nilfs2: do not update log cursor for small change
Super blocks of nilfs are periodically overwritten in order to record
the recent log position. This shortens recovery time after unclean
unmount, but the current implementation performs the update even for a
few blocks of change. If the filesystem gets small changes slowly and
continually, super blocks may be updated excessively.
This moderates the issue by skipping update of log cursor if it does
not cross a segment boundary.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 04e0485..9fd051a 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1951,7 +1951,6 @@
if (update_sr) {
nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,
segbuf->sb_sum.seg_seq, nilfs->ns_cno++);
- set_nilfs_sb_dirty(nilfs);
clear_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
clear_bit(NILFS_SC_DIRTY, &sci->sc_flags);
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 88c8976..f2efc8c 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -47,6 +47,16 @@
nilfs->ns_last_pseg = start_blocknr;
nilfs->ns_last_seq = seq;
nilfs->ns_last_cno = cno;
+
+ if (!nilfs_sb_dirty(nilfs)) {
+ if (nilfs->ns_prev_seq == nilfs->ns_last_seq)
+ goto stay_cursor;
+
+ set_nilfs_sb_dirty(nilfs);
+ }
+ nilfs->ns_prev_seq = nilfs->ns_last_seq;
+
+ stay_cursor:
spin_unlock(&nilfs->ns_last_segment_lock);
}
@@ -267,6 +277,7 @@
nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);
+ nilfs->ns_prev_seq = nilfs->ns_last_seq;
nilfs->ns_seg_seq = nilfs->ns_last_seq;
nilfs->ns_segnum =
nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index 32b4983..f785a7b 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -74,6 +74,7 @@
* @ns_last_seq: sequence value of the latest segment
* @ns_last_cno: checkpoint number of the latest segment
* @ns_prot_seq: least sequence number of segments which must not be reclaimed
+ * @ns_prev_seq: base sequence number used to decide if advance log cursor
* @ns_segctor_sem: segment constructor semaphore
* @ns_dat: DAT file inode
* @ns_cpfile: checkpoint file inode
@@ -151,6 +152,7 @@
u64 ns_last_seq;
__u64 ns_last_cno;
u64 ns_prot_seq;
+ u64 ns_prev_seq;
struct rw_semaphore ns_segctor_sem;