block: add a bdev_is_partition helper

Add a littler helper to make the somewhat arcane bd_contains checks a
little more obvious.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-lib.c

@@ -64,7 +64,7 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		return -EINVAL;
 
 	/* In case the discard request is in a partition */
-	if (bdev->bd_partno)
+	if (bdev_is_partition(bdev))
 		part_offset = bdev->bd_part->start_sect;
 
 	while (nr_sects) {

block/ioctl.c

@@ -23,7 +23,7 @@ static int blkpg_do_ioctl(struct block_device *bdev,
 		return -EACCES;
 	if (copy_from_user(&p, upart, sizeof(struct blkpg_partition)))
 		return -EFAULT;
-	if (bdev != bdev->bd_contains)
+	if (bdev_is_partition(bdev))
 		return -EINVAL;
 
 	if (p.pno <= 0)
@@ -94,7 +94,7 @@ static int blkdev_reread_part(struct block_device *bdev)
 {
 	int ret;
 
-	if (!disk_part_scan_enabled(bdev->bd_disk) || bdev != bdev->bd_contains)
+	if (!disk_part_scan_enabled(bdev->bd_disk) || bdev_is_partition(bdev))
 		return -EINVAL;
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;

block/scsi_ioctl.c

@@ -852,7 +852,7 @@ EXPORT_SYMBOL(scsi_cmd_ioctl);
 
 int scsi_verify_blk_ioctl(struct block_device *bd, unsigned int cmd)
 {
-	if (bd && bd == bd->bd_contains)
+	if (bd && !bdev_is_partition(bd))
 		return 0;
 
 	if (capable(CAP_SYS_RAWIO))

drivers/ide/ide-ioctls.c

@@ -49,7 +49,7 @@ int ide_setting_ioctl(ide_drive_t *drive, struct block_device *bdev,
 	return err >= 0 ? put_user_long(err, arg) : err;
 
 set_val:
-	if (bdev != bdev->bd_contains)
+	if (bdev_is_partition(bdev))
 		err = -EINVAL;
 	else {
 		if (!capable(CAP_SYS_ADMIN))
@@ -257,7 +257,7 @@ int generic_ide_ioctl(ide_drive_t *drive, struct block_device *bdev,
 	switch (cmd) {
 	case HDIO_OBSOLETE_IDENTITY:
 	case HDIO_GET_IDENTITY:
-		if (bdev != bdev->bd_contains)
+		if (bdev_is_partition(bdev))
 			return -EINVAL;
 		return ide_get_identity_ioctl(drive, cmd, argp);
 	case HDIO_GET_NICE:

drivers/md/dm-table.c

@@ -903,7 +903,7 @@ static int device_is_rq_stackable(struct dm_target *ti, struct dm_dev *dev,
 	struct request_queue *q = bdev_get_queue(bdev);
 
 	/* request-based cannot stack on partitions! */
-	if (bdev != bdev->bd_contains)
+	if (bdev_is_partition(bdev))
 		return false;
 
 	return queue_is_mq(q);

drivers/mmc/core/block.c

@@ -723,7 +723,7 @@ static int mmc_blk_check_blkdev(struct block_device *bdev)
 	 * whole block device, not on a partition.  This prevents overspray
 	 * between sibling partitions.
 	 */
-	if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
+	if (!capable(CAP_SYS_RAWIO) || bdev_is_partition(bdev))
 		return -EPERM;
 	return 0;
 }

