Commit 9857a17f authored by John Hubbard's avatar John Hubbard Committed by Linus Torvalds
Browse files

mm/gup: remove try_get_page(), call try_get_compound_head() directly 

try_get_page() is very similar to try_get_compound_head(), and in fact
try_get_page() has fallen a little behind in terms of maintenance:
try_get_compound_head() handles speculative page references more
thoroughly.

There are only two try_get_page() callsites, so just call
try_get_compound_head() directly from those, and remove try_get_page()
entirely.

Also, seeing as how this changes try_get_compound_head() into a non-static
function, provide some kerneldoc documentation for it.

Link: https://lkml.kernel.org/r/20210813044133.1536842-4-jhubbard@nvidia.com


Signed-off-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 54d516b1

arch/s390/mm/fault.c

+1 −1
Original line number Diff line number Diff line
@@ -817,7 +817,7 @@ void do_secure_storage_access(struct pt_regs *regs) 
		break;

	case KERNEL_FAULT:

		page = phys_to_page(addr);

		if (unlikely(!try_get_page(page)))

		if (unlikely(!try_get_compound_head(page, 1)))

			break;

		rc = arch_make_page_accessible(page);

		put_page(page);

fs/pipe.c

+1 −1
Original line number Diff line number Diff line
@@ -191,7 +191,7 @@ EXPORT_SYMBOL(generic_pipe_buf_try_steal); 
 */

bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)

{

	return try_get_page(buf->page);

	return try_get_compound_head(buf->page, 1);

}

EXPORT_SYMBOL(generic_pipe_buf_get);

include/linux/mm.h

+1 −9
Original line number Diff line number Diff line
@@ -1217,15 +1217,7 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags); 
struct page *try_grab_compound_head(struct page *page, int refs,

				    unsigned int flags);





static inline __must_check bool try_get_page(struct page *page)

{

	page = compound_head(page);

	if (WARN_ON_ONCE(page_ref_count(page) <= 0))

		return false;

	page_ref_inc(page);

	return true;

}

struct page *try_get_compound_head(struct page *page, int refs);



static inline void put_page(struct page *page)

{

mm/gup.c

+17 −4
Original line number Diff line number Diff line
@@ -62,11 +62,24 @@ static void put_page_refs(struct page *page, int refs) 
	put_page(page);

}



/*

 * Return the compound head page with ref appropriately incremented,

 * or NULL if that failed.

/**

 * try_get_compound_head() - return the compound head page with refcount

 * appropriately incremented, or NULL if that failed.

 *

 * This handles potential refcount overflow correctly. It also works correctly

 * for various lockless get_user_pages()-related callers, due to the use of

 * page_cache_add_speculative().

 *

 * Even though the name includes "compound_head", this function is still

 * appropriate for callers that have a non-compound @page to get.

 *

 * @page:  pointer to page to be gotten

 * @refs:  the value to add to the page's refcount

 *

 * Return: head page (with refcount appropriately incremented) for success, or

 * NULL upon failure.

 */

static inline struct page *try_get_compound_head(struct page *page, int refs)

struct page *try_get_compound_head(struct page *page, int refs)

{

	struct page *head = compound_head(page);