linux-kernel - [PATCH 5.15 094/172] NFS: Dont overfill uncached readdir pages

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Date:   Mon, 14 Feb 2022 10:25:52 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 094/172] NFS: Dont overfill uncached readdir pages

From: trondmy@...nel.org <trondmy@...nel.org>

[ Upstream commit d9c4e39c1f8f8a8ebaccf00b8f22c14364b2d27e ]

If we're doing an uncached read of the directory, then we ideally want
to read only the exact set of entries that will fit in the buffer
supplied by the getdents() system call. So unlike the case where we're
reading into the page cache, let's send only one READDIR call, before
trying to fill up the buffer.

Fixes: 35df59d3ef69 ("NFS: Reduce number of RPC calls when doing uncached readdir")
Signed-off-by: Trond Myklebust <trond.myklebust@...merspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/nfs/dir.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index db6abd4733bfb..af7881bc6b3e6 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -870,7 +870,8 @@ static int nfs_readdir_xdr_to_array(struct nfs_readdir_descriptor *desc,
 
 		status = nfs_readdir_page_filler(desc, entry, pages, pglen,
 						 arrays, narrays);
-	} while (!status && nfs_readdir_page_needs_filling(page));
+	} while (!status && nfs_readdir_page_needs_filling(page) &&
+		page_mapping(page));
 
 	nfs_readdir_free_pages(pages, array_size);
 out_release_label:
-- 
2.34.1