linux-stable.git/drivers/md/bcache, branch linux-5.6.y Linux kernel stable tree Revert "bcache: ignore pending signals when creating gc and allocator thread" 2020-03-03T03:01:32+00:00 Jens Axboe axboe@kernel.dk 2020-03-03T03:01:32+00:00 764b53b26c9897b0693c934797e898d6cd883a26 This reverts commit 0b96da639a4874311e9b5156405f69ef9fc3bef8. We can't just go flushing random signals, under the assumption that the OOM killer will just do something else. It's not safe from the OOM perspective, and it could also cause other signals to get randomly lost. Signed-off-by: Jens Axboe <axboe@kernel.dk> 
This reverts commit 0b96da639a4874311e9b5156405f69ef9fc3bef8.

We can't just go flushing random signals, under the assumption that the
OOM killer will just do something else. It's not safe from the OOM
perspective, and it could also cause other signals to get randomly lost.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache: remove macro nr_to_fifo_front() 2020-02-13T15:53:50+00:00 Coly Li colyli@suse.de 2020-02-13T14:12:07+00:00 4ec31cb6241d95879aac337cc6b50c45dd10cfcb Macro nr_to_fifo_front() is only used once in btree_flush_write(), it is unncessary indeed. This patch removes this macro and does calculation directly in place. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
Macro nr_to_fifo_front() is only used once in btree_flush_write(),
it is unncessary indeed. This patch removes this macro and does
calculation directly in place.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache: Revert "bcache: shrink btree node cache after bch_btree_check()" 2020-02-13T15:53:49+00:00 Coly Li colyli@suse.de 2020-02-13T14:12:06+00:00 309cc719a2c869b71a7388209a0a80d4284d98fd This reverts commit 1df3877ff6a4810054237c3259d900ded4468969. In my testing, sometimes even all the cached btree nodes are freed, creating gc and allocator kernel threads may still fail. Finally it turns out that kthread_run() may fail if there is pending signal for current task. And the pending signal is sent from OOM killer which is triggered by memory consuption in bch_btree_check(). Therefore explicitly shrinking bcache btree node here does not help, and after the shrinker callback is improved, as well as pending signals are ignored before creating kernel threads, now such operation is unncessary anymore. This patch reverts the commit 1df3877ff6a4 ("bcache: shrink btree node cache after bch_btree_check()") because we have better improvement now. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
This reverts commit 1df3877ff6a4810054237c3259d900ded4468969.

In my testing, sometimes even all the cached btree nodes are freed,
creating gc and allocator kernel threads may still fail. Finally it
turns out that kthread_run() may fail if there is pending signal for
current task. And the pending signal is sent from OOM killer which
is triggered by memory consuption in bch_btree_check().

Therefore explicitly shrinking bcache btree node here does not help,
and after the shrinker callback is improved, as well as pending signals
are ignored before creating kernel threads, now such operation is
unncessary anymore.

This patch reverts the commit 1df3877ff6a4 ("bcache: shrink btree node
cache after bch_btree_check()") because we have better improvement now.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache: ignore pending signals when creating gc and allocator thread 2020-02-13T15:53:49+00:00 Coly Li colyli@suse.de 2020-02-13T14:12:05+00:00 0b96da639a4874311e9b5156405f69ef9fc3bef8 When run a cache set, all the bcache btree node of this cache set will be checked by bch_btree_check(). If the bcache btree is very large, iterating all the btree nodes will occupy too much system memory and the bcache registering process might be selected and killed by system OOM killer. kthread_run() will fail if current process has pending signal, therefore the kthread creating in run_cache_set() for gc and allocator kernel threads are very probably failed for a very large bcache btree. Indeed such OOM is safe and the registering process will exit after the registration done. Therefore this patch flushes pending signals during the cache set start up, specificly in bch_cache_allocator_start() and bch_gc_thread_start(), to make sure run_cache_set() won't fail for large cahced data set. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
When run a cache set, all the bcache btree node of this cache set will
be checked by bch_btree_check(). If the bcache btree is very large,
iterating all the btree nodes will occupy too much system memory and
the bcache registering process might be selected and killed by system
OOM killer. kthread_run() will fail if current process has pending
signal, therefore the kthread creating in run_cache_set() for gc and
allocator kernel threads are very probably failed for a very large
bcache btree.

