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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>
This commit is contained in:
Ryusuke Konishi 2010-06-29 14:42:13 +09:00
parent 6c12516083
commit 325020477a
3 changed files with 13 additions and 1 deletions
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1
fs/nilfs2/segment.c
View File

@ -1951,7 +1951,6 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
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);

11
fs/nilfs2/the_nilfs.c
View File

@ -47,6 +47,16 @@ void nilfs_set_last_segment(struct the_nilfs *nilfs,
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 @@ static int nilfs_store_log_cursor(struct the_nilfs *nilfs,
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);

2
fs/nilfs2/the_nilfs.h
View File

@ -74,6 +74,7 @@ enum {
* @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 @@ struct the_nilfs {
u64 ns_last_seq;
__u64 ns_last_cno;
u64 ns_prot_seq;
u64 ns_prev_seq;
struct rw_semaphore ns_segctor_sem;