| Message ID | 20230308105012.1845-1-tiwai@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] fbdev: Fix incorrect page mapping clearance at fb_deferred_io_release() | expand |
On Wed, Mar 8, 2023 at 11:50 AM Takashi Iwai <tiwai@suse.de> wrote: > > The recent fix for the deferred I/O by the commit > 3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices") > caused a regression when the same fb device is opened/closed while > it's being used. It resulted in a frozen screen even if something > is redrawn there after the close. The breakage is because the patch > was made under a wrong assumption of a single open; in the current > code, fb_deferred_io_release() cleans up the page mapping of the > pageref list and it calls cancel_delayed_work_sync() unconditionally, > where both are no correct behavior for multiple opens. > > This patch adds a refcount for the opens of the device, and applies > the cleanup only when all files get closed. > > As both fb_deferred_io_open() and _close() are called always in the > fb_info lock (mutex), it's safe to use the normal int for the > refcounting. > > Also, a useless BUG_ON() is dropped. > > Fixes: 3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices") > Cc: <stable@vger.kernel.org> > Signed-off-by: Takashi Iwai <tiwai@suse.de> Looks good to me Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com> > --- > v1->v2: > * Rename to fb_deferred_io_lastclose() > * Rename the new field from opens to open_count > * Removed unused variable > * More comments about fb_info locking > > drivers/video/fbdev/core/fb_defio.c | 17 +++++++++++++---- > include/linux/fb.h | 1 + > 2 files changed, 14 insertions(+), 4 deletions(-) > > diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c > index aa5f059d0222..274f5d0fa247 100644 > --- a/drivers/video/fbdev/core/fb_defio.c > +++ b/drivers/video/fbdev/core/fb_defio.c > @@ -305,17 +305,18 @@ void fb_deferred_io_open(struct fb_info *info, > struct inode *inode, > struct file *file) > { > + struct fb_deferred_io *fbdefio = info->fbdefio; > + > file->f_mapping->a_ops = &fb_deferred_io_aops; > + fbdefio->open_count++; > } > EXPORT_SYMBOL_GPL(fb_deferred_io_open); > > -void fb_deferred_io_release(struct fb_info *info) > +static void fb_deferred_io_lastclose(struct fb_info *info) > { > - struct fb_deferred_io *fbdefio = info->fbdefio; > struct page *page; > int i; > > - BUG_ON(!fbdefio); > cancel_delayed_work_sync(&info->deferred_work); > > /* clear out the mapping that we setup */ > @@ -324,13 +325,21 @@ void fb_deferred_io_release(struct fb_info *info) > page->mapping = NULL; > } > } > + > +void fb_deferred_io_release(struct fb_info *info) > +{ > + struct fb_deferred_io *fbdefio = info->fbdefio; > + > + if (!--fbdefio->open_count) > + fb_deferred_io_lastclose(info); > +} > EXPORT_SYMBOL_GPL(fb_deferred_io_release); > > void fb_deferred_io_cleanup(struct fb_info *info) > { > struct fb_deferred_io *fbdefio = info->fbdefio; > > - fb_deferred_io_release(info); > + fb_deferred_io_lastclose(info); > > kvfree(info->pagerefs); > mutex_destroy(&fbdefio->lock); > diff --git a/include/linux/fb.h b/include/linux/fb.h > index d8d20514ea05..02d09cb57f6c 100644 > --- a/include/linux/fb.h > +++ b/include/linux/fb.h > @@ -212,6 +212,7 @@ struct fb_deferred_io { > /* delay between mkwrite and deferred handler */ > unsigned long delay; > bool sort_pagereflist; /* sort pagelist by offset */ > + 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 */ > /* callback */ > -- > 2.35.3 >
Added to drm-misc-fixes. Thanks a lot for the patch. Am 08.03.23 um 11:50 schrieb Takashi Iwai: > The recent fix for the deferred I/O by the commit > 3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices") > caused a regression when the same fb device is opened/closed while > it's being used. It resulted in a frozen screen even if something > is redrawn there after the close. The breakage is because the patch > was made under a wrong assumption of a single open; in the current > code, fb_deferred_io_release() cleans up the page mapping of the > pageref list and it calls cancel_delayed_work_sync() unconditionally, > where both are no correct behavior for multiple opens. > > This patch adds a refcount for the opens of the device, and applies > the cleanup only when all files get closed. > > As both fb_deferred_io_open() and _close() are called always in the > fb_info lock (mutex), it's safe to use the normal int for the > refcounting. > > Also, a useless BUG_ON() is dropped. > > Fixes: 3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices") > Cc: <stable@vger.kernel.org> > Signed-off-by: Takashi Iwai <tiwai@suse.de> > --- > v1->v2: > * Rename to fb_deferred_io_lastclose() > * Rename the new field from opens to open_count > * Removed unused variable > * More comments about fb_info locking > > drivers/video/fbdev/core/fb_defio.c | 17 +++++++++++++---- > include/linux/fb.h | 1 + > 2 files changed, 14 insertions(+), 4 deletions(-) > > diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c > index aa5f059d0222..274f5d0fa247 100644 > --- a/drivers/video/fbdev/core/fb_defio.c > +++ b/drivers/video/fbdev/core/fb_defio.c > @@ -305,17 +305,18 @@ void fb_deferred_io_open(struct fb_info *info, > struct inode *inode, > struct file *file) > { > + struct fb_deferred_io *fbdefio = info->fbdefio; > + > file->f_mapping->a_ops = &fb_deferred_io_aops; > + fbdefio->open_count++; > } > EXPORT_SYMBOL_GPL(fb_deferred_io_open); > > -void fb_deferred_io_release(struct fb_info *info) > +static void fb_deferred_io_lastclose(struct fb_info *info) > { > - struct fb_deferred_io *fbdefio = info->fbdefio; > struct page *page; > int i; > > - BUG_ON(!fbdefio); > cancel_delayed_work_sync(&info->deferred_work); > > /* clear out the mapping that we setup */ > @@ -324,13 +325,21 @@ void fb_deferred_io_release(struct fb_info *info) > page->mapping = NULL; > } > } > + > +void fb_deferred_io_release(struct fb_info *info) > +{ > + struct fb_deferred_io *fbdefio = info->fbdefio; > + > + if (!--fbdefio->open_count) > + fb_deferred_io_lastclose(info); > +} > EXPORT_SYMBOL_GPL(fb_deferred_io_release); > > void fb_deferred_io_cleanup(struct fb_info *info) > { > struct fb_deferred_io *fbdefio = info->fbdefio; > > - fb_deferred_io_release(info); > + fb_deferred_io_lastclose(info); > > kvfree(info->pagerefs); > mutex_destroy(&fbdefio->lock); > diff --git a/include/linux/fb.h b/include/linux/fb.h > index d8d20514ea05..02d09cb57f6c 100644 > --- a/include/linux/fb.h > +++ b/include/linux/fb.h > @@ -212,6 +212,7 @@ struct fb_deferred_io { > /* delay between mkwrite and deferred handler */ > unsigned long delay; > bool sort_pagereflist; /* sort pagelist by offset */ > + 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 */ > /* callback */
diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c index aa5f059d0222..274f5d0fa247 100644 --- a/drivers/video/fbdev/core/fb_defio.c +++ b/drivers/video/fbdev/core/fb_defio.c @@ -305,17 +305,18 @@ void fb_deferred_io_open(struct fb_info *info, struct inode *inode, struct file *file) { + struct fb_deferred_io *fbdefio = info->fbdefio; + file->f_mapping->a_ops = &fb_deferred_io_aops; + fbdefio->open_count++; } EXPORT_SYMBOL_GPL(fb_deferred_io_open); -void fb_deferred_io_release(struct fb_info *info) +static void fb_deferred_io_lastclose(struct fb_info *info) { - struct fb_deferred_io *fbdefio = info->fbdefio; struct page *page; int i; - BUG_ON(!fbdefio); cancel_delayed_work_sync(&info->deferred_work); /* clear out the mapping that we setup */ @@ -324,13 +325,21 @@ void fb_deferred_io_release(struct fb_info *info) page->mapping = NULL; } } + +void fb_deferred_io_release(struct fb_info *info) +{ + struct fb_deferred_io *fbdefio = info->fbdefio; + + if (!--fbdefio->open_count) + fb_deferred_io_lastclose(info); +} EXPORT_SYMBOL_GPL(fb_deferred_io_release); void fb_deferred_io_cleanup(struct fb_info *info) { struct fb_deferred_io *fbdefio = info->fbdefio; - fb_deferred_io_release(info); + fb_deferred_io_lastclose(info); kvfree(info->pagerefs); mutex_destroy(&fbdefio->lock); diff --git a/include/linux/fb.h b/include/linux/fb.h index d8d20514ea05..02d09cb57f6c 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -212,6 +212,7 @@ struct fb_deferred_io { /* delay between mkwrite and deferred handler */ unsigned long delay; bool sort_pagereflist; /* sort pagelist by offset */ + 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 */ /* callback */
The recent fix for the deferred I/O by the commit 3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices") caused a regression when the same fb device is opened/closed while it's being used. It resulted in a frozen screen even if something is redrawn there after the close. The breakage is because the patch was made under a wrong assumption of a single open; in the current code, fb_deferred_io_release() cleans up the page mapping of the pageref list and it calls cancel_delayed_work_sync() unconditionally, where both are no correct behavior for multiple opens. This patch adds a refcount for the opens of the device, and applies the cleanup only when all files get closed. As both fb_deferred_io_open() and _close() are called always in the fb_info lock (mutex), it's safe to use the normal int for the refcounting. Also, a useless BUG_ON() is dropped. Fixes: 3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices") Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de> --- v1->v2: * Rename to fb_deferred_io_lastclose() * Rename the new field from opens to open_count * Removed unused variable * More comments about fb_info locking drivers/video/fbdev/core/fb_defio.c | 17 +++++++++++++---- include/linux/fb.h | 1 + 2 files changed, 14 insertions(+), 4 deletions(-)