~mathiaz/+junk/ceph-new-pkg-review

v0.17
- kclient: fix multiple mds mdsmap decoding
- kclient: fix mon subscription renewal
- crush: fix crush map creation with empty buckets (occurs on larger clusters)
- osdmap: fix encoding bug (crashes kclient); make kclient not crash
- msgr: simplified policy, failure model
- mon: less push, more pull
- mon: request routing
- mon cluster expansion
- osd: fix pg parsing, restarts on larger clusters

v0.18
- osd: basic ENOSPC handling
- big endian fixes (required protocol/disk format change)
- osd: improved object -> pg hash function; selectable
- crush: selectable hash function(s)
- mds restart bug fixes
- kclient: mds reconnect bug fixes
- fixed mds log trimming bug
- fixed mds cap vs snap deadlock
- filestore: faster flushing
- uclient,kclient: snapshot fixes
- mds: fix recursive accounting bug
- uclient: fixes for 32bit clients
- auth: 'none' security framework
- mon: "safely" bail on write errors (e.g. ENOSPC)
- mds: fix replay/reconnect race (caused (fast) client reconnect to fail)
- mds: misc journal replay, session fixes

v0.19
- ms_dispatch fairness
- kclient: bad fsid deadlock fix
- tids in fixed msg header (protocol change)
- feature bits during connection handshake
- remove erank from ceph_entity_addr
- disk format, compat/incompat bits
- journal format improvements
- kclient: cephx
- improved truncation
- cephx: lots of fixes
- mkcephfs: cephx support
- debian: packaging fixes

v0.20
- osd: new filestore, journaling infrastructure
- msgr: wire protocol improvements (lower per-message overhead)
- mds: reduced memory utilization (still more to do!)
- mds: many single mds fixes
- mds: many clustered mds fixes
- auth: many auth_x cleanups, fixes, improvements
- kclient: many bug fixes
- librados: some cleanup, c++ api now usable

v0.21

- 

- qa: snap test.  maybe walk through 2.6.* kernel trees?
- osd: rebuild pg log
- osd: handle storage errors
- rebuild mds hierarchy
- kclient: retry alloc on ENOMEM when reading from connection?

filestore
- throttling
- flush objects onto primary during recovery
- audit queue_transaction calls for dependencies
- convert apply_transaction calls in handle_map to queue?
  - need an osdmap cache layer?

clients need to handle MClassAck, or anybody using that will die

bugs
- mds states
  - closing -> opening transition
- mds prepare_force_open_sessions, then import aborts.. session is still OPENING but no client_session is sent...
- rm -r failure (on kernel tree)
- dbench 1, restart mds (may take a few times), dbench will error out.

