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Tue, 4 Feb 2025 08:21:55 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id q0/2MiPOoWeXaQAAD6G6ig (envelope-from ); Tue, 04 Feb 2025 08:21:55 +0000 Message-ID: Date: Tue, 4 Feb 2025 09:21:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/3] fb_defio: do not use deprecated page->mapping, index fields To: Lorenzo Stoakes , Andrew Morton Cc: Jaya Kumar , Simona Vetter , Helge Deller , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox , David Hildenbrand , Kajtar Zsolt , Maira Canal References: <3542c5bb74d2487cf45d1d02ee5e73a05c4d279a.1738347308.git.lorenzo.stoakes@oracle.com> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: <3542c5bb74d2487cf45d1d02ee5e73a05c4d279a.1738347308.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: pfx4rc4ooo9bkaweh57zujqbui9u9uy5 X-Rspam-User: X-Rspamd-Queue-Id: D2D45140004 X-Rspamd-Server: rspam03 X-HE-Tag: 1738657317-725318 X-HE-Meta: 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 Aap2JOBH 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Am 31.01.25 um 19:28 schrieb Lorenzo Stoakes: > With the introduction of mapping_wrprotect_page() 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 snese. > > 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. > > Signed-off-by: Lorenzo Stoakes > Tested-by: Kajtar Zsolt > --- > drivers/video/fbdev/core/fb_defio.c | 38 +++++++++-------------------- > include/linux/fb.h | 1 + > 2 files changed, 12 insertions(+), 27 deletions(-) > > diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c > index 65363df8e81b..b9bab27a8c0f 100644 > --- a/drivers/video/fbdev/core/fb_defio.c > +++ b/drivers/video/fbdev/core/fb_defio.c > @@ -69,14 +69,6 @@ static struct fb_deferred_io_pageref *fb_deferred_io_pageref_lookup(struct fb_in > 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 > + if (!vmf->vma->vm_file) > printk(KERN_ERR "no mapping available\n"); fb_err() here. > > - 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_page() > + * 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. > */ > @@ -274,14 +263,13 @@ 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); > 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_page(fbdefio->mapping, pgoff, 1, page); > } > > /* driver's callback with pagereflist */ > @@ -337,6 +325,7 @@ void fb_deferred_io_open(struct fb_info *info, > { > struct fb_deferred_io *fbdefio = info->fbdefio; > > + fbdefio->mapping = file->f_mapping; Does this still work if more than one program opens the file? Best regard Thomas > file->f_mapping->a_ops = &fb_deferred_io_aops; > fbdefio->open_count++; > } > @@ -344,13 +333,7 @@ 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 +353,6 @@ 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 5ba187e08cf7..cd653862ab99 100644 > --- 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); -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)