Re: [RFC v2 3/4] locks: Split insert/delete block functions into flock/posix parts

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On 03/03/2015 01:55 AM, Jeff Layton wrote:
> On Mon,  2 Mar 2015 15:25:12 +0100
> Daniel Wagner <daniel.wagner@xxxxxxxxxxxx> wrote:
> 
>> The locks_insert/delete_block() functions are used for flock, posix
>> and leases types. blocked_lock_lock is used to serialize all access to
>> fl_link, fl_block, fl_next and blocked_hash. Here, we prepare the
>> stage for using blocked_lock_lock to protect blocked_hash.
>>
>> Signed-off-by: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
>> Cc: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
>> Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
>> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
>> ---
>>  fs/locks.c | 48 ++++++++++++++++++++++++++++++++++++++++--------
>>  1 file changed, 40 insertions(+), 8 deletions(-)
>>
>> diff --git a/fs/locks.c b/fs/locks.c
>> index 4498da0..02821dd 100644
>> --- a/fs/locks.c
>> +++ b/fs/locks.c
>> @@ -611,11 +611,20 @@ static void locks_delete_global_blocked(struct file_lock *waiter)
>>   */
>>  static void __locks_delete_block(struct file_lock *waiter)
>>  {
>> -	locks_delete_global_blocked(waiter);
>>  	list_del_init(&waiter->fl_block);
>>  	waiter->fl_next = NULL;
>>  }
>>  
>> +/* Posix block variant of __locks_delete_block.
>> + *
>> + * Must be called with blocked_lock_lock held.
>> + */
>> +static void __locks_delete_posix_block(struct file_lock *waiter)
>> +{
>> +	locks_delete_global_blocked(waiter);
>> +	__locks_delete_block(waiter);
>> +}
>> +
>>  static void locks_delete_block(struct file_lock *waiter)
>>  {
>>  	spin_lock(&blocked_lock_lock);
>> @@ -623,6 +632,13 @@ static void locks_delete_block(struct file_lock *waiter)
>>  	spin_unlock(&blocked_lock_lock);
>>  }
>>  
>> +static void locks_delete_posix_block(struct file_lock *waiter)
>> +{
>> +	spin_lock(&blocked_lock_lock);
>> +	__locks_delete_posix_block(waiter);
>> +	spin_unlock(&blocked_lock_lock);
>> +}
>> +
>>  /* Insert waiter into blocker's block list.
>>   * We use a circular list so that processes can be easily woken up in
>>   * the order they blocked. The documentation doesn't require this but
>> @@ -639,7 +655,17 @@ static void __locks_insert_block(struct file_lock *blocker,
>>  	BUG_ON(!list_empty(&waiter->fl_block));
>>  	waiter->fl_next = blocker;
>>  	list_add_tail(&waiter->fl_block, &blocker->fl_block);
>> -	if (IS_POSIX(blocker) && !IS_OFDLCK(blocker))
>> +}
>> +
>> +/* Posix block variant of __locks_insert_block.
>> + *
>> + * Must be called with flc_lock and blocked_lock_lock held.
>> + */
>> +static void __locks_insert_posix_block(struct file_lock *blocker,
>> +					struct file_lock *waiter)
>> +{
>> +	__locks_insert_block(blocker, waiter);
>> +	if (!IS_OFDLCK(blocker))
>>  		locks_insert_global_blocked(waiter);
>>  }
>>
> 
> In many ways OFD locks act more like flock locks than POSIX ones. In
> particular, there is no deadlock detection there, so once your
> conversion is done to more widely use the percpu locks, then you should
> be able to avoid taking the blocked_lock_lock for OFD locks as well.
> The 4th patch in this series doesn't currently do that.
> 
> You may want to revisit this patch such that the IS_OFDLCK checks are
> done earlier, so that you can avoid taking the blocked_lock_lock if
> IS_POSIX and !IS_OFDLCK.

Thanks for the explanation. I was not entirely sure what to do here
and forgot to ask.

I have fixed that stuff and now I am testing it. Though it seems
that there is a memory leak which can be triggered with 

	while true; rm -rf /tmp/a; ./lease02 /tmp/a; done

and this happens also without any of my patches. Still trying to
figure out what's happening. Hopefully I just see a ghost.

slabtop tells me that ftrace_event_field is constantly growing:

 Active / Total Objects (% used)    : 968819303 / 968828665 (100.0%)
 Active / Total Slabs (% used)      : 11404623 / 11404623 (100.0%)
 Active / Total Caches (% used)     : 72 / 99 (72.7%)
 Active / Total Size (% used)       : 45616199.68K / 45619608.73K (100.0%)
 Minimum / Average / Maximum Object : 0.01K / 0.05K / 16.00K

  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME                   
967510630 967510630   2%    0.05K 11382478       85  45529912K ftrace_event_field
154368 154368 100%    0.03K   1206      128      4824K kmalloc-32
121856 121856 100%    0.01K    238      512       952K kmalloc-8
121227 121095  99%    0.08K   2377       51      9508K Acpi-State

