libceph, rbd: replace zero-length array with flexible-array

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
var

libceph, rbd: replace zero-length array with flexible-array

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
int stuff;
struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <[email protected]>
Reviewed-by: Ilya Dryomov <[email protected]>
Signed-off-by: Ilya Dryomov <[email protected]>

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rbd: support for object-map and fast-diff

Speed up reads, discards and zeroouts through RBD_OBJ_FLAG_MAY_EXIST
and RBD_OBJ_FLAG_NOOP_FOR_NONEXISTENT based on object map.

Invalid object maps are not

rbd: support for object-map and fast-diff

Speed up reads, discards and zeroouts through RBD_OBJ_FLAG_MAY_EXIST
and RBD_OBJ_FLAG_NOOP_FOR_NONEXISTENT based on object map.

Invalid object maps are not trusted, but still updated. Note that we
never iterate, resize or invalidate object maps. If object-map feature
is enabled but object map fails to load, we just fail the requester
(either "rbd map" or I/O, by way of post-acquire action).

Signed-off-by: Ilya Dryomov <[email protected]>

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rbd: RBD_V{1,2}_DATA_FORMAT macros

... and also fix up the comment -- format 1 data objects have always
been 12 hex digits long.

Signed-off-by: Ilya Dryomov <[email protected]>
Reviewed-by: Jason

rbd: RBD_V{1,2}_DATA_FORMAT macros

... and also fix up the comment -- format 1 data objects have always
been 12 hex digits long.

Signed-off-by: Ilya Dryomov <[email protected]>
Reviewed-by: Jason Dillaman <[email protected]>

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rbd: kill rbd_image_header::{crypt_type,comp_type}

Image format 1 is deprecated and format 2 doesn't have these. Also,
__rbd_dev_create() takes care of zeroing (or otherwise initializing)
format 2

rbd: kill rbd_image_header::{crypt_type,comp_type}

Image format 1 is deprecated and format 2 doesn't have these. Also,
__rbd_dev_create() takes care of zeroing (or otherwise initializing)
format 2 specific fields.

Signed-off-by: Ilya Dryomov <[email protected]>
Reviewed-by: Jason Dillaman <[email protected]>

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rbd: support for exclusive-lock feature

Add basic support for RBD_FEATURE_EXCLUSIVE_LOCK feature. Maintenance
operations (resize, snapshot create, etc) are offloaded to librbd via
returning -EOPNOT

rbd: support for exclusive-lock feature

Add basic support for RBD_FEATURE_EXCLUSIVE_LOCK feature. Maintenance
operations (resize, snapshot create, etc) are offloaded to librbd via
returning -EOPNOTSUPP - librbd should request the lock and execute the
operation.

Signed-off-by: Ilya Dryomov <[email protected]>
Reviewed-by: Mike Christie <[email protected]>
Tested-by: Mike Christie <[email protected]>

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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_

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 <[email protected]>
Reviewed-by: Sage Weil <[email protected]>

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rbd: define some new format constants

Define constant symbols related to the rbd format 2 object names.
This begins to bring this version of the "rbd_types.h" header
more in line with the current us

rbd: define some new format constants

Define constant symbols related to the rbd format 2 object names.
This begins to bring this version of the "rbd_types.h" header
more in line with the current user-space version of that file.
Complete reconciliation of differences will be done at some
point later, as a separate task.

Signed-off-by: Alex Elder <[email protected]>
Reviewed-by: Josh Durgin <[email protected]>

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rbd: rename block_name -> object_prefix

In the on-disk image header structure there is a field "block_name"
which represents what we now call the "object prefix" for an rbd
image. Rename this field

rbd: rename block_name -> object_prefix

In the on-disk image header structure there is a field "block_name"
which represents what we now call the "object prefix" for an rbd
image. Rename this field "object_prefix" to be consistent with
modern usage.

This appears to be the only remaining vestige of the use of "block"
in symbols that represent objects in the rbd code.

This addresses http://tracker.newdream.net/issues/1761

Signed-off-by: Alex Elder <[email protected]>
Reviewed-by: Josh Durgin <[email protected]>
Reviewed-by: Dan Mick <[email protected]>

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rbd: dynamically allocate image name

There is no need to impose a small limit the length of the rbd image
name recorded in a struct rbd_dev. Remove the limitation by
allocating space for the image

rbd: dynamically allocate image name

There is no need to impose a small limit the length of the rbd image
name recorded in a struct rbd_dev. Remove the limitation by
allocating space for the image name dynamically.

Signed-off-by: Alex Elder <[email protected]>
Reviewed-by: Josh Durgin <[email protected]>

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rbd: small changes

Here is another set of small code tidy-ups:
- Define SECTOR_SHIFT and SECTOR_SIZE, and use these symbolic
names throughout. Tell the blk_queue system our physical

rbd: small changes

Here is another set of small code tidy-ups:
- Define SECTOR_SHIFT and SECTOR_SIZE, and use these symbolic
names throughout. Tell the blk_queue system our physical
block size, in the (unlikely) event we want to use something
other than the default.
- Delete the definition of struct rbd_info, which is never used.
- Move the definition of dev_to_rbd() down in its source file,
just above where it gets first used, and change its name to
dev_to_rbd_dev().
- Replace an open-coded operation in rbd_dev_release() to use
dev_to_rbd_dev() instead.
- Calculate the segment size for a given rbd_device just once in
rbd_init_disk().
- Use the '%zd' conversion specifier in rbd_snap_size_show(),
since the value formatted is a size_t.
- Switch to the '%llu' conversion specifier in rbd_snap_id_show().
since the value formatted is unsigned.

Signed-off-by: Alex Elder <[email protected]>

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rbd: introduce rados block device (rbd), based on libceph

The rados block device (rbd), based on osdblk, creates a block device
that is backed by objects stored in the Ceph distributed object storag

rbd: introduce rados block device (rbd), based on libceph

The rados block device (rbd), based on osdblk, creates a block device
that is backed by objects stored in the Ceph distributed object storage
cluster. Each device consists of a single metadata object and data
striped over many data objects.

The rbd driver supports read-only snapshots.

Signed-off-by: Yehuda Sadeh <[email protected]>
Signed-off-by: Sage Weil <[email protected]>

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