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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: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Christoph 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
John Hubbard 2021-09-02 14:53:54 -07:00 committed by Linus Torvalds
parent 54d516b1d6
commit 9857a17f20
4 changed files with 20 additions and 15 deletions
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2
arch/s390/mm/fault.c
View File

@ -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);

2
fs/pipe.c
View File

@ -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);

10
include/linux/mm.h
View File

@ -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)
{

21
mm/gup.c
View File

@ -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);