Re: [PATCH 28/31] block: replace fmode_t with a block-specific type for block open flags

[Christian Brauner <brauner@kernel.org>]

On Wed, Jun 07, 2023 at 11:21:24AM +0200, Christian Brauner wrote:
> On Tue, Jun 06, 2023 at 09:39:47AM +0200, Christoph Hellwig wrote:
> > The only overlap between the block open flags mapped into the fmode_t and
> > other uses of fmode_t are FMODE_READ and FMODE_WRITE.  Define a new
> 
> and FMODE_EXCL afaict
> 
> > blk_mode_t instead for use in blkdev_get_by_*, ->open and ->ioctl and
> > stop abusing fmode_t.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> >  arch/um/drivers/ubd_kern.c          |  8 +++---
> >  arch/xtensa/platforms/iss/simdisk.c |  2 +-
> >  block/bdev.c                        | 32 +++++++++++-----------
> >  block/blk-zoned.c                   |  8 +++---
> >  block/blk.h                         | 11 ++++----
> >  block/fops.c                        | 26 +++++++++++++-----
> >  block/genhd.c                       |  8 +++---
> >  block/ioctl.c                       | 42 +++++++++--------------------
> >  drivers/block/amiflop.c             | 12 ++++-----
> >  drivers/block/aoe/aoeblk.c          |  4 +--
> >  drivers/block/ataflop.c             | 25 +++++++++--------
> >  drivers/block/drbd/drbd_main.c      |  7 ++---
> >  drivers/block/drbd/drbd_nl.c        |  2 +-
> >  drivers/block/floppy.c              | 28 +++++++++----------
> >  drivers/block/loop.c                | 22 +++++++--------
> >  drivers/block/mtip32xx/mtip32xx.c   |  4 +--
> >  drivers/block/nbd.c                 |  4 +--
> >  drivers/block/pktcdvd.c             | 17 ++++++------
> >  drivers/block/rbd.c                 |  2 +-
> >  drivers/block/rnbd/rnbd-clt.c       |  4 +--
> >  drivers/block/rnbd/rnbd-srv.c       |  4 +--
> >  drivers/block/sunvdc.c              |  2 +-
> >  drivers/block/swim.c                | 16 +++++------
> >  drivers/block/swim3.c               | 24 ++++++++---------
> >  drivers/block/ublk_drv.c            |  2 +-
> >  drivers/block/xen-blkback/xenbus.c  |  2 +-
> >  drivers/block/xen-blkfront.c        |  2 +-
> >  drivers/block/z2ram.c               |  2 +-
> >  drivers/block/zram/zram_drv.c       |  6 ++---
> >  drivers/cdrom/cdrom.c               |  4 +--
> >  drivers/cdrom/gdrom.c               |  4 +--
> >  drivers/md/bcache/bcache.h          |  2 +-
> >  drivers/md/bcache/request.c         |  4 +--
> >  drivers/md/bcache/super.c           |  6 ++---
> >  drivers/md/dm-cache-target.c        | 12 ++++-----
> >  drivers/md/dm-clone-target.c        | 10 +++----
> >  drivers/md/dm-core.h                |  7 +++--
> >  drivers/md/dm-era-target.c          |  6 +++--
> >  drivers/md/dm-ioctl.c               | 10 +++----
> >  drivers/md/dm-snap.c                |  4 +--
> >  drivers/md/dm-table.c               | 11 ++++----
> >  drivers/md/dm-thin.c                |  9 ++++---
> >  drivers/md/dm-verity-fec.c          |  2 +-
> >  drivers/md/dm-verity-target.c       |  6 ++---
> >  drivers/md/dm.c                     | 10 +++----
> >  drivers/md/dm.h                     |  2 +-
> >  drivers/md/md.c                     |  8 +++---
> >  drivers/mmc/core/block.c            |  8 +++---
> >  drivers/mtd/devices/block2mtd.c     |  4 +--
> >  drivers/mtd/mtd_blkdevs.c           |  4 +--
> >  drivers/mtd/ubi/block.c             |  5 ++--
> >  drivers/nvme/host/core.c            |  2 +-
> >  drivers/nvme/host/ioctl.c           |  8 +++---
> >  drivers/nvme/host/multipath.c       |  2 +-
> >  drivers/nvme/host/nvme.h            |  4 +--
> >  drivers/nvme/target/io-cmd-bdev.c   |  2 +-
> >  drivers/s390/block/dasd.c           |  6 ++---
