This function also re-open connections to OSD/MON, and re-send in-flight
OSD requests after re-opening connections to OSD.
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
- support for rbd object-map and fast-diff features (myself). This
will speed up reads, discards and things like snap diffs on sparse
images.
- ceph.snap.btime vxattr to expose snapshot creation time (David
Disseldorp). This will be used to integrate with "Restore Previous
Versions" feature added in Windows 7 for folks who reexport ceph
through SMB.
- security xattrs for ceph (Zheng Yan). Only selinux is supported
for now due to the limitations of ->dentry_init_security().
- support for MSG_ADDR2, FS_BTIME and FS_CHANGE_ATTR features (Jeff
Layton). This is actually a single feature bit which was missing
because of the filesystem pieces. With this in, the kernel client
will finally be reported as "luminous" by "ceph features" -- it is
still being reported as "jewel" even though all required Luminous
features were implemented in 4.13.
- stop NULL-terminating ceph vxattrs (Jeff Layton). The convention
with xattrs is to not terminate and this was causing inconsistencies
with ceph-fuse.
- change filesystem time granularity from 1 us to 1 ns, again fixing
an inconsistency with ceph-fuse (Luis Henriques).
On top of this there are some additional dentry name handling and cap
flushing fixes from Zheng. Finally, Jeff is formally taking over for
Zheng as the filesystem maintainer.
-----BEGIN PGP SIGNATURE-----
iQFHBAABCAAxFiEEydHwtzie9C7TfviiSn/eOAIR84sFAl0u+X8THGlkcnlvbW92
QGdtYWlsLmNvbQAKCRBKf944AhHzi9byB/9fIxzoxtDMvixtJabuGSJRtlijDlWF
GlO6yIWCXl/8v8easR2PCF75U/xv0+QFQmze8PVi8u4Xz589P247NnEuyEZ9n84i
aCavARho6QLZPEL+B04NaqoHBl+ORKQTA6eKGhyKwRp/rn83z5Ubuw2tN7krHT3b
kCY61FuTQGxNY2o/WKv/iLwINYr7H23hCf0WwyyKH1bp7OegiQ14Ebn1NtfS3sMx
hS6h8Ya826vmUW0bCSS/9kzKYBCjksTig0HphUOHq6BoZJs++0b7GukIulRyuLfD
J9Gr9HGPoDCVzdmFfpn2FSlxdmqfO9amUSagd0ftLQfFlPlrpoULi0GW
=Bgxr
-----END PGP SIGNATURE-----
Merge tag 'ceph-for-5.3-rc1' of git://github.com/ceph/ceph-client
Pull ceph updates from Ilya Dryomov:
"Lots of exciting things this time!
- support for rbd object-map and fast-diff features (myself). This
will speed up reads, discards and things like snap diffs on sparse
images.
- ceph.snap.btime vxattr to expose snapshot creation time (David
Disseldorp). This will be used to integrate with "Restore Previous
Versions" feature added in Windows 7 for folks who reexport ceph
through SMB.
- security xattrs for ceph (Zheng Yan). Only selinux is supported for
now due to the limitations of ->dentry_init_security().
- support for MSG_ADDR2, FS_BTIME and FS_CHANGE_ATTR features (Jeff
Layton). This is actually a single feature bit which was missing
because of the filesystem pieces. With this in, the kernel client
will finally be reported as "luminous" by "ceph features" -- it is
still being reported as "jewel" even though all required Luminous
features were implemented in 4.13.
- stop NULL-terminating ceph vxattrs (Jeff Layton). The convention
with xattrs is to not terminate and this was causing
inconsistencies with ceph-fuse.
- change filesystem time granularity from 1 us to 1 ns, again fixing
an inconsistency with ceph-fuse (Luis Henriques).
On top of this there are some additional dentry name handling and cap
flushing fixes from Zheng. Finally, Jeff is formally taking over for
Zheng as the filesystem maintainer"
* tag 'ceph-for-5.3-rc1' of git://github.com/ceph/ceph-client: (71 commits)
ceph: fix end offset in truncate_inode_pages_range call
ceph: use generic_delete_inode() for ->drop_inode
ceph: use ceph_evict_inode to cleanup inode's resource
ceph: initialize superblock s_time_gran to 1
MAINTAINERS: take over for Zheng as CephFS kernel client maintainer
rbd: setallochint only if object doesn't exist
rbd: support for object-map and fast-diff
rbd: call rbd_dev_mapping_set() from rbd_dev_image_probe()
libceph: export osd_req_op_data() macro
libceph: change ceph_osdc_call() to take page vector for response
libceph: bump CEPH_MSG_MAX_DATA_LEN (again)
rbd: new exclusive lock wait/wake code
rbd: quiescing lock should wait for image requests
rbd: lock should be quiesced on reacquire
rbd: introduce copyup state machine
rbd: rename rbd_obj_setup_*() to rbd_obj_init_*()
rbd: move OSD request allocation into object request state machines
rbd: factor out __rbd_osd_setup_discard_ops()
rbd: factor out rbd_osd_setup_copyup()
rbd: introduce obj_req->osd_reqs list
...
