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mm/gup: Convert try_grab_page() to use a folio 

Hoist the folio conversion and the folio_ref_count() check to the
top of the function instead of using the one buried in try_get_page().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Matthew Wilcox (Oracle) 2022-02-04 10:32:01 -05:00
parent ece1ed7bfa
commit 5fec071990
1 changed files with 13 additions and 15 deletions
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28
mm/gup.c
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@ -174,15 +174,14 @@ static void put_compound_head(struct page *page, int refs, unsigned int flags)
/**
* try_grab_page() - elevate a page's refcount by a flag-dependent amount
* @page: pointer to page to be grabbed
* @flags: gup flags: these are the FOLL_* flag values.
*
* This might not do anything at all, depending on the flags argument.
*
* "grab" names in this file mean, "look at flags to decide whether to use
* FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
*
* @page: pointer to page to be grabbed
* @flags: gup flags: these are the FOLL_* flag values.
*
* Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same
* time. Cases: please see the try_grab_folio() documentation, with
* "refs=1".
@ -193,29 +192,28 @@ static void put_compound_head(struct page *page, int refs, unsigned int flags)
*/
bool __must_check try_grab_page(struct page *page, unsigned int flags)
{
struct folio *folio = page_folio(page);
WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == (FOLL_GET | FOLL_PIN));
if (WARN_ON_ONCE(folio_ref_count(folio) <= 0))
return false;
if (flags & FOLL_GET)
return try_get_page(page);
folio_ref_inc(folio);
else if (flags & FOLL_PIN) {
page = compound_head(page);
if (WARN_ON_ONCE(page_ref_count(page) <= 0))
return false;
/*
* Similar to try_grab_compound_head(): be sure to *also*
* Similar to try_grab_folio(): be sure to *also*
* increment the normal page refcount field at least once,
* so that the page really is pinned.
*/
if (PageHead(page)) {
page_ref_add(page, 1);
atomic_add(1, compound_pincount_ptr(page));
if (folio_test_large(folio)) {
folio_ref_add(folio, 1);
atomic_add(1, folio_pincount_ptr(folio));
} else {
page_ref_add(page, GUP_PIN_COUNTING_BIAS);
folio_ref_add(folio, GUP_PIN_COUNTING_BIAS);
}
mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1);
node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, 1);
}
return true;