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From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: akpm@linux-foundation.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	Jeff Layton <jlayton@kernel.org>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	William Kucharski <william.kucharski@oracle.com>,
	David Howells <dhowells@redhat.com>
Subject: [PATCH v13 12/32] mm: Handle per-folio private data
Date: Mon, 12 Jul 2021 20:01:44 +0100	[thread overview]
Message-ID: <20210712190204.80979-13-willy@infradead.org> (raw)
In-Reply-To: <20210712190204.80979-1-willy@infradead.org>

Add folio_get_private() which mirrors page_private() -- ie folio private
data is the same as page private data.  The only difference is that these
return a void * instead of an unsigned long, which matches the majority
of users.

Turn attach_page_private() into folio_attach_private() and reimplement
attach_page_private() as a wrapper.  No filesystem which uses page private
data currently supports compound pages, so we're free to define the rules.
attach_page_private() may only be called on a head page; if you want
to add private data to a tail page, you can call set_page_private()
directly (and shouldn't increment the page refcount!  That should be
done when adding private data to the head page / folio).

This saves 813 bytes of text with the distro-derived config that I'm
testing due to removing the calls to compound_head() in get_page()
& put_page().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: David Howells <dhowells@redhat.com>
---
 include/linux/mm_types.h | 11 +++++++++
 include/linux/pagemap.h  | 48 ++++++++++++++++++++++++----------------
 2 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 7a11b25cf50f..c15b4af8ef4d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -309,6 +309,12 @@ static inline atomic_t *compound_pincount_ptr(struct page *page)
 #define PAGE_FRAG_CACHE_MAX_SIZE	__ALIGN_MASK(32768, ~PAGE_MASK)
 #define PAGE_FRAG_CACHE_MAX_ORDER	get_order(PAGE_FRAG_CACHE_MAX_SIZE)
 
+/*
+ * page_private can be used on tail pages.  However, PagePrivate is only
+ * checked by the VM on the head page.  So page_private on the tail pages
+ * should be used for data that's ancillary to the head page (eg attaching
+ * buffer heads to tail pages after attaching buffer heads to the head page)
+ */
 #define page_private(page)		((page)->private)
 
 static inline void set_page_private(struct page *page, unsigned long private)
@@ -316,6 +322,11 @@ static inline void set_page_private(struct page *page, unsigned long private)
 	page->private = private;
 }
 
+static inline void *folio_get_private(struct folio *folio)
+{
+	return folio->private;
+}
+
 struct page_frag_cache {
 	void * va;
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index db1726b1bc1c..df18df0ab01b 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -184,42 +184,52 @@ static inline bool page_cache_get_speculative(struct page *page)
 }
 
 /**
- * attach_page_private - Attach private data to a page.
- * @page: Page to attach data to.
- * @data: Data to attach to page.
+ * folio_attach_private - Attach private data to a folio.
+ * @folio: Folio to attach data to.
+ * @data: Data to attach to folio.
  *
- * Attaching private data to a page increments the page's reference count.
- * The data must be detached before the page will be freed.
+ * Attaching private data to a folio increments the page's reference count.
+ * The data must be detached before the folio will be freed.
  */
-static inline void attach_page_private(struct page *page, void *data)
+static inline void folio_attach_private(struct folio *folio, void *data)
 {
-	get_page(page);
-	set_page_private(page, (unsigned long)data);
-	SetPagePrivate(page);
+	folio_get(folio);
+	folio->private = data;
+	folio_set_private_flag(folio);
 }
 
 /**
- * detach_page_private - Detach private data from a page.
- * @page: Page to detach data from.
+ * folio_detach_private - Detach private data from a folio.
+ * @folio: Folio to detach data from.
  *
- * Removes the data that was previously attached to the page and decrements
+ * Removes the data that was previously attached to the folio and decrements
  * the refcount on the page.
  *
- * Return: Data that was attached to the page.
+ * Return: Data that was attached to the folio.
  */
-static inline void *detach_page_private(struct page *page)
+static inline void *folio_detach_private(struct folio *folio)
 {
-	void *data = (void *)page_private(page);
+	void *data = folio_get_private(folio);
 
-	if (!PagePrivate(page))
+	if (!folio_private(folio))
 		return NULL;
-	ClearPagePrivate(page);
-	set_page_private(page, 0);
-	put_page(page);
+	folio_clear_private_flag(folio);
+	folio->private = NULL;
+	folio_put(folio);
 
 	return data;
 }
 
+static inline void attach_page_private(struct page *page, void *data)
+{
+	folio_attach_private(page_folio(page), data);
+}
+
+static inline void *detach_page_private(struct page *page)
+{
+	return folio_detach_private(page_folio(page));
+}
+
 #ifdef CONFIG_NUMA
 extern struct page *__page_cache_alloc(gfp_t gfp);
 #else
-- 
2.30.2


  parent reply	other threads:[~2021-07-12 19:09 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-12 19:01 [PATCH v13a 00/32] Memory folios Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 01/32] mm: Convert get_page_unless_zero() to return bool Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 02/32] mm: Introduce struct folio Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 03/32] mm: Add folio_pgdat(), folio_zone() and folio_zonenum() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 04/32] mm/vmstat: Add functions to account folio statistics Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 05/32] mm/debug: Add VM_BUG_ON_FOLIO() and VM_WARN_ON_ONCE_FOLIO() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 06/32] mm: Add folio reference count functions Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 07/32] mm: Add folio_put() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 08/32] mm: Add folio_get() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 09/32] mm: Add folio_try_get_rcu() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 10/32] mm: Add folio flag manipulation functions Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 11/32] mm/lru: Add folio LRU functions Matthew Wilcox (Oracle)
2021-07-12 19:01 ` Matthew Wilcox (Oracle) [this message]
2021-07-12 19:01 ` [PATCH v13 13/32] mm/filemap: Add folio_index(), folio_file_page() and folio_contains() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 14/32] mm/filemap: Add folio_next_index() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 15/32] mm/filemap: Add folio_pos() and folio_file_pos() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 16/32] mm/util: Add folio_mapping() and folio_file_mapping() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 17/32] mm/filemap: Add folio_unlock() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 18/32] mm/filemap: Add folio_lock() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 19/32] mm/filemap: Add folio_lock_killable() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 20/32] mm/filemap: Add __folio_lock_async() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 21/32] mm/filemap: Add folio_wait_locked() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 22/32] mm/filemap: Add __folio_lock_or_retry() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 23/32] mm/swap: Add folio_rotate_reclaimable() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 24/32] mm/filemap: Add folio_end_writeback() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 25/32] mm/writeback: Add folio_wait_writeback() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 26/32] mm/writeback: Add folio_wait_stable() Matthew Wilcox (Oracle)
2021-07-12 19:01 ` [PATCH v13 27/32] mm/filemap: Add folio_wait_bit() Matthew Wilcox (Oracle)
2021-07-12 19:02 ` [PATCH v13 28/32] mm/filemap: Add folio_wake_bit() Matthew Wilcox (Oracle)
2021-07-12 19:02 ` [PATCH v13 29/32] mm/filemap: Convert page wait queues to be folios Matthew Wilcox (Oracle)
2021-07-12 19:02 ` [PATCH v13 30/32] mm/filemap: Add folio private_2 functions Matthew Wilcox (Oracle)
2021-07-12 19:02 ` [PATCH v13 31/32] fs/netfs: Add folio fscache functions Matthew Wilcox (Oracle)
2021-07-12 19:02 ` [PATCH v13 32/32] mm: Add folio_mapped() Matthew Wilcox (Oracle)

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