- kclient lockdep warning
[ 1615.328733] =======================================================
[ 1615.331050] [ INFO: possible circular locking dependency detected ]
[ 1615.331050] 2.6.34-rc2 #22
[ 1615.331050] -------------------------------------------------------
[ 1615.331050] fixdep/3263 is trying to acquire lock:
[ 1615.331050]  (&osdc->request_mutex){+.+...}, at: [<ffffffffa007b66c>] ceph_osdc_start_request+0x4d/0x278 [ceph]
[ 1615.331050] 
[ 1615.331050] but task is already holding lock:
[ 1615.331050]  (&mm->mmap_sem){++++++}, at: [<ffffffff810208c0>] do_page_fault+0x104/0x278
[ 1615.331050] 
[ 1615.331050] which lock already depends on the new lock.
[ 1615.331050] 
[ 1615.331050] 
[ 1615.331050] the existing dependency chain (in reverse order) is:
[ 1615.331050] 
[ 1615.331050] -> #3 (&mm->mmap_sem){++++++}:
[ 1615.331050]        [<ffffffff81059fd3>] validate_chain+0xa4d/0xd28
[ 1615.331050]        [<ffffffff8105aa7f>] __lock_acquire+0x7d1/0x84e
[ 1615.331050]        [<ffffffff8105ab84>] lock_acquire+0x88/0xa5
[ 1615.331050]        [<ffffffff81094daf>] might_fault+0x90/0xb3
[ 1615.331050]        [<ffffffff81390d1e>] memcpy_fromiovecend+0x54/0x8e
[ 1615.331050]        [<ffffffff813b6ea7>] ip_generic_getfrag+0x2a/0x8f
[ 1615.331050]        [<ffffffff813b5da2>] ip_append_data+0x5f6/0x971
[ 1615.331050]        [<ffffffff813d35bf>] udp_sendmsg+0x4e8/0x603
[ 1615.331050]        [<ffffffff813d91e3>] inet_sendmsg+0x46/0x53
[ 1615.331050]        [<ffffffff813878c1>] sock_sendmsg+0xd4/0xf5
[ 1615.331050]        [<ffffffff81387e0f>] sys_sendto+0xdf/0x107
[ 1615.331050]        [<ffffffff810029eb>] system_call_fastpath+0x16/0x1b
[ 1615.331050] 
[ 1615.331050] -> #2 (sk_lock-AF_INET){+.+.+.}:
[ 1615.331050]        [<ffffffff81059fd3>] validate_chain+0xa4d/0xd28
[ 1615.331050]        [<ffffffff8105aa7f>] __lock_acquire+0x7d1/0x84e
[ 1615.331050]        [<ffffffff8105ab84>] lock_acquire+0x88/0xa5
[ 1615.331050]        [<ffffffff8138a562>] lock_sock_nested+0xeb/0xff
[ 1615.331050]        [<ffffffff813da29d>] inet_stream_connect+0x2b/0x25c
[ 1615.331050]        [<ffffffffa006eea6>] try_write+0x26e/0x102c [ceph]
[ 1615.331050]        [<ffffffffa00705ba>] con_work+0x126/0x6bc [ceph]
[ 1615.529553]        [<ffffffff8104774e>] worker_thread+0x1e8/0x2fa
[ 1615.529553]        [<ffffffff8104a4aa>] kthread+0x7d/0x85
[ 1615.529553]        [<ffffffff81003794>] kernel_thread_helper+0x4/0x10
[ 1615.529553] 
[ 1615.529553] -> #1 (&con->mutex){+.+.+.}:
[ 1615.529553]        [<ffffffff81059fd3>] validate_chain+0xa4d/0xd28
[ 1615.529553]        [<ffffffff8105aa7f>] __lock_acquire+0x7d1/0x84e
[ 1615.529553]        [<ffffffff8105ab84>] lock_acquire+0x88/0xa5
[ 1615.529553]        [<ffffffff81425727>] mutex_lock_nested+0x62/0x32c
[ 1615.529553]        [<ffffffffa0070cd3>] ceph_con_send+0xb3/0x244 [ceph]
[ 1615.529553]        [<ffffffffa007b591>] __send_request+0x108/0x196 [ceph]
[ 1615.529553]        [<ffffffffa007b794>] ceph_osdc_start_request+0x175/0x278 [ceph]
[ 1615.529553]        [<ffffffffa006029d>] ceph_writepages_start+0xb23/0x112a [ceph]
[ 1615.529553]        [<ffffffff810849aa>] do_writepages+0x1f/0x28
[ 1615.529553]        [<ffffffff810ca5e8>] writeback_single_inode+0xb6/0x1f5
[ 1615.529553]        [<ffffffff810cad9b>] writeback_inodes_wb+0x2d1/0x378
[ 1615.529553]        [<ffffffff810cafa8>] wb_writeback+0x166/0x1e0
[ 1615.529553]        [<ffffffff810cb154>] wb_do_writeback+0x83/0x1d3
[ 1615.529553]        [<ffffffff810cb2d2>] bdi_writeback_task+0x2e/0x9b
[ 1615.529553]        [<ffffffff8108fd73>] bdi_start_fn+0x71/0xd2
