fb_defio: do not use deprecated page->mapping, index fields

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@oracle.com: 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@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Tested-by: Kajtar Zsolt <soci@c64.rulez.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: Maíra Canal <mcanal@igalia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index 65363df8e81b5a7f02b3bd24393f1ee4404aed3d..4fc93f253e0603443be680e6487bdcc6938fb390 100644 (file)
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/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(struct vm_fault *vmf)
        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_page(struct fb_info *info, unsigned long
 
        /*
         * 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 work_struct *work)
        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 *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_info *info)
 
        kvfree(info->pagerefs);
        mutex_destroy(&fbdefio->lock);
+       fbdefio->mapping = NULL;
 }
 EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);

diff --git a/include/linux/fb.h b/include/linux/fb.h
index 5ba187e08cf7596e5e62613e671bca693ad5aa98..cd653862ab99818c3c64c9435616209b089cf02f 100644 (file)
--- a/include/linux/fb.h
+++ b/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);