Indeed such OOM is safe and the registering process will exit after
the registration done. Therefore this patch flushes pending signals
during the cache set start up, specificly in bch_cache_allocator_start()
and bch_gc_thread_start(), to make sure run_cache_set() won't fail for
large cahced data set.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache: check return value of prio_read() 2020-02-01T14:55:39+00:00 Coly Li colyli@suse.de 2020-02-01T14:42:35+00:00 49d08d596e85f39ded48e85df362827cbab1f5ae Now if prio_read() failed during starting a cache set, we can print out error message in run_cache_set() and handle the failure properly. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
Now if prio_read() failed during starting a cache set, we can print
out error message in run_cache_set() and handle the failure properly.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache: fix incorrect data type usage in btree_flush_write() 2020-02-01T14:55:39+00:00 Coly Li colyli@suse.de 2020-02-01T14:42:34+00:00 d1c3cc34f5a78b38d2b809b289d912c3560545df Dan Carpenter points out that from commit 2aa8c529387c ("bcache: avoid unnecessary btree nodes flushing in btree_flush_write()"), there is a incorrect data type usage which leads to the following static checker warning: drivers/md/bcache/journal.c:444 btree_flush_write() warn: 'ref_nr' unsigned <= 0 drivers/md/bcache/journal.c 422 static void btree_flush_write(struct cache_set *c) 423 { 424 struct btree *b, *t, *btree_nodes[BTREE_FLUSH_NR]; 425 unsigned int i, nr, ref_nr; ^^^^^^ 426 atomic_t *fifo_front_p, *now_fifo_front_p; 427 size_t mask; 428 429 if (c->journal.btree_flushing) 430 return; 431 432 spin_lock(&c->journal.flush_write_lock); 433 if (c->journal.btree_flushing) { 434 spin_unlock(&c->journal.flush_write_lock); 435 return; 436 } 437 c->journal.btree_flushing = true; 438 spin_unlock(&c->journal.flush_write_lock); 439 440 /* get the oldest journal entry and check its refcount */ 441 spin_lock(&c->journal.lock); 442 fifo_front_p = &fifo_front(&c->journal.pin); 443 ref_nr = atomic_read(fifo_front_p); 444 if (ref_nr <= 0) { ^^^^^^^^^^^ Unsigned can't be less than zero. 445 /* 446 * do nothing if no btree node references 447 * the oldest journal entry 448 */ 449 spin_unlock(&c->journal.lock); 450 goto out; 451 } 452 spin_unlock(&c->journal.lock); As the warning information indicates, local varaible ref_nr in unsigned int type is wrong, which does not matche atomic_read() and the "<= 0" checking. This patch fixes the above error by defining local variable ref_nr as int type. Fixes: 2aa8c529387c ("bcache: avoid unnecessary btree nodes flushing in btree_flush_write()") Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
Dan Carpenter points out that from commit 2aa8c529387c ("bcache: avoid
unnecessary btree nodes flushing in btree_flush_write()"), there is a
incorrect data type usage which leads to the following static checker
warning:
	drivers/md/bcache/journal.c:444 btree_flush_write()
	warn: 'ref_nr' unsigned <= 0

drivers/md/bcache/journal.c
   422  static void btree_flush_write(struct cache_set *c)
   423  {
   424          struct btree *b, *t, *btree_nodes[BTREE_FLUSH_NR];
   425          unsigned int i, nr, ref_nr;
                                    ^^^^^^

   426          atomic_t *fifo_front_p, *now_fifo_front_p;
   427          size_t mask;
   428
   429          if (c->journal.btree_flushing)
   430                  return;
   431
   432          spin_lock(&c->journal.flush_write_lock);
   433          if (c->journal.btree_flushing) {
   434                  spin_unlock(&c->journal.flush_write_lock);
   435                  return;
   436          }
   437          c->journal.btree_flushing = true;
   438          spin_unlock(&c->journal.flush_write_lock);
   439
   440          /* get the oldest journal entry and check its refcount */
   441          spin_lock(&c->journal.lock);
   442          fifo_front_p = &fifo_front(&c->journal.pin);
   443          ref_nr = atomic_read(fifo_front_p);
   444          if (ref_nr <= 0) {
                    ^^^^^^^^^^^
Unsigned can't be less than zero.

