diff options
Diffstat (limited to 'mm/gup.c')
| -rw-r--r-- | mm/gup.c | 78 |
1 files changed, 70 insertions, 8 deletions
@@ -29,6 +29,22 @@ struct follow_page_context { unsigned int page_mask; }; +static void hpage_pincount_add(struct page *page, int refs) +{ + VM_BUG_ON_PAGE(!hpage_pincount_available(page), page); + VM_BUG_ON_PAGE(page != compound_head(page), page); + + atomic_add(refs, compound_pincount_ptr(page)); +} + +static void hpage_pincount_sub(struct page *page, int refs) +{ + VM_BUG_ON_PAGE(!hpage_pincount_available(page), page); + VM_BUG_ON_PAGE(page != compound_head(page), page); + + atomic_sub(refs, compound_pincount_ptr(page)); +} + /* * Return the compound head page with ref appropriately incremented, * or NULL if that failed. @@ -70,8 +86,25 @@ static __maybe_unused struct page *try_grab_compound_head(struct page *page, if (flags & FOLL_GET) return try_get_compound_head(page, refs); else if (flags & FOLL_PIN) { - refs *= GUP_PIN_COUNTING_BIAS; - return try_get_compound_head(page, refs); + /* + * When pinning a compound page of order > 1 (which is what + * hpage_pincount_available() checks for), use an exact count to + * track it, via hpage_pincount_add/_sub(). + * + * However, be sure to *also* increment the normal page refcount + * field at least once, so that the page really is pinned. + */ + if (!hpage_pincount_available(page)) + refs *= GUP_PIN_COUNTING_BIAS; + + page = try_get_compound_head(page, refs); + if (!page) + return NULL; + + if (hpage_pincount_available(page)) + hpage_pincount_add(page, refs); + + return page; } WARN_ON_ONCE(1); @@ -106,12 +139,25 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags) if (flags & FOLL_GET) return try_get_page(page); else if (flags & FOLL_PIN) { + int refs = 1; + page = compound_head(page); if (WARN_ON_ONCE(page_ref_count(page) <= 0)) return false; - page_ref_add(page, GUP_PIN_COUNTING_BIAS); + if (hpage_pincount_available(page)) + hpage_pincount_add(page, 1); + else + refs = GUP_PIN_COUNTING_BIAS; + + /* + * Similar to try_grab_compound_head(): even if using the + * hpage_pincount_add/_sub() routines, be sure to + * *also* increment the normal page refcount field at least + * once, so that the page really is pinned. + */ + page_ref_add(page, refs); } return true; @@ -120,12 +166,17 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags) #ifdef CONFIG_DEV_PAGEMAP_OPS static bool __unpin_devmap_managed_user_page(struct page *page) { - int count; + int count, refs = 1; if (!page_is_devmap_managed(page)) return false; - count = page_ref_sub_return(page, GUP_PIN_COUNTING_BIAS); + if (hpage_pincount_available(page)) + hpage_pincount_sub(page, 1); + else + refs = GUP_PIN_COUNTING_BIAS; + + count = page_ref_sub_return(page, refs); /* * devmap page refcounts are 1-based, rather than 0-based: if @@ -157,6 +208,8 @@ static bool __unpin_devmap_managed_user_page(struct page *page) */ void unpin_user_page(struct page *page) { + int refs = 1; + page = compound_head(page); /* @@ -168,7 +221,12 @@ void unpin_user_page(struct page *page) if (__unpin_devmap_managed_user_page(page)) return; - if (page_ref_sub_and_test(page, GUP_PIN_COUNTING_BIAS)) + if (hpage_pincount_available(page)) + hpage_pincount_sub(page, 1); + else + refs = GUP_PIN_COUNTING_BIAS; + + if (page_ref_sub_and_test(page, refs)) __put_page(page); } EXPORT_SYMBOL(unpin_user_page); @@ -1955,8 +2013,12 @@ EXPORT_SYMBOL(get_user_pages_unlocked); static void put_compound_head(struct page *page, int refs, unsigned int flags) { - if (flags & FOLL_PIN) - refs *= GUP_PIN_COUNTING_BIAS; + if (flags & FOLL_PIN) { + if (hpage_pincount_available(page)) + hpage_pincount_sub(page, refs); + else + refs *= GUP_PIN_COUNTING_BIAS; + } VM_BUG_ON_PAGE(page_ref_count(page) < refs, page); /* |