> >  drivers/s390/block/dasd_genhd.c     |  3 ++-
> >  drivers/s390/block/dasd_int.h       |  3 ++-
> >  drivers/s390/block/dasd_ioctl.c     |  2 +-
> >  drivers/s390/block/dcssblk.c        |  4 +--
> >  drivers/scsi/sd.c                   | 19 ++++++-------
> >  drivers/scsi/sr.c                   | 10 +++----
> >  drivers/target/target_core_iblock.c |  5 ++--
> >  drivers/target/target_core_pscsi.c  |  4 +--
> >  fs/btrfs/dev-replace.c              |  2 +-
> >  fs/btrfs/super.c                    |  4 +--
> >  fs/btrfs/volumes.c                  | 16 +++++------
> >  fs/btrfs/volumes.h                  |  4 +--
> >  fs/erofs/super.c                    |  2 +-
> >  fs/ext4/super.c                     |  2 +-
> >  fs/jfs/jfs_logmgr.c                 |  2 +-
> >  fs/nfs/blocklayout/dev.c            |  5 ++--
> >  fs/ocfs2/cluster/heartbeat.c        |  3 ++-
> >  fs/reiserfs/journal.c               |  4 +--
> >  fs/xfs/xfs_super.c                  |  2 +-
> >  include/linux/blkdev.h              | 30 ++++++++++++++++-----
> >  include/linux/cdrom.h               |  3 ++-
> >  include/linux/device-mapper.h       |  8 +++---
> >  kernel/power/swap.c                 |  6 ++---
> >  mm/swapfile.c                       |  2 +-
> >  81 files changed, 324 insertions(+), 311 deletions(-)
> > 
> > diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
> > index 20c1a16199c503..50206feac577d5 100644
> > --- a/arch/um/drivers/ubd_kern.c
> > +++ b/arch/um/drivers/ubd_kern.c
> > @@ -108,9 +108,9 @@ static inline void ubd_set_bit(__u64 bit, unsigned char *data)
> >  static DEFINE_MUTEX(ubd_lock);
> >  static DEFINE_MUTEX(ubd_mutex); /* replaces BKL, might not be needed */
> >  
> > -static int ubd_open(struct gendisk *disk, fmode_t mode);
> > +static int ubd_open(struct gendisk *disk, blk_mode_t mode);
> >  static void ubd_release(struct gendisk *disk);
> > -static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
> > +static int ubd_ioctl(struct block_device *bdev, blk_mode_t mode,
> >  		     unsigned int cmd, unsigned long arg);
> >  static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);
> >  
> > @@ -1154,7 +1154,7 @@ static int __init ubd_driver_init(void){
> >  
> >  device_initcall(ubd_driver_init);
> >  
> > -static int ubd_open(struct gendisk *disk, fmode_t mode)
> > +static int ubd_open(struct gendisk *disk, blk_mode_t mode)
> >  {
> >  	struct ubd *ubd_dev = disk->private_data;
> >  	int err = 0;
> > @@ -1389,7 +1389,7 @@ static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
> >  	return 0;
> >  }
> >  
> > -static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
> > +static int ubd_ioctl(struct block_device *bdev, blk_mode_t mode,
> >  		     unsigned int cmd, unsigned long arg)
> >  {
> >  	struct ubd *ubd_dev = bdev->bd_disk->private_data;
> > diff --git a/arch/xtensa/platforms/iss/simdisk.c b/arch/xtensa/platforms/iss/simdisk.c
> > index 2ad9da3de0d90f..178cf96ca10acb 100644
> > --- a/arch/xtensa/platforms/iss/simdisk.c
> > +++ b/arch/xtensa/platforms/iss/simdisk.c
> > @@ -120,7 +120,7 @@ static void simdisk_submit_bio(struct bio *bio)
> >  	bio_endio(bio);
> >  }
> >  
> > -static int simdisk_open(struct gendisk *disk, fmode_t mode)
> > +static int simdisk_open(struct gendisk *disk, blk_mode_t mode)
> >  {
> >  	struct simdisk *dev = disk->private_data;
> >  
> > diff --git a/block/bdev.c b/block/bdev.c
> > index db63e5bcc46ffa..bd558a9ba3cd97 100644
> > --- a/block/bdev.c
> > +++ b/block/bdev.c
> > @@ -93,7 +93,7 @@ EXPORT_SYMBOL(invalidate_bdev);
> >   * Drop all buffers & page cache for given bdev range. This function bails
> >   * with error if bdev has other exclusive owner (such as filesystem).