   445                  /*
   446                   * do nothing if no btree node references
   447                   * the oldest journal entry
   448                   */
   449                  spin_unlock(&c->journal.lock);
   450                  goto out;
   451          }
   452          spin_unlock(&c->journal.lock);

As the warning information indicates, local varaible ref_nr in unsigned
int type is wrong, which does not matche atomic_read() and the "<= 0"
checking.

This patch fixes the above error by defining local variable ref_nr as
int type.

Fixes: 2aa8c529387c ("bcache: avoid unnecessary btree nodes flushing in btree_flush_write()")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache: add readahead cache policy options via sysfs interface 2020-02-01T14:55:39+00:00 Coly Li colyli@suse.de 2020-02-01T14:42:33+00:00 038ba8cc1bffc51250add4a9b9249d4331576d8f In year 2007 high performance SSD was still expensive, in order to save more space for real workload or meta data, the readahead I/Os for non-meta data was bypassed and not cached on SSD. In now days, SSD price drops a lot and people can find larger size SSD with more comfortable price. It is unncessary to alway bypass normal readahead I/Os to save SSD space for now. This patch adds options for readahead data cache policies via sysfs file /sys/block/bcache<N>/readahead_cache_policy, the options are, - "all": cache all readahead data I/Os. - "meta-only": only cache meta data, and bypass other regular I/Os. If users want to make bcache continue to only cache readahead request for metadata and bypass regular data readahead, please set "meta-only" to this sysfs file. By default, bcache will back to cache all read- ahead requests now. Cc: stable@vger.kernel.org Signed-off-by: Coly Li <colyli@suse.de> Acked-by: Eric Wheeler <bcache@linux.ewheeler.net> Cc: Michael Lyle <mlyle@lyle.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
In year 2007 high performance SSD was still expensive, in order to
save more space for real workload or meta data, the readahead I/Os
for non-meta data was bypassed and not cached on SSD.

In now days, SSD price drops a lot and people can find larger size
SSD with more comfortable price. It is unncessary to alway bypass
normal readahead I/Os to save SSD space for now.

This patch adds options for readahead data cache policies via sysfs
file /sys/block/bcache<N>/readahead_cache_policy, the options are,
- "all": cache all readahead data I/Os.
- "meta-only": only cache meta data, and bypass other regular I/Os.

If users want to make bcache continue to only cache readahead request
for metadata and bypass regular data readahead, please set "meta-only"
to this sysfs file. By default, bcache will back to cache all read-
ahead requests now.

Cc: stable@vger.kernel.org
Signed-off-by: Coly Li <colyli@suse.de>
Acked-by: Eric Wheeler <bcache@linux.ewheeler.net>
Cc: Michael Lyle <mlyle@lyle.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache: explicity type cast in bset_bkey_last() 2020-02-01T14:55:39+00:00 Coly Li colyli@suse.de 2020-02-01T14:42:32+00:00 7c02b0055f774ed9afb6e1c7724f33bf148ffdc0 In bset.h, macro bset_bkey_last() is defined as, bkey_idx((struct bkey *) (i)->d, (i)->keys) Parameter i can be variable type of data structure, the macro always works once the type of struct i has member 'd' and 'keys'. bset_bkey_last() is also used in macro csum_set() to calculate the checksum of a on-disk data structure. When csum_set() is used to calculate checksum of on-disk bcache super block, the parameter 'i' data type is struct cache_sb_disk. Inside struct cache_sb_disk (also in struct cache_sb) the member keys is __u16 type. But bkey_idx() expects unsigned int (a 32bit width), so there is problem when sending parameters via stack to call bkey_idx(). Sparse tool from Intel 0day kbuild system reports this incompatible problem. bkey_idx() is part of user space API, so the simplest fix is to cast the (i)->keys to unsigned int type in macro bset_bkey_last(). Reported-by: kbuild test robot <lkp@intel.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
In bset.h, macro bset_bkey_last() is defined as,
    bkey_idx((struct bkey *) (i)->d, (i)->keys)

Parameter i can be variable type of data structure, the macro always
works once the type of struct i has member 'd' and 'keys'.

bset_bkey_last() is also used in macro csum_set() to calculate the
checksum of a on-disk data structure. When csum_set() is used to
calculate checksum of on-disk bcache super block, the parameter 'i'
data type is struct cache_sb_disk. Inside struct cache_sb_disk (also in
struct cache_sb) the member keys is __u16 type. But bkey_idx() expects
unsigned int (a 32bit width), so there is problem when sending
parameters via stack to call bkey_idx().

