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 diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index 6db1fef..418d5d7 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 diff --git a/fs/xfs/xfs_log.h b/fs/xfs/xfs_log.h index 2c622be..748d312 100644 --- a/fs/xfs/xfs_log.h +++ b/fs/xfs/xfs_log.h @@ -152,6 +152,7 @@ int xfs_log_mount(struct xfs_mount *mp, int num_bblocks); int xfs_log_mount_finish(struct xfs_mount *mp); xfs_lsn_t xlog_assign_tail_lsn(struct xfs_mount *mp); +xfs_lsn_t xlog_assign_tail_lsn_locked(struct xfs_mount *mp); void xfs_log_space_wake(struct xfs_mount *mp); int xfs_log_notify(struct xfs_mount *mp, struct xlog_in_core *iclog, diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c index 1dead07..77acc53 100644 --- a/fs/xfs/xfs_trans_ail.c +++ b/fs/xfs/xfs_trans_ail.c @@ -79,7 +79,7 @@ xfs_ail_check( * Return a pointer to the first item in the AIL. If the AIL is empty, then * return NULL. */ -static xfs_log_item_t * +xfs_log_item_t * xfs_ail_min( struct xfs_ail *ailp) { @@ -667,11 +667,15 @@ xfs_trans_ail_update_bulk( if (!list_empty(&tmp)) xfs_ail_splice(ailp, cur, &tmp, lsn); - spin_unlock(&ailp->xa_lock); - if (mlip_changed && !XFS_FORCED_SHUTDOWN(ailp->xa_mount)) { - xlog_assign_tail_lsn(ailp->xa_mount); + if (mlip_changed) { + if (!XFS_FORCED_SHUTDOWN(ailp->xa_mount)) + xlog_assign_tail_lsn_locked(ailp->xa_mount); + spin_unlock(&ailp->xa_lock); + xfs_log_space_wake(ailp->xa_mount); + } else { + spin_unlock(&ailp->xa_lock); } } @@ -729,11 +733,15 @@ xfs_trans_ail_delete_bulk( if (mlip == lip) mlip_changed = 1; } - spin_unlock(&ailp->xa_lock); - if (mlip_changed && !XFS_FORCED_SHUTDOWN(ailp->xa_mount)) { - xlog_assign_tail_lsn(ailp->xa_mount); + if (mlip_changed) { + if (!XFS_FORCED_SHUTDOWN(ailp->xa_mount)) + xlog_assign_tail_lsn_locked(ailp->xa_mount); + spin_unlock(&ailp->xa_lock); + xfs_log_space_wake(ailp->xa_mount); + } else { + spin_unlock(&ailp->xa_lock); } } diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h index 8ab2ced..46a1ebd 100644 --- a/fs/xfs/xfs_trans_priv.h +++ b/fs/xfs/xfs_trans_priv.h @@ -102,6 +102,7 @@ xfs_trans_ail_delete( void xfs_ail_push(struct xfs_ail *, xfs_lsn_t); void xfs_ail_push_all(struct xfs_ail *); +struct xfs_log_item *xfs_ail_min(struct xfs_ail *ailp); xfs_lsn_t xfs_ail_min_lsn(struct xfs_ail *ailp); struct xfs_log_item * xfs_trans_ail_cursor_first(struct xfs_ail *ailp, -- cgit v0.10.2