path: root/fs/xfs/xfs_trans_ail.c

/*
 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
 * Copyright (c) 2008 Dave Chinner
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_trans_priv.h"
#include "xfs_error.h"

STATIC void xfs_ail_insert(struct xfs_ail *, xfs_log_item_t *);
STATIC xfs_log_item_t * xfs_ail_delete(struct xfs_ail *, xfs_log_item_t *);
STATIC xfs_log_item_t * xfs_ail_min(struct xfs_ail *);
STATIC xfs_log_item_t * xfs_ail_next(struct xfs_ail *, xfs_log_item_t *);

#ifdef DEBUG
STATIC void xfs_ail_check(struct xfs_ail *, xfs_log_item_t *);
#else
#define	xfs_ail_check(a,l)
#endif /* DEBUG */


/*
 * This is called by the log manager code to determine the LSN
 * of the tail of the log.  This is exactly the LSN of the first
 * item in the AIL.  If the AIL is empty, then this function
 * returns 0.
 *
 * We need the AIL lock in order to get a coherent read of the
 * lsn of the last item in the AIL.
 */
xfs_lsn_t
xfs_trans_ail_tail(
	struct xfs_ail	*ailp)
{
	xfs_lsn_t	lsn;
	xfs_log_item_t	*lip;

	spin_lock(&ailp->xa_lock);
	lip = xfs_ail_min(ailp);
	if (lip == NULL) {
		lsn = (xfs_lsn_t)0;
	} else {
		lsn = lip->li_lsn;
	}
	spin_unlock(&ailp->xa_lock);

	return lsn;
}

/*
 * xfs_trans_push_ail
 *
 * This routine is called to move the tail of the AIL forward.  It does this by
 * trying to flush items in the AIL whose lsns are below the given
 * threshold_lsn.
 *
 * the push is run asynchronously in a separate thread, so we return the tail
 * of the log right now instead of the tail after the push. This means we will
 * either continue right away, or we will sleep waiting on the async thread to
 * do its work.
 *
 * We do this unlocked - we only need to know whether there is anything in the
 * AIL at the time we are called. We don't need to access the contents of
 * any of the objects, so the lock is not needed.
 */
void
xfs_trans_ail_push(
	struct xfs_ail	*ailp,
	xfs_lsn_t	threshold_lsn)
{
	xfs_log_item_t	*lip;

	lip = xfs_ail_min(ailp);
	if (lip && !XFS_FORCED_SHUTDOWN(ailp->xa_mount)) {
		if (XFS_LSN_CMP(threshold_lsn, ailp->xa_target) > 0)
			xfsaild_wakeup(ailp, threshold_lsn);
	}
}

/*
 * AIL traversal cursor initialisation.
 *
 * The cursor keeps track of where our current traversal is up
 * to by tracking the next ƣtem in the list for us. However, for
 * this to be safe, removing an object from the AIL needs to invalidate
 * any cursor that points to it. hence the traversal cursor needs to
 * be linked to the struct xfs_ail so that deletion can search all the
 * active cursors for invalidation.
 *
 * We don't link the push cursor because it is embedded in the struct
 * xfs_ail and hence easily findable.
 */
STATIC void
xfs_trans_ail_cursor_init(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur)
{
	cur->item = NULL;
	if (cur == &ailp->xa_cursors)
		return;

	cur->next = ailp->xa_cursors.next;
	ailp->xa_cursors.next = cur;
}

/*
 * Set the cursor to the next item, because when we look
 * up the cursor the current item may have been freed.
 */
STATIC void
xfs_trans_ail_cursor_set(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur,
	struct xfs_log_item	*lip)
{
	if (lip)
		cur->item = xfs_ail_next(ailp, lip);
}

/*
 * Get the next item in the traversal and advance the cursor.
 * If the cursor was invalidated (inidicated by a lip of 1),
 * restart the traversal.
 */
struct xfs_log_item *
xfs_trans_ail_cursor_next(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur)
{
	struct xfs_log_item	*lip = cur->item;

	if ((__psint_t)lip & 1)
		lip = xfs_ail_min(ailp);
	xfs_trans_ail_cursor_set(ailp, cur, lip);
	return lip;
}

/*
 * Now that the traversal is complete, we need to remove the cursor
 * from the list of traversing cursors. Avoid removing the embedded
 * push cursor, but use the fact it is always present to make the
 * list deletion simple.
 */
void
xfs_trans_ail_cursor_done(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*done)
{
	struct xfs_ail_cursor	*prev = NULL;
	struct xfs_ail_cursor	*cur;

	done->item = NULL;
	if (done == &ailp->xa_cursors)
		return;
	prev = &ailp->xa_cursors;
	for (cur = prev->next; cur; prev = cur, cur = prev->next) {
		if (cur == done) {
			prev->next = cur->next;
			break;
		}
	}
	ASSERT(cur);
}

/*
 * Invalidate any cursor that is pointing to this item. This is
 * called when an item is removed from the AIL. Any cursor pointing
 * to this object is now invalid and the traversal needs to be
 * terminated so it doesn't reference a freed object. We set the
 * cursor item to a value of 1 so we can distinguish between an
 * invalidation and the end of the list when getting the next item
 * from the cursor.
 */
STATIC void
xfs_trans_ail_cursor_clear(
	struct xfs_ail		*ailp,
	struct xfs_log_item	*lip)
{
	struct xfs_ail_cursor	*cur;

	/* need to search all cursors */
	for (cur = &ailp->xa_cursors; cur; cur = cur->next) {
		if (cur->item == lip)
			cur->item = (struct xfs_log_item *)
					((__psint_t)cur->item | 1);
	}
}

/*
 * Return the item in the AIL with the current lsn.
 * Return the current tree generation number for use
 * in calls to xfs_trans_next_ail().
 */
xfs_log_item_t *
xfs_trans_ail_cursor_first(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur,
	xfs_lsn_t		lsn)
{
	xfs_log_item_t		*lip;

	xfs_trans_ail_cursor_init(ailp, cur);
	lip = xfs_ail_min(ailp);
	if (lsn == 0)
		goto out;

	list_for_each_entry(lip, &ailp->xa_ail, li_ail) {
		if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
			goto out;
	}
	lip = NULL;
out:
	xfs_trans_ail_cursor_set(ailp, cur, lip);
	return lip;
}

/*
 * xfsaild_push does the work of pushing on the AIL.  Returning a timeout of
 * zero indicates that the caller should sleep until woken.
 */
long
xfsaild_push(
	struct xfs_ail	*ailp,
	xfs_lsn_t	*last_lsn)
{
	long		tout = 0;
	xfs_lsn_t	last_pushed_lsn = *last_lsn;
	xfs_lsn_t	target =  ailp->xa_target;
	xfs_lsn_t	lsn;
	xfs_log_item_t	*lip;
	int		flush_log, count, stuck;
	xfs_mount_t	*mp = ailp->xa_mount;
	struct xfs_ail_cursor	*cur = &ailp->xa_cursors;
	int