xfs: move xfs_dialloc_roll() into xfs_dialloc()

Get rid of the confusing ialloc_context and failure handling around
xfs_dialloc() by moving xfs_dialloc_roll() into xfs_dialloc().

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_ialloc.c

@@ -1682,7 +1682,7 @@ xfs_dialloc_ag(
 	return error;
 }
 
-int
+static int
 xfs_dialloc_roll(
 	struct xfs_trans	**tpp,
 	struct xfs_buf		*agibp)
@@ -1723,30 +1723,18 @@ xfs_dialloc_roll(
  * Mode is used to tell whether the new inode will need space, and whether it
  * is a directory.
  *
- * This function is designed to be called twice if it has to do an allocation
- * to make more free inodes.  On the first call, *IO_agbp should be set to NULL.
- * If an inode is available without having to performn an allocation, an inode
- * number is returned.  In this case, *IO_agbp is set to NULL.  If an allocation
- * needs to be done, xfs_dialloc returns the current AGI buffer in *IO_agbp.
- * The caller should then commit the current transaction, allocate a
- * new transaction, and call xfs_dialloc() again, passing in the previous value
- * of *IO_agbp.  IO_agbp should be held across the transactions. Since the AGI
- * buffer is locked across the two calls, the second call is guaranteed to have
- * a free inode available.
- *
  * Once we successfully pick an inode its number is returned and the on-disk
  * data structures are updated.  The inode itself is not read in, since doing so
  * would break ordering constraints with xfs_reclaim.
  */
 int
 xfs_dialloc(
-	struct xfs_trans	*tp,
+	struct xfs_trans	**tpp,
 	xfs_ino_t		parent,
 	umode_t			mode,
-	struct xfs_buf		**IO_agbp,
 	xfs_ino_t		*inop)
 {
-	struct xfs_mount	*mp = tp->t_mountp;
+	struct xfs_mount	*mp = (*tpp)->t_mountp;
 	struct xfs_buf		*agbp;
 	xfs_agnumber_t		agno;
 	int			error;
@@ -1757,21 +1745,11 @@ xfs_dialloc(
 	struct xfs_ino_geometry	*igeo = M_IGEO(mp);
 	bool			okalloc = true;
 
-	if (*IO_agbp) {
-		/*
-		 * If the caller passes in a pointer to the AGI buffer,
-		 * continue where we left off before.  In this case, we
-		 * know that the allocation group has free inodes.
-		 */
-		agbp = *IO_agbp;
-		goto out_alloc;
-	}
-
 	/*
 	 * We do not have an agbp, so select an initial allocation
 	 * group for inode allocation.
 	 */
-	start_agno = xfs_ialloc_ag_select(tp, parent, mode);
+	start_agno = xfs_ialloc_ag_select(*tpp, parent, mode);
 	if (start_agno == NULLAGNUMBER) {
 		*inop = NULLFSINO;
 		return 0;
@@ -1806,7 +1784,7 @@ xfs_dialloc(
 		}
 
 		if (!pag->pagi_init) {
-			error = xfs_ialloc_pagi_init(mp, tp, agno);
+			error = xfs_ialloc_pagi_init(mp, *tpp, agno);
 			if (error)
 				goto out_error;
 		}
@@ -1821,7 +1799,7 @@ xfs_dialloc(
 		 * Then read in the AGI buffer and recheck with the AGI buffer
 		 * lock held.
 		 */
-		error = xfs_ialloc_read_agi(mp, tp, agno, &agbp);
+		error = xfs_ialloc_read_agi(mp, *tpp, agno, &agbp);
 		if (error)
 			goto out_error;
 
@@ -1834,9 +1812,9 @@ xfs_dialloc(
 			goto nextag_relse_buffer;
 
 
-		error = xfs_ialloc_ag_alloc(tp, agbp, &ialloced);
+		error = xfs_ialloc_ag_alloc(*tpp, agbp, &ialloced);
 		if (error) {
-			xfs_trans_brelse(tp, agbp);
+			xfs_trans_brelse(*tpp, agbp);
 
 			if (error != -ENOSPC)
 				goto out_error;
@@ -1848,21 +1826,25 @@ xfs_dialloc(
 
 		if (ialloced) {
 			/*
-			 * We successfully allocated some inodes, return
-			 * the current context to the caller so that it
-			 * can commit the current transaction and call
-			 * us again where we left off.
+			 * We successfully allocated space for an inode cluster
+			 * in this AG.  Roll the transaction so that we can
+			 * allocate one of the new inodes.
 			 */
 			ASSERT(pag->pagi_freecount > 0);
 			xfs_perag_put(pag);
 
