linux-kernel - [PATCH v2 2/3] 9p: Introduce option for negative dentry cache retention time

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Message-ID: <7e38e7bd31674208ab2b0de909c0744feda2c03f.1769013622.git.repk@triplefau.lt>
Date: Wed, 21 Jan 2026 20:56:09 +0100
From: Remi Pommarel <repk@...plefau.lt>
To: v9fs@...ts.linux.dev
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
 Eric Van Hensbergen <ericvh@...nel.org>,
 Latchesar Ionkov <lucho@...kov.net>,
 Dominique Martinet <asmadeus@...ewreck.org>,
 Christian Schoenebeck <linux_oss@...debyte.com>,
 Remi Pommarel <repk@...plefau.lt>
Subject: [PATCH v2 2/3] 9p: Introduce option for negative dentry cache
 retention time

Add support for a new mount option in v9fs that allows users to specify
the duration for which negative dentries are retained in the cache. The
retention time can be set in milliseconds using the ndentrytmo option.

For the same consistency reasons, this option should only be used in
exclusive or read-only mount scenarios, aligning with the cache=loose
usage.

Signed-off-by: Remi Pommarel <repk@...plefau.lt>
---
 fs/9p/v9fs.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index 1da7ab186478..f58a2718e412 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -39,7 +39,7 @@ enum {
 	 * source if we rejected it as EINVAL */
 	Opt_source,
 	/* Options that take integer arguments */
-	Opt_debug, Opt_dfltuid, Opt_dfltgid, Opt_afid,
+	Opt_debug, Opt_dfltuid, Opt_dfltgid, Opt_afid, Opt_ndentrytmo,
 	/* String options */
 	Opt_uname, Opt_remotename, Opt_cache, Opt_cachetag,
 	/* Options that take no arguments */
@@ -93,6 +93,7 @@ const struct fs_parameter_spec v9fs_param_spec[] = {
 	fsparam_string	("access",	Opt_access),
 	fsparam_flag	("posixacl",	Opt_posixacl),
 	fsparam_u32	("locktimeout",	Opt_locktimeout),
+	fsparam_s32	("ndentrytmo",	Opt_ndentrytmo),
 
 	/* client options */
 	fsparam_u32	("msize",	Opt_msize),
@@ -159,6 +160,8 @@ int v9fs_show_options(struct seq_file *m, struct dentry *root)
 			   from_kgid_munged(&init_user_ns, v9ses->dfltgid));
 	if (v9ses->afid != ~0)
 		seq_printf(m, ",afid=%u", v9ses->afid);
+	if (v9ses->ndentry_timeout != 0)
+		seq_printf(m, ",ndentrytmo=%d", v9ses->ndentry_timeout);
 	if (strcmp(v9ses->uname, V9FS_DEFUSER) != 0)
 		seq_printf(m, ",uname=%s", v9ses->uname);
 	if (strcmp(v9ses->aname, V9FS_DEFANAME) != 0)
@@ -337,6 +340,10 @@ int v9fs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		session_opts->session_lock_timeout = (long)result.uint_32 * HZ;
 		break;
 
+	case Opt_ndentrytmo:
+		session_opts->ndentry_timeout = result.int_32;
+		break;
+
 	/* Options for client */
 	case Opt_msize:
 		if (result.uint_32 < 4096) {
-- 
2.50.1