queue-6.12/fs-nfs-fix-readdir-slow-start-regression.patch

From 77f3db922e8c8a251c448d1030cc6d25657775f5 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Sat, 27 Dec 2025 12:46:29 +0200
Subject: fs/nfs: Fix readdir slow-start regression

From: Sagi Grimberg <sagi@grimberg.me>

[ Upstream commit 42e7c876b182da65723700f6bc507a8aecb10d3b ]

Commit 580f236737d1 ("NFS: Adjust the amount of readahead
performed by NFS readdir") reduces the amount of readahead names
caching done by the client.

The downside of this approach is READDIR now may suffer from
a slow-start issue, where initially it will fetch names that fit
in a single page, then in 2, 4, 8 until the maximum supported
transfer size (usually 1M).

This patch tries to take a balanced approach between mitigating
the slow-start issue still maintaining some efficiency gains.

Fixes: 580f236737d1 ("NFS: Adjust the amount of readahead performed by NFS readdir")
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfs/dir.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 1cf1b2ddbf549..5b90f8727e683 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -72,7 +72,7 @@ const struct address_space_operations nfs_dir_aops = {
 	.free_folio = nfs_readdir_clear_array,
 };
 
-#define NFS_INIT_DTSIZE PAGE_SIZE
+#define NFS_INIT_DTSIZE SZ_64K
 
 static struct nfs_open_dir_context *
 alloc_nfs_open_dir_context(struct inode *dir)
@@ -83,7 +83,7 @@ alloc_nfs_open_dir_context(struct inode *dir)
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
 	if (ctx != NULL) {
 		ctx->attr_gencount = nfsi->attr_gencount;
-		ctx->dtsize = NFS_INIT_DTSIZE;
+		ctx->dtsize = min(NFS_SERVER(dir)->dtsize, NFS_INIT_DTSIZE);
 		spin_lock(&dir->i_lock);
 		if (list_empty(&nfsi->open_files) &&
 		    (nfsi->cache_validity & NFS_INO_DATA_INVAL_DEFER))
-- 
2.51.0