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SubjectRe: [PATCH] osdblk: a Linux block device for OSD objects
James Bottomley wrote:
>> + 1) Map a Linux block device to an existing OSD object.
>> +
>> + In this example, we will use partition id 1234, object id 5678,
>> + OSD device /dev/osd1.
>> +
>> + $ echo "1234 5678 /dev/osd1" > /sys/class/osdblk/add
>> +
>> +
>> + 2) List all active blkdev<->object mappings.
>> +
>> + In this example, we have performed step #1 twice, creating two blkdevs,
>> + mapped to two separate OSD objects.
>> +
>> + $ cat /sys/class/osdblk/list
>> + 0 174 1234 5678 /dev/osd1
>> + 1 179 1994 897123 /dev/osd0
>
> This is a slight violation of the one piece of data per sysfs file
> rule ... might it not be better as a file named <partid>-<objid> linking
> to the osd device location in sysfs?

Yeah... I leaned more towards a consolidated table, as it was
elegantly implemented in just a few lines of code, including locking :)


>> + The columns, in order, are:
>> + - blkdev unique id
>> + - blkdev assigned major
>> + - OSD object partition id
>> + - OSD object id
>> + - OSD device
>> +
>> +
>> + 3) Remove an active blkdev<->object mapping.
>> +


>> + unsigned long obj_id;
>> + char osd_path[0];
>> +};
>> +
>> +static struct class *class_osdblk; /* /sys/class/osdblk */
>> +static struct mutex ctl_mutex; /* Serialize open/close/setup/teardown */
>> +static struct osdblk_device *osdblk_devs[OSDBLK_MAX_DEVS];
>
> Might it not be better to do this as a linked list on the private dev
> structure instead? This only works if you have one entry
> in /sys/class/osdblock per device because now you have a device private
> pointer to hang it off

converted to list



>> +static int osdblk_get_free_req(struct osdblk_device *osdev)
>> +{
>> + int i;
>> +
>> + for (i = 0; i < OSDBLK_MAX_REQ; i++) {
>> + if (!osdev->req[i].rq)
>> + return i;
>> + }
>
> Rather than using a static list of outstanding requests, I think you
> could probably use the block tag handling infrastructure for all of this

converted to use blk-tag.c gadgetry

Thanks for the review!

Jeff




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