Since handle_reply() does not use its con argument, remove it.
Signed-off-by: Shraddha Barke <shraddha.6596@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This covers only the simplest case - an object size sized write, but
it's still useful in tiering setups when EC is used for the base tier
as writefull op can be proxied, saving an object promotion.
Even though updating ceph_osdc_new_request() to allow writefull should
just be a matter of fixing an assert, I didn't do it because its only
user is cephfs. All other sites were updated.
Reflects ceph.git commit 7bfb7f9025a8ee0d2305f49bf0336d2424da5b5b.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
This
struct ceph_timespec ceph_ts;
...
con_out_kvec_add(con, sizeof(ceph_ts), &ceph_ts);
wraps ceph_ts into a kvec and adds it to con->out_kvec array, yet
ceph_ts becomes invalid on return from prepare_write_keepalive(). As
a result, we send out bogus keepalive2 stamps. Fix this by encoding
into a ceph_timespec member, similar to how acks are read and written.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Yan, Zheng <zyan@redhat.com>
Pull Ceph update from Sage Weil:
"There are a few fixes for snapshot behavior with CephFS and support
for the new keepalive protocol from Zheng, a libceph fix that affects
both RBD and CephFS, a few bug fixes and cleanups for RBD from Ilya,
and several small fixes and cleanups from Jianpeng and others"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client:
ceph: improve readahead for file holes
ceph: get inode size for each append write
libceph: check data_len in ->alloc_msg()
libceph: use keepalive2 to verify the mon session is alive
rbd: plug rbd_dev->header.object_prefix memory leak
rbd: fix double free on rbd_dev->header_name
libceph: set 'exists' flag for newly up osd
ceph: cleanup use of ceph_msg_get
ceph: no need to get parent inode in ceph_open
ceph: remove the useless judgement
ceph: remove redundant test of head->safe and silence static analysis warnings
ceph: fix queuing inode to mdsdir's snaprealm
libceph: rename con_work() to ceph_con_workfn()
libceph: Avoid holding the zero page on ceph_msgr_slab_init errors
libceph: remove the unused macro AES_KEY_SIZE
ceph: invalidate dirty pages after forced umount
ceph: EIO all operations after forced umount
Only ->alloc_msg() should check data_len of the incoming message
against the preallocated ceph_msg, doing it in the messenger is not
right. The contract is that either ->alloc_msg() returns a ceph_msg
which will fit all of the portions of the incoming message, or it
returns NULL and possibly sets skip, signaling whether NULL is due to
an -ENOMEM. ->alloc_msg() should be the only place where we make the
skip/no-skip decision.
I stumbled upon this while looking at con/osd ref counting. Right now,
if we get a non-extent message with a larger data portion than we are
prepared for, ->alloc_msg() returns a ceph_msg, and then, when we skip
it in the messenger, we don't put the con/osd ref acquired in
ceph_con_in_msg_alloc() (which is normally put in process_message()),
so this also fixes a memory leak.
An existing BUG_ON in ceph_msg_data_cursor_init() ensures we don't
corrupt random memory should a buggy ->alloc_msg() return an unfit
ceph_msg.
While at it, I changed the "unknown tid" dout() to a pr_warn() to make
sure all skips are seen and unified format strings.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Even though it's static, con_work(), being a work func, shows up in
various stacktraces a lot. Prefix it with ceph_.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
ceph_msgr_slab_init may fail due to a temporary ENOMEM.
Delay a bit the initialization of zero_page in ceph_msgr_init and
reorder its cleanup in _ceph_msgr_exit so it's done in reverse
order of setup.
BUG_ON() will not suffer to be postponed in case it is triggered.
Signed-off-by: Benoît Canet <benoit.canet@nodalink.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This removes the no longer used macro AES_KEY_SIZE as no functions use
this macro anymore and thus this macro can be removed due it no longer
being required.
Signed-off-by: Nicholas Krause <xerofoify@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Many file systems that implement the show_options hook fail to correctly
escape their output which could lead to unescaped characters (e.g. new
lines) leaking into /proc/mounts and /proc/[pid]/mountinfo files. This
could lead to confusion, spoofed entries (resulting in things like
systemd issuing false d-bus "mount" notifications), and who knows what
else. This looks like it would only be the root user stepping on
themselves, but it's possible weird things could happen in containers or
in other situations with delegated mount privileges.
Here's an example using overlay with setuid fusermount trusting the
contents of /proc/mounts (via the /etc/mtab symlink). Imagine the use
of "sudo" is something more sneaky:
$ BASE="ovl"
$ MNT="$BASE/mnt"
$ LOW="$BASE/lower"
$ UP="$BASE/upper"
$ WORK="$BASE/work/ 0 0
none /proc fuse.pwn user_id=1000"
$ mkdir -p "$LOW" "$UP" "$WORK"
$ sudo mount -t overlay -o "lowerdir=$LOW,upperdir=$UP,workdir=$WORK" none /mnt
$ cat /proc/mounts
none /root/ovl/mnt overlay rw,relatime,lowerdir=ovl/lower,upperdir=ovl/upper,workdir=ovl/work/ 0 0
none /proc fuse.pwn user_id=1000 0 0
$ fusermount -u /proc
$ cat /proc/mounts
cat: /proc/mounts: No such file or directory
This fixes the problem by adding new seq_show_option and
seq_show_option_n helpers, and updating the vulnerable show_option
handlers to use them as needed. Some, like SELinux, need to be open
coded due to unusual existing escape mechanisms.
