lustre/kernel_patches/patches/quota-avoid-dqget-calls-sles11sp2.patch

   1 In dquot_initialize(), we'd call dqget() only when i_dquot not
   2 initialized, which can avoid 2 pair of dqget()/dqput() in most
   3 case. It could relieve the global locks contenion caused by
   4 dqget()/dqput().
   5 --- linux-3.0/fs/quota/dquot.c.orig     2013-07-18 09:46:28.000000000 -0400
   6 +++ linux-3.0/fs/quota/dquot.c  2013-07-18 09:49:20.000000000 -0400
   7 @@ -1342,8 +1342,8 @@
   8  static void __dquot_initialize(struct inode *inode, int type)
   9  {
  10         unsigned int id = 0;
  11 -       int cnt;
  12 -       struct dquot *got[MAXQUOTAS];
  13 +       int cnt, ret = 0, dq_get = 0;
  14 +       struct dquot *got[MAXQUOTAS] = { NULL, NULL };
  15         struct super_block *sb = inode->i_sb;
  16         qsize_t rsv;
  17
  18 @@ -1352,7 +1352,14 @@
  19         if (!dquot_active(inode))
  20                 return;
  21
  22 -       /* First get references to structures we might need. */
  23 +       /* In most case, the i_dquot should have been initialized, except
  24 +        * the newly allocated one. We'd always try to skip the dqget() and
  25 +        * dqput() calls to avoid unnecessary global lock contention. */
  26 +       if (!(inode->i_state & I_NEW))
  27 +               goto init_idquot;
  28 +
  29 +get_dquots:
  30 +       dq_get = 1;
  31         for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
  32                 got[cnt] = NULL;
  33                 if (type != -1 && cnt != type)
  34 @@ -1367,7 +1374,7 @@
  35                 }
  36                 got[cnt] = dqget(sb, id, cnt);
  37         }
  38 -
  39 +init_idquot:
  40         spin_lock(&inode->i_lock);
  41         if (IS_NOQUOTA(inode))
  42                 goto out_err;
  43 @@ -1381,10 +1388,14 @@
  44                 /* Avoid races with quotaoff() */
  45                 if (!sb_has_quota_active(sb, cnt))
  46                         continue;
  47 -               /* We could race with quotaon or dqget() could have failed */
  48 -               if (!got[cnt])
  49 -                       continue;
  50                 if (!inode->i_dquot[cnt]) {
  51 +                       if (dq_get == 0) {
  52 +                               spin_unlock(&inode->i_lock);
  53 +                               goto get_dquots;
  54 +                       }
  55 +                       /* We could race with quotaon or dqget() could have failed */
  56 +                       if (!got[cnt])
  57 +                               continue;
  58                         inode->i_dquot[cnt] = got[cnt];
  59                         got[cnt] = NULL;
  60                         /*
  61 @@ -1388,7 +1399,7 @@
  62                          * did a write before quota was turned on
  63                          */
  64                         rsv = inode_get_rsv_space(inode);
  65 -                       if (unlikely(rsv)) {
  66 +                       if (unlikely(rsv) && likely(inode->i_dquot[cnt])) {
  67                                 spin_lock(&dq_data_lock);
  68                                 dquot_resv_space(inode->i_dquot[cnt], rsv);
  69                                 spin_unlock(&dq_data_lock);
  70 @@ -1488,7 +1399,8 @@
  71         spin_unlock(&inode->i_lock);
  72
  73         /* Drop unused references */
  74 -       dqput_all(got);
  75 +       if (dq_get)
  76 +               dqput_all(got);
  77  }
  78
  79  void dquot_initialize(struct inode *inode)