drivers/s390/block/dasd_ioctl.c

@@ -277,7 +277,7 @@ dasd_ioctl_format(struct block_device *bdev, void __user *argp)
 		dasd_put_device(base);
 		return -EFAULT;
 	}
-	if (bdev != bdev->bd_contains) {
+	if (bdev_is_partition(bdev)) {
 		pr_warn("%s: The specified DASD is a partition and cannot be formatted\n",
 			dev_name(&base->cdev->dev));
 		dasd_put_device(base);
@@ -304,7 +304,7 @@ static int dasd_ioctl_check_format(struct block_device *bdev, void __user *argp)
 	base = dasd_device_from_gendisk(bdev->bd_disk);
 	if (!base)
 		return -ENODEV;
-	if (bdev != bdev->bd_contains) {
+	if (bdev_is_partition(bdev)) {
 		pr_warn("%s: The specified DASD is a partition and cannot be checked\n",
 			dev_name(&base->cdev->dev));
 		rc = -EINVAL;
@@ -362,7 +362,7 @@ static int dasd_ioctl_release_space(struct block_device *bdev, void __user *argp
 		rc = -EROFS;
 		goto out_err;
 	}
-	if (bdev != bdev->bd_contains) {
+	if (bdev_is_partition(bdev)) {
 		pr_warn("%s: The specified DASD is a partition and tracks cannot be released\n",
 			dev_name(&base->cdev->dev));
 		rc = -EINVAL;
@@ -540,7 +540,7 @@ dasd_ioctl_set_ro(struct block_device *bdev, void __user *argp)
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
-	if (bdev != bdev->bd_contains)
+	if (bdev_is_partition(bdev))
 		// ro setting is not allowed for partitions
 		return -EINVAL;
 	if (get_user(intval, (int __user *)argp))

fs/nfsd/blocklayout.c

@@ -170,7 +170,7 @@ nfsd4_block_proc_getdeviceinfo(struct super_block *sb,
 		struct nfs4_client *clp,
 		struct nfsd4_getdeviceinfo *gdp)
 {
-	if (sb->s_bdev != sb->s_bdev->bd_contains)
+	if (bdev_is_partition(sb->s_bdev))
 		return nfserr_inval;
 	return nfserrno(nfsd4_block_get_device_info_simple(sb, gdp));
 }
@@ -382,7 +382,7 @@ nfsd4_scsi_proc_getdeviceinfo(struct super_block *sb,
 		struct nfs4_client *clp,
 		struct nfsd4_getdeviceinfo *gdp)
 {
-	if (sb->s_bdev != sb->s_bdev->bd_contains)
+	if (bdev_is_partition(sb->s_bdev))
 		return nfserr_inval;
 	return nfserrno(nfsd4_block_get_device_info_scsi(sb, clp, gdp));
 }

include/linux/blkdev.h

@@ -1353,6 +1353,11 @@ static inline int sb_issue_zeroout(struct super_block *sb, sector_t block,
 
 extern int blk_verify_command(unsigned char *cmd, fmode_t mode);
 
+static inline bool bdev_is_partition(struct block_device *bdev)
+{
+	return bdev->bd_partno;
+}
+
 enum blk_default_limits {
 	BLK_MAX_SEGMENTS	= 128,
 	BLK_SAFE_MAX_SECTORS	= 255,
@@ -1469,7 +1474,7 @@ static inline int bdev_alignment_offset(struct block_device *bdev)
 
 	if (q->limits.misaligned)
 		return -1;
-	if (bdev != bdev->bd_contains)
+	if (bdev_is_partition(bdev))
 		return queue_limit_alignment_offset(&q->limits,
 				bdev->bd_part->start_sect);
 	return q->limits.alignment_offset;
@@ -1510,7 +1515,7 @@ static inline int bdev_discard_alignment(struct block_device *bdev)
 {
 	struct request_queue *q = bdev_get_queue(bdev);
 
-	if (bdev != bdev->bd_contains)
+	if (bdev_is_partition(bdev))
 		return queue_limit_discard_alignment(&q->limits,
 				bdev->bd_part->start_sect);
 	return q->limits.discard_alignment;

kernel/trace/blktrace.c

@@ -527,7 +527,7 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 	 * and scsi-generic block devices we create a temporary new debugfs
 	 * directory that will be removed once the trace ends.
 	 */
-	if (bdev && bdev == bdev->bd_contains)
+	if (bdev && !bdev_is_partition(bdev))
 		dir = q->debugfs_dir;
 	else
 		bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root);