Merge branch 'xfs-dax-fixes-for-4.5' into for-next

fs/xfs/xfs_file.c

@@ -402,19 +402,26 @@ xfs_file_splice_read(
 	if (XFS_FORCED_SHUTDOWN(ip->i_mount))
 		return -EIO;
 
-	xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
-
 	trace_xfs_file_splice_read(ip, count, *ppos, ioflags);
 
-	/* for dax, we need to avoid the page cache */
-	if (IS_DAX(VFS_I(ip)))
-		ret = default_file_splice_read(infilp, ppos, pipe, count, flags);
-	else
-		ret = generic_file_splice_read(infilp, ppos, pipe, count, flags);
-	if (ret > 0)
-		XFS_STATS_ADD(ip->i_mount, xs_read_bytes, ret);
+	/*
+	 * DAX inodes cannot ues the page cache for splice, so we have to push
+	 * them through the VFS IO path. This means it goes through
+	 * ->read_iter, which for us takes the XFS_IOLOCK_SHARED. Hence we
+	 * cannot lock the splice operation at this level for DAX inodes.
+	 */
+	if (IS_DAX(VFS_I(ip))) {
+		ret = default_file_splice_read(infilp, ppos, pipe, count,
+					       flags);
+		goto out;
+	}
 
+	xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
+	ret = generic_file_splice_read(infilp, ppos, pipe, count, flags);
 	xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
+out:
+	if (ret > 0)
+		XFS_STATS_ADD(ip->i_mount, xs_read_bytes, ret);
 	return ret;
 }
 

fs/xfs/xfs_iomap.c

@@ -203,15 +203,20 @@ xfs_iomap_write_direct(
 	 * this outside the transaction context, but if we commit and then crash
 	 * we may not have zeroed the blocks and this will be exposed on
 	 * recovery of the allocation. Hence we must zero before commit.
+	 *
 	 * Further, if we are mapping unwritten extents here, we need to zero
 	 * and convert them to written so that we don't need an unwritten extent
 	 * callback for DAX. This also means that we need to be able to dip into
-	 * the reserve block pool if there is no space left but we need to do
-	 * unwritten extent conversion.
+	 * the reserve block pool for bmbt block allocation if there is no space
+	 * left but we need to do unwritten extent conversion.
 	 */
+
 	if (IS_DAX(VFS_I(ip))) {
 		bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;
-		tp->t_flags |= XFS_TRANS_RESERVE;
+		if (ISUNWRITTEN(imap)) {
+			tp->t_flags |= XFS_TRANS_RESERVE;
+			resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
+		}
 	}
 	error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write,
 				  resblks, resrtextents);