b=22074 block if grant is available or maybe available soon

[fs/lustre-release.git] / lustre / osc / osc_request.c

diff --git a/lustre/osc/osc_request.c b/lustre/osc/osc_request.c
index 68452b0..074308e 100644 (file)
--- a/lustre/osc/osc_request.c
+++ b/lustre/osc/osc_request.c
@@ -2818,10 +2818,14 @@ static int osc_enter_cache(const struct lu_env *env,
             osc_enter_cache_try(env, cli, loi, oap, 0))
                 RETURN(0);
 
             osc_enter_cache_try(env, cli, loi, oap, 0))
                 RETURN(0);
 

-        /* Make sure that there are write rpcs in flight to wait for.  This
-         * is a little silly as this object may not have any pending but
-         * other objects sure might. */
-        if (cli->cl_w_in_flight) {
+        /* It is safe to block as a cache waiter as long as there is grant
+         * space available or the hope of additional grant being returned
+         * when an in flight write completes.  Using the write back cache
+         * if possible is preferable to sending the data synchronously
+         * because write pages can then be merged in to large requests.
+         * The addition of this cache waiter will causing pending write
+         * pages to be sent immediately. */
+        if (cli->cl_w_in_flight || cli->cl_avail_grant >= CFS_PAGE_SIZE) {

                 cfs_list_add_tail(&ocw.ocw_entry, &cli->cl_cache_waiters);
                 cfs_waitq_init(&ocw.ocw_waitq);
                 ocw.ocw_oap = oap;
                 cfs_list_add_tail(&ocw.ocw_entry, &cli->cl_cache_waiters);
                 cfs_waitq_init(&ocw.ocw_waitq);
                 ocw.ocw_oap = oap;