[ 1615.529553]        [<ffffffff8104a4aa>] kthread+0x7d/0x85
[ 1615.529553]        [<ffffffff81003794>] kernel_thread_helper+0x4/0x10
[ 1615.529553] 
[ 1615.529553] -> #0 (&osdc->request_mutex){+.+...}:
[ 1615.529553]        [<ffffffff81059cbf>] validate_chain+0x739/0xd28
[ 1615.529553]        [<ffffffff8105aa7f>] __lock_acquire+0x7d1/0x84e
[ 1615.529553]        [<ffffffff8105ab84>] lock_acquire+0x88/0xa5
[ 1615.529553]        [<ffffffff81425727>] mutex_lock_nested+0x62/0x32c
[ 1615.529553]        [<ffffffffa007b66c>] ceph_osdc_start_request+0x4d/0x278 [ceph]
[ 1615.529553]        [<ffffffffa007d8b6>] ceph_osdc_readpages+0x123/0x222 [ceph]
[ 1615.529553]        [<ffffffffa005f4b7>] ceph_readpages+0x193/0x456 [ceph]
[ 1615.529553]        [<ffffffff81085bd1>] __do_page_cache_readahead+0x17d/0x1f5
[ 1615.529553]        [<ffffffff81085c65>] ra_submit+0x1c/0x20
[ 1615.529553]        [<ffffffff81085fab>] ondemand_readahead+0x264/0x277
[ 1615.529553]        [<ffffffff81086092>] page_cache_sync_readahead+0x33/0x35
[ 1615.529553]        [<ffffffff8107f0d7>] filemap_fault+0x143/0x31f
[ 1615.529553]        [<ffffffff810913bf>] __do_fault+0x50/0x415
[ 1615.529553]        [<ffffffff810934d9>] handle_mm_fault+0x334/0x6a6
[ 1615.529553]        [<ffffffff810209af>] do_page_fault+0x1f3/0x278
[ 1615.529553]        [<ffffffff814281ff>] page_fault+0x1f/0x30
[ 1615.529553] 
[ 1615.529553] other info that might help us debug this:
[ 1615.529553] 
[ 1615.529553] 1 lock held by fixdep/3263:
[ 1615.529553]  #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff810208c0>] do_page_fault+0x104/0x278
[ 1615.529553] 
[ 1615.529553] stack backtrace:
[ 1615.529553] Pid: 3263, comm: fixdep Not tainted 2.6.34-rc2 #22
[ 1615.529553] Call Trace:
[ 1615.529553]  [<ffffffff81058f49>] print_circular_bug+0xb3/0xc1
[ 1615.529553]  [<ffffffff81059cbf>] validate_chain+0x739/0xd28
[ 1615.529553]  [<ffffffff810099d7>] ? native_sched_clock+0x37/0x71
[ 1615.824177]  [<ffffffff8105aa7f>] __lock_acquire+0x7d1/0x84e
[ 1615.824177]  [<ffffffff8105ab84>] lock_acquire+0x88/0xa5
[ 1615.824177]  [<ffffffffa007b66c>] ? ceph_osdc_start_request+0x4d/0x278 [ceph]
[ 1615.824177]  [<ffffffffa007b66c>] ? ceph_osdc_start_request+0x4d/0x278 [ceph]
[ 1615.824177]  [<ffffffff81425727>] mutex_lock_nested+0x62/0x32c
[ 1615.824177]  [<ffffffffa007b66c>] ? ceph_osdc_start_request+0x4d/0x278 [ceph]
[ 1615.824177]  [<ffffffffa007b66c>] ceph_osdc_start_request+0x4d/0x278 [ceph]
[ 1615.824177]  [<ffffffffa007d8b6>] ceph_osdc_readpages+0x123/0x222 [ceph]
[ 1615.824177]  [<ffffffffa005f4b7>] ceph_readpages+0x193/0x456 [ceph]
[ 1615.824177]  [<ffffffff810099d7>] ? native_sched_clock+0x37/0x71
[ 1615.824177]  [<ffffffff81056580>] ? get_lock_stats+0x19/0x4c
[ 1615.824177]  [<ffffffff81085bd1>] __do_page_cache_readahead+0x17d/0x1f5
[ 1615.824177]  [<ffffffff81085ad0>] ? __do_page_cache_readahead+0x7c/0x1f5
[ 1615.824177]  [<ffffffff8107d848>] ? find_get_page+0xd9/0x12d
[ 1615.824177]  [<ffffffff81085c65>] ra_submit+0x1c/0x20
[ 1615.916887]  [<ffffffff81085fab>] ondemand_readahead+0x264/0x277
[ 1615.916887]  [<ffffffff81086092>] page_cache_sync_readahead+0x33/0x35
[ 1615.931403]  [<ffffffff8107f0d7>] filemap_fault+0x143/0x31f
[ 1615.931403]  [<ffffffff810913bf>] __do_fault+0x50/0x415
[ 1615.931403]  [<ffffffff8105aa99>] ? __lock_acquire+0x7eb/0x84e
[ 1615.946963]  [<ffffffff810934d9>] handle_mm_fault+0x334/0x6a6
[ 1615.946963]  [<ffffffff810209af>] do_page_fault+0x1f3/0x278
[ 1615.946963]  [<ffffffff814281ff>] page_fault+0x1f/0x30

- kclient: moonbeamer gets this with iozone -a...
[17608.696906] ------------[ cut here ]------------
[17608.701761] WARNING: at lib/kref.c:43 kref_get+0x23/0x2a()
[17608.707584] Hardware name: PDSMi
[17608.711056] Modules linked in: aes_x86_64 aes_generic ceph fan ac battery ehci_hcd container uhci_hcd thermal button processor
        
[17608.723268] Pid: 19594, comm: sync Not tainted 2.6.32-rc2 #12
[17608.729255] Call Trace:
[17608.731835]  [<ffffffff81252a6d>] ? kref_get+0x23/0x2a
[17608.737209]  [<ffffffff81044f9a>] warn_slowpath_common+0x77/0x8f
[17608.743457]  [<ffffffff81044fc1>] warn_slowpath_null+0xf/0x11
[17608.749395]  [<ffffffff81252a6d>] kref_get+0x23/0x2a
[17608.754634]  [<ffffffffa006e9be>] ceph_mdsc_sync+0xd7/0x305 [ceph]
[17608.761061]  [<ffffffff8145d8b6>] ? mutex_unlock+0x9/0xb
[17608.766618]  [<ffffffffa0078bf3>] ? ceph_osdc_sync+0xe7/0x173 [ceph]
[17608.773199]  [<ffffffffa004d906>] ceph_syncfs+0x4e/0xc8 [ceph]
[17608.779235]  [<ffffffff810f6084>] __sync_filesystem+0x5e/0x72
[17608.785195]  [<ffffffff810f6142>] sync_filesystems+0xaa/0x101
[17608.791122]  [<ffffffff810f61e0>] sys_sync+0x12/0x2e
[17608.796331]  [<ffffffff8100baeb>] system_call_fastpath+0x16/0x1b
[17608.802560] ---[ end trace 36481c4089b3d493 ]---
[17608.807461] BUG: unable to handle kernel paging request at 0000001200000635
[17608.811372] IP: [<ffffffff81252a2c>] kref_put+0x31/0x4f
[17608.811372] PGD 11c7c8067 PUD 0 
[17608.811372] Oops: 0002 [#1] PREEMPT SMP 
[17608.811372] last sysfs file: /sys/kernel/uevent_seqnum
[17608.811372] CPU 0 
[17608.811372] Modules linked in: aes_x86_64 aes_generic ceph fan ac battery ehci_hcd container uhci_hcd thermal button processor
        
