xfs: Don't directly reference m_perag in allocation code

Start abstracting the perag references so that the indexing of the
structures is not directly coded into all the places that uses the
perag structures. This will allow us to separate the use of the
perag structure and the way it is indexed and hence avoid the known
deadlocks related to growing a busy filesystem.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_alloc.c

@@ -1662,11 +1662,13 @@ xfs_free_ag_extent(
 		xfs_agf_t	*agf;
 		xfs_perag_t	*pag;		/* per allocation group data */
 
+		pag = xfs_perag_get(mp, agno);
+		pag->pagf_freeblks += len;
+		xfs_perag_put(pag);
+
 		agf = XFS_BUF_TO_AGF(agbp);
-		pag = &mp->m_perag[agno];
 		be32_add_cpu(&agf->agf_freeblks, len);
 		xfs_trans_agblocks_delta(tp, len);
-		pag->pagf_freeblks += len;
 		XFS_WANT_CORRUPTED_GOTO(
 			be32_to_cpu(agf->agf_freeblks) <=
 			be32_to_cpu(agf->agf_length),
@@ -1969,10 +1971,12 @@ xfs_alloc_get_freelist(
 	xfs_trans_brelse(tp, agflbp);
 	if (be32_to_cpu(agf->agf_flfirst) == XFS_AGFL_SIZE(mp))
 		agf->agf_flfirst = 0;
-	pag = &mp->m_perag[be32_to_cpu(agf->agf_seqno)];
+
+	pag = xfs_perag_get(mp, be32_to_cpu(agf->agf_seqno));
 	be32_add_cpu(&agf->agf_flcount, -1);
 	xfs_trans_agflist_delta(tp, -1);
 	pag->pagf_flcount--;
+	xfs_perag_put(pag);
 
 	logflags = XFS_AGF_FLFIRST | XFS_AGF_FLCOUNT;
 	if (btreeblk) {
@@ -2078,7 +2082,8 @@ xfs_alloc_put_freelist(
 	be32_add_cpu(&agf->agf_fllast, 1);
 	if (be32_to_cpu(agf->agf_fllast) == XFS_AGFL_SIZE(mp))
 		agf->agf_fllast = 0;
-	pag = &mp->m_perag[be32_to_cpu(agf->agf_seqno)];
+
+	pag = xfs_perag_get(mp, be32_to_cpu(agf->agf_seqno));
 	be32_add_cpu(&agf->agf_flcount, 1);
 	xfs_trans_agflist_delta(tp, 1);
 	pag->pagf_flcount++;
@@ -2089,6 +2094,7 @@ xfs_alloc_put_freelist(
 		pag->pagf_btreeblks--;
 		logflags |= XFS_AGF_BTREEBLKS;
 	}
+	xfs_perag_put(pag);
 
 	xfs_alloc_log_agf(tp, agbp, logflags);
 
@@ -2152,7 +2158,6 @@ xfs_read_agf(
 		xfs_trans_brelse(tp, *bpp);
 		return XFS_ERROR(EFSCORRUPTED);
 	}
-
 	XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_AGF, XFS_AGF_REF);
 	return 0;
 }
@@ -2184,7 +2189,7 @@ xfs_alloc_read_agf(
 	ASSERT(!XFS_BUF_GETERROR(*bpp));
 
 	agf = XFS_BUF_TO_AGF(*bpp);
-	pag = &mp->m_perag[agno];
+	pag = xfs_perag_get(mp, agno);
 	if (!pag->pagf_init) {
 		pag->pagf_freeblks = be32_to_cpu(agf->agf_freeblks);
 		pag->pagf_btreeblks = be32_to_cpu(agf->agf_btreeblks);
@@ -2211,6 +2216,7 @@ xfs_alloc_read_agf(
 		       be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNTi]));
 	}
 #endif
+	xfs_perag_put(pag);
 	return 0;
 }
 