[akpm@linux-foundation.org: add lost chunk, per Kees]
[keescook@chromium.org: seq_show_option should be using const parameters]
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Jan Kara <jack@suse.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Cc: J. R. Okajima <hooanon05g@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
addr_is_blank() should return true if family is neither AF_INET nor
AF_INET6. This is what its counterpart entity_addr_t::is_blank_ip() is
doing and it is the right thing to do: in process_banner() we check if
our address is blank and if it is "learn" it from our peer. As it is,
we never learn our address and always send out a blank one. This goes
way back to ceph.git commit dd732cbfc1c9 ("use sockaddr_storage; and
some ipv6 support groundwork") from 2009.
While at at, do not open-code ipv6_addr_any() and use INADDR_ANY
constant instead of 0.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Grab a reference on a network namespace of the 'rbd map' (in case of
rbd) or 'mount' (in case of ceph) process and use that to open sockets
instead of always using init_net and bailing if network namespace is
anything but init_net. Be careful to not share struct ceph_client
instances between different namespaces and don't add any code in the
!CONFIG_NET_NS case.
This is based on a patch from Hong Zhiguo <zhiguohong@tencent.com>.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Pull Ceph updates from Sage Weil:
"We have a pile of bug fixes from Ilya, including a few patches that
sync up the CRUSH code with the latest from userspace.
There is also a long series from Zheng that fixes various issues with
snapshots, inline data, and directory fsync, some simplification and
improvement in the cap release code, and a rework of the caching of
directory contents.
To top it off there are a few small fixes and cleanups from Benoit and
Hong"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (40 commits)
rbd: use GFP_NOIO in rbd_obj_request_create()
crush: fix a bug in tree bucket decode
libceph: Fix ceph_tcp_sendpage()'s more boolean usage
libceph: Remove spurious kunmap() of the zero page
rbd: queue_depth map option
rbd: store rbd_options in rbd_device
rbd: terminate rbd_opts_tokens with Opt_err
ceph: fix ceph_writepages_start()
rbd: bump queue_max_segments
ceph: rework dcache readdir
crush: sync up with userspace
crush: fix crash from invalid 'take' argument
ceph: switch some GFP_NOFS memory allocation to GFP_KERNEL
ceph: pre-allocate data structure that tracks caps flushing
ceph: re-send flushing caps (which are revoked) in reconnect stage
ceph: send TID of the oldest pending caps flush to MDS
ceph: track pending caps flushing globally
ceph: track pending caps flushing accurately
libceph: fix wrong name "Ceph filesystem for Linux"
ceph: fix directory fsync
...
struct crush_bucket_tree::num_nodes is u8, so ceph_decode_8_safe()
should be used. -Wconversion catches this, but I guess it went
unnoticed in all the noise it spews. The actual problem (at least for
common crushmaps) isn't the u32 -> u8 truncation though - it's the
advancement by 4 bytes instead of 1 in the crushmap buffer.
Fixes: http://tracker.ceph.com/issues/2759
Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Josh Durgin <jdurgin@redhat.com>
From struct ceph_msg_data_cursor in include/linux/ceph/messenger.h:
bool last_piece; /* current is last piece */
In ceph_msg_data_next():
*last_piece = cursor->last_piece;
A call to ceph_msg_data_next() is followed by:
ret = ceph_tcp_sendpage(con->sock, page, page_offset,
length, last_piece);
while ceph_tcp_sendpage() is:
static int ceph_tcp_sendpage(struct socket *sock, struct page *page,
int offset, size_t size, bool more)
The logic is inverted: correct it.
Signed-off-by: Benoît Canet <benoit.canet@nodalink.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
ceph_tcp_sendpage already does the work of mapping/unmapping
the zero page if needed.
Signed-off-by: Benoît Canet <benoit.canet@nodalink.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
.. up to ceph.git commit 1db1abc8328d ("crush: eliminate ad hoc diff
between kernel and userspace"). This fixes a bunch of recently pulled
coding style issues and makes includes a bit cleaner.
A patch "crush:Make the function crush_ln static" from Nicholas Krause
<xerofoify@gmail.com> is folded in as crush_ln() has been made static
in userspace as well.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Verify that the 'take' argument is a valid device or bucket.
Otherwise ignore it (do not add the value to the working vector).
Reflects ceph.git commit 9324d0a1af61e1c234cc48e2175b4e6320fff8f4.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
modinfo libceph prints the module name "Ceph filesystem for Linux",
which is same as the real fs module ceph. It's confusing.
