ocfs2: Fix possible deadlock when extending quota file

In OCFS2, allocator locks rank above transaction start. Thus we
cannot extend quota file from inside a transaction less we could
deadlock.

We solve the problem by starting transaction not already in
ocfs2_acquire_dquot() but only in ocfs2_local_read_dquot() and
ocfs2_global_read_dquot() and we allocate blocks to quota files before starting
the transaction.  In case we crash, quota files will just have a few blocks
more but that's no problem since we just use them next time we extend the
quota file.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

2 files changed, 57 insertions, 63 deletions

diff --git a/fs/ocfs2/journal.h b/fs/ocfs2/journal.h
index 4a4d3b55fd22..2c3222aec622 100644
--- a/fs/ocfs2/journal.h
+++ b/fs/ocfs2/journal.h
@@ -363,11 +363,6 @@ static inline int ocfs2_quota_trans_credits(struct super_block *sb)
         return credits;
 }
 
-/* Number of credits needed for removing quota structure from file */
-int ocfs2_calc_qdel_credits(struct super_block *sb, int type);
-/* Number of credits needed for initialization of new quota structure */
-int ocfs2_calc_qinit_credits(struct super_block *sb, int type);
-
 /* group extend. inode update and last group update. */
 #define OCFS2_GROUP_EXTEND_CREDITS      (OCFS2_INODE_UPDATE_CREDITS + 1)
 
diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c
index d604a6aa0a22..bf7742d0ee3b 100644
--- a/fs/ocfs2/quota_global.c
+++ b/fs/ocfs2/quota_global.c
@@ -215,11 +215,7 @@ ssize_t ocfs2_quota_write(struct super_block *sb, int type,
                 loff_t rounded_end =
                                 ocfs2_align_bytes_to_blocks(sb, off + len);
 
-                down_write(&OCFS2_I(gqinode)->ip_alloc_sem);
-                err = ocfs2_extend_no_holes(gqinode, rounded_end, off);
-                up_write(&OCFS2_I(gqinode)->ip_alloc_sem);
-                if (err < 0)
-                        goto out;
+                /* Space is already allocated in ocfs2_global_read_dquot() */
                 err = ocfs2_simple_size_update(gqinode,
                                                oinfo->dqi_gqi_bh,
                                                rounded_end);
@@ -405,13 +401,36 @@ int ocfs2_global_write_info(struct super_block *sb, int type)
         return err;
 }
 
+static int ocfs2_global_qinit_alloc(struct super_block *sb, int type)
+{
+        struct ocfs2_mem_dqinfo *oinfo = sb_dqinfo(sb, type)->dqi_priv;
+
+        /*
+         * We may need to allocate tree blocks and a leaf block but not the
+         * root block
+         */
+        return oinfo->dqi_gi.dqi_qtree_depth;
+}
+
+static int ocfs2_calc_global_qinit_credits(struct super_block *sb, int type)
+{
+        /* We modify all the allocated blocks, tree root, and info block */
+        return (ocfs2_global_qinit_alloc(sb, type) + 2) *
+                        OCFS2_QUOTA_BLOCK_UPDATE_CREDITS;
+}
+
 /* Read in information from global quota file and acquire a reference to it.
  * dquot_acquire() has already started the transaction and locked quota file */
 int ocfs2_global_read_dquot(struct dquot *dquot)
 {
         int err, err2, ex = 0;
-        struct ocfs2_mem_dqinfo *info =
-                        sb_dqinfo(dquot->dq_sb, dquot->dq_type)->dqi_priv;
+        struct super_block *sb = dquot->dq_sb;
+        int type = dquot->dq_type;
+        struct ocfs2_mem_dqinfo *info = sb_dqinfo(sb, type)->dqi_priv;
+        struct ocfs2_super *osb = OCFS2_SB(sb);
+        struct inode *gqinode = info->dqi_gqinode;
+        int need_alloc = ocfs2_global_qinit_alloc(sb, type);
+        handle_t *handle = NULL;
 
         err = ocfs2_qinfo_lock(info, 0);
         if (err < 0)
@@ -422,14 +441,33 @@ int ocfs2_global_read_dquot(struct dquot *dquot)
         OCFS2_DQUOT(dquot)->dq_use_count++;
         OCFS2_DQUOT(dquot)->dq_origspace = dquot->dq_dqb.dqb_curspace;
         OCFS2_DQUOT(dquot)->dq_originodes = dquot->dq_dqb.dqb_curinodes;
+        ocfs2_qinfo_unlock(info, 0);
+
         if (!dquot->dq_off) {   /* No real quota entry? */
-                /* Upgrade to exclusive lock for allocation */
-                ocfs2_qinfo_unlock(info, 0);
-                err = ocfs2_qinfo_lock(info, 1);
-                if (err < 0)
-                        goto out_qlock;
                 ex = 1;
+                /*
+                 * Add blocks to quota file before we start a transaction since
+                 * locking allocators ranks above a transaction start
+                 */
+                WARN_ON(journal_current_handle());
+                down_write(&OCFS2_I(gqinode)->ip_alloc_sem);
+                err = ocfs2_extend_no_holes(gqinode,
+                        gqinode->i_size + (need_alloc << sb->s_blocksize_bits),
+                        gqinode->i_size);
+                up_write(&OCFS2_I(gqinode)->ip_alloc_sem);
+                if (err < 0)
+                        goto out;
+        }
+
+        handle = ocfs2_start_trans(osb,
+                                   ocfs2_calc_global_qinit_credits(sb, type));
+        if (IS_ERR(handle)) {
+                err = PTR_ERR(handle);
+                goto out;
         }
+        err = ocfs2_qinfo_lock(info, ex);
+        if (err < 0)
+                goto out_trans;
         err = qtree_write_dquot(&info->dqi_gi, dquot);
         if (ex && info_dirty(sb_dqinfo(dquot->dq_sb, dquot->dq_type))) {
                 err2 = __ocfs2_global_write_info(dquot->dq_sb, dquot->dq_type);
@@ -441,6 +479,9 @@ out_qlock:
                 ocfs2_qinfo_unlock(info, 1);
         else
                 ocfs2_qinfo_unlock(info, 0);
+out_trans:
+        if (handle)
+                ocfs2_commit_trans(osb, handle);
 out:
         if (err < 0)
                 mlog_errno(err);
@@ -638,24 +679,17 @@ out:
         return status;
 }
 
