[v4,19/25] proc/task_mmu: Ignore ZONE_DEVICE pages

Commit Message

Alistair Popple Dec. 17, 2024, 5:13 a.m. UTC

The procfs mmu files such as smaps currently ignore device dax and fs
dax pages because these pages are considered special. To maintain
existing behaviour once these pages are treated as normal pages and
returned from vm_normal_page() add tests to explicitly skip them.

Signed-off-by: Alistair Popple <[e-mail]>
---
 fs/proc/task_mmu.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

Comments

David Hildenbrand Dec. 17, 2024, 10:31 p.m. UTC | #1

On 17.12.24 06:13, Alistair Popple wrote:
> The procfs mmu files such as smaps currently ignore device dax and fs
> dax pages because these pages are considered special. To maintain
> existing behaviour once these pages are treated as normal pages and
> returned from vm_normal_page() add tests to explicitly skip them.
> 
> Signed-off-by: Alistair Popple <[e-mail]>
> ---
>   fs/proc/task_mmu.c | 18 ++++++++++++++----
>   1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 38a5a3e..c9b227a 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -801,6 +801,8 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
>   
>   	if (pte_present(ptent)) {
>   		page = vm_normal_page(vma, addr, ptent);
> +		if (page && (is_device_dax_page(page) || is_fsdax_page(page)))

This "is_device_dax_page(page) || is_fsdax_page(page)" is a common theme 
here, likely we should have a special helper?


But, don't we actually want to include them in the smaps output now? I 
think we want.

The rmap code will indicate these pages in /proc/meminfo, per-node info, 
in the memcg ... as "Mapped:" etc.

So likely we just want to also indicate them here, or is there any 
downsides we know of?

Patch

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 38a5a3e..c9b227a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -801,6 +801,8 @@  static void smaps_pte_entry(pte_t *pte, unsigned long addr,
 
 	if (pte_present(ptent)) {
 		page = vm_normal_page(vma, addr, ptent);
+		if (page && (is_device_dax_page(page) || is_fsdax_page(page)))
+			page = NULL;
 		young = pte_young(ptent);
 		dirty = pte_dirty(ptent);
 		present = true;
@@ -849,6 +851,8 @@  static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
 
 	if (pmd_present(*pmd)) {
 		page = vm_normal_page_pmd(vma, addr, *pmd);
+		if (page && (is_device_dax_page(page) || is_fsdax_page(page)))
+			page = NULL;
 		present = true;
 	} else if (unlikely(thp_migration_supported() && is_swap_pmd(*pmd))) {
 		swp_entry_t entry = pmd_to_swp_entry(*pmd);
@@ -1378,7 +1382,7 @@  static inline bool pte_is_pinned(struct vm_area_struct *vma, unsigned long addr,
 	if (likely(!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags)))
 		return false;
 	folio = vm_normal_folio(vma, addr, pte);
-	if (!folio)
+	if (!folio || folio_is_device_dax(folio) || folio_is_fsdax(folio))
 		return false;
 	return folio_maybe_dma_pinned(folio);
 }
@@ -1703,6 +1707,8 @@  static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
 			frame = pte_pfn(pte);
 		flags |= PM_PRESENT;
 		page = vm_normal_page(vma, addr, pte);
+		if (page && (is_device_dax_page(page) || is_fsdax_page(page)))
+			page = NULL;
 		if (pte_soft_dirty(pte))
 			flags |= PM_SOFT_DIRTY;
 		if (pte_uffd_wp(pte))
@@ -2089,7 +2095,9 @@  static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
 
 		if (p->masks_of_interest & PAGE_IS_FILE) {
 			page = vm_normal_page(vma, addr, pte);
-			if (page && !PageAnon(page))
+			if (page && !PageAnon(page) &&
+			    !is_device_dax_page(page) &&
+			    !is_fsdax_page(page))
 				categories |= PAGE_IS_FILE;
 		}
 
@@ -2151,7 +2159,9 @@  static unsigned long pagemap_thp_category(struct pagemap_scan_private *p,
 
 		if (p->masks_of_interest & PAGE_IS_FILE) {
 			page = vm_normal_page_pmd(vma, addr, pmd);
-			if (page && !PageAnon(page))
+			if (page && !PageAnon(page) &&
+			    !is_device_dax_page(page) &&
+			    !is_fsdax_page(page))
 				categories |= PAGE_IS_FILE;
 		}
 
@@ -2914,7 +2924,7 @@  static struct page *can_gather_numa_stats_pmd(pmd_t pmd,
 		return NULL;
 
 	page = vm_normal_page_pmd(vma, addr, pmd);
-	if (!page)
+	if (!page || is_device_dax_page(page) || is_fsdax_page(page))
 		return NULL;
 
 	if (PageReserved(page))