Signed-off-by: Hong Zhiguo <zhiguohong@tencent.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
- return -ETIMEDOUT instead of -EIO in case of timeout
- wait_event_interruptible_timeout() returns time left until timeout
and since it can be almost LONG_MAX we had better assign it to long
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
There are currently three libceph-level timeouts that the user can
specify on mount: mount_timeout, osd_idle_ttl and osdkeepalive. All of
these are in seconds and no checking is done on user input: negative
values are accepted, we multiply them all by HZ which may or may not
overflow, arbitrarily large jiffies then get added together, etc.
There is also a bug in the way mount_timeout=0 is handled. It's
supposed to mean "infinite timeout", but that's not how wait.h APIs
treat it and so __ceph_open_session() for example will busy loop
without much chance of being interrupted if none of ceph-mons are
there.
Fix all this by verifying user input, storing timeouts capped by
msecs_to_jiffies() in jiffies and using the new ceph_timeout_jiffies()
helper for all user-specified waits to handle infinite timeouts
correctly.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
This one sneaked in through vfs tree with commit 2b777c9dd9
("ceph_sync_read: stop poking into iov_iter guts").
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Conflicts:
drivers/net/phy/amd-xgbe-phy.c
drivers/net/wireless/iwlwifi/Kconfig
include/net/mac80211.h
iwlwifi/Kconfig and mac80211.h were both trivial overlapping
changes.
The drivers/net/phy/amd-xgbe-phy.c file got removed in 'net-next' and
the bug fix that happened on the 'net' side is already integrated
into the rest of the amd-xgbe driver.
Signed-off-by: David S. Miller <davem@davemloft.net>
This reverts commit ba9d114ec5.
.. which introduced a regression that prevented all lingering requests
requeued in kick_requests() from ever being sent to the OSDs, resulting
in a lot of missed notifies. In retrospect it's pretty obvious that
r_req_lru_item item in the case of lingering requests can be used not
only for notarget, but also for unsent linkage due to how tightly
actual map and enqueue operations are coupled in __map_request().
The assertion that was being silenced is taken care of in the previous
("libceph: request a new osdmap if lingering request maps to no osd")
commit: by always kicking homeless lingering requests we ensure that
none of them ends up on the notarget list outside of the critical
section guarded by request_mutex.
Cc: stable@vger.kernel.org # 3.18+, needs b049453221 "libceph: request a new osdmap if lingering request maps to no osd"
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
This commit does two things. First, if there are any homeless
lingering requests, we now request a new osdmap even if the osdmap that
is being processed brought no changes, i.e. if a given lingering
request turned homeless in one of the previous epochs and remained
homeless in the current epoch. Not doing so leaves us with a stale
osdmap and as a result we may miss our window for reestablishing the
watch and lose notifies.
MON=1 OSD=1:
# cat linger-needmap.sh
#!/bin/bash
rbd create --size 1 test
DEV=$(rbd map test)
ceph osd out 0
rbd map dne/dne # obtain a new osdmap as a side effect (!)
sleep 1
ceph osd in 0
rbd resize --size 2 test
# rbd info test | grep size -> 2M
# blockdev --getsize $DEV -> 1M
N.B.: Not obtaining a new osdmap in between "osd out" and "osd in"
above is enough to make it miss that resize notify, but that is a
bug^Wlimitation of ceph watch/notify v1.
Second, homeless lingering requests are now kicked just like those
lingering requests whose mapping has changed. This is mainly to
recognize that a homeless lingering request makes no sense and to
preserve the invariant that a registered lingering request is not
sitting on any of r_req_lru_item lists. This spares us a WARN_ON,
which commit ba9d114ec5 ("libceph: clear r_req_lru_item in
__unregister_linger_request()") tried to fix the _wrong_ way.
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
This is long overdue, and is part of cleaning up how we allocate kernel
sockets that don't reference count struct net.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This is an improved straw bucket that correctly avoids any data movement
between items A and B when neither A nor B's weights are changed. Said
differently, if we adjust the weight of item C (including adding it anew
or removing it completely), we will only see inputs move to or from C,
never between other items in the bucket.
Notably, there is not intermediate scaling factor that needs to be
calculated. The mapping function is a simple function of the item weights.
The below commits were squashed together into this one (mostly to avoid
adding and then yanking a ~6000 lines worth of crush_ln_table):
- crush: add a straw2 bucket type
- crush: add crush_ln to calculate nature log efficently
- crush: improve straw2 adjustment slightly
- crush: change crush_ln to provide 32 more digits
- crush: fix crush_get_bucket_item_weight and bucket destroy for straw2
- crush/mapper: fix divide-by-0 in straw2
(with div64_s64() for draw = ln / w and INT64_MIN -> S64_MIN - need
to create a proper compat.h in ceph.git)
Reflects ceph.git commits 242293c908e923d474910f2b8203fa3b41eb5a53,
32a1ead92efcd351822d22a5fc37d159c65c1338,
6289912418c4a3597a11778bcf29ed5415117ad9,
35fcb04e2945717cf5cfe150b9fa89cb3d2303a1,
6445d9ee7290938de1e4ee9563912a6ab6d8ee5f,
b5921d55d16796e12d66ad2c4add7305f9ce2353.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Crush temporary buffers are allocated as per replica size configured
by the user. When there are more final osds (to be selected as per
rule) than the replicas, buffer overlaps and it causes crash. Now, it
ensures that at most num-rep osds are selected even if more number of
osds are allowed by the rule.
