staging: lustre: osc: fix max_dirty_mb tunable setting limit

The OSC tunable max_dirty_mb must be set to a value strictly lower
than 2048, as it is assumed by OSS in ofd_grant_alloc() routine.
Signed-off-by: Gregoire Pichon <gregoire.pichon@bull.net>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-7218
Reviewed-on: http://review.whamcloud.com/16652Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/osc/lproc_osc.c

@@ -162,7 +162,7 @@ static ssize_t max_dirty_mb_store(struct kobject *kobj,
 	pages_number *= 1 << (20 - PAGE_SHIFT); /* MB -> pages */
 
 	if (pages_number <= 0 ||
-	    pages_number > OSC_MAX_DIRTY_MB_MAX << (20 - PAGE_SHIFT) ||
+	    pages_number >= OSC_MAX_DIRTY_MB_MAX << (20 - PAGE_SHIFT) ||
 	    pages_number > totalram_pages / 4) /* 1/4 of RAM */
 		return -ERANGE;