Re: [PATCH 1/1] XFS: Replace custom AIL linked-list code with struct list_head

["Josef 'Jeff' Sipek" <jeffpc@josefsipek.net>]

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On Tue, Feb 05, 2008 at 11:44:51PM -0500, Josef 'Jeff' Sipek wrote:
> Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
> ---
> This patch assumes you already have Dave Chinner's patch for
> xfsidbg_xlogitem and xfsidbg_xaildump is needed.
>
> Changes since V2:
> 
> - remove extra parenthesis
> 
> Changes since V1:
> 
> - Pass around a pointer to the AIL, not the struct list_head
> - Make sure things compile & run with CONFIG_XFS_DEBUG
> ---
>  fs/xfs/xfs_mount.h     |    2 +-
>  fs/xfs/xfs_trans.h     |    7 +--
>  fs/xfs/xfs_trans_ail.c |  149 +++++++++++++++++++----------------------------
>  3 files changed, 62 insertions(+), 96 deletions(-)
> 
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index f7c620e..435d625 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -220,7 +220,7 @@ extern void	xfs_icsb_sync_counters_flags(struct xfs_mount *, int);
>  #endif
>  
>  typedef struct xfs_ail {
> -	xfs_ail_entry_t		xa_ail;
> +	struct list_head	xa_ail;
>  	uint			xa_gen;
>  	struct task_struct	*xa_task;
>  	xfs_lsn_t		xa_target;
> diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
> index 7f40628..50ce02b 100644
> --- a/fs/xfs/xfs_trans.h
> +++ b/fs/xfs/xfs_trans.h
> @@ -113,13 +113,8 @@ struct xfs_mount;
>  struct xfs_trans;
>  struct xfs_dquot_acct;
>  
> -typedef struct xfs_ail_entry {
> -	struct xfs_log_item	*ail_forw;	/* AIL forw pointer */
> -	struct xfs_log_item	*ail_back;	/* AIL back pointer */
> -} xfs_ail_entry_t;
> -
>  typedef struct xfs_log_item {
> -	xfs_ail_entry_t			li_ail;		/* AIL pointers */
> +	struct list_head		li_ail;		/* AIL pointers */
>  	xfs_lsn_t			li_lsn;		/* last on-disk lsn */
>  	struct xfs_log_item_desc	*li_desc;	/* ptr to current desc*/
>  	struct xfs_mount		*li_mountp;	/* ptr to fs mount */
> diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
> index 4d6330e..0fe9d59 100644
> --- a/fs/xfs/xfs_trans_ail.c
> +++ b/fs/xfs/xfs_trans_ail.c
> @@ -28,13 +28,13 @@
>  #include "xfs_trans_priv.h"
>  #include "xfs_error.h"
>  
> -STATIC void xfs_ail_insert(xfs_ail_entry_t *, xfs_log_item_t *);
> -STATIC xfs_log_item_t * xfs_ail_delete(xfs_ail_entry_t *, xfs_log_item_t *);
> -STATIC xfs_log_item_t * xfs_ail_min(xfs_ail_entry_t *);
> -STATIC xfs_log_item_t * xfs_ail_next(xfs_ail_entry_t *, xfs_log_item_t *);
> +STATIC void xfs_ail_insert(xfs_ail_t *, xfs_log_item_t *);
> +STATIC xfs_log_item_t * xfs_ail_delete(xfs_ail_t *, xfs_log_item_t *);
> +STATIC xfs_log_item_t * xfs_ail_min(xfs_ail_t *);
> +STATIC xfs_log_item_t * xfs_ail_next(xfs_ail_t *, xfs_log_item_t *);
>  
>  #ifdef DEBUG
> -STATIC void xfs_ail_check(xfs_ail_entry_t *, xfs_log_item_t *);
