Return to xfs_trans_ail.c CVS log

Up to [Development] / xfs-linux-nodel

Get rid of dead code, simplify the AIL push code, and
rework the locking to avoid holding the AIL lock while
calling the log code to update its notion of the tail.

#include <sys/debug.h>
#ifdef SIM
#define _KERNEL	1
#endif
#include <sys/param.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#ifdef SIM
#undef _KERNEL
#endif
#ifndef SIM
#include <sys/systm.h>
#endif
#include "xfs_types.h"
#include "xfs_inum.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_log.h"
#include "xfs_trans_priv.h"

#ifdef SIM
#include "sim.h"
#endif

STATIC void
xfs_ail_insert(
	xfs_ail_entry_t	*base,
	xfs_log_item_t	*lip);

STATIC xfs_log_item_t *
xfs_ail_delete(
	xfs_ail_entry_t	*base,
	xfs_log_item_t	*lip);

STATIC xfs_log_item_t *
xfs_ail_min(
	xfs_ail_entry_t	*base);

STATIC xfs_log_item_t *
xfs_ail_next(
	xfs_ail_entry_t	*base,
	xfs_log_item_t	*lip);

#ifdef XFSDEBUG
STATIC void
xfs_ail_check(
	xfs_ail_entry_t *base);
#else
#define	xfs_ail_check(a)
#endif /* XFSDEBUG */


/*
 * 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_tail_ail(
	xfs_mount_t	*mp)
{
	int		s;
	xfs_lsn_t	lsn;
	xfs_log_item_t	*lip;

	s = AIL_LOCK(mp);
	lip = xfs_ail_min(&(mp->m_ail));
	if (lip == NULL) {
		lsn = (xfs_lsn_t)0;
	} else {
		lsn = lip->li_lsn;
	}
	AIL_UNLOCK(mp, s);

	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 routine returns the lsn of the tail of the log.
 */
xfs_lsn_t
xfs_trans_push_ail(
	xfs_mount_t		*mp,
	xfs_lsn_t		threshold_lsn)
{
	xfs_lsn_t		lsn;
	xfs_log_item_t		*lip;
	int			s;
	int			gen;
	int			restarts;
	int			lock_result;
	int			flush_log;
#define	XFS_TRANS_PUSH_AIL_RESTARTS	10

	s = AIL_LOCK(mp);
	lip = xfs_trans_first_ail(mp, &gen);
	if (lip == NULL) {
		/*
		 * Just return if the AIL is empty.
		 */
		AIL_UNLOCK(mp, s);
		return (xfs_lsn_t)0;
	}

	/*
	 * While the item we are looking at is below the given threshold
	 * try to flush it out.  Make sure to limit the number of times
	 * we allow xfs_trans_next_ail() to restart scanning from the
	 * beginning of the list.  We can't stop until we've at least
	 * tried to push on everything in the AIL with an LSN less than
	 * the given threshold.
	 */
	flush_log = 0;
	restarts = 0;
	while (((restarts < XFS_TRANS_PUSH_AIL_RESTARTS) &&
		(XFS_LSN_CMP(lip->li_lsn, threshold_lsn) < 0))) {
		/*
		 * If we can lock the item without sleeping, unlock
		 * the AIL lock and flush the item.  Then re-grab the
		 * AIL lock so we can look for the next item on the
		 * AIL.  Since we unlock the AIL while we flush the
		 * item, the next routine may start over again at the
		 * the beginning of the list if anything has changed.
		 * That is what the generation count is for.
		 *
		 * If we can't lock the item, either its holder will flush
		 * it or it is already being flushed or it is being relogged.
		 * In any of these case it is being taken care of and we
		 * can just skip to the next item in the list.
		 */
		lock_result = IOP_TRYLOCK(lip);
		switch (lock_result) {
		case XFS_ITEM_SUCCESS:
			AIL_UNLOCK(mp, s);
			IOP_PUSH(lip);
			s = AIL_LOCK(mp);
			break;
		case XFS_ITEM_PINNED:
			flush_log = 1;
			break;
		case XFS_ITEM_LOCKED:
		case XFS_ITEM_FLUSHING:
			break;
		default:
			ASSERT(0);
			break;
		}

