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Commit 1c304625 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Ben Myers
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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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarMark Tinguely <tinguely@sgi.com>
Signed-off-by: default avatarBen Myers <bpm@sgi.com>
parent 32ce90a4

fs/xfs/xfs_log.c

+23 −8
Original line number Diff line number Diff line
@@ -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

fs/xfs/xfs_log.h

+1 −0
Original line number Diff line number Diff line
@@ -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,

fs/xfs/xfs_trans_ail.c

+15 −7
Original line number Diff line number Diff line
@@ -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);



	if (mlip_changed) {

		if (!XFS_FORCED_SHUTDOWN(ailp->xa_mount))

			xlog_assign_tail_lsn_locked(ailp->xa_mount);

		spin_unlock(&ailp->xa_lock);



	if (mlip_changed && !XFS_FORCED_SHUTDOWN(ailp->xa_mount)) {

		xlog_assign_tail_lsn(ailp->xa_mount);

		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;

	}



	if (mlip_changed) {

		if (!XFS_FORCED_SHUTDOWN(ailp->xa_mount))

			xlog_assign_tail_lsn_locked(ailp->xa_mount);

		spin_unlock(&ailp->xa_lock);



	if (mlip_changed && !XFS_FORCED_SHUTDOWN(ailp->xa_mount)) {

		xlog_assign_tail_lsn(ailp->xa_mount);

		xfs_log_space_wake(ailp->xa_mount);

	} else {

		spin_unlock(&ailp->xa_lock);

	}

}

fs/xfs/xfs_trans_priv.h

+1 −0
Original line number Diff line number Diff line
@@ -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,