src/patches/suse-2.6.27.39/patches.fixes/ocfs2-dlm-fix-race-in-adding-removing-lockres-to-f.patch

   1 From: Sunil Mushran <sunil.mushran@oracle.com>
   2 Date: Tue, 16 Dec 2008 15:49:22 -0800
   3 Subject: ocfs2/dlm: Fix race in adding/removing lockres' to/from the tracking list
   4 Patch-mainline: 2.6.30
   5 References: bnc#408304
   6
   7 This patch adds a new lock, dlm->tracking_lock, to protect adding/removing
   8 lockres' to/from the dlm->tracking_list. We were previously using dlm->spinlock
   9 for the same, but that proved inadequate as we could be freeing a lockres from
  10 a context that did not hold that lock. As the new lock only protects this list,
  11 we can explicitly take it when removing the lockres from the tracking list.
  12
  13 This bug was exposed when testing multiple processes concurrently flock() the
  14 same file.
  15
  16 Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
  17 Signed-off-by: Mark Fasheh <mfasheh@suse.com>
  18 ---
  19  fs/ocfs2/dlm/dlmcommon.h |    3 ++
  20  fs/ocfs2/dlm/dlmdebug.c  |   53 ++++++++++++++++++++-------------------------
  21  fs/ocfs2/dlm/dlmdomain.c |    1 +
  22  fs/ocfs2/dlm/dlmmaster.c |   10 ++++++++
  23  4 files changed, 38 insertions(+), 29 deletions(-)
  24
  25 diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
  26 index d5a86fb..bb53714 100644
  27 --- a/fs/ocfs2/dlm/dlmcommon.h
  28 +++ b/fs/ocfs2/dlm/dlmcommon.h
  29 @@ -140,6 +140,7 @@ struct dlm_ctxt
  30         unsigned int purge_count;
  31         spinlock_t spinlock;
  32         spinlock_t ast_lock;
  33 +       spinlock_t track_lock;
  34         char *name;
  35         u8 node_num;
  36         u32 key;
  37 @@ -316,6 +317,8 @@ struct dlm_lock_resource
  38          * put on a list for the dlm thread to run. */
  39         unsigned long    last_used;
  40
  41 +       struct dlm_ctxt *dlm;
  42 +
  43         unsigned migration_pending:1;
  44         atomic_t asts_reserved;
  45         spinlock_t spinlock;
  46 diff --git a/fs/ocfs2/dlm/dlmdebug.c b/fs/ocfs2/dlm/dlmdebug.c
  47 index 1b81dcb..b32f60a 100644
  48 --- a/fs/ocfs2/dlm/dlmdebug.c
  49 +++ b/fs/ocfs2/dlm/dlmdebug.c
  50 @@ -630,43 +630,38 @@ static void *lockres_seq_start(struct seq_file *m, loff_t *pos)
  51  {
  52         struct debug_lockres *dl = m->private;
  53         struct dlm_ctxt *dlm = dl->dl_ctxt;
  54 +       struct dlm_lock_resource *oldres = dl->dl_res;
  55         struct dlm_lock_resource *res = NULL;
  56 +       struct list_head *track_list;
  57
  58 -       spin_lock(&dlm->spinlock);
  59 +       spin_lock(&dlm->track_lock);
  60 +       if (oldres)
  61 +               track_list = &oldres->tracking;
  62 +       else
  63 +               track_list = &dlm->tracking_list;
  64
  65 -       if (dl->dl_res) {
  66 -               list_for_each_entry(res, &dl->dl_res->tracking, tracking) {
  67 -                       if (dl->dl_res) {
  68 -                               dlm_lockres_put(dl->dl_res);
  69 -                               dl->dl_res = NULL;
  70 -                       }
  71 -                       if (&res->tracking == &dlm->tracking_list) {
  72 -                               mlog(0, "End of list found, %p\n", res);
  73 -                               dl = NULL;
  74 -                               break;
  75 -                       }
  76 +       list_for_each_entry(res, track_list, tracking) {
  77 +               if (&res->tracking == &dlm->tracking_list)
  78 +                       res = NULL;
  79 +               else
  80                         dlm_lockres_get(res);
