Change RBD_MAX_SNAP_NAME_LEN to be based on NAME_MAX.  That is a
practical limit for the length of a snapshot name (based on the
presence of a directory using the name under /sys/bus/rbd to
represent the snapshot).

The /sys entry is created by prefixing it with "snap_"; define that
prefix symbolically, and take its length into account in defining
the snapshot name length limit.

Enforce the limit in rbd_add_parse_args().  Also delete a dout()
call in that function that was not meant to be committed.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NDan Mick <dan.mick@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

This adds a verification that an rbd image's object order is
within the upper and lower bounds supported by this implementation.

It must be at least 9 (SECTOR_SHIFT), because the Linux bio system
assumes that minimum granularity.

It also must be less than 32 (at the moment anyway) because there
exist spots in the code that store the size of a "segment" (object
backing an rbd image) in a signed int variable, which can be 32 bits
including the sign.  We should be able to relax this limit once
we've verified the code uses 64-bit types where needed.

Note that the CLI tool already limits the order to the range 12-25.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

The two calls to rbd_do_op() from rbd_rq_fn() differ only in the
value passed for the snapshot id and the snapshot context.

For reads the snapshot always comes from the mapping, and for writes
the snapshot id is always CEPH_NOSNAP.

The snapshot context is always null for reads.  For writes, the
snapshot context always comes from the rbd header, but it is
acquired under protection of header semaphore and could change
thereafter, so we can't simply use what's available inside
rbd_do_op().

Eliminate the snapid parameter from rbd_do_op(), and set it
based on the I/O direction inside that function instead.  Always
pass the snapshot context acquired in the caller, but reset it
to a null pointer inside rbd_do_op() if the operation is a read.

As a result, there is no difference in the read and write calls
to rbd_do_op() made in rbd_rq_fn(), so just call it unconditionally.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

The only callers of rbd_do_op() are in rbd_rq_fn(), where call one
is used for writes and the other used for reads.  The request passed
to rbd_do_op() already encodes the I/O direction, and that
information can be used inside the function to set the opcode and
flags value (rather than passing them in as arguments).

So get rid of the opcode and flags arguments to rbd_do_op().
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Both rbd_req_read() and rbd_req_write() are simple wrapper routines
for rbd_do_op(), and each is only called once.  Replace each wrapper
call with a direct call to rbd_do_op(), and get rid of the wrapper
functions.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

The name of the "read-only" mapping option was inadvertently changed
in this commit:

    f84344f3 rbd: separate mapping info in rbd_dev

Revert that hunk to return it to what it should be.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NDan Mick <dan.mick@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

When rbd_dev_probe() calls rbd_dev_image_id() it expects to get
a 0 return code if successful, but it is getting a positive value.

The reason is that rbd_dev_image_id() returns the value it gets from
rbd_req_sync_exec(), which returns the number of bytes read in as a
result of the request.  (This ultimately comes from
ceph_copy_from_page_vector() in rbd_req_sync_op()).

Force the return value to 0 when successful in rbd_dev_image_id().
Do the same in rbd_dev_v2_object_prefix().
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>
Reviewed-by: NDan Mick <dan.mick@inktank.com>

In rbd_dev_id_put(), there's a loop that's intended to determine
the maximum device id in use.  But it isn't doing that at all,
the effect of how it's written is to simply use the just-put id
number, which ignores whole purpose of this function.

Fix the bug.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Now that v2 images support is fully implemented, have
rbd_dev_v2_probe() return 0 to indicate a successful probe.

(Note that an image that implements layering will fail
the probe early because of the feature chekc.)
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Version 2 images have two sets of feature bit fields.  The first
indicates features possibly used by the image.  The second indicates
features that the client *must* support in order to use the image.

When an image (or snapshot) is first examined, we need to make sure
that the local implementation supports the image's required
features.  If not, fail the probe for the image.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Define a new function rbd_dev_v2_refresh() to update/refresh the
snapshot context for a format version 2 rbd image.  This function
will update anything that is not fixed for the life of an rbd
image--at the moment this is mainly the snapshot context and (for
a base mapping) the size.

Update rbd_refresh_header() so it selects which function to use
based on the image format.

Rename __rbd_refresh_header() to be rbd_dev_v1_refresh()
to be consistent with the naming of its version 2 counterpart.
Similarly rename rbd_refresh_header() to be rbd_dev_refresh().

Unrelated--we use rbd_image_format_valid() here.  Delete the other
use of it, which was primarily put in place to ensure that function
was referenced at the time it was defined.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Encapsulate the code that handles updating the size of a mapping
after an rbd image has been refreshed.  This is done in anticipation
of the next patch, which will make this common code for format 1 and
2 images.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

This shouldn't actually be possible because the layout struct is
constructed from the RBD header and validated then.

