On 2017/4/12 下午2:26, NeilBrown wrote:
> The intention when creating the "new_array" parameter and the
> possibility of having array names line "md_HOME" was to transition
> away from the old way of creating arrays and to eventually only use
> this new way.
>
> The "old" way of creating array is to create a device node in /dev
> and then open it. The act of opening creates the array.
> This is problematic because sometimes the device node can be opened
> when we don't want to create an array. This can easily happen
> when some rule triggered by udev looks at a device as it is being
> destroyed. The node in /dev continues to exist for a short period
> after an array is stopped, and opening it during this time recreates
> the array (as an inactive array).
>
> Unfortunately no clear plan for the transition was created. It is now
> time to fix that.
>
> This patch allows devices with numeric names, like "md999" to be
> created by writing to "new_array". This will only work if the minor
> number given is not already in use. This will allow mdadm to
> support the creation of arrays with numbers > 511 (currently not
> possible) by writing to new_array.
> mdadm can, at some point, use this approach to create *all* arrays,
> which will allow the transition to only using the new-way.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxxx>
Acted-by: Coly Li <colyli@xxxxxxx>
> ---
> drivers/md/md.c | 34 ++++++++++++++++++++++++++++------
> 1 file changed, 28 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 9fe930109012..c3d3bae947a1 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -5164,6 +5164,14 @@ static void no_op(struct percpu_ref *r) {}
>
> static int md_alloc(dev_t dev, char *name)
> {
> + /* If dev is zero, name is the name of a device to allocate with
> + * an arbitrary minor number. It will be "md_???"
> + * If dev is non-zero it must be a device number with a MAJOR of
> + * MD_MAJOR or mdp_major. In this case, if "name" is NULL, then
> + * the device is being created by opening a node in /dev.
> + * If "name" is not NULL, the device is being created by
> + * writing to /sys/module/md_mod/parameters/new_array.
> + */
> static DEFINE_MUTEX(disks_mutex);
> struct mddev *mddev = mddev_find(dev);
> struct gendisk *disk;
> @@ -5189,7 +5197,7 @@ static int md_alloc(dev_t dev, char *name)
> if (mddev->gendisk)
> goto abort;
>
> - if (name) {
> + if (name && !dev) {
> /* Need to ensure that 'name' is not a duplicate.
> */
> struct mddev *mddev2;
> @@ -5203,6 +5211,11 @@ static int md_alloc(dev_t dev, char *name)
> }
> spin_unlock(&all_mddevs_lock);
> }
> + if (name && dev)
> + /*
> + * Creating /dev/mdNNN via "newarray", so adjust hold_active.
> + */
> + mddev->hold_active = UNTIL_STOP;
>
> error = -ENOMEM;
> mddev->queue = blk_alloc_queue(GFP_KERNEL);
> @@ -5279,21 +5292,30 @@ static struct kobject *md_probe(dev_t dev, int *part, void *data)
>
> static int add_named_array(const char *val, struct kernel_param *kp)
> {
> - /* val must be "md_*" where * is not all digits.
> - * We allocate an array with a large free minor number, and
> + /* val must be "md_*" or "mdNNN".
> + * For "md_*" we allocate an array with a large free minor number, and
> * set the name to val. val must not already be an active name.
> + * For "mdNNN" we allocate an array with the minor number NNN
> + * which must not already be in use.
> */
> int len = strlen(val);
> char buf[DISK_NAME_LEN];
> + unsigned long devnum;
>
> while (len && val[len-1] == '\n')
> len--;
> if (len >= DISK_NAME_LEN)
> return -E2BIG;
> strlcpy(buf, val, len+1);
> - if (strncmp(buf, "md_", 3) != 0)
> - return -EINVAL;
> - return md_alloc(0, buf);
> + if (strncmp(buf, "md_", 3) == 0)
> + return md_alloc(0, buf);
> + if (strncmp(buf, "md", 2) == 0 &&
> + isdigit(buf[2]) &&
> + kstrtoul(buf+2, 10, &devnum) == 0 &&
> + devnum <= MINORMASK)
> + return md_alloc(MKDEV(MD_MAJOR, devnum), NULL);
> +
> + return -EINVAL;
> }
>
> static void md_safemode_timeout(unsigned long data)
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
