[PATCH 10/10] nbd: Create size change events for userspace

Markus Pargmann
2015-07-27T07:15:01Z

The userspace needs to know when nbd devices are ready for use.
Currently no events are created for the userspace which doesn't work for
systemd.

See the discussion here: https://github.com/systemd/systemd/pull/358

This patch uses a central point to setup the nbd-internal sizes. A ioctl
to set a size does not lead to a visible size change. The size of the
block device will be kept at 0 until nbd is connected. As soon as it
connects, the size will be changed to the real value and a uevent is
created. When disconnecting, the blockdevice is set to 0 size and
another uevent is generated.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
---
drivers/block/nbd.c | 74 ++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 54 insertions(+), 20 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 1176a3b27a7e..95eb2904c324 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -97,6 +97,11 @@ static inline struct device *nbd_to_dev(struct nbd_device *nbd)
return disk_to_dev(nbd->disk);
}

+static bool nbd_is_connected(struct nbd_device *nbd)
+{
+ return !!nbd->task_recv;
+}
+
static const char *nbdcmd_to_ascii(int cmd)
{
switch (cmd) {
@@ -109,6 +114,43 @@ static const char *nbdcmd_to_ascii(int cmd)
return "invalid";
}

+static int nbd_size_clear(struct nbd_device *nbd, struct block_device *bdev)
+{
+ bdev->bd_inode->i_size = 0;
+ set_blocksize(bdev, 0);
+ set_capacity(nbd->disk, 0);
+ kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
+
+ return 0;
+}
+
+static int nbd_size_update(struct nbd_device *nbd, struct block_device *bdev)
+{
+ int ret;
+
+ if (!nbd_is_connected(nbd))
+ return 0;
+
+ ret = set_blocksize(bdev, nbd->blksize);
+ if (ret)
+ return ret;
+
+ bdev->bd_inode->i_size = nbd->bytesize;
+ set_capacity(nbd->disk, nbd->bytesize >> 9);
+ kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
+
+ return 0;
+}
+
+static int nbd_size_set(struct nbd_device *nbd, struct block_device *bdev,
+ int blocksize, int nr_blocks)
+{
+ nbd->blksize = blocksize;
+ nbd->bytesize = blocksize * nr_blocks;
+
+ return nbd_size_update(nbd, bdev);
+}
+
static void nbd_end_request(struct nbd_device *nbd, struct request *req)
{
int error = req->errors ? -EIO : 0;
@@ -399,7 +441,7 @@ static struct device_attribute pid_attr = {
.show = pid_show,
};

-static int nbd_thread_recv(struct nbd_device *nbd)
+static int nbd_thread_recv(struct nbd_device *nbd, struct block_device *bdev)
{
struct request *req;
int ret;
@@ -417,6 +459,8 @@ static int nbd_thread_recv(struct nbd_device *nbd)
return ret;
}

+ nbd_size_update(nbd, bdev);
+
while (1) {
req = nbd_read_stat(nbd);
if (IS_ERR(req)) {
@@ -427,6 +471,8 @@ static int nbd_thread_recv(struct nbd_device *nbd)
nbd_end_request(nbd, req);
}

+ nbd_size_clear(nbd, bdev);
+
device_remove_file(disk_to_dev(nbd->disk), &pid_attr);

nbd->task_recv = NULL;
@@ -681,19 +727,14 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
}

case NBD_SET_BLKSIZE:
- nbd->blksize = arg;
- nbd->bytesize &= ~(nbd->blksize-1);
- bdev->bd_inode->i_size = nbd->bytesize;
- set_blocksize(bdev, nbd->blksize);
- set_capacity(nbd->disk, nbd->bytesize >> 9);
- return 0;
+ return nbd_size_set(nbd, bdev, arg, nbd->bytesize / arg);

case NBD_SET_SIZE:
- nbd->bytesize = arg & ~(nbd->blksize-1);
- bdev->bd_inode->i_size = nbd->bytesize;
- set_blocksize(bdev, nbd->blksize);
- set_capacity(nbd->disk, nbd->bytesize >> 9);
- return 0;
+ return nbd_size_set(nbd, bdev, nbd->blksize,
+ arg / nbd->blksize);
+
+ case NBD_SET_SIZE_BLOCKS:
+ return nbd_size_set(nbd, bdev, nbd->blksize, arg);

case NBD_SET_TIMEOUT:
nbd->xmit_timeout = arg * HZ;
@@ -709,13 +750,6 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
nbd->flags = arg;
return 0;

- case NBD_SET_SIZE_BLOCKS:
- nbd->bytesize = ((u64) arg) * nbd->blksize;
- bdev->bd_inode->i_size = nbd->bytesize;
- set_blocksize(bdev, nbd->blksize);
- set_capacity(nbd->disk, nbd->bytesize >> 9);
- return 0;
-
case NBD_DO_IT: {
struct task_struct *thread;
struct socket *sock;
@@ -746,7 +780,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
}

nbd_dev_dbg_init(nbd);
- error = nbd_thread_recv(nbd);
+ error = nbd_thread_recv(nbd, bdev);
nbd_dev_dbg_close(nbd);
kthread_stop(thread);

--
2.1.4