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

Christian Brauner
2023-06-07T09:21:36Z

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)

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)