Reflects ceph.git commits 6b4d1aa99718e3b367496326c1e64551330fabc0,
234b066ba04976783d15ff2abc3e81b6cc06fb10.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Split ceph_show_options() into two pieces and move the piece
responsible for printing client (libceph) options into net/ceph. This
way people adding a libceph option wouldn't have to remember to update
code in fs/ceph.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
- specific con->error_msg messages (e.g. "protocol version mismatch")
end up getting overwritten by a catch-all "socket error on read
/ write", introduced in commit 3a140a0d5c ("libceph: report socket
read/write error message")
- "bad message sequence # for incoming message" loses to "bad crc" due
to the fact that -EBADMSG is used for both
Fix it, and tidy up con->error_msg assignments and pr_errs while at it.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This reverts commit 89baaa570a.
Dirty page throttling should be sufficient for us in the general case
so there is no need to use __GFP_MEMALLOC - it would be needed only in
the swap-over-rbd case, which we currently don't support. (It would
probably take approximately the commit that is being reverted to add
that support, but we would also need the "swap" option to distinguish
from the general case and make sure swap ceph_client-s aren't shared
with anything else.) See ceph-devel threads [1] and [2] for the
details of why enabling pfmemalloc reserves for all cases is a bad
thing.
On top of potential system lockups related to drained emergency
reserves, this turned out to cause ceph lockups in case peers are on
the same host and communicating via loopback due to sk_filter()
dropping pfmemalloc skbs on the receiving side because the receiving
loopback socket is not tagged with SOCK_MEMALLOC.
[1] "SOCK_MEMALLOC vs loopback"
http://www.spinics.net/lists/ceph-devel/msg22998.html
[2] "[PATCH] libceph: don't set memalloc flags in loopback case"
http://www.spinics.net/lists/ceph-devel/msg23392.html
Conflicts:
net/ceph/messenger.c [ context: tcp_nodelay option ]
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Sage Weil <sage@redhat.com>
Cc: stable@vger.kernel.org # 3.18+, needs backporting
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Mel Gorman <mgorman@suse.de>
Pull Ceph changes from Sage Weil:
"On the RBD side, there is a conversion to blk-mq from Christoph,
several long-standing bug fixes from Ilya, and some cleanup from
Rickard Strandqvist.
On the CephFS side there is a long list of fixes from Zheng, including
improved session handling, a few IO path fixes, some dcache management
correctness fixes, and several blocking while !TASK_RUNNING fixes.
The core code gets a few cleanups and Chaitanya has added support for
TCP_NODELAY (which has been used on the server side for ages but we
somehow missed on the kernel client).
There is also an update to MAINTAINERS to fix up some email addresses
and reflect that Ilya and Zheng are doing most of the maintenance for
RBD and CephFS these days. Do not be surprised to see a pull request
come from one of them in the future if I am unavailable for some
reason"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (27 commits)
MAINTAINERS: update Ceph and RBD maintainers
libceph: kfree() in put_osd() shouldn't depend on authorizer
libceph: fix double __remove_osd() problem
rbd: convert to blk-mq
ceph: return error for traceless reply race
ceph: fix dentry leaks
ceph: re-send requests when MDS enters reconnecting stage
ceph: show nocephx_require_signatures and notcp_nodelay options
libceph: tcp_nodelay support
rbd: do not treat standalone as flatten
ceph: fix atomic_open snapdir
ceph: properly mark empty directory as complete
client: include kernel version in client metadata
ceph: provide seperate {inode,file}_operations for snapdir
ceph: fix request time stamp encoding
ceph: fix reading inline data when i_size > PAGE_SIZE
ceph: avoid block operation when !TASK_RUNNING (ceph_mdsc_close_sessions)
ceph: avoid block operation when !TASK_RUNNING (ceph_get_caps)
ceph: avoid block operation when !TASK_RUNNING (ceph_mdsc_sync)
rbd: fix error paths in rbd_dev_refresh()
...
a255651d4c ("ceph: ensure auth ops are defined before use") made
kfree() in put_osd() conditional on the authorizer. A mechanical
mistake most likely - fix it.
Cc: Alex Elder <elder@linaro.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Reviewed-by: Alex Elder <elder@linaro.org>
It turns out it's possible to get __remove_osd() called twice on the
same OSD. That doesn't sit well with rb_erase() - depending on the
shape of the tree we can get a NULL dereference, a soft lockup or
a random crash at some point in the future as we end up touching freed
memory. One scenario that I was able to reproduce is as follows:
<osd3 is idle, on the osd lru list>
<con reset - osd3>
con_fault_finish()
osd_reset()
<osdmap - osd3 down>
ceph_osdc_handle_map()
<takes map_sem>
kick_requests()
<takes request_mutex>
reset_changed_osds()
__reset_osd()
__remove_osd()
<releases request_mutex>
<releases map_sem>
<takes map_sem>
<takes request_mutex>
__kick_osd_requests()
__reset_osd()
__remove_osd() <-- !!!
A case can be made that osd refcounting is imperfect and reworking it
would be a proper resolution, but for now Sage and I decided to fix
this by adding a safe guard around __remove_osd().
