[XFS] Stack footprint reduction for xfs_swapext (used from xfs_fsr)

SGI-PV: 913332
SGI-Modid: xfs-linux:xfs-kern:198926a
Signed-off-by: Eric Sandeen <sandeen@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>

fs/xfs/xfs_dfrag.c

@@ -65,9 +65,9 @@
  */
 int
 xfs_swapext(
-	xfs_swapext_t	__user *sxp)
+	xfs_swapext_t	__user *sxu)
 {
-	xfs_swapext_t	sx;
+	xfs_swapext_t	*sxp;
 	xfs_inode_t     *ip=NULL, *tip=NULL, *ips[2];
 	xfs_trans_t     *tp;
 	xfs_mount_t     *mp;
@@ -76,20 +76,29 @@ xfs_swapext(
 	vnode_t		*vp, *tvp;
 	bhv_desc_t      *bdp, *tbdp;
 	vn_bhv_head_t   *bhp, *tbhp;
-	uint		lock_flags=0;
+	static uint	lock_flags = XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL;
 	int		ilf_fields, tilf_fields;
 	int		error = 0;
-	xfs_ifork_t	tempif, *ifp, *tifp;
+	xfs_ifork_t	*tempifp, *ifp, *tifp;
 	__uint64_t	tmp;
 	int		aforkblks = 0;
 	int		taforkblks = 0;
-	int		locked = 0;
+	char		locked = 0;
 
-	if (copy_from_user(&sx, sxp, sizeof(sx)))
-		return XFS_ERROR(EFAULT);
+	sxp = kmem_alloc(sizeof(xfs_swapext_t), KM_MAYFAIL);
+	tempifp = kmem_alloc(sizeof(xfs_ifork_t), KM_MAYFAIL);
+	if (!sxp || !tempifp) {
+		error = XFS_ERROR(ENOMEM);
+		goto error0;
+	}
+
+	if (copy_from_user(sxp, sxu, sizeof(xfs_swapext_t))) {
+		error = XFS_ERROR(EFAULT);
+		goto error0;
+	}
 
 	/* Pull information for the target fd */
-	if (((fp = fget((int)sx.sx_fdtarget)) == NULL) ||
+	if (((fp = fget((int)sxp->sx_fdtarget)) == NULL) ||
 	    ((vp = LINVFS_GET_VP(fp->f_dentry->d_inode)) == NULL))  {
 		error = XFS_ERROR(EINVAL);
 		goto error0;
@@ -104,7 +113,7 @@ xfs_swapext(
 		ip = XFS_BHVTOI(bdp);
 	}
 
-	if (((tfp = fget((int)sx.sx_fdtmp)) == NULL) ||
+	if (((tfp = fget((int)sxp->sx_fdtmp)) == NULL) ||
 	    ((tvp = LINVFS_GET_VP(tfp->f_dentry->d_inode)) == NULL)) {
 		error = XFS_ERROR(EINVAL);
 		goto error0;
@@ -131,7 +140,7 @@ xfs_swapext(
 
 	mp = ip->i_mount;
 
-	sbp = &sx.sx_stat;
+	sbp = &sxp->sx_stat;
 
 	if (XFS_FORCED_SHUTDOWN(mp)) {
 		error =  XFS_ERROR(EIO);
@@ -148,7 +157,7 @@ xfs_swapext(
 		ips[0] = tip;
 		ips[1] = ip;
 	}
-	lock_flags = XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL;
+
 	xfs_lock_inodes(ips, 2, 0, lock_flags);
 
 	/* Check permissions */
@@ -192,9 +201,9 @@ xfs_swapext(
 	}
 
 	/* Verify all data are being swapped */
-	if (sx.sx_offset != 0 ||
-	    sx.sx_length != ip->i_d.di_size ||
-	    sx.sx_length != tip->i_d.di_size) {
+	if (sxp->sx_offset != 0 ||
+	    sxp->sx_length != ip->i_d.di_size ||
+	    sxp->sx_length != tip->i_d.di_size) {
 		error = XFS_ERROR(EFAULT);
 		goto error0;
 	}
@@ -255,7 +264,8 @@ xfs_swapext(
 		xfs_iunlock(ip,  XFS_IOLOCK_EXCL);
 		xfs_iunlock(tip, XFS_IOLOCK_EXCL);
 		xfs_trans_cancel(tp, 0);
-		return error;
+		locked = 0;
+		goto error0;
 	}
 	xfs_lock_inodes(ips, 2, 0, XFS_ILOCK_EXCL);
 
@@ -266,10 +276,8 @@ xfs_swapext(
 	     (ip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL)) {
 		error = xfs_bmap_count_blocks(tp, ip, XFS_ATTR_FORK, &aforkblks);
 		if (error) {
-			xfs_iunlock(ip,  lock_flags);
-			xfs_iunlock(tip, lock_flags);
 			xfs_trans_cancel(tp, 0);
-			return error;
+			goto error0;
 		}
 	}
 	if ( ((XFS_IFORK_Q(tip) != 0) && (tip->i_d.di_anextents > 0)) &&
@@ -277,10 +285,8 @@ xfs_swapext(
 		error = xfs_bmap_count_blocks(tp, tip, XFS_ATTR_FORK,
 			&taforkblks);
 		if (error) {
-			xfs_iunlock(ip,  lock_flags);
-			xfs_iunlock(tip, lock_flags);
 			xfs_trans_cancel(tp, 0);
-			return error;
+			goto error0;
 		}
 	}
 
@@ -289,9 +295,9 @@ xfs_swapext(
 	 */
 	ifp = &ip->i_df;
 	tifp = &tip->i_df;
-	tempif = *ifp;	/* struct copy */
-	*ifp = *tifp;	/* struct copy */
-	*tifp = tempif;	/* struct copy */
+	*tempifp = *ifp;	/* struct copy */
+	*ifp = *tifp;		/* struct copy */
+	*tifp = *tempifp;	/* struct copy */
 
 	/*
 	 * Fix the on-disk inode values
@@ -369,11 +375,7 @@ xfs_swapext(
 	}
 
 	error = xfs_trans_commit(tp, XFS_TRANS_SWAPEXT, NULL);
-
-	fput(fp);
-	fput(tfp);
-
-	return error;
+	locked = 0;
 
  error0:
 	if (locked) {
@@ -381,8 +383,15 @@ xfs_swapext(
 		xfs_iunlock(tip, lock_flags);
 	}
 
-	if (fp != NULL) fput(fp);
-	if (tfp != NULL) fput(tfp);
+	if (fp != NULL)
+		fput(fp);
+	if (tfp != NULL)
+		fput(tfp);
+
+	if (sxp != NULL)
+		kmem_free(sxp, sizeof(xfs_swapext_t));
+	if (tempifp != NULL)
+		kmem_free(tempifp, sizeof(xfs_ifork_t));
 
 	return error;
 }