-			*IO_agbp = agbp;
+			error = xfs_dialloc_roll(tpp, agbp);
+			if (error) {
+				xfs_buf_relse(agbp);
+				return error;
+			}
+
 			*inop = NULLFSINO;
-			return 0;
+			goto out_alloc;
 		}
 
 nextag_relse_buffer:
-		xfs_trans_brelse(tp, agbp);
+		xfs_trans_brelse(*tpp, agbp);
 nextag:
 		xfs_perag_put(pag);
 		if (++agno == mp->m_sb.sb_agcount)
@@ -1874,8 +1856,7 @@ xfs_dialloc(
 	}
 
 out_alloc:
-	*IO_agbp = NULL;
-	return xfs_dialloc_ag(tp, agbp, parent, inop);
+	return xfs_dialloc_ag(*tpp, agbp, parent, inop);
 out_error:
 	xfs_perag_put(pag);
 	return error;

fs/xfs/libxfs/xfs_ialloc.h

@@ -32,39 +32,20 @@ xfs_make_iptr(struct xfs_mount *mp, struct xfs_buf *b, int o)
 	return xfs_buf_offset(b, o << (mp)->m_sb.sb_inodelog);
 }
 
-int
-xfs_dialloc_roll(
-	struct xfs_trans	**tpp,
-	struct xfs_buf		*agibp);
-
 /*
  * Allocate an inode on disk.
  * Mode is used to tell whether the new inode will need space, and whether
  * it is a directory.
  *
- * To work within the constraint of one allocation per transaction,
- * xfs_dialloc() is designed to be called twice if it has to do an
- * allocation to make more free inodes.  If an inode is
- * available without an allocation, agbp would be set to the current
- * agbp and alloc_done set to false.
- * If an allocation needed to be done, agbp would be set to the
- * inode header of the allocation group and alloc_done set to true.
- * The caller should then commit the current transaction and allocate a new
- * transaction.  xfs_dialloc() should then be called again with
- * the agbp value returned from the previous call.
- *
  * Once we successfully pick an inode its number is returned and the
  * on-disk data structures are updated.  The inode itself is not read
  * in, since doing so would break ordering constraints with xfs_reclaim.
- *
- * *agbp should be set to NULL on the first call, *alloc_done set to FALSE.
  */
 int					/* error */
 xfs_dialloc(
-	struct xfs_trans *tp,		/* transaction pointer */
+	struct xfs_trans **tpp,		/* double pointer of transaction */
 	xfs_ino_t	parent,		/* parent inode (directory) */
 	umode_t		mode,		/* mode bits for new inode */
-	struct xfs_buf	**agbp,		/* buf for a.g. inode header */
 	xfs_ino_t	*inop);		/* inode number allocated */
 
 /*

fs/xfs/xfs_inode.c

@@ -909,7 +909,6 @@ xfs_dir_ialloc(
 	prid_t			prid,
 	struct xfs_inode	**ipp)
 {
-	struct xfs_buf		*ialloc_context = NULL;
 	xfs_ino_t		parent_ino = dp ? dp->i_ino : 0;
 	xfs_ino_t		ino;
 	int			error;
@@ -918,43 +917,12 @@ xfs_dir_ialloc(
 
 	/*
 	 * Call the space management code to pick the on-disk inode to be
-	 * allocated and replenish the freelist.  Since we can only do one
-	 * allocation per transaction without deadlocks, we will need to
-	 * commit the current transaction and start a new one.
-	 * If xfs_dialloc did an allocation to replenish the freelist, it
-	 * returns the bp containing the head of the freelist as
-	 * ialloc_context. We will hold a lock on it across the transaction
-	 * commit so that no other process can steal the inode(s) that we've
-	 * just allocated.
-	 */
-	error = xfs_dialloc(*tpp, parent_ino, mode, &ialloc_context, &ino);
+	 * allocated.
+	 */
+	error = xfs_dialloc(tpp, parent_ino, mode, &ino);
 	if (error)
 		return error;
 
-	/*
-	 * If the AGI buffer is non-NULL, then we were unable to get an
-	 * inode in one operation.  We need to commit the current
-	 * transaction and call xfs_dialloc() again.  It is guaranteed
-	 * to succeed the second time.
-	 */
-	if (ialloc_context) {
-		error = xfs_dialloc_roll(tpp, ialloc_context);
-		if (error) {
-			xfs_buf_relse(ialloc_context);
-			return error;
-		}
-		/*
-		 * Call dialloc again. Since we've locked out all other
-		 * allocations in this allocation group, this call should
-		 * always succeed.
-		 */
-		error = xfs_dialloc(*tpp, parent_ino, mode, &ialloc_context,
-				&ino);
-		if (error)
-			return error;
-		ASSERT(!ialloc_context);
-	}
-
 	if (ino == NULLFSINO)
 		return -ENOSPC;