From 1c30462542bac8abffb4823638b6b1659c1cfcf5 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 23 Apr 2012 15:58:33 +1000 Subject: xfs: allow assigning the tail lsn with the AIL lock held Provide a variant of xlog_assign_tail_lsn that has the AIL lock already held. By doing so we do an additional atomic_read + atomic_set under the lock, which comes down to two instructions. Switch xfs_trans_ail_update_bulk and xfs_trans_ail_delete_bulk to the new version to reduce the number of lock roundtrips, and prepare for a new addition that would require a third lock roundtrip in xfs_trans_ail_delete_bulk. This addition is also the reason for slightly rearranging the conditionals and relying on xfs_log_space_wake for checking that the filesystem has been shut down internally. Signed-off-by: Christoph Hellwig Reviewed-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_log.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) (limited to 'fs/xfs/xfs_log.c') diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index 6db1fef38bff..418d5d7bc52b 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -916,27 +916,42 @@ xfs_log_need_covered(xfs_mount_t *mp) * We may be holding the log iclog lock upon entering this routine. */ xfs_lsn_t -xlog_assign_tail_lsn( +xlog_assign_tail_lsn_locked( struct xfs_mount *mp) { - xfs_lsn_t tail_lsn; struct log *log = mp->m_log; + struct xfs_log_item *lip; + xfs_lsn_t tail_lsn; + + assert_spin_locked(&mp->m_ail->xa_lock); /* * To make sure we always have a valid LSN for the log tail we keep * track of the last LSN which was committed in log->l_last_sync_lsn, - * and use that when the AIL was empty and xfs_ail_min_lsn returns 0. - * - * If the AIL has been emptied we also need to wake any process - * waiting for this condition. + * and use that when the AIL was empty. */ - tail_lsn = xfs_ail_min_lsn(mp->m_ail); - if (!tail_lsn) + lip = xfs_ail_min(mp->m_ail); + if (lip) + tail_lsn = lip->li_lsn; + else tail_lsn = atomic64_read(&log->l_last_sync_lsn); atomic64_set(&log->l_tail_lsn, tail_lsn); return tail_lsn; } +xfs_lsn_t +xlog_assign_tail_lsn( + struct xfs_mount *mp) +{ + xfs_lsn_t tail_lsn; + + spin_lock(&mp->m_ail->xa_lock); + tail_lsn = xlog_assign_tail_lsn_locked(mp); + spin_unlock(&mp->m_ail->xa_lock); + + return tail_lsn; +} + /* * Return the space in the log between the tail and the head. The head * is passed in the cycle/bytes formal parms. In the special case where -- cgit v1.2.1