> +STATIC void xfs_ail_check(xfs_ail_t *, xfs_log_item_t *);
>  #else
>  #define	xfs_ail_check(a,l)
>  #endif /* DEBUG */
> @@ -57,7 +57,7 @@ xfs_trans_tail_ail(
>  	xfs_log_item_t	*lip;
>  
>  	spin_lock(&mp->m_ail_lock);
> -	lip = xfs_ail_min(&(mp->m_ail.xa_ail));
> +	lip = xfs_ail_min(&mp->m_ail);
>  	if (lip == NULL) {
>  		lsn = (xfs_lsn_t)0;
>  	} else {
> @@ -91,7 +91,7 @@ xfs_trans_push_ail(
>  {
>  	xfs_log_item_t		*lip;
>  
> -	lip = xfs_ail_min(&mp->m_ail.xa_ail);
> +	lip = xfs_ail_min(&mp->m_ail);
>  	if (lip && !XFS_FORCED_SHUTDOWN(mp)) {
>  		if (XFS_LSN_CMP(threshold_lsn, mp->m_ail.xa_target) > 0)
>  			xfsaild_wakeup(mp, threshold_lsn);
> @@ -111,15 +111,17 @@ xfs_trans_first_push_ail(
>  {
>  	xfs_log_item_t	*lip;
>  
> -	lip = xfs_ail_min(&(mp->m_ail.xa_ail));
> +	lip = xfs_ail_min(&mp->m_ail);
>  	*gen = (int)mp->m_ail.xa_gen;
>  	if (lsn == 0)
>  		return lip;
>  
> -	while (lip && (XFS_LSN_CMP(lip->li_lsn, lsn) < 0))
> -		lip = lip->li_ail.ail_forw;
> +	list_for_each_entry(lip, &mp->m_ail.xa_ail, li_ail) {
> +		if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
> +			return lip;
> +	}
>  
> -	return lip;
> +	return NULL;
>  }
>  
>  /*
> @@ -326,7 +328,7 @@ xfs_trans_unlocked_item(
>  	 * the call to xfs_log_move_tail() doesn't do anything if there's
>  	 * not enough free space to wake people up so we're safe calling it.
>  	 */
> -	min_lip = xfs_ail_min(&mp->m_ail.xa_ail);
> +	min_lip = xfs_ail_min(&mp->m_ail);
>  
>  	if (min_lip == lip)
>  		xfs_log_move_tail(mp, 1);
> @@ -354,15 +356,13 @@ xfs_trans_update_ail(
>  	xfs_log_item_t	*lip,
>  	xfs_lsn_t	lsn) __releases(mp->m_ail_lock)
>  {
> -	xfs_ail_entry_t		*ailp;
>  	xfs_log_item_t		*dlip=NULL;
>  	xfs_log_item_t		*mlip;	/* ptr to minimum lip */
>  
> -	ailp = &(mp->m_ail.xa_ail);
> -	mlip = xfs_ail_min(ailp);
> +	mlip = xfs_ail_min(&mp->m_ail);
>  
>  	if (lip->li_flags & XFS_LI_IN_AIL) {
> -		dlip = xfs_ail_delete(ailp, lip);
> +		dlip = xfs_ail_delete(&mp->m_ail, lip);
>  		ASSERT(dlip == lip);
>  	} else {
>  		lip->li_flags |= XFS_LI_IN_AIL;
> @@ -370,11 +370,11 @@ xfs_trans_update_ail(
>  
>  	lip->li_lsn = lsn;
>  
> -	xfs_ail_insert(ailp, lip);
> +	xfs_ail_insert(&mp->m_ail, lip);
>  	mp->m_ail.xa_gen++;
>  
>  	if (mlip == dlip) {
> -		mlip = xfs_ail_min(&(mp->m_ail.xa_ail));
> +		mlip = xfs_ail_min(&mp->m_ail);
>  		spin_unlock(&mp->m_ail_lock);
>  		xfs_log_move_tail(mp, mlip->li_lsn);
>  	} else {
> @@ -404,14 +404,12 @@ xfs_trans_delete_ail(
>  	xfs_mount_t	*mp,
>  	xfs_log_item_t	*lip) __releases(mp->m_ail_lock)
>  {
> -	xfs_ail_entry_t		*ailp;
>  	xfs_log_item_t		*dlip;
>  	xfs_log_item_t		*mlip;
>  
>  	if (lip->li_flags & XFS_LI_IN_AIL) {
> -		ailp = &(mp->m_ail.xa_ail);
> -		mlip = xfs_ail_min(ailp);
> -		dlip = xfs_ail_delete(ailp, lip);
> +		mlip = xfs_ail_min(&mp->m_ail);