[17608.811372] Pid: 19594, comm: sync Tainted: G        W  2.6.32-rc2 #12 PDSMi
[17608.811372] RIP: 0010:[<ffffffff81252a2c>]  [<ffffffff81252a2c>] kref_put+0x31/0x4f
[17608.811372] RSP: 0018:ffff8801137f5e28  EFLAGS: 00010206
[17608.811372] RAX: 0000001200000495 RBX: 0000001200000635 RCX: 0000000000000000
[17608.811372] RDX: 0000000000000000 RSI: 0000000000000040 RDI: 0000001200000635
[17608.811372] RBP: ffff8801137f5e38 R08: 0000000000000000 R09: ffff8801137f5e28
[17608.811372] R10: ffff8801137f5e38 R11: ffffffff8145c5ad R12: ffffffffa00675ae
[17608.811372] R13: ffff880119d02508 R14: ffff880119d02510 R15: 0000000000055fad
[17608.811372] FS:  00007fadcfcd96e0(0000) GS:ffff88002f000000(0000) knlGS:0000000000000000
[17608.811372] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[17608.811372] CR2: 0000001200000635 CR3: 00000001136cd000 CR4: 00000000000006f0
[17608.811372] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[17608.811372] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
        
[17608.811372] Process sync (pid: 19594, threadinfo ffff8801137f4000, task ffff88011bf70480)
[17608.811372] Stack:
[17608.811372]  ffff880103726e18 ffff880103726c00 ffff8801137f5e58 ffffffffa00733f1
[17608.811372] <0> ffff880103726e18 ffffffffa00733a2 ffff8801137f5e78 ffffffff81252a3e
[17608.811372] <0> 0000000000000000 ffff880103726c00 ffff8801137f5ef8 ffffffffa006ea19
[17608.811372] Call Trace:
[17608.811372]  [<ffffffffa00733f1>] ceph_mdsc_release_request+0x4f/0x12a [ceph]
[17608.811372]  [<ffffffffa00733a2>] ? ceph_mdsc_release_request+0x0/0x12a [ceph]
[17608.811372]  [<ffffffff81252a3e>] kref_put+0x43/0x4f
[17608.811372]  [<ffffffffa006ea19>] ceph_mdsc_sync+0x132/0x305 [ceph]
[17608.811372]  [<ffffffff8145d8b6>] ? mutex_unlock+0x9/0xb
[17608.811372]  [<ffffffffa0078bf3>] ? ceph_osdc_sync+0xe7/0x173 [ceph]
[17608.811372]  [<ffffffffa004d906>] ceph_syncfs+0x4e/0xc8 [ceph]
[17608.811372]  [<ffffffff810f6084>] __sync_filesystem+0x5e/0x72
[17608.811372]  [<ffffffff810f6142>] sync_filesystems+0xaa/0x101
[17608.811372]  [<ffffffff810f61e0>] sys_sync+0x12/0x2e
        
[17608.811372]  [<ffffffff8100baeb>] system_call_fastpath+0x16/0x1b
[17608.811372] Code: 49 89 f4 4d 85 e4 be 40 00 00 00 53 48 89 fb 74 0e 49 81 fc 2d 09 0d 81 75 11 be 41 00 00 00 48 c7 c7 62 f8 5c 81 e8 86 25 df ff <f0> ff 0b 0f 94 c0 31 d2 84 c0 74 0b 48 89 df 41 ff d4 ba 01 00 
[17608.811372] RIP  [<ffffffff81252a2c>] kref_put+0x31/0x4f
[17608.811372]  RSP <ffff8801137f5e28>
[17608.811372] CR2: 0000001200000635
[17609.074355] ---[ end trace 36481c4089b3d494 ]---


?- bonnie++ -u root -d /mnt/ceph/ -s 0 -n 1
(03:35:29 PM) Isteriat: Using uid:0, gid:0.
(03:35:29 PM) Isteriat: Create files in sequential order...done.
(03:35:29 PM) Isteriat: Stat files in sequential order...Expected 1024 files but only got 0
(03:35:29 PM) Isteriat: Cleaning up test directory after error.

- osd pg split breaks if not all osds are up...

