xfs: trim the mapp array accordingly in xfs_da_grow_inode_int

Take a look at the for-loop in xfs_da_grow_inode_int:
======
for(){
        nmap = min(XFS_BMAP_MAX_NMAP, count);
        ...
        error = xfs_bmapi_write(...,&mapp[mapi], &nmap);//(..., $1, $2)
        ...
        mapi += nmap;
}
=====
where $1 stands for the start address of the array,
while $2 is used to indicate the size of the array.

The array $1 will advance by $nmap in each iteration after
the allocation of extents.
But the size $2 still remains unchanged, which is determined by
min(XFS_BMAP_MAX_NMAP, count).

It seems that it has forgotten to trim the mapp array after each
iteration, so change it.
Signed-off-by: Shida Zhang <zhangshida@kylinos.cn>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_da_btree.c

@@ -2192,8 +2192,8 @@ xfs_da_grow_inode_int(
 		 */
 		mapp = kmem_alloc(sizeof(*mapp) * count, 0);
 		for (b = *bno, mapi = 0; b < *bno + count; ) {
-			nmap = min(XFS_BMAP_MAX_NMAP, count);
 			c = (int)(*bno + count - b);
+			nmap = min(XFS_BMAP_MAX_NMAP, c);
 			error = xfs_bmapi_write(tp, dp, b, c,
 					xfs_bmapi_aflag(w)|XFS_BMAPI_METADATA,
 					args->total, &mapp[mapi], &nmap);