X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=blobdiff_plain;f=lustre%2Fosc%2Fosc_request.c;h=074308e63b71a9076ad2375f6cc08149f9b830e8;hp=68452b059153f1557d9f6d5489280e8dd6ff8ddb;hb=e817ad5b75570e433a70228ce9226e910bc35188;hpb=9f604f5da06a2aa428388905ca9158b128e5016c

diff --git a/lustre/osc/osc_request.c b/lustre/osc/osc_request.c
index 68452b0..074308e 100644
--- 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);
 
-        /* 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;