Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To:     Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>, Jens Axboe <axboe@kernel.dk>,
        Chaitanya Kulkarni <kch@nvidia.com>,
        Kees Cook <keescook@chromium.org>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Chuck Lever <chuck.lever@oracle.com>,
        Baptiste Lepers <baptiste.lepers@gmail.com>,
        linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     "Fabio M. De Francesco" <fmdefrancesco@gmail.com>,
        Ira Weiny <ira.weiny@intel.com>
Subject: [PATCH] nfs: Replace kmap() with kmap_local_page()
Date:   Tue, 28 Jun 2022 20:24:26 +0200
Message-Id: <20220628182426.944-1-fmdefrancesco@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The use of kmap() is being deprecated in favor of kmap_local_page().

With kmap_local_page(), the mapping is per thread, CPU local and not
globally visible. Furthermore, the mapping can be acquired from any context
(including interrupts).

Therefore, use kmap_local_page() in nfs_do_filldir() because this mapping
is per thread, CPU local, and not globally visible.

Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---

I cannot test this patch for several reasons. While these changes seem safe
and trivial, I would feel better if people familiar with NFS could take the
time to properly test this patch. Thank you.

 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 0c4e8dd6aa96..8b89f10d8899 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1084,7 +1084,7 @@ static void nfs_do_filldir(struct nfs_readdir_descriptor *desc,
 	struct nfs_cache_array *array;
 	unsigned int i;
 
-	array = kmap(desc->page);
+	array = kmap_local_page(desc->page);
 	for (i = desc->cache_entry_index; i < array->size; i++) {
 		struct nfs_cache_array_entry *ent;
 
@@ -1110,7 +1110,7 @@ static void nfs_do_filldir(struct nfs_readdir_descriptor *desc,
 	if (array->page_is_eof)
 		desc->eof = !desc->eob;
 
-	kunmap(desc->page);
+	kunmap_local(array);
 	dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling ended @ cookie %llu\n",
 			(unsigned long long)desc->dir_cookie);
 }
-- 
2.36.1