-int ocfs2_calc_qdel_credits(struct super_block *sb, int type)
+static int ocfs2_calc_qdel_credits(struct super_block *sb, int type)
 {
-        struct ocfs2_mem_dqinfo *oinfo;
-        int features[MAXQUOTAS] = { OCFS2_FEATURE_RO_COMPAT_USRQUOTA,
-                                    OCFS2_FEATURE_RO_COMPAT_GRPQUOTA };
-
-        if (!OCFS2_HAS_RO_COMPAT_FEATURE(sb, features[type]))
-                return 0;
-
-        oinfo = sb_dqinfo(sb, type)->dqi_priv;
+        struct ocfs2_mem_dqinfo *oinfo = sb_dqinfo(sb, type)->dqi_priv;
         /*
          * We modify tree, leaf block, global info, local chunk header,
          * global and local inode; OCFS2_QINFO_WRITE_CREDITS already
          * accounts for inode update
          */
-        return oinfo->dqi_gi.dqi_qtree_depth +
+        return (oinfo->dqi_gi.dqi_qtree_depth + 2) *
+               OCFS2_QUOTA_BLOCK_UPDATE_CREDITS +
                OCFS2_QINFO_WRITE_CREDITS +
-               2 * OCFS2_QUOTA_BLOCK_UPDATE_CREDITS +
                OCFS2_INODE_UPDATE_CREDITS;
 }
 
@@ -688,36 +722,10 @@ out:
         return status;
 }
 
-int ocfs2_calc_qinit_credits(struct super_block *sb, int type)
-{
-        struct ocfs2_mem_dqinfo *oinfo;
-        int features[MAXQUOTAS] = { OCFS2_FEATURE_RO_COMPAT_USRQUOTA,
-                                    OCFS2_FEATURE_RO_COMPAT_GRPQUOTA };
-        struct ocfs2_dinode *lfe, *gfe;
-
-        if (!OCFS2_HAS_RO_COMPAT_FEATURE(sb, features[type]))
-                return 0;
-
-        oinfo = sb_dqinfo(sb, type)->dqi_priv;
-        gfe = (struct ocfs2_dinode *)oinfo->dqi_gqi_bh->b_data;
-        lfe = (struct ocfs2_dinode *)oinfo->dqi_lqi_bh->b_data;
-        /* We can extend local file + global file. In local file we
-         * can modify info, chunk header block and dquot block. In
-         * global file we can modify info, tree and leaf block */
-        return ocfs2_calc_extend_credits(sb, &lfe->id2.i_list, 0) +
-               ocfs2_calc_extend_credits(sb, &gfe->id2.i_list, 0) +
-               OCFS2_LOCAL_QINFO_WRITE_CREDITS +
-               2 * OCFS2_QUOTA_BLOCK_UPDATE_CREDITS +
-               oinfo->dqi_gi.dqi_qtree_depth +
-               2 * OCFS2_QUOTA_BLOCK_UPDATE_CREDITS;
-}
-
 static int ocfs2_acquire_dquot(struct dquot *dquot)
 {
-        handle_t *handle;
         struct ocfs2_mem_dqinfo *oinfo =
                         sb_dqinfo(dquot->dq_sb, dquot->dq_type)->dqi_priv;
-        struct ocfs2_super *osb = OCFS2_SB(dquot->dq_sb);
         int status = 0;
 
         mlog_entry("id=%u, type=%d", dquot->dq_id, dquot->dq_type);
@@ -726,16 +734,7 @@ static int ocfs2_acquire_dquot(struct dquot *dquot)
         status = ocfs2_lock_global_qf(oinfo, 1);
         if (status < 0)
                 goto out;
-        handle = ocfs2_start_trans(osb,
-                ocfs2_calc_qinit_credits(dquot->dq_sb, dquot->dq_type));
-        if (IS_ERR(handle)) {
-                status = PTR_ERR(handle);
-                mlog_errno(status);
-                goto out_ilock;
-        }
         status = dquot_acquire(dquot);
-        ocfs2_commit_trans(osb, handle);
-out_ilock:
         ocfs2_unlock_global_qf(oinfo, 1);
 out:
         mlog_exit(status);