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[PATCH 2/6] XFS: Don't directly reference m_perag in allocation code

To: xfs@xxxxxxxxxxx
Subject: [PATCH 2/6] XFS: Don't directly reference m_perag in allocation code
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 15 Dec 2009 17:11:13 +1100
In-reply-to: <1260857477-2368-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1260857477-2368-1-git-send-email-david@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
---
 fs/xfs/xfs_alloc.c       |   81 +++++++++++++++++++++++++--------------------
 fs/xfs/xfs_alloc_btree.c |    9 ++++-
 2 files changed, 52 insertions(+), 38 deletions(-)

diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index a1c65fc..3cb533c 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),
@@ -1969,7 +1971,8 @@ 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--;
@@ -2078,7 +2081,8 @@ 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 +2093,7 @@ xfs_alloc_put_freelist(
                pag->pagf_btreeblks--;
                logflags |= XFS_AGF_BTREEBLKS;
        }
+       xfs_perag_put(pag);
 
        xfs_alloc_log_agf(tp, agbp, logflags);
 
@@ -2152,7 +2157,6 @@ 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 +2188,7 @@ 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 +2215,7 @@ xfs_alloc_read_agf(
                       be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNTi]));
        }
 #endif
+       xfs_perag_put(pag);
        return 0;
 }
 
@@ -2271,7 +2276,7 @@ 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 +2346,7 @@ 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 +2405,7 @@ xfs_alloc_vextent(
                                        }
                                }
                        }
+                       xfs_perag_put(args->pag);
                }
                up_read(&mp->m_peraglock);
                if (bump_rotor || (type == XFS_ALLOCTYPE_ANY_AG)) {
@@ -2427,8 +2433,10 @@ 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 +2463,7 @@ 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 +2473,7 @@ 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 +2495,15 @@ 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 +2511,11 @@ 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 +2530,8 @@ 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 +2539,23 @@ 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);
 }
 
 
@@ -2560,21 +2569,20 @@ 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;
        int                     cnt;
 
-       mp = tp->t_mountp;
-
-       spin_lock(&mp->m_perag[agno].pagb_lock);
-       cnt = mp->m_perag[agno].pagb_count;
+       pag = xfs_perag_get(tp->t_mountp, agno);
+       spin_lock(&pag->pagb_lock);
+       cnt = pag->pagb_count;
 
        uend = bno + len - 1;
 
        /* search pagb_list for this slot, skipping open slots */
-       for (bsy = mp->m_perag[agno].pagb_list; cnt; bsy++) {
+       for (bsy = pag->pagb_list; cnt; bsy++) {
 
                /*
                 * (start1,length1) within (start2, length2)
@@ -2589,7 +2597,7 @@ xfs_alloc_search_busy(xfs_trans_t *tp,
                }
        }
 
-       trace_xfs_alloc_busysearch(mp, agno, bno, len, !!cnt);
+       trace_xfs_alloc_busysearch(tp->t_mountp, agno, bno, len, !!cnt);
 
        /*
         * If a block was found, force the log through the LSN of the
@@ -2597,9 +2605,10 @@ xfs_alloc_search_busy(xfs_trans_t *tp,
         */
        if (cnt) {
                lsn = bsy->busy_tp->t_commit_lsn;
-               spin_unlock(&mp->m_perag[agno].pagb_lock);
-               xfs_log_force(mp, lsn, XFS_LOG_FORCE|XFS_LOG_SYNC);
+               spin_unlock(&pag->pagb_lock);
+               xfs_log_force(tp->t_mountp, lsn, XFS_LOG_FORCE|XFS_LOG_SYNC);
        } else {
-               spin_unlock(&mp->m_perag[agno].pagb_lock);
+               spin_unlock(&pag->pagb_lock);
        }
+       xfs_perag_put(pag);
 }
diff --git a/fs/xfs/xfs_alloc_btree.c b/fs/xfs/xfs_alloc_btree.c
index adbd914..b726e10 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);
 }
 
-- 
1.6.5

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