LU-12142 readahead: limit over reservation

[fs/lustre-release.git] / lustre / llite / rw.c

diff --git a/lustre/llite/rw.c b/lustre/llite/rw.c
index 9202524..743e2c1 100644 (file)
--- a/lustre/llite/rw.c
+++ b/lustre/llite/rw.c
@@ -777,6 +777,14 @@ static int ll_readahead(const struct lu_env *env, struct cl_io *io,
                        vio->vui_ra_start_idx + vio->vui_ra_pages - 1;
                pages_min = vio->vui_ra_start_idx + vio->vui_ra_pages -
                                ria->ria_start_idx;
+                /**
+                 * For performance reason, exceeding @ra_max_pages
+                 * are allowed, but this should be limited with RPC
+                 * size in case a large block size read issued. Trim
+                 * to RPC boundary.
+                 */
+               pages_min = min(pages_min, ras->ras_rpc_pages -
+                               (ria->ria_start_idx % ras->ras_rpc_pages));
        }
 
        /* don't over reserved for mmap range read */