This is on proper hardware. On a kvm guest, fasync_cache grows fast and finally the
guest runs out of memory. systemd tries hard to restart everything and fails constantly:

[  187.021758] systemd invoked oom-killer: gfp_mask=0x200da, order=0, oom_score_adj=0
[  187.022337] systemd cpuset=/ mems_allowed=0
[  187.022662] CPU: 3 PID: 1 Comm: systemd Not tainted 4.0.0-rc1+ #380
[  187.023117] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140709_153950- 04/01/2014
[  187.023801]  ffff88007c918000 ffff88007c9179c8 ffffffff81b4f9be ffffffff8116a9cc
[  187.024373]  0000000000000000 ffff88007c917a88 ffffffff8116a9d1 000000007c917a58
[  187.024940]  ffffffff8224bc98 ffff88007c917a28 0000000000000092 ffffffff81c1b780
[  187.025515] Call Trace:
[  187.025698]  [<ffffffff81b4f9be>] dump_stack+0x4c/0x65
[  187.026083]  [<ffffffff8116a9cc>] ? dump_header.isra.13+0x7c/0x450
[  187.026525]  [<ffffffff8116a9d1>] dump_header.isra.13+0x81/0x450
[  187.026958]  [<ffffffff810a45c6>] ? trace_hardirqs_on_caller+0x16/0x240
[  187.027437]  [<ffffffff810a47fd>] ? trace_hardirqs_on+0xd/0x10
[  187.027859]  [<ffffffff814fe5c4>] ? ___ratelimit+0x84/0x110
[  187.028264]  [<ffffffff8116b378>] oom_kill_process+0x1e8/0x4c0
[  187.028683]  [<ffffffff8105fda5>] ? has_ns_capability_noaudit+0x5/0x170
[  187.029167]  [<ffffffff8116baf4>] __out_of_memory+0x4a4/0x510
[  187.029579]  [<ffffffff8116bd2b>] out_of_memory+0x5b/0x80
[  187.029970]  [<ffffffff81170f2e>] __alloc_pages_nodemask+0xa0e/0xb60
[  187.030434]  [<ffffffff811ad863>] read_swap_cache_async+0xe3/0x180
[  187.030881]  [<ffffffff811ad9ed>] swapin_readahead+0xed/0x190
[  187.031300]  [<ffffffff8119bcae>] handle_mm_fault+0xbbe/0x1180
[  187.031719]  [<ffffffff81046bed>] __do_page_fault+0x1ed/0x4c0
[  187.032138]  [<ffffffff81046ecc>] do_page_fault+0xc/0x10
[  187.032520]  [<ffffffff81b5ddc2>] page_fault+0x22/0x30
[  187.032889] Mem-Info:
[  187.033066] DMA per-cpu:
[  187.033254] CPU    0: hi:    0, btch:   1 usd:   0
[  187.033596] CPU    1: hi:    0, btch:   1 usd:   0
[  187.033941] CPU    2: hi:    0, btch:   1 usd:   0
[  187.034292] CPU    3: hi:    0, btch:   1 usd:   0
[  187.034637] DMA32 per-cpu:
[  187.034837] CPU    0: hi:  186, btch:  31 usd:  51
[  187.035185] CPU    1: hi:  186, btch:  31 usd:   0
[  187.035529] CPU    2: hi:  186, btch:  31 usd:   0
[  187.035873] CPU    3: hi:  186, btch:  31 usd:  32
[  187.036221] active_anon:5 inactive_anon:0 isolated_anon:0
[  187.036221]  active_file:238 inactive_file:194 isolated_file:0
[  187.036221]  unevictable:0 dirty:0 writeback:8 unstable:0
[  187.036221]  free:3361 slab_reclaimable:4651 slab_unreclaimable:493909
[  187.036221]  mapped:347 shmem:0 pagetables:400 bounce:0
[  187.036221]  free_cma:0
[  187.038385] DMA free:7848kB min:44kB low:52kB high:64kB active_anon:4kB inactive_anon:12kB active_file:0kB inactive_file:4kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15992kB managed:15908kB mlocked:0kB dirty:0kB writeback:8kB mapped:4kB shmem:0kB slab_reclaimable:12kB slab_unreclaimable:7880kB kernel_stack:32kB pagetables:36kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:132 all_unreclaimable? yes
[  187.041138] lowmem_reserve[]: 0 1952 1952 1952
[  187.041510] DMA32 free:5596kB min:5628kB low:7032kB high:8440kB active_anon:16kB inactive_anon:0kB active_file:952kB inactive_file:772kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:2080640kB managed:2004912kB mlocked:0kB dirty:0kB writeback:24kB mapped:1384kB shmem:0kB slab_reclaimable:18592kB slab_unreclaimable:1967756kB kernel_stack:1968kB pagetables:1564kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:12716 all_unreclaimable? yes
[  187.044442] lowmem_reserve[]: 0 0 0 0
[  187.044756] DMA: 4*4kB (UEM) 2*8kB (UM) 5*16kB (UEM) 2*32kB (UE) 2*64kB (EM) 3*128kB (UEM) 2*256kB (EM) 3*512kB (UEM) 3*1024kB (UEM) 1*2048kB (R) 0*4096kB = 7856kB
[  187.046022] DMA32: 190*4kB (UER) 6*8kB (R) 1*16kB (R) 1*32kB (R) 0*64kB 0*128kB 1*256kB (R) 1*512kB (R) 0*1024kB 0*2048kB 1*4096kB (R) = 5720kB
[  187.047128] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
[  187.047724] 554 total pagecache pages
[  187.047991] 60 pages in swap cache
[  187.048259] Swap cache stats: add 102769, delete 102709, find 75688/136761
[  187.048748] Free swap  = 1041456kB