@@ -2271,7 +2277,7 @@ xfs_alloc_vextent(
 		 */
 		args->agno = XFS_FSB_TO_AGNO(mp, args->fsbno);
 		down_read(&mp->m_peraglock);
-		args->pag = &mp->m_perag[args->agno];
+		args->pag = xfs_perag_get(mp, args->agno);
 		args->minleft = 0;
 		error = xfs_alloc_fix_freelist(args, 0);
 		args->minleft = minleft;
@@ -2341,7 +2347,7 @@ xfs_alloc_vextent(
 		 */
 		down_read(&mp->m_peraglock);
 		for (;;) {
-			args->pag = &mp->m_perag[args->agno];
+			args->pag = xfs_perag_get(mp, args->agno);
 			if (no_min) args->minleft = 0;
 			error = xfs_alloc_fix_freelist(args, flags);
 			args->minleft = minleft;
@@ -2400,6 +2406,7 @@ xfs_alloc_vextent(
 					}
 				}
 			}
+			xfs_perag_put(args->pag);
 		}
 		up_read(&mp->m_peraglock);
 		if (bump_rotor || (type == XFS_ALLOCTYPE_ANY_AG)) {
@@ -2427,8 +2434,10 @@ xfs_alloc_vextent(
 			args->len);
 #endif
 	}
+	xfs_perag_put(args->pag);
 	return 0;
 error0:
+	xfs_perag_put(args->pag);
 	up_read(&mp->m_peraglock);
 	return error;
 }
@@ -2455,7 +2464,7 @@ xfs_free_extent(
 	ASSERT(args.agno < args.mp->m_sb.sb_agcount);
 	args.agbno = XFS_FSB_TO_AGBNO(args.mp, bno);
 	down_read(&args.mp->m_peraglock);
-	args.pag = &args.mp->m_perag[args.agno];
+	args.pag = xfs_perag_get(args.mp, args.agno);
 	if ((error = xfs_alloc_fix_freelist(&args, XFS_ALLOC_FLAG_FREEING)))
 		goto error0;
 #ifdef DEBUG
@@ -2465,6 +2474,7 @@ xfs_free_extent(
 #endif
 	error = xfs_free_ag_extent(tp, args.agbp, args.agno, args.agbno, len, 0);
 error0:
+	xfs_perag_put(args.pag);
 	up_read(&args.mp->m_peraglock);
 	return error;
 }
@@ -2486,15 +2496,15 @@ xfs_alloc_mark_busy(xfs_trans_t *tp,
 		    xfs_agblock_t bno,
 		    xfs_extlen_t len)
 {
-	xfs_mount_t		*mp;
 	xfs_perag_busy_t	*bsy;
+	struct xfs_perag	*pag;
 	int			n;
 
-	mp = tp->t_mountp;
-	spin_lock(&mp->m_perag[agno].pagb_lock);
+	pag = xfs_perag_get(tp->t_mountp, agno);
+	spin_lock(&pag->pagb_lock);
 
 	/* search pagb_list for an open slot */
-	for (bsy = mp->m_perag[agno].pagb_list, n = 0;
+	for (bsy = pag->pagb_list, n = 0;
 	     n < XFS_PAGB_NUM_SLOTS;
 	     bsy++, n++) {
 		if (bsy->busy_tp == NULL) {
@@ -2502,11 +2512,11 @@ xfs_alloc_mark_busy(xfs_trans_t *tp,
 		}
 	}
 
-	trace_xfs_alloc_busy(mp, agno, bno, len, n);
+	trace_xfs_alloc_busy(tp->t_mountp, agno, bno, len, n);
 
 	if (n < XFS_PAGB_NUM_SLOTS) {
-		bsy = &mp->m_perag[agno].pagb_list[n];
-		mp->m_perag[agno].pagb_count++;
+		bsy = &pag->pagb_list[n];
+		pag->pagb_count++;
 		bsy->busy_start = bno;
 		bsy->busy_length = len;
 		bsy->busy_tp = tp;
@@ -2521,7 +2531,8 @@ xfs_alloc_mark_busy(xfs_trans_t *tp,
 		xfs_trans_set_sync(tp);
 	}
 
-	spin_unlock(&mp->m_perag[agno].pagb_lock);
+	spin_unlock(&pag->pagb_lock);
+	xfs_perag_put(pag);
 }
 
 void
@@ -2529,24 +2540,23 @@ xfs_alloc_clear_busy(xfs_trans_t *tp,
 		     xfs_agnumber_t agno,
 		     int idx)
 {
-	xfs_mount_t		*mp;
+	struct xfs_perag	*pag;
 	xfs_perag_busy_t	*list;
 
-	mp = tp->t_mountp;
-
-	spin_lock(&mp->m_perag[agno].pagb_lock);
-	list = mp->m_perag[agno].pagb_list;
-
 	ASSERT(idx < XFS_PAGB_NUM_SLOTS);
+	pag = xfs_perag_get(tp->t_mountp, agno);
+	spin_lock(&pag->pagb_lock);
+	list = pag->pagb_list;
 
-	trace_xfs_alloc_unbusy(mp, agno, idx, list[idx].busy_tp == tp);
+	trace_xfs_alloc_unbusy(tp->t_mountp, agno, idx, list[idx].busy_tp == tp);
 
 	if (list[idx].busy_tp == tp) {
 		list[idx].busy_tp = NULL;
-		mp->m_perag[agno].pagb_count--;
+		pag->pagb_count--;
 	}
 