- mds recovery flag set on inode that didn't get recovered??
- osd pg split breaks if not all osds are up...
- mislinked directory?  (cpusr.sh, mv /c/* /c/t, more cpusr, ls /c/t)


filestore performance notes
- write ordering options
  - fs only (no journal)
  - fs, journal
  - fs + journal in parallel
  - journal sync, then fs
- and the issues
  - latency
  - effect of a btrfs hang
  - unexpected error handling (EIO, ENOSPC)
  - impact on ack, sync ordering semantics.
  - how to throttle request stream to disk io rate
  - rmw vs delayed mode

- if journal is on fs, then
  - throttling isn't an issue, but
  - fs stalls are also journal stalls

- fs only
  - latency: commits are bad.
  - hang: bad.
  - errors: could be handled, aren't
  - acks: supported
  - throttle: fs does it
  - rmw: pg toggles mode
- fs, journal
  - latency: good, unless fs hangs
  - hang: bad.  latency spikes.  overall throughput drops.
  - errors: could probably be handled, isn't.
  - acks: supported
  - throttle: btrfs does it (by hanging), which leads to a (necessary) latency spike
  - rmw: pg toggles mode
- fs | journal
  - latency: good
  - hang: no latency spike.  fs throughput may drop, to the extent btrfs throughput necessarily will.
  - errors: not detected until later.  could journal addendum record.  or die (like we do now)
  - acks: could be flexible.. maybe supported, maybe not.  will need some extra locking smarts?
  - throttle: ??
  - rmw: rmw must block on prior fs writes.
- journal, fs (writeahead)
  - latency: good (commit only, no acks)
  - hang: same as |
  - errors: same as |
  - acks: never.
  - throttle: ??
  - rmw: rmw must block on prior fs writes.
  * JourningObjectStore interface needs work?



greg
- csync data import/export tool?
- uclient: readdir from cache
- mds: basic auth checks

later
- document on-wire protocol
- client reconnect after long eviction; and slow delayed reconnect
- repair
- mds security enforcement
- client, user authentication
- cas
- osd failure declarations
- rename over old files should flush data, or revert back to old contents
- clean up SimpleMessenger interface and usage a little. Can probably unify
	some/all of shutdown, wait, destroy. Possibly move destroy into put()
	and make get/put usage more consistent/stringently mandated.

rados
- snapc interface
  - mon: allocate snapid, adjust pool_t seq
  - librados: snapc manipulation, set pool handle snapc
- make rest interface superset of s3?
  - create/delete snapshots
  - list, access snapped version
- perl swig wrapper
- 'rados call foo.bar'?
- merge pgs
- autosize pg_pools?

repair
- namespace reconstruction tool
- repair pg (rebuild log)  (online or offline?  ./cosd --repair_pg 1.ef?)
- repair file ioctl?
- are we concerned about
  - scrubbing
  - reconstruction after loss of subset of cdirs
  - reconstruction after loss of md log
- data object 
  - path backpointers?
  - parent dir pointer?
- mds scrubbing

kclient
- mdsc: preallocate reply(ies?)
- mdsc: mempool for cap writeback?
- osdc: combine request, request+reply messages into single pool.
- ENOMEM
  - message pools
  - sockets?  (this can actual generates a lockdep warning :/)
- fs-portable file layout virtual xattr (see Andreas' -fsdevel thread)
- statlite
- add cap to release if we get fouled up in fill_inode et al?
- fix up ESTALE handling
- don't retry on ENOMEM on non-nofail requests in kick_requests
- make cap import/export more efficient?
- flock, fnctl locks
- ACLs
  - init security xattrs
- should we try to ref CAP_PIN on special inodes that are open?  
- fix readdir vs fragment race by keeping a separate frag pos, and ignoring dentries below it
- inotify for updates from other clients?

vfs issues
- a getattr mask would be really nice

filestore
- make min sync interval self-tuning (ala xfs, ext3?)
- get file csum?
- clonerange writeahead journal data into objects?

btrfs
- clone compressed inline extents
- ioctl to pull out data csum?