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 <idryomov@gmail.com>
We already have one exported wrapper around it for extent.osd_data and
rbd_object_map_update_finish() needs another one for cls.request_data.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
This will be used for loading object map. rbd_obj_read_sync() isn't
suitable because object map must be accessed through class methods.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
This time for rbd object map. Object maps are limited in size to
256000000 objects, two bits per object.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
This list item remained from when we had safe and unsafe replies
(commit vs ack). It has since become a private list item for use by
clients.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Client uses this flag to tell mds if there is more cap snap need to
flush. It's mainly for the case that client needs to re-send cap/snap
flushes after mds failover, but CEPH_CAP_ANY_FILE_WR on corresponding
inodes are all released before mds failover.
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Now that the client can handle either address formatting, advertise to
the peer that we can support it.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
...ditto for the decode function. We only use these functions to fix
up banner addresses now, so let's name them more appropriately.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Going forward, we'll have different address types so let's use
the addr2 TYPE_LEGACY for internal tracking rather than TYPE_NONE.
Also, make ceph_pr_addr print the address type value as well.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Switch the MonMap decoder to use the new decoding routine for
entity_addr_t's.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Add a function for decoding an entity_addr_t. Once
CEPH_FEATURE_MSG_ADDR2 is enabled, the server daemons will start
encoding entity_addr_t differently.
Add a new helper function that can handle either format.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This function is entirely unused.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
When calling debugfs functions, there is no need to ever check the
return value. The function can work or not, but the code logic should
never do something different based on this.
This cleanup allows the return value of the functions to be made void,
as no logic should care if these files succeed or not.
Cc: "Yan, Zheng" <zyan@redhat.com>
Cc: Sage Weil <sage@redhat.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: ceph-devel@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20190612145538.GA18772@kroah.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
GCC9 is throwing a lot of warnings about unaligned accesses by
callers of ceph_pr_addr. All of the current callers are passing a
pointer to the sockaddr inside struct ceph_entity_addr.
Fix it to take a pointer to a struct ceph_entity_addr instead,
and then have the function make a copy of the sockaddr before
printing it.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
clang complains about assigning a variable to itself during the
declaration:
fs/ceph/ioctl.c:187:26: error: variable 'oid' is uninitialized when used within its own initialization [-Werror,-Wuninitialized]
CEPH_DEFINE_OID_ONSTACK(oid);
^~~
include/linux/ceph/osdmap.h:122:52: note: expanded from macro 'CEPH_DEFINE_OID_ONSTACK'
struct ceph_object_id oid = CEPH_OID_INIT_ONSTACK(oid)
~~~ ^~~
include/linux/ceph/osdmap.h:120:29: note: expanded from macro 'CEPH_OID_INIT_ONSTACK'
({ ceph_oid_init(&oid); oid; })
^~~
We use this trick in other places, but it is completely unnecessary
here, as we can just use a regular struct initializer.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
To support snapshot nfs re-export, we need a way to lookup snapped
inode by file handle. For directory inode, snapped metadata are always
stored together with head inode. Client just need to pass vinodeno_t
to MDS. For non-directory inode, there can be multiple version of
snapped inodes and they can be stored in different dirfrags. Besides
vinodeno_t, client also need to tell mds from which dirfrag it got the
snapped inode.
Another problem of supporting snapshot nfs re-export is that there
can be multiple paths to access a snapped inode. For example:
mkdir -p d1/d2/d3
mkdir d1/.snap/s1
Paths 'd1/.snap/s1/d2/d3', 'd1/d2/.snap/_s1_<inode number of d1>/d3'
and 'd1/d2/d3/.snap/_s1_<inode number of d1>' are all reference to the
same snapped inode. For a given snapped inode, There is no convenient
way to get the first form and the second form paths. For simplicity,
ceph_get_parent() return snapdir for snapped directory inode.
