pNFS: Don't send LAYOUTGET on OPEN for read, if we already have cache…

…d data If we're only opening the file for reading, and the file is empty and/or we already have cached data, then heuristically optimise away the LAYOUTGET. Signed-off-by: Trond Myklebust <[email protected]>
cail · May 31, 2018 · 64294b0 · 64294b0
1 parent 8dc9656
commit 64294b0
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
@@ -2046,6 +2046,11 @@ static void _lgopen_prepare_attached(struct nfs4_opendata *data,
 	struct nfs4_layoutget *lgp;
 	struct pnfs_layout_hdr *lo;
 
+	/* Heuristic: don't send layoutget if we have cached data */
+	if (rng.iomode == IOMODE_READ &&
+	   (i_size_read(ino) == 0 || ino->i_mapping->nrpages != 0))
+		return;
+
 	lo = _pnfs_grab_empty_layout(ino, ctx);
 	if (!lo)
 		return;