The quilt patch titled
Subject: fb_defio: do not use deprecated page->mapping, index fields
has been removed from the -mm tree. Its filename was
fb_defio-do-not-use-deprecated-page-mapping-index-fields.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Subject: fb_defio: do not use deprecated page->mapping, index fields
Date: Sat, 8 Feb 2025 15:52:56 +0000
With the introduction of mapping_wrprotect_range() there is no need to use
folio_mkclean() in order to write-protect mappings of frame buffer pages,
and therefore no need to inappropriately set kernel-allocated page->index,
mapping fields to permit this operation.
Instead, store the pointer to the page cache object for the mapped driver
in the fb_deferred_io object, and use the already stored page offset from
the pageref object to look up mappings in order to write-protect them.
This is justified, as for the page objects to store a mapping pointer at
the point of assignment of pages, they must all reference the same
underlying address_space object. Since the life time of the pagerefs is
also the lifetime of the fb_deferred_io object, storing the pointer here
makes sense.
This eliminates the need for all of the logic around setting and
maintaining page->index,mapping which we remove.
This eliminates the use of folio_mkclean() entirely but otherwise should
have no functional change.
[lorenzo.stoakes@xxxxxxxxxx: fixup unused variable warnings]
Link: https://lkml.kernel.org/r/d4018405-2762-4385-a816-e54cc23839ac@lucifer.local
Link: https://lkml.kernel.org/r/81171ab16c14e3df28f6de9d14982cee528d8519.1739029358.git.lorenzo.stoakes@xxxxxxxxxx
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Tested-by: Kajtar Zsolt <soci@xxxxxxxxxxxxx>
Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Helge Deller <deller@xxxxxx>
Cc: Jaya Kumar <jayakumar.lkml@xxxxxxxxx>
Cc: MaÃra Canal <mcanal@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Simona Vetter <simona.vetter@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/video/fbdev/core/fb_defio.c | 43 +++++++++-----------------
include/linux/fb.h | 1
2 files changed, 16 insertions(+), 28 deletions(-)
--- a/drivers/video/fbdev/core/fb_defio.c~fb_defio-do-not-use-deprecated-page-mapping-index-fields
+++ a/drivers/video/fbdev/core/fb_defio.c
@@ -69,14 +69,6 @@ out:
return pageref;
}
-static void fb_deferred_io_pageref_clear(struct fb_deferred_io_pageref *pageref)
-{
- struct page *page = pageref->page;
-
- if (page)
- page->mapping = NULL;
-}
-
static struct fb_deferred_io_pageref *fb_deferred_io_pageref_get(struct fb_info *info,
unsigned long offset,
struct page *page)
@@ -140,13 +132,10 @@ static vm_fault_t fb_deferred_io_fault(s
if (!page)
return VM_FAULT_SIGBUS;
- if (vmf->vma->vm_file)
- page->mapping = vmf->vma->vm_file->f_mapping;
- else
- printk(KERN_ERR "no mapping available\n");
+ if (!vmf->vma->vm_file)
+ fb_err(info, "no mapping available\n");
- BUG_ON(!page->mapping);
- page->index = vmf->pgoff; /* for folio_mkclean() */
+ BUG_ON(!info->fbdefio->mapping);
vmf->page = page;
return 0;
@@ -194,9 +183,9 @@ static vm_fault_t fb_deferred_io_track_p
/*
* We want the page to remain locked from ->page_mkwrite until
- * the PTE is marked dirty to avoid folio_mkclean() being called
- * before the PTE is updated, which would leave the page ignored
- * by defio.
+ * the PTE is marked dirty to avoid mapping_wrprotect_range()
+ * being called before the PTE is updated, which would leave
+ * the page ignored by defio.
* Do this by locking the page here and informing the caller
* about it with VM_FAULT_LOCKED.
*/
@@ -274,15 +263,17 @@ static void fb_deferred_io_work(struct w
struct fb_deferred_io_pageref *pageref, *next;
struct fb_deferred_io *fbdefio = info->fbdefio;
- /* here we mkclean the pages, then do all deferred IO */
+ /* here we wrprotect the page's mappings, then do all deferred IO. */
mutex_lock(&fbdefio->lock);
+#ifdef CONFIG_MMU
list_for_each_entry(pageref, &fbdefio->pagereflist, list) {
- struct folio *folio = page_folio(pageref->page);
+ struct page *page = pageref->page;
+ pgoff_t pgoff = pageref->offset >> PAGE_SHIFT;
- folio_lock(folio);
- folio_mkclean(folio);
- folio_unlock(folio);
+ mapping_wrprotect_range(fbdefio->mapping, pgoff,
+ page_to_pfn(page), 1);
}
+#endif
/* driver's callback with pagereflist */
fbdefio->deferred_io(info, &fbdefio->pagereflist);
@@ -337,6 +328,7 @@ void fb_deferred_io_open(struct fb_info
{
struct fb_deferred_io *fbdefio = info->fbdefio;
+ fbdefio->mapping = file->f_mapping;
file->f_mapping->a_ops = &fb_deferred_io_aops;
fbdefio->open_count++;
}
@@ -344,13 +336,7 @@ EXPORT_SYMBOL_GPL(fb_deferred_io_open);
static void fb_deferred_io_lastclose(struct fb_info *info)
{
- unsigned long i;
-
flush_delayed_work(&info->deferred_work);
-
- /* clear out the mapping that we setup */
- for (i = 0; i < info->npagerefs; ++i)
- fb_deferred_io_pageref_clear(&info->pagerefs[i]);
}
void fb_deferred_io_release(struct fb_info *info)
@@ -370,5 +356,6 @@ void fb_deferred_io_cleanup(struct fb_in
kvfree(info->pagerefs);
mutex_destroy(&fbdefio->lock);
+ fbdefio->mapping = NULL;
}
EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
--- a/include/linux/fb.h~fb_defio-do-not-use-deprecated-page-mapping-index-fields
+++ a/include/linux/fb.h
@@ -225,6 +225,7 @@ struct fb_deferred_io {
int open_count; /* number of opened files; protected by fb_info lock */
struct mutex lock; /* mutex that protects the pageref list */
struct list_head pagereflist; /* list of pagerefs for touched pages */
+ struct address_space *mapping; /* page cache object for fb device */
/* callback */
struct page *(*get_page)(struct fb_info *info, unsigned long offset);
void (*deferred_io)(struct fb_info *info, struct list_head *pagelist);
_
Patches currently in -mm which might be from lorenzo.stoakes@xxxxxxxxxx are
mm-mremap-correctly-handle-partial-mremap-of-vma-starting-at-0.patch
mm-mremap-refactor-mremap-system-call-implementation.patch
mm-mremap-introduce-and-use-vma_remap_struct-threaded-state.patch
mm-mremap-initial-refactor-of-move_vma.patch
mm-mremap-complete-refactor-of-move_vma.patch
mm-mremap-refactor-move_page_tables-abstracting-state.patch
mm-mremap-thread-state-through-move-page-table-operation.patch
