This allows creating a device-mapper device, opening it, and setting it to be deleted when unused in a single atomic operation. Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx> --- drivers/md/dm-ioctl.c | 67 +++++++++++++++++++++++++++++------ include/uapi/linux/dm-ioctl.h | 16 ++++++++- 2 files changed, 72 insertions(+), 11 deletions(-) diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 36fc6ae4737a05ab53ab67a8ccee525cb5fda082..05438dedcd17b7cac470fcc5a9721d67daad4bfb 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -853,9 +853,21 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param) static int dev_create(struct file *filp, struct dm_ioctl *param, size_t param_size) { - int r, m = DM_ANY_MINOR; + int r, m = DM_ANY_MINOR, fd; struct mapped_device *md; + /* Do not allow unknown flags */ + if (param->flags > (2 * DM_FILE_DESCRIPTOR_FLAG - 1)) + return -EINVAL; + + /* + * Do not allow creating a device that would just be destroyed + * before the ioctl returns. + */ + if ((param->flags & DM_DEFERRED_REMOVE) && + !(param->flags & DM_FILE_DESCRIPTOR_FLAG)) + return -EINVAL; + r = check_name(param->name); if (r) return r; @@ -867,20 +879,55 @@ static int dev_create(struct file *filp, struct dm_ioctl *param, size_t param_si if (r) return r; - r = dm_hash_insert(param->name, *param->uuid ? param->uuid : NULL, md); - if (r) { - dm_put(md); - dm_destroy(md); - return r; - } - param->flags &= ~DM_INACTIVE_PRESENT_FLAG; + r = dm_hash_insert(param->name, *param->uuid ? param->uuid : NULL, md); + if (r) + goto out_put; + + if (param->flags & DM_FILE_DESCRIPTOR_FLAG) { + struct block_device *bdev = dm_disk(md)->part0; + struct file *file; + + fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC); + if (fd < 0) { + r = fd; + goto out_put; + } + + file = blkdev_get_file(bdev, O_RDWR|O_CLOEXEC, NULL); + if (IS_ERR(file)) { + r = PTR_ERR(file); + goto out_put_fd; + } + + /* + * Simulate opening the device. The other checks in + * dm_blk_open() are not necessary becuase we have a reference + * to the `struct md`. + */ + atomic_inc(&md->open_count); + fd_install(fd, file); + param->file_descriptor = fd; + } + + /* + * If userspace requests it, automatically delete the device + * when it is no longer used + */ + if (param->flags & DM_DEFERRED_REMOVE) + set_bit(DMF_DEFERRED_REMOVE, &md->flags); + __dev_status(md, param); - dm_put(md); - return 0; + +out_put_fd: + put_unused_fd(fd); +out_put: + dm_put(md); + dm_destroy(md); + return r; } /* diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h index 7edf335778bae1cb206f6dd4d44e9cf7fb9da35c..30a6260ed7e06ff71fad1675dd4e7f9325d752a6 100644 --- a/include/uapi/linux/dm-ioctl.h +++ b/include/uapi/linux/dm-ioctl.h @@ -136,7 +136,13 @@ struct dm_ioctl { * For output, the ioctls return the event number, not the cookie. */ __u32 event_nr; /* in/out */ - __u32 padding; + + union { + /* Padding for named devices */ + __u32 padding; + /* For anonymous devices, this is a file descriptor. */ + __u32 file_descriptor; + }; __u64 dev; /* in/out */ @@ -382,4 +388,12 @@ enum { */ #define DM_IMA_MEASUREMENT_FLAG (1 << 19) /* In */ +/* + * If set in a DM_DEV_CREATE ioctl(), sets the file_descriptor field + * to a valid file descriptor. This can be combined with DM_DEFERRED_REMOVE + * to cause the device to be destroyed when the file descriptor is closed + * and is otherwise unused. + */ +#define DM_FILE_DESCRIPTOR_FLAG (1 << 20) /* In */ + #endif /* _LINUX_DM_IOCTL_H */ -- Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel