nilfs2: mark minor flag for checkpoint created by internal operation

Nilfs creates checkpoints even for garbage collection or metadata updates
such as checkpoint mode change.  So, user often sees checkpoints created
only by such internal operations.

This is inconvenient in some situations.  For example, application that
monitors checkpoints and changes them to snapshots, will fall into an
infinite loop because it cannot distinguish internally created
checkpoints.

This patch solves this sort of problem by adding a flag to checkpoint for
identification.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/segment.c

@@ -462,6 +462,9 @@ static void nilfs_segctor_begin_finfo(struct nilfs_sc_info *sci,
 	sci->sc_binfo_ptr = sci->sc_finfo_ptr;
 	nilfs_segctor_map_segsum_entry(
 		sci, &sci->sc_binfo_ptr, sizeof(struct nilfs_finfo));
+
+	if (inode->i_sb && !test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
+		set_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
 	/* skip finfo */
 }
 
@@ -887,6 +890,11 @@ static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
 	raw_cp->cp_create = cpu_to_le64(sci->sc_seg_ctime);
 	raw_cp->cp_cno = cpu_to_le64(nilfs->ns_cno);
 
+	if (test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
+		nilfs_checkpoint_clear_minor(raw_cp);
+	else
+		nilfs_checkpoint_set_minor(raw_cp);
+
 	nilfs_write_inode_common(sbi->s_ifile, &raw_cp->cp_ifile_inode, 1);
 	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
 	return 0;
@@ -2091,6 +2099,7 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 		nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,
 				       segbuf->sb_sum.seg_seq, nilfs->ns_cno);
 
+		clear_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
 		clear_bit(NILFS_SC_DIRTY, &sci->sc_flags);
 		set_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
 	} else

fs/nilfs2/segment.h

@@ -185,6 +185,9 @@ enum {
 	NILFS_SC_SUPER_ROOT,	/* The latest segment has a super root */
 	NILFS_SC_PRIOR_FLUSH,	/* Requesting immediate flush without making a
 				   checkpoint */
+	NILFS_SC_HAVE_DELTA,	/* Next checkpoint will have update of files
+				   other than DAT, cpfile, sufile, or files
+				   moved by GC */
 };
 
 /* sc_state */

include/linux/nilfs2_fs.h

@@ -470,6 +470,7 @@ enum {
 	NILFS_CHECKPOINT_SNAPSHOT,
 	NILFS_CHECKPOINT_INVALID,
 	NILFS_CHECKPOINT_SKETCH,
+	NILFS_CHECKPOINT_MINOR,
 };
 
 #define NILFS_CHECKPOINT_FNS(flag, name)				\
@@ -494,6 +495,7 @@ nilfs_checkpoint_##name(const struct nilfs_checkpoint *cp)		\
 
 NILFS_CHECKPOINT_FNS(SNAPSHOT, snapshot)
 NILFS_CHECKPOINT_FNS(INVALID, invalid)
+NILFS_CHECKPOINT_FNS(MINOR, minor)
 
 /**
  * struct nilfs_cpinfo - checkpoint information
@@ -526,6 +528,7 @@ nilfs_cpinfo_##name(const struct nilfs_cpinfo *cpinfo)			\
 
 NILFS_CPINFO_FNS(SNAPSHOT, snapshot)
 NILFS_CPINFO_FNS(INVALID, invalid)
+NILFS_CPINFO_FNS(MINOR, minor)
 
 
 /**