linux-kernel - [PATCH RFC DRAFT 04/50] pidfs: raise DCACHE

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Message-Id: <20251021-work-namespace-nstree-listns-v1-4-ad44261a8a5b@kernel.org>
Date: Tue, 21 Oct 2025 13:43:10 +0200
From: Christian Brauner <brauner@...nel.org>
To: linux-fsdevel@...r.kernel.org, Josef Bacik <josef@...icpanda.com>, 
 Jeff Layton <jlayton@...nel.org>
Cc: Jann Horn <jannh@...gle.com>, Mike Yuan <me@...dnzj.com>, 
 Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, 
 Lennart Poettering <mzxreary@...inter.de>, 
 Daan De Meyer <daan.j.demeyer@...il.com>, Aleksa Sarai <cyphar@...har.com>, 
 Amir Goldstein <amir73il@...il.com>, Tejun Heo <tj@...nel.org>, 
 Johannes Weiner <hannes@...xchg.org>, Thomas Gleixner <tglx@...utronix.de>, 
 Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
 linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, bpf@...r.kernel.org, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 netdev@...r.kernel.org, Arnd Bergmann <arnd@...db.de>, 
 Christian Brauner <brauner@...nel.org>
Subject: [PATCH RFC DRAFT 04/50] pidfs: raise DCACHE_DONTCACHE explicitly

While pidfs dentries are never hashed and thus retain_dentry() will never
consider them for placing them on the LRU it isn't great to always have
to go and remember that. Raise DCACHE_DONTCACHE explicitly as a visual
marker that dentries aren't kept but freed immediately instead.

Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 fs/pidfs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/pidfs.c b/fs/pidfs.c
index 0ef5b47d796a..db236427fc2c 100644
--- a/fs/pidfs.c
+++ b/fs/pidfs.c
@@ -1022,6 +1022,7 @@ static int pidfs_init_fs_context(struct fs_context *fc)
 
 	fc->s_iflags |= SB_I_NOEXEC;
 	fc->s_iflags |= SB_I_NODEV;
+	ctx->s_d_flags |= DCACHE_DONTCACHE;
 	ctx->ops = &pidfs_sops;
 	ctx->eops = &pidfs_export_operations;
 	ctx->dops = &pidfs_dentry_operations;

-- 
2.47.3