staging: lustre: fix bug in osc_enter_cache_try

The lustre-release patch commit bdc5bb52c554 ("LU-4933 osc:
Automatically increase the max_dirty_mb") changed

-       if (cli->cl_dirty + PAGE_CACHE_SIZE <= cli->cl_dirty_max &&
+       if (cli->cl_dirty_pages < cli->cl_dirty_max_pages &&

When this patch landed in Linux a couple of years later, it landed as

-       if (cli->cl_dirty + PAGE_SIZE <= cli->cl_dirty_max &&
+       if (cli->cl_dirty_pages <= cli->cl_dirty_max_pages &&

which is clearly different ('<=' vs '<'), and allows cl_dirty_pages to
increase beyond cl_dirty_max_pages - which causes a latter assertion
to fails.

Fixes: 3147b268 ("staging: lustre: osc: Automatically increase the max_dirty_mb")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/include/obd.h

@@ -191,7 +191,7 @@ struct client_obd {
 	struct sptlrpc_flavor    cl_flvr_mgc;   /* fixed flavor of mgc->mgs */
 
 	/* the grant values are protected by loi_list_lock below */
-	unsigned long		 cl_dirty_pages;	/* all _dirty_ in pahges */
+	unsigned long		 cl_dirty_pages;	/* all _dirty_ in pages */
 	unsigned long		 cl_dirty_max_pages;	/* allowed w/o rpc */
 	unsigned long		 cl_dirty_transit;	/* dirty synchronous */
 	unsigned long		 cl_avail_grant;	/* bytes of credit for ost */

drivers/staging/lustre/lustre/osc/osc_cache.c

@@ -1529,7 +1529,7 @@ static int osc_enter_cache_try(struct client_obd *cli,
 	if (rc < 0)
 		return 0;
 
-	if (cli->cl_dirty_pages <= cli->cl_dirty_max_pages &&
+	if (cli->cl_dirty_pages < cli->cl_dirty_max_pages &&
 	    atomic_long_read(&obd_dirty_pages) + 1 <= obd_max_dirty_pages) {
 		osc_consume_write_grant(cli, &oap->oap_brw_page);
 		if (transient) {