2 files changed, 21 insertions, 7 deletions

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 6ea5f872e2de..6572ea4bc4df 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -442,12 +442,6 @@ int nilfs_ioctl_prepare_clean_segments(struct the_nilfs *nilfs,
         const char *msg;
         int ret;
 
-        ret = nilfs_ioctl_move_blocks(nilfs, &argv[0], kbufs[0]);
-        if (ret < 0) {
-                msg = "cannot read source blocks";
-                goto failed;
-        }
-
         ret = nilfs_ioctl_delete_checkpoints(nilfs, &argv[1], kbufs[1]);
         if (ret < 0) {
                 /*
@@ -548,7 +542,25 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
                 }
         }
 
-        ret = nilfs_clean_segments(inode->i_sb, argv, kbufs);
+        /*
+         * nilfs_ioctl_move_blocks() will call nilfs_gc_iget(),
+         * which will operates an inode list without blocking.
+         * To protect the list from concurrent operations,
+         * nilfs_ioctl_move_blocks should be atomic operation.
+         */
+        if (test_and_set_bit(THE_NILFS_GC_RUNNING, &nilfs->ns_flags)) {
+                ret = -EBUSY;
+                goto out_free;
+        }
+
+        ret = nilfs_ioctl_move_blocks(nilfs, &argv[0], kbufs[0]);
+        if (ret < 0)
+                printk(KERN_ERR "NILFS: GC failed during preparation: "
+                        "cannot read source blocks: err=%d\n", ret);
+        else
+                ret = nilfs_clean_segments(inode->i_sb, argv, kbufs);
+
+        clear_nilfs_gc_running(nilfs);
 
  out_free:
         while (--n >= 0)
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index 68e9626e3d44..20abd55881e0 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -37,6 +37,7 @@ enum {
         THE_NILFS_LOADED,       /* Roll-back/roll-forward has done and
                                    the latest checkpoint was loaded */
         THE_NILFS_DISCONTINUED, /* 'next' pointer chain has broken */
+        THE_NILFS_GC_RUNNING,   /* gc process is running */
 };
 
 /**
@@ -195,6 +196,7 @@ static inline int nilfs_##name(struct the_nilfs *nilfs)			\
 THE_NILFS_FNS(INIT, init)
 THE_NILFS_FNS(LOADED, loaded)
 THE_NILFS_FNS(DISCONTINUED, discontinued)
+THE_NILFS_FNS(GC_RUNNING, gc_running)
 
 /* Minimum interval of periodical update of superblocks (in seconds) */
 #define NILFS_SB_FREQ           10