search for: _wait_cb

...amp;page->_refcount, > - atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE, > + dax_layout_is_idle_page(page), TASK_INTERRUPTIBLE, > 0, 0, xfs_wait_dax_page(inode)); > } I still think a litte helper macro would be nice here: #define dax_wait_page(_inode, _page, _wait_cb) \ ___wait_var_event(&(_page)->_refcount, \ atomic_read(&(_page)->_refcount) == 1, \ TASK_INTERRUPTIBLE, dax_layout_is_idle_page(_page), \ TASK_INTERRUPTIBLE, 0, 0, _wait_cb(_inode));

...x.h @@ -243,6 +243,16 @@ static inline bool dax_mapping(struct address_space *mapping) return mapping->host && IS_DAX(mapping->host); } +static inline bool dax_layout_is_idle_page(struct page *page) +{ + return page_ref_count(page) == 1; +} + +#define dax_wait_page(_inode, _page, _wait_cb) \ + ___wait_var_event(&(_page)->_refcount, \ + dax_layout_is_idle_page(_page), \ + TASK_INTERRUPTIBLE, 0, 0, _wait_cb(_inode)) + #ifdef CONFIG_DEV_DAX_HMEM_DEVICES void hmem_register_device(int target_nid, struct resource *r); #else -- 2.20.1

This is still an RFC because after looking at the pmem/dax code some more, I realized that the ZONE_DEVICE struct pages are being inserted into the process' page tables with vmf_insert_mixed() and a zero refcount on the ZONE_DEVICE struct page. This is sort of OK because insert_pfn() increments the reference count on the pgmap which is what prevents memunmap_pages() from freeing the struct

Matthew Wilcox, Ira Weiny, and others have complained that ZONE_DEVICE struct page reference counting is ugly because they are "free" when the reference count is one instead of zero. This leads to explicit checks for ZONE_DEVICE pages in places like put_page(), GUP, THP splitting, and page migration which have to adjust the expected reference count when determining if the page is

...ux/dax.h +++ b/include/linux/dax.h @@ -245,7 +245,7 @@ static inline bool dax_mapping(struct address_space *mapping) static inline bool dax_layout_is_idle_page(struct page *page) { - return page_ref_count(page) == 1; + return page_ref_count(page) == 0; } #define dax_wait_page(_inode, _page, _wait_cb) \ diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 86c6c368ce9b..2f63747caf56 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -66,9 +66,10 @@ enum memory_type { struct dev_pagemap_ops { /* - * Called once the page refcount reaches 1. (ZONE_DE...