Messages in this thread Patch in this message | | | Subject | [PATCH 2/3] fbdev: Make deferred I/O work as advertized | From | Markus Armbruster <> | Date | Mon, 25 Feb 2008 14:03:52 +0100 |
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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 <jayakumar.lkml@gmail.com> Date: 2008-02-18 13:41:26
Signed-off-by: Jaya Kumar <jayakumar.lkml@gmail.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
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);
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