> >   */
> > -int truncate_bdev_range(struct block_device *bdev, fmode_t mode,
> > +int truncate_bdev_range(struct block_device *bdev, blk_mode_t mode,
> >  			loff_t lstart, loff_t lend)
> >  {
> >  	/*
> > @@ -101,14 +101,14 @@ int truncate_bdev_range(struct block_device *bdev, fmode_t mode,
> >  	 * while we discard the buffer cache to avoid discarding buffers
> >  	 * under live filesystem.
> >  	 */
> > -	if (!(mode & FMODE_EXCL)) {
> > +	if (!(mode & BLK_OPEN_EXCL)) {
> >  		int err = bd_prepare_to_claim(bdev, truncate_bdev_range, NULL);
> >  		if (err)
> >  			goto invalidate;
> >  	}
> >  
> >  	truncate_inode_pages_range(bdev->bd_inode->i_mapping, lstart, lend);
> > -	if (!(mode & FMODE_EXCL))
> > +	if (!(mode & BLK_OPEN_EXCL))
> >  		bd_abort_claiming(bdev, truncate_bdev_range);
> >  	return 0;
> >  
> > @@ -647,7 +647,7 @@ static void blkdev_flush_mapping(struct block_device *bdev)
> >  	bdev_write_inode(bdev);
> >  }
> >  
> > -static int blkdev_get_whole(struct block_device *bdev, fmode_t mode)
> > +static int blkdev_get_whole(struct block_device *bdev, blk_mode_t mode)
> >  {
> >  	struct gendisk *disk = bdev->bd_disk;
> >  	int ret;
> > @@ -679,7 +679,7 @@ static void blkdev_put_whole(struct block_device *bdev)
> >  		bdev->bd_disk->fops->release(bdev->bd_disk);
> >  }
> >  
> > -static int blkdev_get_part(struct block_device *part, fmode_t mode)
> > +static int blkdev_get_part(struct block_device *part, blk_mode_t mode)
> >  {
> >  	struct gendisk *disk = part->bd_disk;
> >  	int ret;
> > @@ -743,11 +743,11 @@ void blkdev_put_no_open(struct block_device *bdev)
> >  {
> >  	put_device(&bdev->bd_device);
> >  }
> > -
> > +	
> 
> nit: This is whitespace damage, I think. There's a trailing tab.
> 
> >  /**
> >   * blkdev_get_by_dev - open a block device by device number
> >   * @dev: device number of block device to open
> > - * @mode: FMODE_* mask
> > + * @mode: open mode (BLK_OPEN_*)
> >   * @holder: exclusive holder identifier
> >   * @hops: holder operations
> >   *
> > @@ -765,7 +765,7 @@ void blkdev_put_no_open(struct block_device *bdev)
> >   * RETURNS:
> >   * Reference to the block_device on success, ERR_PTR(-errno) on failure.
> >   */
> > -struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder,
> > +struct block_device *blkdev_get_by_dev(dev_t dev, blk_mode_t mode, void *holder,
> >  		const struct blk_holder_ops *hops)
> >  {
> >  	bool unblock_events = true;
> > @@ -775,8 +775,8 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder,
> >  
> >  	ret = devcgroup_check_permission(DEVCG_DEV_BLOCK,
> >  			MAJOR(dev), MINOR(dev),
> > -			((mode & FMODE_READ) ? DEVCG_ACC_READ : 0) |
> > -			((mode & FMODE_WRITE) ? DEVCG_ACC_WRITE : 0));
> > +			((mode & BLK_OPEN_READ) ? DEVCG_ACC_READ : 0) |
> > +			((mode & BLK_OPEN_WRITE) ? DEVCG_ACC_WRITE : 0));
> >  	if (ret)
> >  		return ERR_PTR(ret);
> >  
> > @@ -786,12 +786,12 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder,
> >  	disk = bdev->bd_disk;
> >  
> >  	if (holder) {
> > -		mode |= FMODE_EXCL;
> > +		mode |= BLK_OPEN_EXCL;
> >  		ret = bd_prepare_to_claim(bdev, holder, hops);
> >  		if (ret)
> >  			goto put_blkdev;
> >  	} else {
> > -		if (WARN_ON_ONCE(mode & FMODE_EXCL)) {
> > +		if (WARN_ON_ONCE(mode & BLK_OPEN_EXCL)) {
> >  			ret = -EIO;
> >  			goto put_blkdev;
> >  		}
> > @@ -821,7 +821,7 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder,
> >  		 * writeable reference is too fragile given the way @mode is
> >  		 * used in blkdev_get/put().
