nilfs2/ioctl.c

@@ -337,6 +337,7 @@ static int nilfs_ioctl_move_blocks(struct super_block *sb,
 				   struct nilfs_argv *argv, void *buf)
 {
 	size_t nmembs = argv->v_nmembs;
+	struct the_nilfs *nilfs = NILFS_SB(sb)->s_nilfs;
 	struct inode *inode;
 	struct nilfs_vdesc *vdesc;
 	struct buffer_head *bh, *n;
@@ -353,6 +354,17 @@ static int nilfs_ioctl_move_blocks(struct super_block *sb,
 			ret = PTR_ERR(inode);
 			goto failed;
 		}
+		if (list_empty(&NILFS_I(inode)->i_dirty)) {
+			/*
+			 * Add the inode to GC inode list. Garbage Collection
+			 * is serialized and no two processes manipulate the
+			 * list simultaneously.
+			 */
+			igrab(inode);
+			list_add(&NILFS_I(inode)->i_dirty,
+				 &nilfs->ns_gc_inodes);
+		}
+
 		do {
 			ret = nilfs_ioctl_move_inode_block(inode, vdesc,
 							   &buffers);