Sparse tool from Intel 0day kbuild system reports this incompatible
problem. bkey_idx() is part of user space API, so the simplest fix is
to cast the (i)->keys to unsigned int type in macro bset_bkey_last().

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache: fix memory corruption in bch_cache_accounting_clear() 2020-02-01T14:55:39+00:00 Coly Li colyli@suse.de 2020-02-01T14:42:31+00:00 5bebf7486d4f4940b2a8e4009beb1dff5041853d Commit 83ff9318c44ba ("bcache: not use hard coded memset size in bch_cache_accounting_clear()") tries to make the code more easy to understand by removing the hard coded number with following change, void bch_cache_accounting_clear(...) { memset(&acc->total.cache_hits, 0, - sizeof(unsigned long) * 7); + sizeof(struct cache_stats)); } Unfortunately the change was wrong (it also tells us the original code was not easy to correctly understand). The hard coded number 7 is used because in struct cache_stats, 15 struct cache_stats { 16 struct kobject kobj; 17 18 unsigned long cache_hits; 19 unsigned long cache_misses; 20 unsigned long cache_bypass_hits; 21 unsigned long cache_bypass_misses; 22 unsigned long cache_readaheads; 23 unsigned long cache_miss_collisions; 24 unsigned long sectors_bypassed; 25 26 unsigned int rescale; 27 }; only members in LINE 18-24 want to be set to 0. It is wrong to use 'sizeof(struct cache_stats)' to replace 'sizeof(unsigned long) * 7), the memory objects behind acc->total is staled by this change. Сорокин Артем Сергеевич reports that by the following steps, kernel panic will be triggered, 1. Create new set: make-bcache -B /dev/nvme1n1 -C /dev/sda --wipe-bcache 2. Run in /sys/fs/bcache/<uuid>: echo 1 > clear_stats && cat stats_five_minute/cache_bypass_hits I can reproduce the panic and get following dmesg with KASAN enabled, [22613.172742] ================================================================== [22613.172862] BUG: KASAN: null-ptr-deref in sysfs_kf_seq_show+0x117/0x230 [22613.172864] Read of size 8 at addr 0000000000000000 by task cat/6753 [22613.172870] CPU: 1 PID: 6753 Comm: cat Not tainted 5.5.0-rc7-lp151.28.16-default+ #11 [22613.172872] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/29/2019 [22613.172873] Call Trace: [22613.172964] dump_stack+0x8b/0xbb [22613.172968] ? sysfs_kf_seq_show+0x117/0x230 [22613.172970] ? sysfs_kf_seq_show+0x117/0x230 [22613.173031] __kasan_report+0x176/0x192 [22613.173064] ? pr_cont_kernfs_name+0x40/0x60 [22613.173067] ? sysfs_kf_seq_show+0x117/0x230 [22613.173070] kasan_report+0xe/0x20 [22613.173072] sysfs_kf_seq_show+0x117/0x230 [22613.173105] seq_read+0x199/0x6d0 [22613.173110] vfs_read+0xa5/0x1a0 [22613.173113] ksys_read+0x110/0x160 [22613.173115] ? kernel_write+0xb0/0xb0 [22613.173177] do_syscall_64+0x77/0x290 [22613.173238] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [22613.173241] RIP: 0033:0x7fc2c886ac61 [22613.173244] Code: fe ff ff 48 8d 3d c7 a0 09 00 48 83 ec 08 e8 46 03 02 00 66 0f 1f 44 00 00 8b 05 ca fb 2c 00 48 63 ff 85 c0 75 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 57 f3 c3 0f 1f 44 00 00 55 53 48 89 d5 48 89 [22613.173245] RSP: 002b:00007ffebe776d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [22613.173248] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007fc2c886ac61 [22613.173249] RDX: 0000000000020000 RSI: 00007fc2c8cca000 RDI: 0000000000000003 [22613.173250] RBP: 0000000000020000 R08: ffffffffffffffff R09: 0000000000000000 [22613.173251] R10: 000000000000038c R11: 0000000000000246 R12: 00007fc2c8cca000 [22613.173253] R13: 0000000000000003 R14: 00007fc2c8cca00f R15: 0000000000020000 [22613.173255] ================================================================== [22613.173256] Disabling lock debugging due to kernel taint [22613.173350] BUG: kernel NULL pointer dereference, address: 0000000000000000 [22613.178380] #PF: supervisor read access in kernel mode [22613.180959] #PF: error_code(0x0000) - not-present page [22613.183444] PGD 0 P4D 0 [22613.184867] Oops: 0000 [#1] SMP KASAN PTI [22613.186797] CPU: 1 PID: 6753 Comm: cat Tainted: G B 5.5.0-rc7-lp151.28.16-default+ #11 [22613.191253] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/29/2019 [22613.196706] RIP: 0010:sysfs_kf_seq_show+0x117/0x230 [22613.199097] Code: ff 48 8b 0b 48 8b 44 24 08 48 01 e9 eb a6 31 f6 48 89 cf ba 