Commit 0f089235 authored by Logan Gunthorpe's avatar Logan Gunthorpe Committed by Jens Axboe
Browse files

mm: allow multiple error returns in try_grab_page() 



In order to add checks for P2PDMA memory into try_grab_page(), expand
the error return from a bool to an int/error code. Update all the
callsites handle change in usage.

Also remove the WARN_ON_ONCE() call at the callsites seeing there
already is a WARN_ON_ONCE() inside the function if it fails.

Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Reviewed-by: default avatarDan Williams <dan.j.williams@intel.com>
Reviewed-by: default avatarChaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221021174116.7200-2-logang@deltatee.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 5b2560c4

include/linux/mm.h

+1 −1
Original line number Diff line number Diff line
@@ -1129,7 +1129,7 @@ static inline void get_page(struct page *page) 
	folio_get(page_folio(page));

}



bool __must_check try_grab_page(struct page *page, unsigned int flags);

int __must_check try_grab_page(struct page *page, unsigned int flags);



static inline __must_check bool try_get_page(struct page *page)

{

mm/gup.c

+14 −12
Original line number Diff line number Diff line
@@ -202,17 +202,19 @@ static void gup_put_folio(struct folio *folio, int refs, unsigned int flags) 
 * time. Cases: please see the try_grab_folio() documentation, with

 * "refs=1".

 *

 * Return: true for success, or if no action was required (if neither FOLL_PIN

 * nor FOLL_GET was set, nothing is done). False for failure: FOLL_GET or

 * FOLL_PIN was set, but the page could not be grabbed.

 * Return: 0 for success, or if no action was required (if neither FOLL_PIN

 * nor FOLL_GET was set, nothing is done). A negative error code for failure:

 *

 *   -ENOMEM		FOLL_GET or FOLL_PIN was set, but the page could not

 *			be grabbed.

 */

bool __must_check try_grab_page(struct page *page, unsigned int flags)

int __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;

		return -ENOMEM;



	if (flags & FOLL_GET)

		folio_ref_inc(folio);
@@ -232,7 +234,7 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags) 
		node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, 1);

	}



	return true;

	return 0;

}



/**
@@ -624,8 +626,9 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, 
		       !PageAnonExclusive(page), page);



	/* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */

	if (unlikely(!try_grab_page(page, flags))) {

		page = ERR_PTR(-ENOMEM);

	ret = try_grab_page(page, flags);

	if (unlikely(ret)) {

		page = ERR_PTR(ret);

		goto out;

	}

	/*
@@ -960,10 +963,9 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address, 
			goto unmap;

		*page = pte_page(*pte);

	}

	if (unlikely(!try_grab_page(*page, gup_flags))) {

		ret = -ENOMEM;

	ret = try_grab_page(*page, gup_flags);

	if (unlikely(ret))

		goto unmap;

	}

out:

	ret = 0;

unmap:
@@ -2536,7 +2538,7 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr, 
		}

		SetPageReferenced(page);

		pages[*nr] = page;

		if (unlikely(!try_grab_page(page, flags))) {

		if (unlikely(try_grab_page(page, flags))) {

			undo_dev_pagemap(nr, nr_start, flags, pages);

			break;

		}

mm/huge_memory.c

+13 −6
Original line number Diff line number Diff line
@@ -1035,6 +1035,7 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, 
	unsigned long pfn = pmd_pfn(*pmd);

	struct mm_struct *mm = vma->vm_mm;

	struct page *page;

	int ret;



	assert_spin_locked(pmd_lockptr(mm, pmd));
@@ -1066,8 +1067,9 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, 
	if (!*pgmap)

		return ERR_PTR(-EFAULT);

	page = pfn_to_page(pfn);

	if (!try_grab_page(page, flags))

		page = ERR_PTR(-ENOMEM);

	ret = try_grab_page(page, flags);

	if (ret)

		page = ERR_PTR(ret);



	return page;

}
@@ -1193,6 +1195,7 @@ struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, 
	unsigned long pfn = pud_pfn(*pud);

	struct mm_struct *mm = vma->vm_mm;

	struct page *page;

	int ret;



	assert_spin_locked(pud_lockptr(mm, pud));
@@ -1226,8 +1229,10 @@ struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, 
	if (!*pgmap)

		return ERR_PTR(-EFAULT);

	page = pfn_to_page(pfn);

	if (!try_grab_page(page, flags))

		page = ERR_PTR(-ENOMEM);



	ret = try_grab_page(page, flags);

	if (ret)

		page = ERR_PTR(ret);



	return page;

}
@@ -1435,6 +1440,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 
{

	struct mm_struct *mm = vma->vm_mm;

	struct page *page;

	int ret;



	assert_spin_locked(pmd_lockptr(mm, pmd));
@@ -1459,8 +1465,9 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 
	VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&

			!PageAnonExclusive(page), page);



	if (!try_grab_page(page, flags))

		return ERR_PTR(-ENOMEM);

	ret = try_grab_page(page, flags);

	if (ret)

		return ERR_PTR(ret);



	if (flags & FOLL_TOUCH)

		touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);

mm/hugetlb.c

+9 −8
Original line number Diff line number Diff line
@@ -7243,14 +7243,15 @@ follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long address, int flags 
		page = pte_page(pte) +

			((address & ~huge_page_mask(h)) >> PAGE_SHIFT);

		/*

		 * try_grab_page() should always succeed here, because: a) we

		 * hold the pmd (ptl) lock, and b) we've just checked that the

		 * huge pmd (head) page is present in the page tables. The ptl

		 * prevents the head page and tail pages from being rearranged

		 * in any way. So this page must be available at this point,

		 * unless the page refcount overflowed:

		 */

		if (WARN_ON_ONCE(!try_grab_page(page, flags))) {

		 * try_grab_page() should always be able to get the page here,

		 * because: a) we hold the pmd (ptl) lock, and b) we've just

		 * checked that the huge pmd (head) page is present in the

		 * page tables. The ptl prevents the head page and tail pages

		 * from being rearranged in any way. So this page must be

		 * available at this point, unless the page refcount

		 * overflowed:

		 */

		if (try_grab_page(page, flags)) {

			page = NULL;

			goto out;

		}
@@ -7288,7 +7289,7 @@ follow_huge_pud(struct mm_struct *mm, unsigned long address, 
	pte = huge_ptep_get((pte_t *)pud);

	if (pte_present(pte)) {

		page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);

		if (WARN_ON_ONCE(!try_grab_page(page, flags))) {

		if (try_grab_page(page, flags)) {

			page = NULL;

			goto out;

		}