rbd: do not allow remove of mounted-on image

There is no check in rbd_remove() to see if anybody holds open the
image being removed.  That's not cool.

Add a simple open count that goes up and down with opens and closes
(releases) of the device, and don't allow an rbd image to be removed
if the count is non-zero.

Protect the updates of the open count value with ctl_mutex to ensure
the underlying rbd device doesn't get removed while concurrently
being opened.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
ceph: don't reference req after put

In __unregister_request(), there is a call to list_del_init()
referencing a request that was the subject of a call to
ceph_osdc_put_request() on the previous line.  This is not
safe, because the request structure could have been freed
by the time we reach the list_del_init().

Fix this by reversing the order of these lines.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-off-by: Sage Weil <sage@inktank.com>
libceph: avoid using freed osd in __kick_osd_requests()

If an osd has no requests and no linger requests, __reset_osd()
will just remove it with a call to __remove_osd().  That drops
a reference to the osd, and therefore the osd may have been free
by the time __reset_osd() returns.  That function offers no
indication this may have occurred, and as a result the osd will
continue to be used even when it's no longer valid.

Change__reset_osd() so it returns an error (ENODEV) when it
deletes the osd being reset.  And change __kick_osd_requests() so it
returns immediately (before referencing osd again) if __reset_osd()
returns *any* error.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
rbd: get rid of RBD_MAX_SEG_NAME_LEN

RBD_MAX_SEG_NAME_LEN represents the maximum length of an rbd object
name (i.e., one of the objects providing storage backing an rbd
image).

Another symbol, MAX_OBJ_NAME_SIZE, is used in the osd client code to
define the maximum length of any object name in an osd request.

Right now they disagree, with RBD_MAX_SEG_NAME_LEN being too big.

There's no real benefit at this point to defining the rbd object
name length limit separate from any other object name, so just
get rid of RBD_MAX_SEG_NAME_LEN and use MAX_OBJ_NAME_SIZE in its
place.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
rbd: remove linger unconditionally

In __unregister_linger_request(), the request is being removed
from the osd client's req_linger list only when the request
has a non-null osd pointer.  It should be done whether or not
the request currently has an osd.

This is most likely a non-issue because I believe the request
will always have an osd when this function is called.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
rbd: don't use ENOTSUPP

ENOTSUPP is not a standard errno (it shows up as "Unknown error 524"
in an error message).  This is what was getting produced when the
the local rbd code does not implement features required by a
discovered rbd image.

Change the error code returned in this case to ENXIO.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
libceph: socket can close in any connection state

A connection's socket can close for any reason, independent of the
state of the connection (and without irrespective of the connection
mutex).  As a result, the connectino can be in pretty much any state
at the time its socket is closed.

Handle those other cases at the top of con_work().  Pull this whole
block of code into a separate function to reduce the clutter.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
libceph: report connection fault with warning

When a connection's socket disconnects, or if there's a protocol
error of some kind on the connection, a fault is signaled and
the connection is reset (closed and reopened, basically).  We
currently get an error message on the log whenever this occurs.

A ceph connection will attempt to reestablish a socket connection
repeatedly if a fault occurs.  This means that these error messages
will get repeatedly added to the log, which is undesirable.

Change the error message to be a warning, so they don't get
logged by default.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
libceph: init osd->o_node in create_osd()

The red-black node node in the ceph osd structure is not initialized
in create_osd().  Because this node can be the subject of a
RB_EMPTY_NODE() call later on, we should ensure the node is
initialized properly for that.  Add a call to RB_CLEAR_NODE()
initialize it.

Signed-off-by: Alex Elder <elder@inktank.com>
libceph: init event->node in ceph_osdc_create_event()

The red-black node node in the ceph osd event structure is not
initialized in create_osdc_create_event().  Because this node can
be the subject of a RB_EMPTY_NODE() call later on, we should ensure
the node is initialized properly for that.

Signed-off-by: Alex Elder <elder@inktank.com>
libceph: don't use rb_init_node() in ceph_osdc_alloc_request()

The red-black node in the ceph osd request structure is initialized
in ceph_osdc_alloc_request() using rbd_init_node().  We do need to
initialize this, because in __unregister_request() we call
RB_EMPTY_NODE(), which expects the node it's checking to have
been initialized.  But rb_init_node() is apparently overkill, and
may in fact be on its way out.  So use RB_CLEAR_NODE() instead.

For a little more background, see this commit:
    4c199a93 rbtree: empty nodes have no color"

Signed-off-by: Alex Elder <elder@inktank.com>
rbd: fix ceph_pg_poolid_by_name()

Currently ceph_pg_poolid_by_name() returns an int, which is used to
encode a ceph pool id.  This could be a problem because a pool id
(at least in some cases) is a 64-bit value.  We have a defined pool
id value that represents "no pool," and that's a very sensible
return value here.

This patch changes ceph_pg_poolid_by_name() to return a 64-bit
pool id value, or CEPH_NOPOOL if the named pool is not found.

The patch also gratuitously renames the function, separating "pool"
from "id" in the name by an underscore.

[This commit is still under discussion.]

Signed-off-by: Alex Elder <elder@inktank.com>
libceph: register request before unregister linger

In kick_requests(), we need to register the request before we
unregister the linger request.  Otherwise the unregister will
reset the request's osd pointer to NULL.

Signed-off-by: Alex Elder <elder@inktank.com>
rbd: get rid of rbd_{get,put}_dev()

The functions rbd_get_dev() and rbd_put_dev() are trivial wrappers
that add no value, and their existence suggests they may do more
than what they do.

Get rid of them.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Dan Mick <dan.mick@inktank.com>
rbd: document rbd_spec structure

I promised Josh I would document whether there were any restrictions
needed for accessing fields of an rbd_spec structure.  This adds a
big block of comments that documents the structure and how it is
used--including the fact that we don't attempt to synchronize access
to it.

Signed-off-by: Alex Elder <elder@inktank.com>
rbd: kill rbd_spec->image_name_len

There may have been a benefit to hanging on to the length of an
image name before, but there is really none now.  The only time it's
used is when probing for rbd images, so we can just compute the
length then.

Signed-off-by: Alex Elder <elder@inktank.com>
rbd: kill rbd_spec->image_id_len

There is no real benefit to keeping the length of an image id, so
get rid of it.

Signed-off-by: Alex Elder <elder@inktank.com>
rbd: use kmemdup()

This replaces two kmalloc()/memcpy() combinations with a single
call to kmemdup().

Signed-off-by: Alex Elder <elder@inktank.com>
ceph: define ceph_encode_8_safe()

It's kind of a silly macro, but ceph_encode_8_safe() is the only one
missing from an otherwise pretty complete set.  It's not used, but
neither are a couple of the others in this set.

While in there, insert some whitespace to tidy up the alignment of
the line-terminating backslashes in some of the macro definitions.

Signed-off-by: Alex Elder <elder@inktank.com>
rbd: define and use rbd_warn()

Define a new function rbd_warn() that produces a boilerplate warning
message, identifying in the resulting message the affected rbd
device in the best way available.  Use it in a few places that now
use pr_warning().

Signed-off-by: Alex Elder <elder@inktank.com>