> +		dlip = xfs_ail_delete(&mp->m_ail, lip);
>  		ASSERT(dlip == lip);
>  
>  
> @@ -420,7 +418,7 @@ xfs_trans_delete_ail(
>  		mp->m_ail.xa_gen++;
>  
>  		if (mlip == dlip) {
> -			mlip = xfs_ail_min(&(mp->m_ail.xa_ail));
> +			mlip = xfs_ail_min(&mp->m_ail);
>  			spin_unlock(&mp->m_ail_lock);
>  			xfs_log_move_tail(mp, (mlip ? mlip->li_lsn : 0));
>  		} else {
> @@ -458,7 +456,7 @@ xfs_trans_first_ail(
>  {
>  	xfs_log_item_t	*lip;
>  
> -	lip = xfs_ail_min(&(mp->m_ail.xa_ail));
> +	lip = xfs_ail_min(&mp->m_ail);
>  	*gen = (int)mp->m_ail.xa_gen;
>  
>  	return lip;
> @@ -482,9 +480,9 @@ xfs_trans_next_ail(
>  
>  	ASSERT(mp && lip && gen);
>  	if (mp->m_ail.xa_gen == *gen) {
> -		nlip = xfs_ail_next(&(mp->m_ail.xa_ail), lip);
> +		nlip = xfs_ail_next(&mp->m_ail, lip);
>  	} else {
> -		nlip = xfs_ail_min(&(mp->m_ail).xa_ail);
> +		nlip = xfs_ail_min(&mp->m_ail);
>  		*gen = (int)mp->m_ail.xa_gen;
>  		if (restarts != NULL) {
>  			XFS_STATS_INC(xs_push_ail_restarts);
> @@ -514,8 +512,7 @@ int
>  xfs_trans_ail_init(
>  	xfs_mount_t	*mp)
>  {
> -	mp->m_ail.xa_ail.ail_forw = (xfs_log_item_t*)&mp->m_ail.xa_ail;
> -	mp->m_ail.xa_ail.ail_back = (xfs_log_item_t*)&mp->m_ail.xa_ail;
> +	INIT_LIST_HEAD(&mp->m_ail.xa_ail);
>  	return xfsaild_start(mp);
>  }
>  
> @@ -534,7 +531,7 @@ xfs_trans_ail_destroy(
>   */
>  STATIC void
>  xfs_ail_insert(
> -	xfs_ail_entry_t	*base,
> +	xfs_ail_t	*ailp,
>  	xfs_log_item_t	*lip)
>  /* ARGSUSED */
>  {
> @@ -543,27 +540,22 @@ xfs_ail_insert(
>  	/*
>  	 * 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;
> +	if (list_empty(&ailp->xa_ail)) {
> +		list_add(&lip->li_ail, &ailp->xa_ail);
>  		return;
>  	}
>  
> -	next_lip = base->ail_back;
> -	while ((next_lip != (xfs_log_item_t*)base) &&
> -	       (XFS_LSN_CMP(next_lip->li_lsn, lip->li_lsn) > 0)) {
> -		next_lip = next_lip->li_ail.ail_back;
> +	list_for_each_entry_reverse(next_lip, &ailp->xa_ail, li_ail) {
> +		if (XFS_LSN_CMP(next_lip->li_lsn, lip->li_lsn) <= 0)
> +			break;
>  	}
> -	ASSERT((next_lip == (xfs_log_item_t*)base) ||
> +
> +	ASSERT((&next_lip->li_ail == &ailp->xa_ail) ||
>  	       (XFS_LSN_CMP(next_lip->li_lsn, lip->li_lsn) <= 0));
> -	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, lip);
> +	list_add(&lip->li_ail, &next_lip->li_ail);
> +
> +	xfs_ail_check(ailp, lip);
>  	return;
>  }
>  
> @@ -573,15 +565,13 @@ xfs_ail_insert(
>  /*ARGSUSED*/
>  STATIC xfs_log_item_t *
>  xfs_ail_delete(
> -	xfs_ail_entry_t	*base,
> +	xfs_ail_t	*ailp,
>  	xfs_log_item_t	*lip)
>  /* ARGSUSED */
>  {
> -	xfs_ail_check(base, lip);
> -	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(ailp, lip);
> +
> +	list_del(&lip->li_ail);
>  
>  	return lip;
>  }
> @@ -592,14 +582,13 @@ xfs_ail_delete(
>   */
>  STATIC xfs_log_item_t *
>  xfs_ail_min(
> -	xfs_ail_entry_t	*base)
