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rbd: lay out header probe infrastructure

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This defines a new function rbd_dev_probe() as a top-level
function for populating detailed information about an rbd device.

It first checks for the existence of a format 2 rbd image id object.
If it exists, the image is assumed to be a format 2 rbd image, and
another function rbd_dev_v2() is called to finish populating
header data for that image.  If it does not exist, it is assumed to
be an old (format 1) rbd image, and calls a similar function
rbd_dev_v1() to populate its header information.

A new field, rbd_dev->format, is defined to record which version
of the rbd image format the device represents.  For a valid mapped
rbd device it will have one of two values, 1 or 2.

So far, the format 2 images are not really supported; this is
laying out the infrastructure for fleshing out that support.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
This commit is contained in:
Alex Elder 2012-07-10 20:30:11 -05:00
parent cd892126c6
commit a30b71b999
1 changed files with 99 additions and 28 deletions
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127
drivers/block/rbd.c
View file

@ -170,6 +170,7 @@ struct rbd_device {
int major; /* blkdev assigned major */
struct gendisk *disk; /* blkdev's gendisk and rq */
u32 image_format; /* Either 1 or 2 */
struct rbd_options rbd_opts;
struct rbd_client *rbd_client;
@ -507,6 +508,11 @@ static void rbd_coll_release(struct kref *kref)
kfree(coll);
}
static bool rbd_image_format_valid(u32 image_format)
{
return image_format == 1 || image_format == 2;
}
static bool rbd_dev_ondisk_valid(struct rbd_image_header_ondisk *ondisk)
{
size_t size;
@ -2584,6 +2590,96 @@ static int rbd_dev_image_id(struct rbd_device *rbd_dev)
return ret;
}
static int rbd_dev_v1_probe(struct rbd_device *rbd_dev)
{
int ret;
size_t size;
/* Version 1 images have no id; empty string is used */
rbd_dev->image_id = kstrdup("", GFP_KERNEL);
if (!rbd_dev->image_id)
return -ENOMEM;
rbd_dev->image_id_len = 0;
/* Record the header object name for this rbd image. */
size = rbd_dev->image_name_len + sizeof (RBD_SUFFIX);
rbd_dev->header_name = kmalloc(size, GFP_KERNEL);
if (!rbd_dev->header_name) {
ret = -ENOMEM;
goto out_err;
}
sprintf(rbd_dev->header_name, "%s%s", rbd_dev->image_name, RBD_SUFFIX);
/* Populate rbd image metadata */
ret = rbd_read_header(rbd_dev, &rbd_dev->header);
if (ret < 0)
goto out_err;
rbd_dev->image_format = 1;
dout("discovered version 1 image, header name is %s\n",
rbd_dev->header_name);
return 0;
out_err:
kfree(rbd_dev->header_name);
rbd_dev->header_name = NULL;
kfree(rbd_dev->image_id);
rbd_dev->image_id = NULL;
return ret;
}
static int rbd_dev_v2_probe(struct rbd_device *rbd_dev)
{
size_t size;
/*
* Image id was filled in by the caller. Record the header
* object name for this rbd image.
*/
size = sizeof (RBD_HEADER_PREFIX) + rbd_dev->image_id_len;
rbd_dev->header_name = kmalloc(size, GFP_KERNEL);
if (!rbd_dev->header_name)
return -ENOMEM;
sprintf(rbd_dev->header_name, "%s%s",
RBD_HEADER_PREFIX, rbd_dev->image_id);
rbd_dev->image_format = 2;
dout("discovered version 2 image, header name is %s\n",
rbd_dev->header_name);
return -ENOTSUPP;
}
/*
* Probe for the existence of the header object for the given rbd
* device. For format 2 images this includes determining the image
* id.
*/
static int rbd_dev_probe(struct rbd_device *rbd_dev)
{
int ret;
/*
* Get the id from the image id object. If it's not a
* format 2 image, we'll get ENOENT back, and we'll assume
* it's a format 1 image.
*/
ret = rbd_dev_image_id(rbd_dev);
if (ret)
ret = rbd_dev_v1_probe(rbd_dev);
else
ret = rbd_dev_v2_probe(rbd_dev);
if (ret)
dout("probe failed, returning %d\n", ret);
return ret;
}
static ssize_t rbd_add(struct bus_type *bus,
const char *buf,
size_t count)
@ -2631,35 +2727,10 @@ static ssize_t rbd_add(struct bus_type *bus,
goto err_out_client;
rbd_dev->pool_id = rc;
rc = rbd_dev_image_id(rbd_dev);
if (!rc) {
rc = -ENOTSUPP; /* Not actually supporting format 2 yet */
goto err_out_client;
}
/* Version 1 images have no id; empty string is used */
rbd_dev->image_id = kstrdup("", GFP_KERNEL);
if (!rbd_dev->image_id) {
rc = -ENOMEM;
goto err_out_client;
}
rbd_dev->image_id_len = 0;
/* Create the name of the header object */
rbd_dev->header_name = kmalloc(rbd_dev->image_name_len
+ sizeof (RBD_SUFFIX),
GFP_KERNEL);
if (!rbd_dev->header_name)
goto err_out_client;
sprintf(rbd_dev->header_name, "%s%s", rbd_dev->image_name, RBD_SUFFIX);
/* Get information about the image being mapped */
rc = rbd_read_header(rbd_dev, &rbd_dev->header);
if (rc)
rc = rbd_dev_probe(rbd_dev);
if (rc < 0)
goto err_out_client;
rbd_assert(rbd_image_format_valid(rbd_dev->image_format));
/* no need to lock here, as rbd_dev is not registered yet */
rc = rbd_dev_snaps_update(rbd_dev);