		lip = xfs_trans_next_ail(mp, lip, &gen, &restarts);
		if (lip == NULL) {
			break;
		}
	}

	if (flush_log) {
		/*
		 * If something we need to push out was pinned, then
		 * push out the log so it will become unpinned and
		 * move forward in the AIL.
		 */
		AIL_UNLOCK(mp, s);
		xfs_log_force(mp, (xfs_lsn_t)0, XFS_LOG_FORCE);
		s = AIL_LOCK(mp);
	}

	lip = xfs_ail_min(&(mp->m_ail));
	if (lip == NULL) {
		lsn = (xfs_lsn_t)0;
	} else {
		lsn = lip->li_lsn;
	}
	
	AIL_UNLOCK(mp, s);
	return lsn;
}	/* xfs_trans_push_ail */

/*
 * This is to be called when an item is unlocked that may have
 * been in the AIL.  It will wake up the first member of the AIL
 * wait list if this item's unlocking might allow it to progress.
 * If the item is in the AIL, then we need to get the AIL lock
 * while doing our checking so we don't race with someone going
 * to sleep waiting for this event in xfs_trans_push_ail().
 */
void
xfs_trans_unlocked_item(
	xfs_mount_t	*mp,
	xfs_log_item_t	*lip)
{
	int		s;
	xfs_log_item_t	*min_lip;

	if (!(lip->li_flags & XFS_LI_IN_AIL)) {
		return;
	}

	s = AIL_LOCK(mp);
	min_lip = xfs_ail_min(&mp->m_ail);
	AIL_UNLOCK(mp, s);

	if (min_lip == lip)
		xfs_log_move_tail(mp, 1);
}	/* xfs_trans_unlocked_item */


/*
 * Update the position of the item in the AIL with the new
 * lsn.  If it is not yet in the AIL, add it.  Otherwise, move
 * it to its new position by removing it and re-adding it.
 *
 * Wakeup anyone with an lsn less than the item's lsn.  If the item
 * we move in the AIL is the minimum one, update the tail lsn in the
 * log manager.
 *
 * Increment the AIL's generation count to indicate that the tree
 * has changed.
 *
 * This function must be called with the AIL lock held.  The lock
 * is dropped before returning, so the caller must pass in the
 * cookie returned by AIL_LOCK.
 */
void
xfs_trans_update_ail(
	xfs_mount_t	*mp,
	xfs_log_item_t	*lip,
	xfs_lsn_t	lsn,
	int		s)
{
	xfs_ail_entry_t		*ailp;
	xfs_log_item_t		*dlip;
	xfs_log_item_t		*mlip;	/* ptr to minimum lip */

	ailp = &(mp->m_ail);
	mlip = xfs_ail_min(ailp);

	if (lip->li_flags & XFS_LI_IN_AIL) {
		dlip = xfs_ail_delete(ailp, lip);
		ASSERT(dlip == lip);
	} else {
		lip->li_flags |= XFS_LI_IN_AIL;
	}

	lip->li_lsn = lsn;

	xfs_ail_insert(ailp, lip);
	mp->m_ail_gen++;

	if (mlip == dlip) {
		mlip = xfs_ail_min(&(mp->m_ail));
		AIL_UNLOCK(mp, s);
		xfs_log_move_tail(mp, mlip->li_lsn);
	} else {
		AIL_UNLOCK(mp, s);
	}