> +	xfs_ail_t	*ailp)
>  /* ARGSUSED */
>  {
> -	register xfs_log_item_t *forw = base->ail_forw;
> -	if (forw == (xfs_log_item_t*)base) {
> +	if (list_empty(&ailp->xa_ail))
>  		return NULL;
> -	}
> -	return forw;
> +
> +	return list_first_entry(&ailp->xa_ail, xfs_log_item_t, li_ail);
>  }
>  
>  /*
> @@ -609,15 +598,14 @@ xfs_ail_min(
>   */
>  STATIC xfs_log_item_t *
>  xfs_ail_next(
> -	xfs_ail_entry_t	*base,
> +	xfs_ail_t	*ailp,
>  	xfs_log_item_t	*lip)
>  /* ARGSUSED */
>  {
> -	if (lip->li_ail.ail_forw == (xfs_log_item_t*)base) {
> +	if (lip->li_ail.next == &ailp->xa_ail)
>  		return NULL;
> -	}
> -	return lip->li_ail.ail_forw;
>  
> +	return list_first_entry(&lip->li_ail, xfs_log_item_t, li_ail);
>  }
>  
>  #ifdef DEBUG
> @@ -626,57 +614,40 @@ xfs_ail_next(
>   */
>  STATIC void
>  xfs_ail_check(
> -	xfs_ail_entry_t *base,
> +	xfs_ail_t 	*ailp,
>  	xfs_log_item_t	*lip)
>  {
>  	xfs_log_item_t	*prev_lip;
>  
> -	prev_lip = base->ail_forw;
> -	if (prev_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);
> +	if (list_empty(&ailp->xa_ail))
>  		return;
> -	}
>  
>  	/*
>  	 * Check the next and previous entries are valid.
>  	 */
>  	ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
> -	prev_lip = lip->li_ail.ail_back;
> -	if (prev_lip != (xfs_log_item_t*)base) {
> -		ASSERT(prev_lip->li_ail.ail_forw == lip);
> +	prev_lip = list_entry(lip->li_ail.prev, xfs_log_item_t, li_ail);
> +	if (&prev_lip->li_ail != &ailp->xa_ail)
>  		ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
> -	}
> -	prev_lip = lip->li_ail.ail_forw;
> -	if (prev_lip != (xfs_log_item_t*)base) {
> -		ASSERT(prev_lip->li_ail.ail_back == lip);
> +
> +	prev_lip = list_entry(lip->li_ail.next, xfs_log_item_t, li_ail);
> +	if (&prev_lip->li_ail != &ailp->xa_ail)
>  		ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) >= 0);
> -	}
>  
>  
>  #ifdef XFS_TRANS_DEBUG
>  	/*
> -	 * Walk the list checking forward and backward pointers,
> -	 * lsn ordering, and that every entry has the XFS_LI_IN_AIL
> -	 * flag set. This is really expensive, so only do it when
> -	 * specifically debugging the transaction subsystem.
> +	 * Walk the list checking lsn ordering, and that every entry has the
> +	 * XFS_LI_IN_AIL flag set. This is really expensive, so only do it
> +	 * when specifically debugging the transaction subsystem.
>  	 */
> -	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);
> +	prev_lip = list_entry(&ailp->xa_ail, xfs_log_item_t, li_ail);
> +	list_for_each_entry(lip, &ailp->xa_ail, li_ail) {
> +		if (&prev_lip->li_ail != &ailp->xa_ail)
>  			ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
> -		}
> -		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 /* XFS_TRANS_DEBUG */
>  }
>  #endif /* DEBUG */
> -- 
> 1.5.4.rc2.85.g9de45-dirty
> 

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