diff mbox series

[v3,08/21] fast_dput(): new rules for refcount

Message ID	20231124060422.576198-8-viro@zeniv.linux.org.uk (mailing list archive)
State	New, archived
Headers	show Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b="t84e8Fxe" From: Al Viro <viro@zeniv.linux.org.uk> To: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org>, Christian Brauner <brauner@kernel.org>, linux-kernel@vger.kernel.org Subject: [PATCH v3 08/21] fast_dput(): new rules for refcount Date: Fri, 24 Nov 2023 06:04:09 +0000 Message-Id: <20231124060422.576198-8-viro@zeniv.linux.org.uk> In-Reply-To: <20231124060422.576198-1-viro@zeniv.linux.org.uk> References: <20231124060200.GR38156@ZenIV> <20231124060422.576198-1-viro@zeniv.linux.org.uk> Precedence: bulk MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: Al Viro <viro@ftp.linux.org.uk>
Series	[v3,01/21] switch nfsd_client_rmdir() to use of simple_recursive_removal() \| expand [v3,01/21] switch nfsd_client_rmdir() to use of simple_recursive_removal() [v3,02/21] coda_flag_children(): cope with dentries turning negative [v3,03/21] dentry: switch the lists of children to hlist [v3,04/21] centralize killing dentry from shrink list [v3,05/21] shrink_dentry_list(): no need to check that dentry refcount is marked dead [v3,06/21] fast_dput(): having ->d_delete() is not reason to delay refcount decrement [v3,07/21] fast_dput(): handle underflows gracefully [v3,08/21] fast_dput(): new rules for refcount [v3,09/21] __dput_to_list(): do decrement of refcount in the callers [v3,10/21] make retain_dentry() neutral with respect to refcounting [v3,11/21] __dentry_kill(): get consistent rules for victim's refcount [v3,12/21] dentry_kill(): don't bother with retain_dentry() on slow path [v3,13/21] Call retain_dentry() with refcount 0 [v3,14/21] fold the call of retain_dentry() into fast_dput() [v3,15/21] don't try to cut corners in shrink_lock_dentry() [v3,16/21] fold dentry_kill() into dput() [v3,17/21] to_shrink_list(): call only if refcount is 0 [v3,18/21] switch select_collect{,2}() to use of to_shrink_list() [v3,19/21] d_prune_aliases(): use a shrink list [v3,20/21] __dentry_kill(): new locking scheme [v3,21/21] retain_dentry(): introduce a trimmed-down lockless variant

Commit Message

Al Viro Nov. 24, 2023, 6:04 a.m. UTC

By now there is only one place in entire fast_dput() where we return
false; that happens after refcount had been decremented and found (under
->d_lock) to be zero.  In that case, just prior to returning false to
caller, fast_dput() forcibly changes the refcount from 0 to 1.

Lift that resetting refcount to 1 into the callers; later in the series
it will be massaged out of existence.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/dcache.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff mbox series

Patch

diff --git a/fs/dcache.c b/fs/dcache.c
index 9edabc7e2e64..a00e9ba22480 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -847,13 +847,6 @@  static inline bool fast_dput(struct dentry *dentry)
 		spin_unlock(&dentry->d_lock);
 		return true;
 	}
-
-	/*
-	 * Re-get the reference we optimistically dropped. We hold the
-	 * lock, and we just tested that it was zero, so we can just
-	 * set it to 1.
-	 */
-	dentry->d_lockref.count = 1;
 	return false;
 }
 
@@ -896,6 +889,7 @@  void dput(struct dentry *dentry)
 		}
 
 		/* Slow case: now with the dentry lock held */
+		dentry->d_lockref.count = 1;
 		rcu_read_unlock();
 
 		if (likely(retain_dentry(dentry))) {
@@ -930,6 +924,7 @@  void dput_to_list(struct dentry *dentry, struct list_head *list)
 		return;
 	}
 	rcu_read_unlock();
+	dentry->d_lockref.count = 1;
 	if (!retain_dentry(dentry))
 		__dput_to_list(dentry, list);
 	spin_unlock(&dentry->d_lock);