> >  		 */
> > -		if ((mode & FMODE_WRITE) && !bdev->bd_write_holder &&
> > +		if ((mode & BLK_OPEN_WRITE) && !bdev->bd_write_holder &&
> >  		    (disk->event_flags & DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE)) {
> >  			bdev->bd_write_holder = true;
> >  			unblock_events = false;
> > @@ -848,7 +848,7 @@ EXPORT_SYMBOL(blkdev_get_by_dev);
> >  /**
> >   * blkdev_get_by_path - open a block device by name
> >   * @path: path to the block device to open
> > - * @mode: FMODE_* mask
> > + * @mode: open mode (BLK_OPEN_*)
> >   * @holder: exclusive holder identifier
> >   *
> >   * Open the block device described by the device file at @path.  If @holder is
> > @@ -861,7 +861,7 @@ EXPORT_SYMBOL(blkdev_get_by_dev);
> >   * RETURNS:
> >   * Reference to the block_device on success, ERR_PTR(-errno) on failure.
> >   */
> > -struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
> > +struct block_device *blkdev_get_by_path(const char *path, blk_mode_t mode,
> >  		void *holder, const struct blk_holder_ops *hops)
> >  {
> >  	struct block_device *bdev;
> > @@ -873,7 +873,7 @@ struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
> >  		return ERR_PTR(error);
> >  
> >  	bdev = blkdev_get_by_dev(dev, mode, holder, hops);
> > -	if (!IS_ERR(bdev) && (mode & FMODE_WRITE) && bdev_read_only(bdev)) {
> > +	if (!IS_ERR(bdev) && (mode & BLK_OPEN_WRITE) && bdev_read_only(bdev)) {
> >  		blkdev_put(bdev, holder);
> >  		return ERR_PTR(-EACCES);
> >  	}
> > diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> > index 02cc2c629ac9be..0f9f97cdddd99c 100644
> > --- a/block/blk-zoned.c
> > +++ b/block/blk-zoned.c
> > @@ -356,8 +356,8 @@ int blkdev_report_zones_ioctl(struct block_device *bdev, unsigned int cmd,
> >  	return 0;
> >  }
> >  
> > -static int blkdev_truncate_zone_range(struct block_device *bdev, fmode_t mode,
> > -				      const struct blk_zone_range *zrange)
> > +static int blkdev_truncate_zone_range(struct block_device *bdev,
> > +		blk_mode_t mode, const struct blk_zone_range *zrange)
> >  {
> >  	loff_t start, end;
> >  
> > @@ -376,7 +376,7 @@ static int blkdev_truncate_zone_range(struct block_device *bdev, fmode_t mode,
> >   * BLKRESETZONE, BLKOPENZONE, BLKCLOSEZONE and BLKFINISHZONE ioctl processing.
> >   * Called from blkdev_ioctl.
