[PATCH v6 10/34] mm, block: Make BIO_PAGE_REFFED/PINNED the same as FOLL_GET/PIN numerically

[David Howells <dhowells@redhat.com>]

Make BIO_PAGE_REFFED the same as FOLL_GET and BIO_PAGE_PINNED the same as
FOLL_PIN numerically so that the BIO_* flags can be passed directly to
page_put_unpin().

Provide a build-time assertion to check this.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Jan Kara <jack@suse.cz>
cc: Christoph Hellwig <hch@lst.de>
cc: Matthew Wilcox <willy@infradead.org>
cc: Logan Gunthorpe <logang@deltatee.com>
cc: linux-block@vger.kernel.org
---

 block/bio.c               |    3 +++
 include/linux/blk_types.h |    1 +
 include/linux/mm.h        |   17 ++++++++++-------
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 5b6a76c3e620..d8c636cefcdd 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1798,6 +1798,9 @@ static int __init init_bio(void)
 {
 	int i;
 
+	BUILD_BUG_ON((1 << BIO_PAGE_REFFED) != FOLL_GET);
+	BUILD_BUG_ON((1 << BIO_PAGE_PINNED) != FOLL_PIN);
+
 	bio_integrity_init();
 
 	for (i = 0; i < ARRAY_SIZE(bvec_slabs); i++) {
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 86711fb0534a..42b40156c517 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -319,6 +319,7 @@ struct bio {
  */
 enum {
 	BIO_PAGE_REFFED,	/* Pages need refs putting (equivalent to FOLL_GET) */
+	BIO_PAGE_PINNED,	/* Pages need unpinning (equivalent to FOLL_PIN) */
 	BIO_CLONED,		/* doesn't own data */
 	BIO_BOUNCED,		/* bio is a bounce bio */
 	BIO_QUIET,		/* Make BIO Quiet */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8e746a930945..f14edb192394 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3074,12 +3074,13 @@ static inline vm_fault_t vmf_error(int err)
 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 			 unsigned int foll_flags);
 
-#define FOLL_WRITE	0x01	/* check pte is writable */
-#define FOLL_TOUCH	0x02	/* mark page accessed */
-#define FOLL_GET	0x04	/* do get_page on page */
-#define FOLL_DUMP	0x08	/* give error on hole if it would be zero */
-#define FOLL_FORCE	0x10	/* get_user_pages read/write w/o permission */
-#define FOLL_NOWAIT	0x20	/* if a disk transfer is needed, start the IO
+#define FOLL_GET	0x01	/* do get_page on page (equivalent to BIO_FOLL_GET) */
+#define FOLL_PIN	0x02	/* pages must be released via unpin_user_page */
+#define FOLL_WRITE	0x04	/* check pte is writable */
+#define FOLL_TOUCH	0x08	/* mark page accessed */
+#define FOLL_DUMP	0x10	/* give error on hole if it would be zero */
+#define FOLL_FORCE	0x20	/* get_user_pages read/write w/o permission */
+#define FOLL_NOWAIT	0x40	/* if a disk transfer is needed, start the IO
 				 * and return without waiting upon it */
 #define FOLL_NOFAULT	0x80	/* do not fault in pages */
 #define FOLL_HWPOISON	0x100	/* check page is hwpoisoned */
@@ -3088,7 +3089,6 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 #define FOLL_ANON	0x8000	/* don't do file mappings */
 #define FOLL_LONGTERM	0x10000	/* mapping lifetime is indefinite: see below */
 #define FOLL_SPLIT_PMD	0x20000	/* split huge pmd before returning */
-#define FOLL_PIN	0x40000	/* pages must be released via unpin_user_page */
 #define FOLL_FAST_ONLY	0x80000	/* gup_fast: prevent fall-back to slow gup */
 #define FOLL_PCI_P2PDMA	0x100000 /* allow returning PCI P2PDMA pages */
 #define FOLL_INTERRUPTIBLE  0x200000 /* allow interrupts from generic signals */
@@ -3098,6 +3098,9 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 #define FOLL_BUF_MASK	FOLL_WRITE
 
 /*
+ * FOLL_GET must be the same bit as BIO_FOLL_GET and FOLL_PIN must be the same
+ * bit as BIO_FOLL_PIN.
+ *
  * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each
  * other. Here is what they mean, and how to use them:
  *