[  187.048995] Total swap = 1048572kB
[  187.049250] 524158 pages RAM
[  187.049463] 0 pages HighMem/MovableOnly
[  187.049739] 18953 pages reserved
[  187.049974] [ pid ]   uid  tgid total_vm      rss nr_ptes nr_pmds swapents oom_score_adj name
[  187.050587] [ 1293]     0  1293    10283        1      23       2      131         -1000 systemd-udevd
[  187.051253] [ 1660]     0  1660    12793       57      24       2      134         -1000 auditd
[  187.051872] [ 1681]    81  1681     6637        1      18       2      124          -900 dbus-daemon
[  187.052529] [ 1725]     0  1725    20707        0      42       3      216         -1000 sshd
[  187.053146] [ 2344]     0  2344     3257        0      11       2       49             0 systemd-cgroups
[  187.053820] [ 2345]     0  2345     3257        0      11       2       55             0 systemd-cgroups
[  187.054497] [ 2350]     0  2350     3257        0      11       2       35             0 systemd-cgroups
[  187.055175] [ 2352]     0  2352     3257        0      12       2       37             0 systemd-cgroups
[  187.055846] [ 2354]     0  2354     3257        0      11       2       43             0 systemd-cgroups
[  187.056530] [ 2355]     0  2355     3257        0      11       2       40             0 systemd-cgroups
[  187.057212] [ 2356]     0  2356     3257        0      11       2       44             0 systemd-cgroups
[  187.057886] [ 2362]     0  2362     3257        0      11       3       33             0 systemd-cgroups
[  187.058564] [ 2371]     0  2371     3257        0      11       2       33             0 systemd-cgroups
[  187.059244] [ 2372]     0  2372     3257        0      10       2       44             0 systemd-cgroups
[  187.059917] [ 2373]     0  2373     3257        0      11       2       39             0 systemd-cgroups
[  187.060600] [ 2376]     0  2376     3257        0      11       2       34             0 systemd-cgroups
[  187.061280] [ 2377]     0  2377     3257        0      10       2       43             0 systemd-cgroups
[  187.061942] [ 2378]     0  2378     3257        0      12       3       34             0 systemd-cgroups
[  187.062598] [ 2379]     0  2379    27502        0      10       3       33             0 agetty
[  187.063200] [ 2385]     0  2385     3257        0      12       2       44             0 systemd-cgroups
[  187.063859] [ 2390]     0  2390     3257        0      11       2       43             0 systemd-cgroups
[  187.064520] [ 2394]     0  2394     3257        0      11       2       41             0 systemd-cgroups
[  187.065182] [ 2397]     0  2397     3257        0      11       2       43             0 systemd-cgroups
[  187.065833] [ 2402]     0  2402     3257        0      11       2       42             0 systemd-cgroups
[  187.066490] [ 2403]     0  2403     3257        0      11       2       44             0 systemd-cgroups
[  187.067148] [ 2404]     0  2404    27502        0      13       3       30             0 agetty
[  187.067743] [ 2410]     0  2410     3257        0      11       2       43             0 systemd-cgroups
[  187.068407] [ 2413]     0  2413     3257        0      11       2       36             0 systemd-cgroups
[  187.069072] [ 2416]     0  2416     3257        0      11       2       49             0 systemd-cgroups
[  187.069720] [ 2417]     0  2417    11861      173      26       2      334             0 (journald)
[  187.070368] Out of memory: Kill process 2417 ((journald)) score 0 or sacrifice child
[  187.070943] Killed process 2417 ((journald)) total-vm:47444kB, anon-rss:0kB, file-rss:692kB
[  187.513857] systemd[1]: Unit systemd-logind.service entered failed state.
[  188.262477] systemd[1]: Unit systemd-journald.service entered failed state.
[  188.315222] systemd[1]: systemd-logind.service holdoff time over, scheduling restart.
[  188.334194] systemd[1]: Stopping Login Service...
[  188.341556] systemd[1]: Starting Login Service...
[  188.408787] systemd[1]: systemd-journald.service holdoff time over, scheduling restart.
[  189.284506] systemd[1]: Stopping Journal Service...
[  189.330806] systemd[1]: Starting Journal Service...
[  189.384800] systemd[1]: Started Journal Service.


cheers,
daniel

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