Furthermore, client may access snapshot of deleted directory. For
example:
mkdir -p d1/d2
mkdir d1/.snap/s1
open d1/.snap/s1/d2
rm -rf d1/d2
<nfs server restart>
The path constucted by ceph_get_parent() and ceph_get_name() is
'<inode of d2>/.snap/_s1_<inode number of d1>'. Futher lookup parent
of <inode of d2> will fail. To workaround this case, this patch uses
d_obtain_root() to get dentry for snapdir of deleted directory.
snapdir dentry has no DCACHE_DISCONNECTED flag set, reconnect_path()
stops when it reaches snapdir dentry.
Link: http://tracker.ceph.com/issues/22105
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Because map updates are distributed lazily, an OSD may not know about
the new blacklist for quite some time after "osd blacklist add" command
is completed. This makes it possible for a blacklisted but still alive
client to overwrite a post-blacklist update, resulting in data
corruption.
Waiting for latest osdmap in ceph_monc_blacklist_add() and thus using
the post-blacklist epoch for all post-blacklist requests ensures that
all such requests "wait" for the blacklist to come into force on their
respective OSDs.
Cc: stable@vger.kernel.org
Fixes: 6305a3b415 ("libceph: support for blacklisting clients")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Jason Dillaman <dillaman@redhat.com>
If number of caps exceed the limit, ceph_trim_dentires() also trim
dentries with valid leases. Trimming dentry releases references to
associated inode, which may evict inode and release caps.
By default, there is no limit for caps count.
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Introduce a new option abort_on_full, default to false. Then
we can get -ENOSPC when the pool is full, or reaches quota.
[ Don't show abort_on_full in /proc/mounts. ]
Signed-off-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
No one is running pre-argonaut. In addition one of the argonaut
features (NOSRCADDR) has been required since day one (and a half,
2.6.34 vs 2.6.35) of the kernel client.
Allow for the possibility of reusing these feature bits later.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Add support for performing remote object copies using the 'copy-from'
operation.
[ Add COPY_FROM to get_num_data_items(). ]
Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Currently message data items are allocated with ceph_msg_data_create()
in setup_request_data() inside send_request(). send_request() has never
been allowed to fail, so each allocation is followed by a BUG_ON:
data = ceph_msg_data_create(...);
BUG_ON(!data);
It's been this way since support for multiple message data items was
added in commit 6644ed7b7e ("libceph: make message data be a pointer")
in 3.10.
There is no reason to delay the allocation of message data items until
the last possible moment and we certainly don't need a linked list of
them as they are only ever appended to the end and never erased. Make
ceph_msg_new2() take max_data_items and adapt the rest of the code.
Reported-by: Jerry Lee <leisurelysw24@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
struct ceph_pagelist cannot be embedded into anything else because it
has its own refcount. Merge allocation and initialization together.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
If the read is large enough, we end up spinning in the messenger:
libceph: osd0 192.168.122.1:6801 io error
libceph: osd0 192.168.122.1:6801 io error
libceph: osd0 192.168.122.1:6801 io error
This is a receive side limit, so only reads were affected.
Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Derive the signature from the entire buffer (both AES cipher blocks)
instead of using just the first half of the first block, leaving out
data_crc entirely.
This addresses CVE-2018-1129.
Link: http://tracker.ceph.com/issues/24837
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
When a client authenticates with a service, an authorizer is sent with
a nonce to the service (ceph_x_authorize_[ab]) and the service responds
with a mutation of that nonce (ceph_x_authorize_reply). This lets the
client verify the service is who it says it is but it doesn't protect
against a replay: someone can trivially capture the exchange and reuse
the same authorizer to authenticate themselves.
Allow the service to reject an initial authorizer with a random
challenge (ceph_x_authorize_challenge). The client then has to respond
with an updated authorizer proving they are able to decrypt the
service's challenge and that the new authorizer was produced for this
specific connection instance.
The accepting side requires this challenge and response unconditionally
if the client side advertises they have CEPHX_V2 feature bit.
This addresses CVE-2018-1128.
Link: http://tracker.ceph.com/issues/24836
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
We already copy authorizer_reply_buf and authorizer_reply_buf_len into
ceph_connection. Factoring out __prepare_write_connect() requires two
more: authorizer_buf and authorizer_buf_len. Store the pointer to the
handshake in con->auth rather than piling on.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
The request mtime field is used all over ceph, and is currently
represented as a 'timespec' structure in Linux. This changes it to
timespec64 to allow times beyond 2038, modifying all users at the
same time.
[ Remove now redundant ts variable in writepage_nounlock(). ]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
ceph_con_keepalive_expired() is the last user of timespec_add() and some
of the last uses of ktime_get_real_ts(). Replacing this with timespec64
based interfaces lets us remove that deprecated API.