Fixes: http://tracker.ceph.com/issues/8087
Cc: Sage Weil <sage@redhat.com>
Cc: stable@vger.kernel.org # 3.9+: 7c6e6fc53e: libceph: assert both regular and lingering lists in __remove_osd()
Cc: stable@vger.kernel.org # 3.9+: cc9f1f518c: libceph: change from BUG to WARN for __remove_osd() asserts
Cc: stable@vger.kernel.org # 3.9+
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Reviewed-by: Alex Elder <elder@linaro.org>
On Mon, Dec 22, 2014 at 5:35 PM, Sage Weil <sage@newdream.net> wrote:
> On Mon, 22 Dec 2014, Ilya Dryomov wrote:
>> Actually, pool op stuff has been unused for over two years - looks like
>> it was added for rbd create_snap and that got ripped out in 2012. It's
>> unlikely we'd ever need to manage pools or snaps from the kernel client
>> so I think it makes sense to nuke it. Sage?
>
> Yep!
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
This allows those get_user_pages calls to pass FAULT_FLAG_ALLOW_RETRY to
the page fault in order to release the mmap_sem during the I/O.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
allow specifying position of extent operation in multi-operations
osd request. This is required for cephfs to convert inline data to
normal data (compare xattr, then write object).
Signed-off-by: Yan, Zheng <zyan@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@redhat.com>
Add CEPH_OSD_OP_CREATE support. Also change libceph to not treat
CEPH_OSD_OP_DELETE as an extent op and add an assert to that end.
Signed-off-by: Yan, Zheng <zyan@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@redhat.com>
Session key is required when calculating message signature. Save the session
key in authorizer, this avoid lookup ticket handler for each message
Signed-off-by: Yan, Zheng <zyan@redhat.com>
Use kvfree() from linux/mm.h instead, which is identical. Also fix the
ceph_buffer comment: we will allocate with kmalloc() up to 32k - the
value of PAGE_ALLOC_COSTLY_ORDER, but that really is just an
implementation detail so don't mention it at all.
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
kick_requests() can put linger requests on the notarget list. This
means we need to clear the much-overloaded req->r_req_lru_item in
__unregister_linger_request() as well, or we get an assertion failure
in ceph_osdc_release_request() - !list_empty(&req->r_req_lru_item).
AFAICT the assumption was that registered linger requests cannot be on
any of req->r_req_lru_item lists, but that's clearly not the case.
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Requests have to be unlinked from both osd->o_requests (normal
requests) and osd->o_linger_requests (linger requests) lists when
clearing req->r_osd. Otherwise __unregister_linger_request() gets
confused and we trip over a !list_empty(&osd->o_linger_requests)
assert in __remove_osd().
MON=1 OSD=1:
# cat remove-osd.sh
#!/bin/bash
rbd create --size 1 test
DEV=$(rbd map test)
ceph osd out 0
sleep 3
rbd map dne/dne # obtain a new osdmap as a side effect
rbd unmap $DEV & # will block
sleep 3
ceph osd in 0
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Commit c27a3e4d66 ("libceph: do not hard code max auth ticket len")
while fixing a buffer overlow tried to keep the same as much of the
surrounding code as possible and introduced an unnecessary kmalloc() in
the unencrypted ticket path. It is likely to fail on huge tickets, so
get rid of it.
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>
This patch has ceph's lib code use the memalloc flags.
If the VM layer needs to write data out to free up memory to handle new
allocation requests, the block layer must be able to make forward progress.
To handle that requirement we use structs like mempools to reserve memory for
objects like bios and requests.
The problem is when we send/receive block layer requests over the network
layer, net skb allocations can fail and the system can lock up.
To solve this, the memalloc related flags were added. NBD, iSCSI
and NFS uses these flags to tell the network/vm layer that it should
use memory reserves to fullfill allcation requests for structs like
skbs.
I am running ceph in a bunch of VMs in my laptop, so this patch was
not tested very harshly.
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Reviewed-by: Ilya Dryomov <idryomov@redhat.com>
Pull Ceph updates from Sage Weil:
"There is the long-awaited discard support for RBD (Guangliang Zhao,
Josh Durgin), a pile of RBD bug fixes that didn't belong in late -rc's
(Ilya Dryomov, Li RongQing), a pile of fs/ceph bug fixes and
performance and debugging improvements (Yan, Zheng, John Spray), and a
smattering of cleanups (Chao Yu, Fabian Frederick, Joe Perches)"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (40 commits)
ceph: fix divide-by-zero in __validate_layout()
rbd: rbd workqueues need a resque worker
libceph: ceph-msgr workqueue needs a resque worker
ceph: fix bool assignments
libceph: separate multiple ops with commas in debugfs output
libceph: sync osd op definitions in rados.h
libceph: remove redundant declaration
ceph: additional debugfs output
ceph: export ceph_session_state_name function
ceph: include the initial ACL in create/mkdir/mknod MDS requests
ceph: use pagelist to present MDS request data
libceph: reference counting pagelist
ceph: fix llistxattr on symlink
ceph: send client metadata to MDS
ceph: remove redundant code for max file size verification
ceph: remove redundant io_iter_advance()
ceph: move ceph_find_inode() outside the s_mutex
ceph: request xattrs if xattr_version is zero
rbd: set the remaining discard properties to enable support
rbd: use helpers to handle discard for layered images correctly
...
