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>

2 files changed, 53 insertions, 38 deletions

diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index 275b1f4f9430..84070f2e0ba4 100644
--- a/fs/xfs/xfs_alloc.c
+++ b/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);
 }
diff --git a/fs/xfs/xfs_alloc_btree.c b/fs/xfs/xfs_alloc_btree.c
index adbd9141aea1..b726e10d2c1c 100644
--- a/fs/xfs/xfs_alloc_btree.c
+++ b/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);
 }