gfs2: Fix fallocate chunk size

The chunk size of allocations in __gfs2_fallocate is calculated
incorrectly.  The size can collapse, causing __gfs2_fallocate to
allocate one block at a time, which is very inefficient.  This needs
fixing in two places:

In gfs2_quota_lock_check, always set ap->allowed to UINT_MAX to indicate
that there is no quota limit.  This fixes callers that rely on
ap->allowed to be set even when quotas are off.

In __gfs2_fallocate, reset max_blks to UINT_MAX in each iteration of the
loop to make sure that allocation limits from one resource group won't
spill over into another resource group.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

fs/gfs2/quota.h

@@ -45,6 +45,8 @@ static inline int gfs2_quota_lock_check(struct gfs2_inode *ip,
 {
 	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
 	int ret;
+
+	ap->allowed = UINT_MAX; /* Assume we are permitted a whole lot */
 	if (sdp->sd_args.ar_quota == GFS2_QUOTA_OFF)
 		return 0;
 	ret = gfs2_quota_lock(ip, NO_UID_QUOTA_CHANGE, NO_GID_QUOTA_CHANGE);