I'm introducing new ceph_encode_timespec64()/ceph_decode_timespec64()
here that take timespec64 structures and convert to/from ceph_timespec,
which is defined to have an unsigned 32-bit tv_sec member. This extends
the range of valid times to year 2106, avoiding the year 2038 overflow.
The ceph file system portion still uses the old functions for inode
timestamps, this will be done separately after the VFS layer is converted.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
The wire format dictates that the length of string fits into 4 bytes.
Take u32 instead of size_t to reflect that.
We were already truncating len in ceph_pagelist_encode_32() -- this
just pushes that truncation one level up.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
The wire format dictates that payload_len fits into 4 bytes. Take u32
instead of size_t to reflect that.
All callers pass a small integer, so no changes required.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
calc_target() isn't supposed to fail with anything but POOL_DNE, in
which case we report that the pool doesn't exist and fail the request
with -ENOENT. Doing this for -ENOMEM is at the very least confusing
and also harmful -- as the preceding requests complete, a short-lived
locator string allocation is likely to succeed after a wait.
(We used to call ceph_object_locator_to_pg() for a pi lookup. In
theory that could fail with -ENOENT, hence the "ret != -ENOENT" warning
being removed.)
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
The intent behind making it a per-request setting was that it would be
set for writes, but not for reads. As it is, the flag is set for all
fs/ceph requests except for pool perm check stat request (technically
a read).
ceph_osdc_abort_on_full() skips reads since the previous commit and
I don't see a use case for marking individual requests.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
In the common case, req->r_callback is called by handle_reply() on the
ceph-msgr worker thread without any locks. If handle_reply() fails, it
is called with both osd->lock and osdc->lock. In the map check case,
it is called with just osdc->lock but held for write. Finally, if the
request is aborted because of -ENOSPC or by ceph_osdc_abort_requests(),
it is called directly on the submitter's thread, again with both locks.
req->r_callback on the submitter's thread is relatively new (introduced
in 4.12) and ripe for deadlocks -- e.g. writeback worker thread waiting
on itself:
inode_wait_for_writeback+0x26/0x40
evict+0xb5/0x1a0
iput+0x1d2/0x220
ceph_put_wrbuffer_cap_refs+0xe0/0x2c0 [ceph]
writepages_finish+0x2d3/0x410 [ceph]
__complete_request+0x26/0x60 [libceph]
complete_request+0x2e/0x70 [libceph]
__submit_request+0x256/0x330 [libceph]
submit_request+0x2b/0x30 [libceph]
ceph_osdc_start_request+0x25/0x40 [libceph]
ceph_writepages_start+0xdfe/0x1320 [ceph]
do_writepages+0x1f/0x70
__writeback_single_inode+0x45/0x330
writeback_sb_inodes+0x26a/0x600
__writeback_inodes_wb+0x92/0xc0
wb_writeback+0x274/0x330
wb_workfn+0x2d5/0x3b0
Defer __complete_request() to a workqueue in all failure cases so it's
never on the same thread as ceph_osdc_start_request() and always called
with no locks held.
Link: http://tracker.ceph.com/issues/23978
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
rstat is not tracked by capability. client can't know if rstat from
non-auth mds is uptodate or not.
Link: http://tracker.ceph.com/issues/23538
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
... and store num_bvecs for client code's convenience.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
This patch adds the infrastructure required to support cephfs quotas as it
is currently implemented in the ceph fuse client. Cephfs quotas can be
set on any directory, and can restrict the number of bytes or the number
of files stored beneath that point in the directory hierarchy.
Quotas are set using the extended attributes 'ceph.quota.max_files' and
'ceph.quota.max_bytes', and can be removed by setting these attributes to
'0'.
Link: http://tracker.ceph.com/issues/22372
Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
In current code, regular file and directory use same struct
ceph_file_info to store fs specific data so the struct has to
include some fields which are only used for directory
(e.g., readdir related info), when having plenty of regular files,
it will lead to memory waste.
This patch introduces dedicated ceph_dir_file_info cache for
readdir related thins. So that regular file does not include those
unused fields anymore.
Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
In preparation for rbd "fancy" striping, introduce ceph_bvec_iter for
working with bio_vec array data buffers. The wrappers are trivial, but
make it look similar to ceph_bio_iter.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
The reason we clone bios is to be able to give each object request
(and consequently each ceph_osd_data/ceph_msg_data item) its own
pointer to a (list of) bio(s). The messenger then initializes its
cursor with cloned bio's ->bi_iter, so it knows where to start reading
from/writing to. That's all the cloned bios are used for: to determine
each object request's starting position in the provided data buffer.
Introduce ceph_bio_iter to do exactly that -- store position within bio
list (i.e. pointer to bio) + position within that bio (i.e. bvec_iter).
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
