nfs: fix redundant readdir request after get eof

When a directory contains 17 files (except . and ..), nfs client sends
a redundant readdir request after get eof.

A simple reproduce,
At NFS server, create a directory with 17 files under exported directory.
 # mkdir test
 # cd test
 # for i in {0..16}  ; do touch $i; done

At NFS client, no matter mounting through nfsv3 or nfsv4,
does ls (or ll) at the created test directory.

A tshark output likes following (for nfsv4),

 # tshark -i eth0 tcp port 2049 -Tfields -e ip.src -e ip.dst -e nfs -e nfs.cookie4

srcip   dstip   SEQUENCE, PUTFH, READDIR        0
dstip   srcip   SEQUENCE PUTFH READDIR  909539109313539306,2108391201987888856,2305312124304486544,2566335452463141496,2978225129081509984,4263037479923412583,4304697173036510679,4666703455469210097,4759208201298769007,4776701232145978803,5338408478512081262,5949498658935544804,5971526429894832903,6294060338267709855,6528840566229532529,8600463293536422524,9223372036854775807
srcip   dstip
srcip   dstip   SEQUENCE, PUTFH, READDIR        9223372036854775807
dstip   srcip   SEQUENCE PUTFH READDIR

The READDIR with cookie 9223372036854775807(0x7FFFFFFFFFFFFFFF) is redundant.

Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 8f3112e71a6a62a489b6796d7065fababa4f3416..e6a51fd94fea876630c2ea8349256ba09ebadb4d 100644 (file)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1089,6 +1089,17 @@ static void nfs_do_filldir(struct nfs_readdir_descriptor *desc,
        for (i = desc->cache_entry_index; i < array->size; i++) {
                struct nfs_cache_array_entry *ent;
 
+               /*
+                * nfs_readdir_handle_cache_misses return force clear at
+                * (cache_misses > NFS_READDIR_CACHE_MISS_THRESHOLD) for
+                * readdir heuristic, NFS_READDIR_CACHE_MISS_THRESHOLD + 1
+                * entries need be emitted here.
+                */
+               if (first_emit && i > NFS_READDIR_CACHE_MISS_THRESHOLD + 2) {
+                       desc->eob = true;
+                       break;
+               }
+
                ent = &array->array[i];
                if (!dir_emit(desc->ctx, ent->name, ent->name_len,
                    nfs_compat_user_ino64(ent->ino), ent->d_type)) {
@@ -1107,10 +1118,6 @@ static void nfs_do_filldir(struct nfs_readdir_descriptor *desc,
                        desc->ctx->pos = desc->dir_cookie;
                else
                        desc->ctx->pos++;
-               if (first_emit && i > NFS_READDIR_CACHE_MISS_THRESHOLD + 1) {
-                       desc->eob = true;
-                       break;
-               }
        }
        if (array->folio_is_eof)
                desc->eof = !desc->eob;