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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771248741; bh=GQODvPKfpe1TuAASNlfZOpKx+opiPpT2Vm9Zk2O6rrw=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=LpeBzW5mKUxVFtLej99Vdf/DLsg/Lz5wVffdIB06ucKJPM75RkE2zw6eu2gjLAXY2 el/H2qkyx1qaloadnIfPom8wn/ga6OBtW96Kv80BBigoWZAesiZnp3CaXK5yO1AZdU OPX9Xd/XtjLC1QmeBSXIZmPE9mhstsztwVmmhHQGEoFGOQ0V9kguWN4aILDUDeOb88 EkJJN7eIrl4ryh405XEph+QaqlOLsNFbrzrvZN28wgbc2mL43EzhIvvPbiC75ijZbf h6at3a+Jt1uSrnUQFUHnP/J3xlPzVLSj0LZrGXC4SfyZ1+k0pOlk2cvdjPTR0Ms4dg X9H6BjBtmKm2w== From: Christian Brauner Date: Mon, 16 Feb 2026 14:31:57 +0100 Subject: [PATCH 01/14] xattr: add rcu_head and rhash_head to struct simple_xattr MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260216-work-xattr-socket-v1-1-c2efa4f74cb7@kernel.org> References: <20260216-work-xattr-socket-v1-0-c2efa4f74cb7@kernel.org> In-Reply-To: <20260216-work-xattr-socket-v1-0-c2efa4f74cb7@kernel.org> To: linux-fsdevel@vger.kernel.org Cc: Jeff Layton , Josef Bacik , Alexander Viro , Jan Kara , linux-kernel@vger.kernel.org, Hugh Dickins , linux-mm@kvack.org, Greg Kroah-Hartman , Tejun Heo , Eric Dumazet , Jakub Kicinski , Jann Horn , netdev@vger.kernel.org, Christian Brauner X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; 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The rhashtable implementation will use rhash_head for hash table linkage and RCU-based lockless reads, requiring that replaced or removed xattr entries be freed via call_rcu() rather than immediately. Add simple_xattr_free_rcu() which schedules RCU-deferred freeing of an xattr entry. This will be used by callers of simple_xattr_set() once they switch to the rhashtable-based xattr store. No functional changes. Signed-off-by: Christian Brauner --- fs/xattr.c | 23 +++++++++++++++++++++++ include/linux/xattr.h | 4 ++++ 2 files changed, 27 insertions(+) diff --git a/fs/xattr.c b/fs/xattr.c index 3e49e612e1ba..9cbb1917bcb2 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -1197,6 +1197,29 @@ void simple_xattr_free(struct simple_xattr *xattr) kvfree(xattr); } +static void simple_xattr_rcu_free(struct rcu_head *head) +{ + struct simple_xattr *xattr; + + xattr = container_of(head, struct simple_xattr, rcu); + simple_xattr_free(xattr); +} + +/** + * simple_xattr_free_rcu - free an xattr object after an RCU grace period + * @xattr: the xattr object + * + * Schedule RCU-deferred freeing of an xattr entry. This is used by + * rhashtable-based callers of simple_xattr_set() that replace or remove + * an existing entry while concurrent RCU readers may still be accessing + * it. + */ +void simple_xattr_free_rcu(struct simple_xattr *xattr) +{ + if (xattr) + call_rcu(&xattr->rcu, simple_xattr_rcu_free); +} + /** * simple_xattr_alloc - allocate new xattr object * @value: value of the xattr object diff --git a/include/linux/xattr.h b/include/linux/xattr.h index 64e9afe7d647..1328f2bfd2ce 100644 --- a/include/linux/xattr.h +++ b/include/linux/xattr.h @@ -16,6 +16,7 @@ #include #include #include +#include #include #include @@ -112,6 +113,8 @@ struct simple_xattrs { struct simple_xattr { struct rb_node rb_node; + struct rhash_head hash_node; + struct rcu_head rcu; char *name; size_t size; char value[]; @@ -122,6 +125,7 @@ void simple_xattrs_free(struct simple_xattrs *xattrs, size_t *freed_space); size_t simple_xattr_space(const char *name, size_t size); struct simple_xattr *simple_xattr_alloc(const void *value, size_t size); void simple_xattr_free(struct simple_xattr *xattr); +void simple_xattr_free_rcu(struct simple_xattr *xattr); int simple_xattr_get(struct simple_xattrs *xattrs, const char *name, void *buffer, size_t size); struct simple_xattr *simple_xattr_set(struct simple_xattrs *xattrs, -- 2.47.3