[PATCH 3/3] xfs: make the dax inode flag advisory

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

We have no ability to change S_DAX on an inode, which means that this
flag is purely advisory.  Remove all the (broken) code that tried to
change the state since it's cluttering up the code for no good reason.
If the kernel ever gains the ability to change S_DAX on the fly we can
always add this back.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/xfs_ioctl.c |   76 ----------------------------------------------------
 1 file changed, 76 deletions(-)


diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index c28f4263bac2..caa90d65aa74 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1002,12 +1002,6 @@ xfs_diflags_to_linux(
 		inode->i_flags |= S_NOATIME;
 	else
 		inode->i_flags &= ~S_NOATIME;
-#if 0	/* disabled until the flag switching races are sorted out */
-	if (xflags & FS_XFLAG_DAX)
-		inode->i_flags |= S_DAX;
-	else
-		inode->i_flags &= ~S_DAX;
-#endif
 }
 
 static int
@@ -1078,63 +1072,6 @@ xfs_ioctl_setattr_drain_writes(
 	return inode_drain_writes(inode);
 }
 
-/*
- * If we are changing DAX flags, we have to ensure the file is clean and any
- * cached objects in the address space are invalidated and removed. This
- * requires us to lock out other IO and page faults similar to a truncate
- * operation. The locks need to be held until the transaction has been committed
- * so that the cache invalidation is atomic with respect to the DAX flag
- * manipulation.
- *
- * The caller must use @join_flags to release the locks which are held on @ip
- * regardless of return value.
- */
-static int
-xfs_ioctl_setattr_dax_invalidate(
-	struct xfs_inode	*ip,
-	struct fsxattr		*fa,
-	int			*join_flags)
-{
-	struct inode		*inode = VFS_I(ip);
-	struct super_block	*sb = inode->i_sb;
-	int			error;
-
-	/*
-	 * It is only valid to set the DAX flag on regular files and
-	 * directories on filesystems where the block size is equal to the page
-	 * size. On directories it serves as an inherited hint so we don't
-	 * have to check the device for dax support or flush pagecache.
-	 */
-	if (fa->fsx_xflags & FS_XFLAG_DAX) {
-		if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
-			return -EINVAL;
-		if (S_ISREG(inode->i_mode) &&
-		    !bdev_dax_supported(xfs_find_bdev_for_inode(VFS_I(ip)),
-				sb->s_blocksize))
-			return -EINVAL;
-	}
-
-	/* If the DAX state is not changing, we have nothing to do here. */
-	if ((fa->fsx_xflags & FS_XFLAG_DAX) && IS_DAX(inode))
-		return 0;
-	if (!(fa->fsx_xflags & FS_XFLAG_DAX) && !IS_DAX(inode))
-		return 0;
-
-	if (S_ISDIR(inode->i_mode))
-		return 0;
-
-	/* lock, flush and invalidate mapping in preparation for flag change */
-	if (*join_flags == 0) {
-		*join_flags = XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL;
-		xfs_ilock(ip, *join_flags);
-		error = filemap_write_and_wait(inode->i_mapping);
-		if (error)
-			return error;
-	}
-
-	return invalidate_inode_pages2(inode->i_mapping);
-}
-
 /*
  * Set up the transaction structure for the setattr operation, checking that we
  * have permission to do so. On success, return a clean transaction and the
@@ -1347,19 +1284,6 @@ xfs_ioctl_setattr(
 		goto error_free_dquots;
 	}
 
-	/*
-	 * Changing DAX config may require inode locking for mapping
-	 * invalidation. These need to be held all the way to transaction commit
-	 * or cancel time, so need to be passed through to
-	 * xfs_ioctl_setattr_get_trans() so it can apply them to the join call
-	 * appropriately.
-	 */
-	code = xfs_ioctl_setattr_dax_invalidate(ip, fa, &join_flags);
-	if (code) {
-		xfs_iunlock(ip, join_flags);
-		goto error_free_dquots;
-	}
-
 	tp = xfs_ioctl_setattr_get_trans(ip, join_flags);
 	if (IS_ERR(tp)) {
 		code = PTR_ERR(tp);