diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c index 1690358b8f01..52b19ec580a4 100644 --- a/drivers/staging/fbtft/fbtft-core.c +++ b/drivers/staging/fbtft/fbtft-core.c @@ -654,6 +654,7 @@ struct fb_info *fbtft_framebuffer_alloc(struct fbtft_display *display, fbops->fb_blank = fbtft_fb_blank; fbdefio->delay = HZ / fps; + fbdefio->sort_pagelist = true; fbdefio->deferred_io = fbtft_deferred_io; fb_deferred_io_init(info); diff --git a/drivers/video/fbdev/broadsheetfb.c b/drivers/video/fbdev/broadsheetfb.c index fd66f4d4a621..b9054f658838 100644 --- a/drivers/video/fbdev/broadsheetfb.c +++ b/drivers/video/fbdev/broadsheetfb.c @@ -1059,6 +1059,7 @@ static const struct fb_ops broadsheetfb_ops = { static struct fb_deferred_io broadsheetfb_defio = { .delay = HZ/4, + .sort_pagelist = true, .deferred_io = broadsheetfb_dpy_deferred_io, }; diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c index 95264a621221..bead69f39ffc 100644 --- a/drivers/video/fbdev/core/fb_defio.c +++ b/drivers/video/fbdev/core/fb_defio.c @@ -92,7 +92,7 @@ static vm_fault_t fb_deferred_io_mkwrite(struct vm_fault *vmf) struct page *page = vmf->page; struct fb_info *info = vmf->vma->vm_private_data; struct fb_deferred_io *fbdefio = info->fbdefio; - struct page *cur; + struct list_head *pos = &fbdefio->pagelist; /* this is a callback we get when userspace first tries to write to the page. we schedule a workqueue. that workqueue @@ -133,14 +133,24 @@ static vm_fault_t fb_deferred_io_mkwrite(struct vm_fault *vmf) if (!list_empty(&page->lru)) goto page_already_added; - /* we loop through the pagelist before adding in order - to keep the pagelist sorted */ - list_for_each_entry(cur, &fbdefio->pagelist, lru) { - if (cur->index > page->index) - break; + if (unlikely(fbdefio->sort_pagelist)) { + /* + * We loop through the pagelist before adding in order to + * keep the pagelist sorted. This has significant overhead + * of O(n^2) with n being the number of written pages. If + * possible, drivers should try to work with unsorted page + * lists instead. + */ + struct page *cur; + + list_for_each_entry(cur, &fbdefio->pagelist, lru) { + if (cur->index > page->index) + break; + } + pos = &cur->lru; } - list_add_tail(&page->lru, &cur->lru); + list_add_tail(&page->lru, pos); page_already_added: mutex_unlock(&fbdefio->lock); diff --git a/drivers/video/fbdev/metronomefb.c b/drivers/video/fbdev/metronomefb.c index 952826557a0c..af858dd23ea6 100644 --- a/drivers/video/fbdev/metronomefb.c +++ b/drivers/video/fbdev/metronomefb.c @@ -568,6 +568,7 @@ static const struct fb_ops metronomefb_ops = { static struct fb_deferred_io metronomefb_defio = { .delay = HZ, + .sort_pagelist = true, .deferred_io = metronomefb_dpy_deferred_io, }; diff --git a/drivers/video/fbdev/udlfb.c b/drivers/video/fbdev/udlfb.c index 0de7b867714a..8603898bf37e 100644 --- a/drivers/video/fbdev/udlfb.c +++ b/drivers/video/fbdev/udlfb.c @@ -982,6 +982,7 @@ static int dlfb_ops_open(struct fb_info *info, int user) if (fbdefio) { fbdefio->delay = DL_DEFIO_WRITE_DELAY; + fbdefio->sort_pagelist = true; fbdefio->deferred_io = dlfb_dpy_deferred_io; } diff --git a/include/linux/fb.h b/include/linux/fb.h index 3d7306c9a706..9a77ab615c36 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -204,6 +204,7 @@ struct fb_pixmap { struct fb_deferred_io { /* delay between mkwrite and deferred handler */ unsigned long delay; + bool sort_pagelist; /* sort pagelist by offset */ struct mutex lock; /* mutex that protects the page list */ struct list_head pagelist; /* list of touched pages */ /* callback */