> >   */
> > -int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
> > +int blkdev_zone_mgmt_ioctl(struct block_device *bdev, blk_mode_t mode,
> >  			   unsigned int cmd, unsigned long arg)
> >  {
> >  	void __user *argp = (void __user *)arg;
> > @@ -390,7 +390,7 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
> >  	if (!bdev_is_zoned(bdev))
> >  		return -ENOTTY;
> >  
> > -	if (!(mode & FMODE_WRITE))
> > +	if (!(mode & BLK_OPEN_WRITE))
> >  		return -EBADF;
> >  
> >  	if (copy_from_user(&zrange, argp, sizeof(struct blk_zone_range)))
> > diff --git a/block/blk.h b/block/blk.h
> > index e28d5d67d31a28..768852a84fefb3 100644
> > --- a/block/blk.h
> > +++ b/block/blk.h
> > @@ -396,7 +396,7 @@ void disk_free_zone_bitmaps(struct gendisk *disk);
> >  void disk_clear_zone_settings(struct gendisk *disk);
> >  int blkdev_report_zones_ioctl(struct block_device *bdev, unsigned int cmd,
> >  		unsigned long arg);
> > -int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
> > +int blkdev_zone_mgmt_ioctl(struct block_device *bdev, blk_mode_t mode,
> >  		unsigned int cmd, unsigned long arg);
> >  #else /* CONFIG_BLK_DEV_ZONED */
> >  static inline void disk_free_zone_bitmaps(struct gendisk *disk) {}
> > @@ -407,7 +407,7 @@ static inline int blkdev_report_zones_ioctl(struct block_device *bdev,
> >  	return -ENOTTY;
> >  }
> >  static inline int blkdev_zone_mgmt_ioctl(struct block_device *bdev,
> > -		fmode_t mode, unsigned int cmd, unsigned long arg)
> > +		blk_mode_t mode, unsigned int cmd, unsigned long arg)
> >  {
> >  	return -ENOTTY;
> >  }
> > @@ -451,7 +451,7 @@ static inline void bio_release_page(struct bio *bio, struct page *page)
> >  
> >  struct request_queue *blk_alloc_queue(int node_id);
> >  
> > -int disk_scan_partitions(struct gendisk *disk, fmode_t mode);
> > +int disk_scan_partitions(struct gendisk *disk, blk_mode_t mode);
> >  
> >  int disk_alloc_events(struct gendisk *disk);
> >  void disk_add_events(struct gendisk *disk);
> > @@ -466,8 +466,9 @@ extern struct device_attribute dev_attr_events_poll_msecs;
> >  
> >  extern struct attribute_group blk_trace_attr_group;
> >  
> > -int truncate_bdev_range(struct block_device *bdev, fmode_t mode, loff_t lstart,
> > -		loff_t lend);
> > +blk_mode_t file_to_blk_mode(struct file *file);
> > +int truncate_bdev_range(struct block_device *bdev, blk_mode_t mode,
> > +		loff_t lstart, loff_t lend);
> >  long blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg);
> >  long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg);
> >  
> > diff --git a/block/fops.c b/block/fops.c
> > index 9f26e25bafa172..928c37a214f785 100644
> > --- a/block/fops.c
> > +++ b/block/fops.c
> > @@ -470,6 +470,24 @@ static int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
> >  	return error;
> >  }
> >  
> > +blk_mode_t file_to_blk_mode(struct file *file)
> > +{
> > +	blk_mode_t mode = 0;
> > +
> > +	if (file->f_mode & FMODE_READ)
> > +		mode |= BLK_OPEN_READ;
> > +	if (file->f_mode & FMODE_WRITE)
> > +		mode |= BLK_OPEN_WRITE;
> > +	if (file->f_mode & FMODE_EXCL)
> > +		mode |= BLK_OPEN_EXCL;
> > +	if ((file->f_flags & O_ACCMODE) == 3)
> 
> I really don't like magic numbers like this.
> 
> Groan, O_RDONLY being defined as 0 strikes again...
> Becuase of this quirk we internally map
> 
> O_RDONLY(0) -> FMODE_READ(1)
> O_WRONLY(1) -> FMODE_WRITE(2)
> O_RDWR(3)   -> (FMODE_READ | FMODE_WRITE)

s/O_RDWR(3)/O_RDWR(2)/

> 
> so checking for the raw 3 here is confusing in addition to being a magic
> number as it could give the impression that what's checked here is
> (O_WRONLY | O_RDWR) which doesn't make sense...
> 
> So my perference would be in descending order of preference:
> 
> (file->f_flags & O_ACCMODE) == (FMODE_READ | FMODE_WRITE)
> 
> or while a little less clear but informative enough for people familiar
> with the O_RDONLY quirk:
> 
> if ((file->f_flags & O_ACCMODE) == O_ACCMODE)