-	spin_unlock(&mp->m_perag[agno].pagb_lock);
+	spin_unlock(&pag->pagb_lock);
+	xfs_perag_put(pag);
 }
 
 
@@ -2560,17 +2570,15 @@ xfs_alloc_search_busy(xfs_trans_t *tp,
 		    xfs_agblock_t bno,
 		    xfs_extlen_t len)
 {
-	xfs_mount_t		*mp;
+	struct xfs_perag	*pag;
 	xfs_perag_busy_t	*bsy;
 	xfs_agblock_t		uend, bend;
 	xfs_lsn_t		lsn = 0;
 	int			cnt;
 
-	mp = tp->t_mountp;
-
-	spin_lock(&mp->m_perag[agno].pagb_lock);
-
-	uend = bno + len - 1;
+	pag = xfs_perag_get(tp->t_mountp, agno);
+	spin_lock(&pag->pagb_lock);
+	cnt = pag->pagb_count;
 
 	/*
 	 * search pagb_list for this slot, skipping open slots. We have to
@@ -2578,8 +2586,9 @@ xfs_alloc_search_busy(xfs_trans_t *tp,
 	 * we have to get the most recent LSN for the log force to push out
 	 * all the transactions that span the range.
 	 */
-	for (cnt = 0; cnt < mp->m_perag[agno].pagb_count; cnt++) {
-		bsy = &mp->m_perag[agno].pagb_list[cnt];
+	uend = bno + len - 1;
+	for (cnt = 0; cnt < pag->pagb_count; cnt++) {
+		bsy = &pag->pagb_list[cnt];
 		if (!bsy->busy_tp)
 			continue;
 
@@ -2591,7 +2600,8 @@ xfs_alloc_search_busy(xfs_trans_t *tp,
 		if (XFS_LSN_CMP(bsy->busy_tp->t_commit_lsn, lsn) > 0)
 			lsn = bsy->busy_tp->t_commit_lsn;
 	}
-	spin_unlock(&mp->m_perag[agno].pagb_lock);
+	spin_unlock(&pag->pagb_lock);
+	xfs_perag_put(pag);
 	trace_xfs_alloc_busysearch(tp->t_mountp, agno, bno, len, lsn);
 
 	/*
@@ -2599,5 +2609,5 @@ xfs_alloc_search_busy(xfs_trans_t *tp,
 	 * transaction that freed the block
 	 */
 	if (lsn)
-		xfs_log_force(mp, lsn, XFS_LOG_FORCE|XFS_LOG_SYNC);
+		xfs_log_force(tp->t_mountp, lsn, XFS_LOG_FORCE|XFS_LOG_SYNC);
 }

fs/xfs/xfs_alloc_btree.c

@@ -61,12 +61,14 @@ xfs_allocbt_set_root(
 	struct xfs_agf		*agf = XFS_BUF_TO_AGF(agbp);
 	xfs_agnumber_t		seqno = be32_to_cpu(agf->agf_seqno);
 	int			btnum = cur->bc_btnum;
+	struct xfs_perag	*pag = xfs_perag_get(cur->bc_mp, seqno);
 
 	ASSERT(ptr->s != 0);
 
 	agf->agf_roots[btnum] = ptr->s;
 	be32_add_cpu(&agf->agf_levels[btnum], inc);
-	cur->bc_mp->m_perag[seqno].pagf_levels[btnum] += inc;
+	pag->pagf_levels[btnum] += inc;
+	xfs_perag_put(pag);
 
 	xfs_alloc_log_agf(cur->bc_tp, agbp, XFS_AGF_ROOTS | XFS_AGF_LEVELS);
 }
@@ -150,6 +152,7 @@ xfs_allocbt_update_lastrec(
 {
 	struct xfs_agf		*agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
 	xfs_agnumber_t		seqno = be32_to_cpu(agf->agf_seqno);
+	struct xfs_perag	*pag;
 	__be32			len;
 	int			numrecs;
 
@@ -193,7 +196,9 @@ xfs_allocbt_update_lastrec(
 	}
 
 	agf->agf_longest = len;
-	cur->bc_mp->m_perag[seqno].pagf_longest = be32_to_cpu(len);
+	pag = xfs_perag_get(cur->bc_mp, seqno);
+	pag->pagf_longest = be32_to_cpu(len);
+	xfs_perag_put(pag);
 	xfs_alloc_log_agf(cur->bc_tp, cur->bc_private.a.agbp, XFS_AGF_LONGEST);
 }