[Cluster-devel] PROBLEM: there exists a wrong return value of function gfs2_set_dqblk()

[张燕]

Summary:
    there exists a wrong return value of function gfs2_set_dqblk().

Bug Description:   

   In function gfs2_set_dqblk() at fs/gfs2/quota.c：1524, the call to gfs2_alloc_get() in line 1599 may return a NULL pointer, and thus function gfs2_set_dqblk() will return the value of variable error. And, the function gfs2_set_dqblk() will return 0 at last when it runs well. However, when the call to gfs2_alloc_get() in line 1599 return a NULL pointer, the value of error is 0. So the function gfs2_set_dqblk() will return 0 to its caller functions when it runs error because of the failing call to gfs2_alloc_get(), leading to a wrong return value of function gfs2_set_dqblk().
The related code snippets in gfs2_set_dqblk() is as following.
gfs2_set_dqblk @@fs/gfs2/quota.c：1524
1524 static int gfs2_set_dqblk(struct super_block *sb, int type, qid_t id,
1525                           struct fs_disk_quota *fdq)
1526 {
	     ...
1573         /* Check for existing entry, if none then alloc new blocks */
1574         error = update_qd(sdp, qd);
1575         if (error)
1576                 goto out_i;
	     ...
1598         if (alloc_required) {
1599                 al = gfs2_alloc_get(ip);  
1600                 if (al == NULL)
1601                         goto out_i;
1602                 gfs2_write_calc_reserv(ip, sizeof(struct gfs2_quota),
1603                                        &data_blocks, &ind_blocks);
1604                 blocks = al->al_requested = 1 + data_blocks + ind_blocks;
1605                 error = gfs2_inplace_reserve(ip);
1606                 if (error)
1607                         goto out_alloc;
1608                 blocks += gfs2_rg_blocks(al);
1609         }
1610 
1611         /* Some quotas span block boundaries and can update two blocks,
1612            adding an extra block to the transaction to handle such quotas */
1613         error = gfs2_trans_begin(sdp, blocks + RES_DINODE + 2, 0);
1614         if (error)
1615                 goto out_release;
	     ...
1627 out_i:
1628         gfs2_glock_dq_uninit(&i_gh);
1629 out_q:
1630         gfs2_glock_dq_uninit(&q_gh);
1631 out_put:
1632         mutex_unlock(&ip->i_inode.i_mutex);
1633         qd_put(qd);
1634         return error;   
1635 }

Generally, the return value of caller functions which call function gfs2_alloc_get() shall be set to -ENOMEM when the call to gfs2_alloc_get() returns a NULL pointer, like the following codes in another file.
leaf_dealloc @@fs/gfs2/dir.c: 1857
1857 static int leaf_dealloc(struct gfs2_inode *dip, u32 index, u32 len,
1858                         u64 leaf_no, void *data)
1859 {
             ...
1876         if (!gfs2_alloc_get(dip)) {
1877                 error = -ENOMEM;
1878                 goto out;
1879         }
             ...
1959 out:
1960         kfree(ht);
1961         return error;
1962 }

Kernel version:
    2.6.39
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