Commit f363e45fd1 ("net/ceph: make ceph_msgr_wq non-reentrant")
effectively removed WQ_MEM_RECLAIM flag from ceph_msgr_wq. This is
wrong - libceph is very much a memory reclaim path, so restore it.
Cc: stable@vger.kernel.org # needs backporting for < 3.12
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
Tested-by: Micha Krause <micha@krausam.de>
Reviewed-by: Sage Weil <sage@redhat.com>
For requests with multiple ops, separate ops with commas instead of \t,
which is a field separator here.
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Bring in missing osd ops and strings, use macros to eliminate multiple
points of maintenance.
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>
this allow pagelist to present data that may be sent multiple times.
Signed-off-by: Yan, Zheng <zyan@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>
queue_work() doesn't "fail to queue", it returns false if work was
already on a queue, which can't happen here since we allocate
event_work right before we queue it. So don't bother at all.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Use the more common pr_warn.
Other miscellanea:
o Coalesce formats
o Realign arguments
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
If the state variable is krealloced successfully, map->osd_state will be
freed, once following two reallocation failed, and exit the function
without resetting map->osd_state, map->osd_state become a wild pointer.
fix it by resetting them after krealloc successfully.
Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
We want "cbc(aes)" algorithm, so select CRYPTO_CBC too, not just
CRYPTO_AES. Otherwise on !CRYPTO_CBC kernels we fail rbd map/mount
with
libceph: error -2 building auth method x request
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Both not yet registered (r_linger && list_empty(&r_linger_item)) and
registered linger requests should use the new tid on resend to avoid
the dup op detection logic on the OSDs, yet we were doing this only for
"registered" case. Factor out and simplify the "registered" logic and
use the new helper for "not registered" case as well.
Fixes: http://tracker.ceph.com/issues/8806
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Pull security subsystem updates from James Morris.
Mostly ima, selinux, smack and key handling updates.
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (65 commits)
integrity: do zero padding of the key id
KEYS: output last portion of fingerprint in /proc/keys
KEYS: strip 'id:' from ca_keyid
KEYS: use swapped SKID for performing partial matching
KEYS: Restore partial ID matching functionality for asymmetric keys
X.509: If available, use the raw subjKeyId to form the key description
KEYS: handle error code encoded in pointer
selinux: normalize audit log formatting
selinux: cleanup error reporting in selinux_nlmsg_perm()
KEYS: Check hex2bin()'s return when generating an asymmetric key ID
ima: detect violations for mmaped files
ima: fix race condition on ima_rdwr_violation_check and process_measurement
ima: added ima_policy_flag variable
ima: return an error code from ima_add_boot_aggregate()
ima: provide 'ima_appraise=log' kernel option
ima: move keyring initialization to ima_init()
PKCS#7: Handle PKCS#7 messages that contain no X.509 certs
PKCS#7: Better handling of unsupported crypto
KEYS: Overhaul key identification when searching for asymmetric keys
KEYS: Implement binary asymmetric key ID handling
...
A previous patch added a ->match_preparse() method to the key type. This is
allowed to override the function called by the iteration algorithm.
Therefore, we can just set a default that simply checks for an exact match of
the key description with the original criterion data and allow match_preparse
to override it as needed.
The key_type::match op is then redundant and can be removed, as can the
user_match() function.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
We hard code cephx auth ticket buffer size to 256 bytes. This isn't
enough for any moderate setups and, in case tickets themselves are not
encrypted, leads to buffer overflows (ceph_x_decrypt() errors out, but
ceph_decode_copy() doesn't - it's just a memcpy() wrapper). Since the
buffer is allocated dynamically anyway, allocated it a bit later, at
the point where we know how much is going to be needed.
Fixes: http://tracker.ceph.com/issues/8979
Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Add a helper for processing individual cephx auth tickets. Needed for
the next commit, which deals with allocating ticket buffers. (Most of
the diff here is whitespace - view with git diff -b).
Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@redhat.com>
We preallocate a few of the message types we get back from the mon. If we
get a larger message than we are expecting, fall back to trying to allocate
a new one instead of blindly using the one we have.
CC: stable@vger.kernel.org
Signed-off-by: Sage Weil <sage@redhat.com>
Reviewed-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Pull Ceph updates from Sage Weil:
"There is a lot of refactoring and hardening of the libceph and rbd
code here from Ilya that fix various smaller bugs, and a few more
important fixes with clone overlap. The main fix is a critical change
to the request_fn handling to not sleep that was exposed by the recent
mutex changes (which will also go to the 3.16 stable series).
Yan Zheng has several fixes in here for CephFS fixing ACL handling,
time stamps, and request resends when the MDS restarts.