00 10 00 00 48 89 4c 24 10 e8 b1 e6 e9 ff 4c 89 ff e8 19 07 ea ff <49> 8b 07 48 85 c0 48 89 44 24 08 0f 84 91 00 00 00 49 8b 6d 00 48 [22613.208016] RSP: 0018:ffff8881d4f8fd78 EFLAGS: 00010246 [22613.210448] RAX: 0000000000000000 RBX: ffff8881eb99b180 RCX: ffffffff810d9ef6 [22613.213691] RDX: 0000000000000001 RSI: 0000000000000246 RDI: 0000000000000246 [22613.216893] RBP: 0000000000001000 R08: fffffbfff072ddcd R09: fffffbfff072ddcd [22613.220075] R10: 0000000000000001 R11: fffffbfff072ddcc R12: ffff8881de5c0200 [22613.223256] R13: ffff8881ed175500 R14: ffff8881eb99b198 R15: 0000000000000000 [22613.226290] FS: 00007fc2c8d3d500(0000) GS:ffff8881f2a80000(0000) knlGS:0000000000000000 [22613.229637] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [22613.231993] CR2: 0000000000000000 CR3: 00000001ec89a004 CR4: 00000000003606e0 [22613.234909] Call Trace: [22613.235931] seq_read+0x199/0x6d0 [22613.237259] vfs_read+0xa5/0x1a0 [22613.239229] ksys_read+0x110/0x160 [22613.240590] ? kernel_write+0xb0/0xb0 [22613.242040] do_syscall_64+0x77/0x290 [22613.243625] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [22613.245450] RIP: 0033:0x7fc2c886ac61 [22613.246706] Code: fe ff ff 48 8d 3d c7 a0 09 00 48 83 ec 08 e8 46 03 02 00 66 0f 1f 44 00 00 8b 05 ca fb 2c 00 48 63 ff 85 c0 75 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 57 f3 c3 0f 1f 44 00 00 55 53 48 89 d5 48 89 [22613.253296] RSP: 002b:00007ffebe776d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [22613.255835] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007fc2c886ac61 [22613.258472] RDX: 0000000000020000 RSI: 00007fc2c8cca000 RDI: 0000000000000003 [22613.260807] RBP: 0000000000020000 R08: ffffffffffffffff R09: 0000000000000000 [22613.263188] R10: 000000000000038c R11: 0000000000000246 R12: 00007fc2c8cca000 [22613.265598] R13: 0000000000000003 R14: 00007fc2c8cca00f R15: 0000000000020000 [22613.268729] Modules linked in: scsi_transport_iscsi af_packet iscsi_ibft iscsi_boot_sysfs vmw_vsock_vmci_transport vsock fuse bnep kvm_intel kvm irqbypass crc32_pclmul crc32c_intel ghash_clmulni_intel snd_ens1371 snd_ac97_codec ac97_bus bcache snd_pcm btusb btrtl btbcm btintel crc64 aesni_intel glue_helper crypto_simd vmw_balloon cryptd bluetooth snd_timer snd_rawmidi snd joydev pcspkr e1000 rfkill vmw_vmci soundcore ecdh_generic ecc gameport i2c_piix4 mptctl ac button hid_generic usbhid sr_mod cdrom ata_generic ehci_pci vmwgfx uhci_hcd drm_kms_helper syscopyarea serio_raw sysfillrect sysimgblt fb_sys_fops ttm ehci_hcd mptspi scsi_transport_spi mptscsih ata_piix mptbase ahci usbcore libahci drm sg dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc scsi_dh_alua [22613.292429] CR2: 0000000000000000 [22613.293563] ---[ end trace a074b26a8508f378 ]--- [22613.295138] RIP: 0010:sysfs_kf_seq_show+0x117/0x230 [22613.296769] Code: ff 48 8b 0b 48 8b 44 24 08 48 01 e9 eb a6 31 f6 48 89 cf ba 00 10 00 00 48 89 4c 24 10 e8 b1 e6 e9 ff 4c 89 ff e8 19 07 ea ff <49> 8b 07 48 85 c0 48 89 44 24 08 0f 84 91 00 00 00 49 8b 6d 00 48 [22613.303553] RSP: 0018:ffff8881d4f8fd78 EFLAGS: 00010246 [22613.305280] RAX: 0000000000000000 RBX: ffff8881eb99b180 RCX: ffffffff810d9ef6 [22613.307924] RDX: 0000000000000001 RSI: 0000000000000246 RDI: 0000000000000246 [22613.310272] RBP: 0000000000001000 R08: fffffbfff072ddcd R09: fffffbfff072ddcd [22613.312685] R10: 0000000000000001 R11: fffffbfff072ddcc R12: ffff8881de5c0200 [22613.315076] R13: ffff8881ed175500 R14: ffff8881eb99b198 R15: 0000000000000000 [22613.318116] FS: 00007fc2c8d3d500(0000) GS:ffff8881f2a80000(0000) knlGS:0000000000000000 [22613.320743] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [22613.322628] CR2: 0000000000000000 CR3: 00000001ec89a004 CR4: 00000000003606e0 Here this patch fixes the following problem by explicity set all the 7 members to 0 in bch_cache_accounting_clear(). Reported-by: Сорокин Артем Сергеевич <a.sorokin@bank-hlynov.ru> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
Commit 83ff9318c44ba ("bcache: not use hard coded memset size in
bch_cache_accounting_clear()") tries to make the code more easy to
understand by removing the hard coded number with following change,
	void bch_cache_accounting_clear(...)
	{
		memset(&acc->total.cache_hits,
			0,
	-		sizeof(unsigned long) * 7);
	+		sizeof(struct cache_stats));
	}