[elder@inktank.com: converted BUG() call to equivalent rbd_assert()]
Signed-off-by: NSage Weil <sage@inktank.com>
Reviewed-by: NAlex Elder <elder@inktank.com>

There are three fields that are not yet updated for format 2 rbd
image headers:  the version of the header object; the encryption
type; and the compression type.  There is no interface defined for
fetching the latter two, so just initialize them explicitly to 0 for
now.

Change rbd_dev_v2_snap_context() so the caller can be supplied the
version for the header object.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Define rbd_dev_v2_snap_name() to fetch the name for a particular
snapshot in a format 2 rbd image.

Define rbd_dev_v2_snap_info() to to be a wrapper for getting the
name, size, and features for a particular snapshot, using an
interface that matches the equivalent function for version 1 images.

Define rbd_dev_snap_info() wrapper function and use it to call the
appropriate function for getting the snapshot name, size, and
features, dependent on the rbd image format.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Fetch the snapshot context for an rbd format 2 image by calling
the "get_snapcontext" method on its header object.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

The features values for an rbd format 2 image are fetched from the
server using a "get_features" method.  The same method is used for
getting the features for a snapshot, so structure this addition with
a generic helper routine that can get this information for either.

The server will provide two 64-bit feature masks, one representing
the features potentially in use for this image (or its snapshot),
and one representing features that must be supported by the client
in order to work with the image.

For the time being, neither of these is really used so we keep
things simple and just record the first feature vector.  Once we
start using these feature masks, what we record and what we expose
to the user will most likely change.
Signed-off-by: NAlex Elder <elder@inktank.com>

The object prefix of an rbd format 2 image is fetched from the
server using a "get_object_prefix" method.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

The size of an rbd format 2 image is fetched from the server using a
"get_size" method.  The same method is used for getting the size of
a snapshot, so structure this addition with a generic helper routine
that we can get this information for either.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

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: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Create a function that encapsulates looking up the name, size and
features related to a given snapshot, which is indicated by its
index in an rbd device's snapshot context array of snapshot ids.

This interface will be used to hide differences between the format 1
and format 2 images.

At the moment this (looking up the name anyway) is slightly less
efficient than what's done currently, but we may be able to optimize
this a bit later on by cacheing the last lookup if it proves to be a
problem.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Record the features values for each rbd image and each of its
snapshots.  This is really something that only becomes meaningful
for version 2 images, so this is just putting in place code
that will form common infrastructure.

It may be useful to expand the sysfs entries--and therefore the
information we maintain--for the image and for each snapshot.
But I'm going to hold off doing that until we start making
active use of the feature bits.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Pass the snapshot id and snapshot size rather than an index
to __rbd_add_snap_dev() to specify values for a new snapshot.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Josh proposed the following change, and I don't think I could
explain it any better than he did:

    From: Josh Durgin <josh.durgin@inktank.com>
    Date: Tue, 24 Jul 2012 14:22:11 -0700
    To: ceph-devel <ceph-devel@vger.kernel.org>
    Message-ID: <500F1203.9050605@inktank.com>

    Right now the kernel still has one piece of rbd management
    duplicated from the rbd command line tool: snapshot creation.
    There's nothing special about snapshot creation that makes it
    advantageous to do from the kernel, so I'd like to remove the
    create_snap sysfs interface.  That is,
	/sys/bus/rbd/devices/<id>/create_snap
    would be removed.

    Does anyone rely on the sysfs interface for creating rbd
    snapshots?  If so, how hard would it be to replace with:

	rbd snap create pool/image@snap

    Is there any benefit to the sysfs interface that I'm missing?

    Josh

This patch implements this proposal, removing the code that
implements the "snap_create" sysfs interface for rbd images.
As a result, quite a lot of other supporting code goes away.
Suggested-by: NJosh Durgin <josh.durgin@inktank.com>
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

New format 2 rbd images are permanently identified by a unique image
id.  Each rbd image also has a name, but the name can be changed.
A format 2 rbd image will have an object--whose name is based on the
image name--which maps an image's name to its image id.

Create a new function rbd_dev_image_id() that checks for the
existence of the image id object, and if it's found, records the
image id in the rbd_device structure.

Create a new rbd device attribute (/sys/bus/rbd/<num>/image_id) that
makes this information available.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

An OSD object method call can be made using rbd_req_sync_exec().
Until now this has only been used for creating a new RBD snapshot,
and that has only required sending data out, not receiving anything
back from the OSD.