Finally, there are a few cleanups from Himangi Saraogi based on
Coccinelle"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (39 commits)
libceph: set last_piece in ceph_msg_data_pages_cursor_init() correctly
rbd: remove extra newlines from rbd_warn() messages
rbd: allocate img_request with GFP_NOIO instead GFP_ATOMIC
rbd: rework rbd_request_fn()
ceph: fix kick_requests()
ceph: fix append mode write
ceph: fix sizeof(struct tYpO *) typo
ceph: remove redundant memset(0)
rbd: take snap_id into account when reading in parent info
rbd: do not read in parent info before snap context
rbd: update mapping size only on refresh
rbd: harden rbd_dev_refresh() and callers a bit
rbd: split rbd_dev_spec_update() into two functions
rbd: remove unnecessary asserts in rbd_dev_image_probe()
rbd: introduce rbd_dev_header_info()
rbd: show the entire chain of parent images
ceph: replace comma with a semicolon
rbd: use rbd_segment_name_free() instead of kfree()
ceph: check zero length in ceph_sync_read()
ceph: reset r_resend_mds after receiving -ESTALE
...
Determining ->last_piece based on the value of ->page_offset + length
is incorrect because length here is the length of the entire message.
->last_piece set to false even if page array data item length is <=
PAGE_SIZE, which results in invalid length passed to
ceph_tcp_{send,recv}page() and causes various asserts to fire.
# cat pages-cursor-init.sh
#!/bin/bash
rbd create --size 10 --image-format 2 foo
FOO_DEV=$(rbd map foo)
dd if=/dev/urandom of=$FOO_DEV bs=1M &>/dev/null
rbd snap create foo@snap
rbd snap protect foo@snap
rbd clone foo@snap bar
# rbd_resize calls librbd rbd_resize(), size is in bytes
./rbd_resize bar $(((4 << 20) + 512))
rbd resize --size 10 bar
BAR_DEV=$(rbd map bar)
# trigger a 512-byte copyup -- 512-byte page array data item
dd if=/dev/urandom of=$BAR_DEV bs=1M count=1 seek=5
The problem exists only in ceph_msg_data_pages_cursor_init(),
ceph_msg_data_pages_advance() does the right thing. The size_t cast is
unnecessary.
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Ceph can use user_match() instead of defining its own identical function.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>
cc: Tommi Virtanen <tommi.virtanen@dreamhost.com>
Make use of key preparsing in Ceph so that quota size determination can take
place prior to keyring locking when a key is being added.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>
cc: Tommi Virtanen <tommi.virtanen@dreamhost.com>
queue_con() bumps osd ref count. We should do the reverse when
canceling con work.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Introduce ceph_osdc_cancel_request() intended for canceling requests
from the higher layers (rbd and cephfs). Because higher layers are in
charge and are supposed to know what and when they are canceling, the
request is not completed, only unref'ed and removed from the libceph
data structures.
__cancel_request() is no longer called before __unregister_request(),
because __unregister_request() unconditionally revokes r_request and
there is no point in trying to do it twice.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
We should check if request is on the linger request list of any of the
OSDs, not whether request is registered or not.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Linger requests that have not yet been registered should not be
unregistered by __unregister_linger_request(). This messes up ref
count and leads to use-after-free.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
It is important that both regular and lingering requests lists are
empty when the OSD is removed.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Add some WARN_ONs to alert us when we try to destroy requests that are
still registered.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Add dout()s to ceph_osdc_request_{get,put}(). Also move them to .c and
turn kref release callback into a static function.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Add dout()s to ceph_msg_{get,put}(). Also move them to .c and turn
kref release callback into a static function.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Abstract out __move_osd_to_lru() logic from __unregister_request() and
__unregister_linger_request().
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
So that:
req->r_osd_item --> osd->o_requests list
req->r_linger_osd_item --> osd->o_linger_requests list
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Pull Ceph updates from Sage Weil:
"This has a mix of bug fixes and cleanups.
Alex's patch fixes a rare race in RBD. Ilya's patches fix an ENOENT
check when a second rbd image is mapped and a couple memory leaks.
Zheng fixes several issues with fragmented directories and multiple
MDSs. Josh fixes a spin/sleep issue, and Josh and Guangliang's
patches fix setting and unsetting RBD images read-only.
Naturally there are several other cleanups mixed in for good measure"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (23 commits)
rbd: only set disk to read-only once
rbd: move calls that may sleep out of spin lock range
rbd: add ioctl for rbd
ceph: use truncate_pagecache() instead of truncate_inode_pages()
ceph: include time stamp in every MDS request
rbd: fix ida/idr memory leak
rbd: use reference counts for image requests
rbd: fix osd_request memory leak in __rbd_dev_header_watch_sync()
rbd: make sure we have latest osdmap on 'rbd map'
libceph: add ceph_monc_wait_osdmap()
libceph: mon_get_version request infrastructure
libceph: recognize poolop requests in debugfs
ceph: refactor readpage_nounlock() to make the logic clearer
mds: check cap ID when handling cap export message
ceph: remember subtree root dirfrag's auth MDS
ceph: introduce ceph_fill_fragtree()
ceph: handle cap import atomically
ceph: pre-allocate ceph_cap struct for ceph_add_cap()
ceph: update inode fields according to issued caps
rbd: replace IS_ERR and PTR_ERR with PTR_ERR_OR_ZERO
...
