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: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221021174116.7200-2-logang@deltatee.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8bbcccb..62a91dc 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -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)
 {

diff --git a/mm/gup.c b/mm/gup.c
index fe195d4..e2f4474 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -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 @@ retry:
                       !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;
                }

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 03fc7e5..01e2de9 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -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);

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 546df97..67f3955 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7243,14 +7243,15 @@ retry:
                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:
+                * 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 (WARN_ON_ONCE(!try_grab_page(page, flags))) {
+               if (try_grab_page(page, flags)) {
                        page = NULL;
                        goto out;
                }
@@ -7288,7 +7289,7 @@ retry:
        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;
                }