  81 -                       dl->dl_res = res;
  82 -                       break;
  83 -               }
  84 -       } else {
  85 -               if (!list_empty(&dlm->tracking_list)) {
  86 -                       list_for_each_entry(res, &dlm->tracking_list, tracking)
  87 -                               break;
  88 -                       dlm_lockres_get(res);
  89 -                       dl->dl_res = res;
  90 -               } else
  91 -                       dl = NULL;
  92 +               break;
  93         }
  94 +       spin_unlock(&dlm->track_lock);
  95
  96 -       if (dl) {
  97 -               spin_lock(&dl->dl_res->spinlock);
  98 -               dump_lockres(dl->dl_res, dl->dl_buf, dl->dl_len - 1);
  99 -               spin_unlock(&dl->dl_res->spinlock);
 100 -       }
 101 +       if (oldres)
 102 +               dlm_lockres_put(oldres);
 103
 104 -       spin_unlock(&dlm->spinlock);
 105 +       dl->dl_res = res;
 106 +
 107 +       if (res) {
 108 +               spin_lock(&res->spinlock);
 109 +               dump_lockres(res, dl->dl_buf, dl->dl_len - 1);
 110 +               spin_unlock(&res->spinlock);
 111 +       } else
 112 +               dl = NULL;
 113
 114 +       /* passed to seq_show */
 115         return dl;
 116  }
 117
 118 diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
 119 index 63f8125..d8d578f 100644
 120 --- a/fs/ocfs2/dlm/dlmdomain.c
 121 +++ b/fs/ocfs2/dlm/dlmdomain.c
 122 @@ -1550,6 +1550,7 @@ static struct dlm_ctxt *dlm_alloc_ctxt(const char *domain,
 123         spin_lock_init(&dlm->spinlock);
 124         spin_lock_init(&dlm->master_lock);
 125         spin_lock_init(&dlm->ast_lock);
 126 +       spin_lock_init(&dlm->track_lock);
 127         INIT_LIST_HEAD(&dlm->list);
 128         INIT_LIST_HEAD(&dlm->dirty_list);
 129         INIT_LIST_HEAD(&dlm->reco.resources);
 130 diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
 131 index 92fd1d7..cbf3abe 100644
 132 --- a/fs/ocfs2/dlm/dlmmaster.c
 133 +++ b/fs/ocfs2/dlm/dlmmaster.c
 134 @@ -505,8 +505,10 @@ void dlm_change_lockres_owner(struct dlm_ctxt *dlm,
 135  static void dlm_lockres_release(struct kref *kref)
 136  {
 137         struct dlm_lock_resource *res;
 138 +       struct dlm_ctxt *dlm;
 139
 140         res = container_of(kref, struct dlm_lock_resource, refs);
 141 +       dlm = res->dlm;
 142
 143         /* This should not happen -- all lockres' have a name
 144          * associated with them at init time. */
 145 @@ -515,6 +517,7 @@ static void dlm_lockres_release(struct kref *kref)
 146         mlog(0, "destroying lockres %.*s\n", res->lockname.len,
 147              res->lockname.name);
 148
 149 +       spin_lock(&dlm->track_lock);
 150         if (!list_empty(&res->tracking))
 151                 list_del_init(&res->tracking);
 152         else {
 153 @@ -522,6 +525,9 @@ static void dlm_lockres_release(struct kref *kref)
 154                      res->lockname.len, res->lockname.name);
 155                 dlm_print_one_lock_resource(res);
 156         }
 157 +       spin_unlock(&dlm->track_lock);
 158 +
 159 +       dlm_put(dlm);
 160
 161         if (!hlist_unhashed(&res->hash_node) ||
 162             !list_empty(&res->granted) ||
 163 @@ -595,6 +601,10 @@ static void dlm_init_lockres(struct dlm_ctxt *dlm,
 164         res->migration_pending = 0;
 165         res->inflight_locks = 0;
 166
 167 +       /* put in dlm_lockres_release */
 168 +       dlm_grab(dlm);
 169 +       res->dlm = dlm;
 170 +
 171         kref_init(&res->refs);
 172
 173         /* just for consistency */
 174 --
 175 1.5.6
 176