We will now need to get data back from an OSD on a method call, so
add parameters to rbd_req_sync_exec() that allow a buffer into which
returned data should be placed to be specified, along with its size.

Previously, rbd_req_sync_exec() passed a null pointer and zero
size to rbd_req_sync_op(); change this so the new inbound buffer
information is provided instead.

Rename the "buf" and "len" parameters in rbd_req_sync_op() to
make it more obvious they are describing inbound data.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

In order to allow both read requests and write requests to be
initiated using rbd_req_sync_exec(), add an OSD flags value
which can be passed down to rbd_req_sync_op().  Rename the "data"
and "len" parameters to be more clear that they represent data
that is outbound.

At this point, this function is still only used (and only works) for
write requests.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

We're ready to handle header object (refresh) events at the point we
call rbd_bus_add_dev().  Set up the watch request on the rbd image
header just after that, and after we've registered the devices for
the snapshots for the initial snapshot context.  Do this before
announce the disk as available for use.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Move the setting of the initial capacity for an rbd image mapping
into rb_init_disk().
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

By the time rbd_dev_snaps_register() gets called during rbd device
initialization, the main device will have already been registered.
Similarly, a header refresh will only occur for an rbd device whose
Linux device is registered.  There is therefore no need to verify
the main device is registered when registering a snapshot device.

For the time being, turn the check into a WARN_ON(), but it can
eventually just go away.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Call rbd_init_disk() from rbd_add() as soon as we have the major
device number for the mapping.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Hold off setting the device id and formatting the device name
in rbd_add() until just before it's needed.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Read the rbd header information and call rbd_dev_set_mapping()
earlier--before registering the block device or setting up the sysfs
entries for the image.  The sysfs entries provide users access to
some information that's only available after doing the rbd header
initialization, so this will make sure it's valid right away.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

rbd_header_set_snap() is a simple initialization routine for an rbd
device's mapping.  It has to be called after the snapshot context
for the rbd_dev has been updated, but can be done before snapshot
devices have been registered.

Change the name to rbd_dev_set_mapping() to better reflect its
purpose, and call it a little sooner, before registering snapshot
devices.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

When a new snapshot is found in an rbd device's updated snapshot
context, __rbd_add_snap_dev() is called to create and insert an
entry in the rbd devices list of snapshots.  In addition, a Linux
device is registered to represent the snapshot.

For version 2 rbd images, it will be undesirable to initialize the
device right away.  So in anticipation of that, this patch separates
the insertion of a snapshot entry in the snaps list from the
creation of devices for those snapshots.

To do this, create a new function rbd_dev_snaps_register() which
traverses the list of snapshots and calls rbd_register_snap_dev()
on any that have not yet been registered.

Rename rbd_dev_snap_devs_update() to be rbd_dev_snaps_update()
to better reflect that only the entry in the snaps list and not
the snapshot's device is affected by the function.

For now, call rbd_dev_snaps_register() immediately after each
call to rbd_dev_snaps_update().
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Move the assignment of the header name for an rbd image a bit later,
outside rbd_add_parse_args() and into its caller.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

An rbd_dev structure maintains a list of current snapshots that have
already been fully initialized.  The entries on the list have type
struct rbd_snap, and each entry contains a copy of information
that's found in the rbd_dev's snapshot context and header.

The only caller of snap_by_name() is rbd_header_set_snap().  In that
call site any positive return value (the index in the snapshot
array) is ignored, so there's no need to return the index in
the snapshot context's id array when it's found.

rbd_header_set_snap() also has only one caller--rbd_add()--and that
call is made after a call to rbd_dev_snap_devs_update().  Because
the rbd_snap structures are initialized in that function, the
current snapshot list can be used instead of the snapshot context to
look up a snapshot's information by name.

Change snap_by_name() so it uses the snapshot list rather than the
rbd_dev's snapshot context in looking up snapshot information.
Return 0 if it's found rather than the snapshot id.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

When rbd_bus_add_dev() is called (one spot--in rbd_add()), the rbd
image header has not even been read yet.  This means that the list
of snapshots will be empty at the time of the call.  As a result,
there is no need for the code that calls rbd_register_snap_dev()
for each entry in that list--so get rid of it.

Once the header has been read (just after returning), a call will
be made to rbd_dev_snap_devs_update(), which will then find every
snapshot in the context to be new and will therefore call
rbd_register_snap_dev() via __rbd_add_snap_dev() accomplishing
the same thing.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

Move the calls to get the header semaphore out of
rbd_header_set_snap() and into its caller.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

This just simplifies a few things in rbd_init_disk(), now that the
previous patch has moved a bunch of initialization code out if it.
Done separately to facilitate review.
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>