Unfortunately the change was wrong (it also tells us the original code
was not easy to correctly understand). The hard coded number 7 is used
because in struct cache_stats,
 15 struct cache_stats {
 16         struct kobject          kobj;
 17
 18         unsigned long cache_hits;
 19         unsigned long cache_misses;
 20         unsigned long cache_bypass_hits;
 21         unsigned long cache_bypass_misses;
 22         unsigned long cache_readaheads;
 23         unsigned long cache_miss_collisions;
 24         unsigned long sectors_bypassed;
 25
 26         unsigned int            rescale;
 27 };
only members in LINE 18-24 want to be set to 0. It is wrong to use
'sizeof(struct cache_stats)' to replace 'sizeof(unsigned long) * 7), the
memory objects behind acc->total is staled by this change.

Сорокин Артем Сергеевич reports that by the following steps, kernel
panic will be triggered,
1. Create new set: make-bcache -B /dev/nvme1n1 -C /dev/sda --wipe-bcache
2. Run in /sys/fs/bcache/<uuid>:
   echo 1 > clear_stats && cat stats_five_minute/cache_bypass_hits

I can reproduce the panic and get following dmesg with KASAN enabled,
[22613.172742] ==================================================================
[22613.172862] BUG: KASAN: null-ptr-deref in sysfs_kf_seq_show+0x117/0x230
[22613.172864] Read of size 8 at addr 0000000000000000 by task cat/6753

