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

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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>
This commit is contained in:
Lorenzo Stoakes
2025-02-08 15:52:56 +00:00
committed by Andrew Morton
parent a4811f53bb
commit 6cdef2ddce
2 changed files with 16 additions and 28 deletions
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43
drivers/video/fbdev/core/fb_defio.c
View File

@@ -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);

1
include/linux/fb.h
View File

@@ -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);