}	/* xfs_trans_update_ail */

/*
 * Delete the given item from the AIL.  It must already be in
 * the AIL.
 *
 * Wakeup anyone with an lsn less than item's lsn.    If the item
 * we delete in the AIL is the minimum one, update the tail lsn in the
 * log manager.
 *
 * Clear the IN_AIL flag from the item, reset its lsn to 0, and
 * bump the AIL's generation count to indicate that the tree
 * has changed.
 *
 * This function must be called with the AIL lock held.  The lock
 * is dropped before returning, so the caller must pass in the
 * cookie returned by AIL_LOCK.
 */
void
xfs_trans_delete_ail(
	xfs_mount_t	*mp,
	xfs_log_item_t	*lip,
	int		s)

{
	xfs_ail_entry_t		*ailp;
	xfs_log_item_t		*dlip;
	xfs_log_item_t		*mlip;

	ASSERT(lip->li_flags & XFS_LI_IN_AIL);

	ailp = &(mp->m_ail);
	mlip = xfs_ail_min(ailp);
	dlip = xfs_ail_delete(ailp, lip);
	ASSERT(dlip == lip);


	lip->li_flags &= ~XFS_LI_IN_AIL;
	lip->li_lsn = 0;
	mp->m_ail_gen++;

	if (mlip == dlip) {
		mlip = xfs_ail_min(&(mp->m_ail));
		AIL_UNLOCK(mp, s);
		xfs_log_move_tail(mp, (mlip ? mlip->li_lsn : 0));
	} else {
		AIL_UNLOCK(mp, s);
	}
}



/*
 * Return the item in the AIL with the smallest lsn.
 * Return the current tree generation number for use
 * in calls to xfs_trans_next_ail().
 */
xfs_log_item_t *
xfs_trans_first_ail(
	xfs_mount_t	*mp,
	int		*gen)
{
	xfs_log_item_t	*lip;

	lip = xfs_ail_min(&(mp->m_ail));
	*gen = (int)mp->m_ail_gen;

	return (lip);
}

/*
 * If the generation count of the tree has not changed since the
 * caller last took something from the AIL, then return the elmt
 * in the tree which follows the one given.  If the count has changed,
 * then return the minimum elmt of the AIL and bump the restarts counter
 * if one is given.
 */
xfs_log_item_t *
xfs_trans_next_ail(
	xfs_mount_t	*mp,
	xfs_log_item_t	*lip,
	int		*gen,
	int		*restarts)
{
	xfs_log_item_t	*nlip;

	if (mp->m_ail_gen == *gen) {
		nlip = xfs_ail_next(&(mp->m_ail), lip);
	} else {
		nlip = xfs_ail_min(&(mp->m_ail));
		if (gen != NULL) {
			*gen = (int)mp->m_ail_gen;
		}
		if (restarts != NULL) {
			(*restarts)++;
		}
	}

	return (nlip);
}


/*
 * The active item list (AIL) is a doubly linked list of log
 * items sorted by ascending lsn.  The base of the list is
 * a forw/back pointer pair embedded in the xfs mount structure.
 * The base is initialized with both pointers pointing to the
 * base.  This case always needs to be distinguished, because
 * the base has no lsn to look at.  We almost always insert
 * at the end of the list, so on inserts we search from the
 * end of the list to find where the new item belongs.
 */

/*
 * Initialize the doubly linked list to point only to itself.
 */
void
xfs_trans_ail_init(
	xfs_mount_t	*mp)
{
	mp->m_ail.ail_forw = (xfs_log_item_t*)&(mp->m_ail);
	mp->m_ail.ail_back = (xfs_log_item_t*)&(mp->m_ail);
	mp->m_ail_wait = NULL;
}

/*
 * Insert the given log item into the AIL.
 * We almost always insert at the end of the list, so on inserts
 * we search from the end of the list to find where the
 * new item belongs.
 */
STATIC void
xfs_ail_insert(
	xfs_ail_entry_t	*base,
	xfs_log_item_t	*lip)
/* ARGSUSED */
{
	xfs_log_item_t	*next_lip;

