[PATCH 2/3] fbdev: Make deferred I/O work as advertized
From: Markus Armbruster <hidden>
Date: 2008-02-25 13:04:18
Also in:
linux-input, lkml, virtualization, xen-devel
Subsystem:
framebuffer layer, the rest · Maintainers:
Helge Deller, Linus Torvalds
Deferred I/O was utterly broken. Reading the mmap()ed framebuffer
worked, but writing it made the VM endlessly invoke
vm_ops.page_mkwrite(). That happened because we failed to set
page->mapping and page->index.
The fix is to set them, and clean up properly before the framebuffer
gets released.
Fix extracted from this linux-fbdev-devel message:
Subject: [PATCH 1/1 2.6.24] fbdev: defio and Metronomefb
From: Jaya Kumar [off-list ref]
Date: 2008-02-18 13:41:26
Signed-off-by: Jaya Kumar <redacted>
Signed-off-by: Markus Armbruster <redacted>
---
drivers/video/fb_defio.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index 0f8cfb9..24843fd 100644
--- a/drivers/video/fb_defio.c
+++ b/drivers/video/fb_defio.c@@ -4,7 +4,7 @@ * Copyright (C) 2006 Jaya Kumar * * This file is subject to the terms and conditions of the GNU General Public - * License. See the file COPYING in the main directory of this archive + * License. See the file COPYING in the main directory of this archive * for more details. */
@@ -31,7 +31,7 @@ static int fb_deferred_io_fault(struct vm_area_struct *vma, unsigned long offset; struct page *page; struct fb_info *info = vma->vm_private_data; - /* info->screen_base is in System RAM */ + /* info->screen_base is virtual memory */ void *screen_base = (void __force *) info->screen_base; offset = vmf->pgoff << PAGE_SHIFT;
@@ -43,6 +43,15 @@ static int fb_deferred_io_fault(struct vm_area_struct *vma, return VM_FAULT_SIGBUS; get_page(page); + + if (vma->vm_file) + page->mapping = vma->vm_file->f_mapping; + else + printk(KERN_ERR "no mapping available\n"); + + BUG_ON(!page->mapping); + page->index = vmf->pgoff; + vmf->page = page; return 0; }
@@ -138,11 +147,20 @@ EXPORT_SYMBOL_GPL(fb_deferred_io_init); void fb_deferred_io_cleanup(struct fb_info *info) { + void *screen_base = (void __force *) info->screen_base; struct fb_deferred_io *fbdefio = info->fbdefio; + struct page *page; + int i; BUG_ON(!fbdefio); cancel_delayed_work(&info->deferred_work); flush_scheduled_work(); + + /* clear out the mapping that we setup */ + for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) { + page = vmalloc_to_page(screen_base + i); + page->mapping = NULL; + } } EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);