osd
- separate reads/writes into separate op queues?
- gracefully handle ENOSPC
- gracefully handle EIO?
- what to do with lost objects.. continue peering?
- segregate backlog from log ondisk?
- preserve pg logs on disk for longer period
- make scrub interruptible
- optionally separate osd interfaces (ips) for clients and osds (replication, peering, etc.)
- pg repair
- pg split should be a work queue
- optimize remove wrt recovery pushes?

uclient
- fix client_lock vs other mutex with C_SafeCond
- clean up check_caps to more closely mirror kclient logic
- readdir from cache
- fix readdir vs fragment race by keeping a separate frag pos, and ignoring dentries below it
- hadoop: clean up assert usage

mds
- special case commit of stray dir to avoid having to commit, re-commit strays?
  - once we commit one stray, we have to re-commit later to remove it, which means we commit other new ones.
- put inode dirty fields into dirty_bits_t to reduce per-inode memory footprint
- don't sync log on every clientreplay request?
- pass issued, wanted into eval(lock) when eval() already has it?  (and otherwise optimize eval paths..)
- add an up:shadow mode?
  - tail the mds log as it is written
  - periodically check head so that we trim, too
- handle slow client reconnect (i.e. after mds has gone active)
- anchor_destroy needs to xlock linklock.. which means it needs a Mutation wrapper?
  - ... when it gets a caller.. someday..
- add FILE_CAP_EXTEND capability bit
- dir fragment
  - maybe just take dftlock for now, to keep it simple.
- dir merge
- snap
  - hard link backpointers
    - anchor source dir
    - build snaprealm for any hardlinked file
    - include snaps for all (primary+remote) parents
  - how do we properly clean up inodes when doing a snap purge?
    - when they are mid-recover?  see 136470cf7ca876febf68a2b0610fa3bb77ad3532
  - what if a recovery is queued, or in progress, and the inode is then cowed?  can that happen?  
  - proper handling of cache expire messages during rejoin phase?
    -> i think cache expires are fine; the rejoin_ack handler just has to behave if rejoining items go missing

- clustered
  - on replay, but dirty scatter replicas on lists so that they get flushed?  or does rejoin handle that?
  - linkage vs cdentry replicas and remote rename....
  - rename: importing inode... also journal imported client map?

mon
- don't allow lpg_num expansion and osd addition at the same time?
- how to shrink cluster?
- how to tell osd to cleanly shut down
- paxos need to clean up old states.
  - default: simple max of (state count, min age), so that we have at least N hours of history, say?
  - osd map: trim only old maps < oldest "in" osd up_from

osdmon
- monitor needs to monitor some osds...

pgmon
- check for orphan pgs
- monitor pg states, notify on out?
- watch osd utilization; adjust overload in cluster map

crush
- allow forcefeed for more complicated rule structures.  (e.g. make force_stack a list< set<int> >)

simplemessenger
- close idle connections?

objectcacher
- read locks?
- maintain more explicit inode grouping instead of wonky hashes

cas
- chunking.  see TTTD in
   ESHGHI, K.
   A framework for analyzing and improving content-based chunking algorithms.
   Tech. Rep. HPL-2005-30(R.1), Hewlett Packard Laboratories, Palo Alto, 2005. 

radosgw
 - handle gracefully location related requests
 - logging control (?)
 - parse date/time better
 - upload using post
 - torrent
 - handle gracefully PUT/GET requestPayment



-- for nicer kclient debug output (everything but messenger, but including msg in/out)
echo 'module ceph +p' > /sys/kernel/debug/dynamic_debug/control ; echo 'file fs/ceph/messenger.c -p' > /sys/kernel/debug/dynamic_debug/control ; echo 'file ' `grep -- --- /sys/kernel/debug/dynamic_debug/control | grep ceph | awk '{print $1}' | sed 's/:/ line /'` +p  > /sys/kernel/debug/dynamic_debug/control ; echo 'file ' `grep -- === /sys/kernel/debug/dynamic_debug/control | grep ceph | awk '{print $1}' | sed 's/:/ line /'` +p  > /sys/kernel/debug/dynamic_debug/control