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>

diff --git a/fs/ocfs2/journal.h b/fs/ocfs2/journal.h
index 4a4d3b5..2c3222a 100644 (file)
--- 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 d604a6a..bf7742d 100644 (file)
--- 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);