Pull networking updates from David Miller:
1) Seccomp BPF filters can now be JIT'd, from Alexei Starovoitov.
2) Multiqueue support in xen-netback and xen-netfront, from Andrew J
Benniston.
3) Allow tweaking of aggregation settings in cdc_ncm driver, from Bjørn
Mork.
4) BPF now has a "random" opcode, from Chema Gonzalez.
5) Add more BPF documentation and improve test framework, from Daniel
Borkmann.
6) Support TCP fastopen over ipv6, from Daniel Lee.
7) Add software TSO helper functions and use them to support software
TSO in mvneta and mv643xx_eth drivers. From Ezequiel Garcia.
8) Support software TSO in fec driver too, from Nimrod Andy.
9) Add Broadcom SYSTEMPORT driver, from Florian Fainelli.
10) Handle broadcasts more gracefully over macvlan when there are large
numbers of interfaces configured, from Herbert Xu.
11) Allow more control over fwmark used for non-socket based responses,
from Lorenzo Colitti.
12) Do TCP congestion window limiting based upon measurements, from Neal
Cardwell.
13) Support busy polling in SCTP, from Neal Horman.
14) Allow RSS key to be configured via ethtool, from Venkata Duvvuru.
15) Bridge promisc mode handling improvements from Vlad Yasevich.
16) Don't use inetpeer entries to implement ID generation any more, it
performs poorly, from Eric Dumazet.
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next: (1522 commits)
rtnetlink: fix userspace API breakage for iproute2 < v3.9.0
tcp: fixing TLP's FIN recovery
net: fec: Add software TSO support
net: fec: Add Scatter/gather support
net: fec: Increase buffer descriptor entry number
net: fec: Factorize feature setting
net: fec: Enable IP header hardware checksum
net: fec: Factorize the .xmit transmit function
bridge: fix compile error when compiling without IPv6 support
bridge: fix smatch warning / potential null pointer dereference
via-rhine: fix full-duplex with autoneg disable
bnx2x: Enlarge the dorq threshold for VFs
bnx2x: Check for UNDI in uncommon branch
bnx2x: Fix 1G-baseT link
bnx2x: Fix link for KR with swapped polarity lane
sctp: Fix sk_ack_backlog wrap-around problem
net/core: Add VF link state control policy
net/fsl: xgmac_mdio is dependent on OF_MDIO
net/fsl: Make xgmac_mdio read error message useful
net_sched: drr: warn when qdisc is not work conserving
...
Sparse complained about this bogus extern on definition of
a function.
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add ceph_monc_wait_osdmap(), which will block until the osdmap with the
specified epoch is received or timeout occurs.
Export both of these as they are going to be needed by rbd.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Add support for mon_get_version requests to libceph. This reuses much
of the ceph_mon_generic_request infrastructure, with one exception.
Older OSDs don't set mon_get_version reply hdr->tid even if the
original request had a non-zero tid, which makes it impossible to
lookup ceph_mon_generic_request contexts by tid in get_generic_reply()
for such replies. As a workaround, we allocate a reply message on the
reply path. This can probably interfere with revoke, but I don't see
a better way.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Recognize poolop requests in debugfs monc dump, fix prink format
specifiers - tid is unsigned.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Commit e2b149cc4b ("crush: add chooseleaf_vary_r tunable") added the
crush_map::chooseleaf_vary_r field but missed the decode part. This
lead to misdirected requests caused by incorrect raw crush mapping
sets.
Fixes: http://tracker.ceph.com/issues/8226
Reported-and-Tested-by: Dmitry Smirnov <onlyjob@member.fsf.org>
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
It has been reported that using ZFSonLinux on rbd will result in memory
corruption. The bug report can be found here:
https://github.com/zfsonlinux/spl/issues/241http://tracker.ceph.com/issues/7790
The reason is that ZFS will send pages with page_count 0 into rbd, which in
turns send them to tcp_sendpage. However, tcp_sendpage cannot deal with
page_count 0, as it will do get_page and put_page, and erroneously free the
page.
This type of issue has been noted before, and handled in iscsi, drbd,
etc. So, rbd should also handle this. This fix address this issue by fall back
to slower sendmsg when page_count 0 detected.
Cc: Sage Weil <sage@inktank.com>
Cc: Yehuda Sadeh <yehuda@inktank.com>
Cc: stable@vger.kernel.org
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Reviewed-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Pull Ceph fixes from Sage Weil:
"First, there is a critical fix for the new primary-affinity function
that went into -rc1.
The second batch of patches from Zheng fix a range of problems with
directory fragmentation, readdir, and a few odds and ends for cephfs"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client:
ceph: reserve caps for file layout/lock MDS requests
ceph: avoid releasing caps that are being used
ceph: clear directory's completeness when creating file
libceph: fix non-default values check in apply_primary_affinity()
ceph: use fpos_cmp() to compare dentry positions
ceph: check directory's completeness before emitting directory entry