	/*
	 * If the list is empty, just insert the item.
	 */
	if (base->ail_back == (xfs_log_item_t*)base) {
		base->ail_forw = lip;
		base->ail_back = lip;
		lip->li_ail.ail_forw = (xfs_log_item_t*)base;
		lip->li_ail.ail_back = (xfs_log_item_t*)base;
		return;
	}

	next_lip = base->ail_back;
	while ((next_lip != (xfs_log_item_t*)base) &&
	       (next_lip->li_lsn > lip->li_lsn)) {
		next_lip = next_lip->li_ail.ail_back;
	}
	ASSERT((next_lip == (xfs_log_item_t*)base) ||
	       (next_lip->li_lsn <= lip->li_lsn));
	lip->li_ail.ail_forw = next_lip->li_ail.ail_forw;
	lip->li_ail.ail_back = next_lip;
	next_lip->li_ail.ail_forw = lip;
	lip->li_ail.ail_forw->li_ail.ail_back = lip;

	xfs_ail_check(base);
	return;
}

/*
 * Delete the given item from the AIL.  Return a pointer to the item.
 */
/*ARGSUSED*/
STATIC xfs_log_item_t *
xfs_ail_delete(
	xfs_ail_entry_t	*base,
	xfs_log_item_t	*lip)
/* ARGSUSED */
{
	lip->li_ail.ail_forw->li_ail.ail_back = lip->li_ail.ail_back;
	lip->li_ail.ail_back->li_ail.ail_forw = lip->li_ail.ail_forw;
	lip->li_ail.ail_forw = NULL;
	lip->li_ail.ail_back = NULL;

	xfs_ail_check(base);
	return lip;
}

/*
 * Return a pointer to the first item in the AIL.
 * If the AIL is empty, then return NULL.
 */
STATIC xfs_log_item_t *
xfs_ail_min(
	xfs_ail_entry_t	*base)
/* ARGSUSED */
{
	if (base->ail_forw == (xfs_log_item_t*)base) {
		return NULL;
	}
	return base->ail_forw;

}

/*
 * Return a pointer to the item which follows
 * the given item in the AIL.  If the given item
 * is the last item in the list, then return NULL.
 */
STATIC xfs_log_item_t *
xfs_ail_next(
	xfs_ail_entry_t	*base,
	xfs_log_item_t	*lip)
/* ARGSUSED */
{
	if (lip->li_ail.ail_forw == (xfs_log_item_t*)base) {
		return NULL;
	}
	return lip->li_ail.ail_forw;

}

#ifdef XFSDEBUG
/*
 * Check that the list is sorted as it should be.
 */
STATIC void
xfs_ail_check(
	xfs_ail_entry_t *base)
{
	xfs_log_item_t	*lip;
	xfs_log_item_t	*prev_lip;

	lip = base->ail_forw;
	if (lip == (xfs_log_item_t*)base) {
		/*
		 * Make sure the pointers are correct when the list
		 * is empty.
		 */
		ASSERT(base->ail_back == (xfs_log_item_t*)base);
		return;
	}

	/*
	 * Walk the list checking forward and backward pointers,
	 * lsn ordering, and that every entry has the XFS_LI_IN_AIL
	 * flag set.
	 */
	prev_lip = (xfs_log_item_t*)base;
	while (lip != (xfs_log_item_t*)base) {
		if (prev_lip != (xfs_log_item_t*)base) {
			ASSERT(prev_lip->li_ail.ail_forw == lip);
			ASSERT(prev_lip->li_lsn <= lip->li_lsn);
		}
		ASSERT(lip->li_ail.ail_back == prev_lip);
		ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
		prev_lip = lip;
		lip = lip->li_ail.ail_forw;
	}
	ASSERT(lip == (xfs_log_item_t*)base);
	ASSERT(base->ail_back == prev_lip);
}
#endif /* XFSDEBUG */