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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 2/6] folio: Add a function to change the private data attached to a folio From: David Howells To: "Matthew Wilcox (Oracle)" Cc: dhowells@redhat.com, Jeff Layton , Ilya Dryomov , linux-fsdevel@vger.kernel.org, linux-cachefs@redhat.com, linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, devel@lists.orangefs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Tue, 24 Aug 2021 14:24:59 +0100 Message-ID: <162981149911.1901565.17776700811659843340.stgit@warthog.procyon.org.uk> In-Reply-To: <162981147473.1901565.1455657509200944265.stgit@warthog.procyon.org.uk> References: <162981147473.1901565.1455657509200944265.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org Add a function, folio_change_private(), that will change the private data attached to a folio, without the need to twiddle the private bit or the refcount. It assumes that folio_add_private() has already been called on the page. Signed-off-by: David Howells Reviewed-by: Matthew Wilcox (Oracle) --- include/linux/pagemap.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index f55d8d9001a9..c8d336e62177 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -229,6 +229,25 @@ static inline void folio_attach_private(struct folio *folio, void *data) folio_set_private(folio); } +/** + * folio_change_private - Change private data on a folio. + * @folio: Folio to change the data on. + * @data: Data to set on the folio. + * + * Change the private data attached to a folio and return the old + * data. The page must previously have had data attached and the data + * must be detached before the folio will be freed. + * + * Return: Data that was previously attached to the folio. + */ +static inline void *folio_change_private(struct folio *folio, void *data) +{ + void *old = folio_get_private(folio); + + folio->private = data; + return old; +} + /** * folio_detach_private - Detach private data from a folio. * @folio: Folio to detach data from.