[22613.172870] CPU: 1 PID: 6753 Comm: cat Not tainted 5.5.0-rc7-lp151.28.16-default+ #11
[22613.172872] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/29/2019
[22613.172873] Call Trace:
[22613.172964]  dump_stack+0x8b/0xbb
[22613.172968]  ? sysfs_kf_seq_show+0x117/0x230
[22613.172970]  ? sysfs_kf_seq_show+0x117/0x230
[22613.173031]  __kasan_report+0x176/0x192
[22613.173064]  ? pr_cont_kernfs_name+0x40/0x60
[22613.173067]  ? sysfs_kf_seq_show+0x117/0x230
[22613.173070]  kasan_report+0xe/0x20
[22613.173072]  sysfs_kf_seq_show+0x117/0x230
[22613.173105]  seq_read+0x199/0x6d0
[22613.173110]  vfs_read+0xa5/0x1a0
[22613.173113]  ksys_read+0x110/0x160
[22613.173115]  ? kernel_write+0xb0/0xb0
[22613.173177]  do_syscall_64+0x77/0x290
[22613.173238]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[22613.173241] RIP: 0033:0x7fc2c886ac61
[22613.173244] Code: fe ff ff 48 8d 3d c7 a0 09 00 48 83 ec 08 e8 46 03 02 00 66 0f 1f 44 00 00 8b 05 ca fb 2c 00 48 63 ff 85 c0 75 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 57 f3 c3 0f 1f 44 00 00 55 53 48 89 d5 48 89
[22613.173245] RSP: 002b:00007ffebe776d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[22613.173248] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007fc2c886ac61
[22613.173249] RDX: 0000000000020000 RSI: 00007fc2c8cca000 RDI: 0000000000000003
[22613.173250] RBP: 0000000000020000 R08: ffffffffffffffff R09: 0000000000000000
[22613.173251] R10: 000000000000038c R11: 0000000000000246 R12: 00007fc2c8cca000
[22613.173253] R13: 0000000000000003 R14: 00007fc2c8cca00f R15: 0000000000020000
[22613.173255] ==================================================================
[22613.173256] Disabling lock debugging due to kernel taint
[22613.173350] BUG: kernel NULL pointer dereference, address: 0000000000000000
[22613.178380] #PF: supervisor read access in kernel mode
[22613.180959] #PF: error_code(0x0000) - not-present page
[22613.183444] PGD 0 P4D 0
[22613.184867] Oops: 0000 [#1] SMP KASAN PTI
[22613.186797] CPU: 1 PID: 6753 Comm: cat Tainted: G    B             5.5.0-rc7-lp151.28.16-default+ #11
[22613.191253] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/29/2019
[22613.196706] RIP: 0010:sysfs_kf_seq_show+0x117/0x230
[22613.199097] Code: ff 48 8b 0b 48 8b 44 24 08 48 01 e9 eb a6 31 f6 48 89 cf ba 00 10 00 00 48 89 4c 24 10 e8 b1 e6 e9 ff 4c 89 ff e8 19 07 ea ff <49> 8b 07 48 85 c0 48 89 44 24 08 0f 84 91 00 00 00 49 8b 6d 00 48
[22613.208016] RSP: 0018:ffff8881d4f8fd78 EFLAGS: 00010246
[22613.210448] RAX: 0000000000000000 RBX: ffff8881eb99b180 RCX: ffffffff810d9ef6
[22613.213691] RDX: 0000000000000001 RSI: 0000000000000246 RDI: 0000000000000246
[22613.216893] RBP: 0000000000001000 R08: fffffbfff072ddcd R09: fffffbfff072ddcd
[22613.220075] R10: 0000000000000001 R11: fffffbfff072ddcc R12: ffff8881de5c0200
[22613.223256] R13: ffff8881ed175500 R14: ffff8881eb99b198 R15: 0000000000000000
[22613.226290] FS:  00007fc2c8d3d500(0000) GS:ffff8881f2a80000(0000) knlGS:0000000000000000
[22613.229637] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[22613.231993] CR2: 0000000000000000 CR3: 00000001ec89a004 CR4: 00000000003606e0
[22613.234909] Call Trace:
[22613.235931]  seq_read+0x199/0x6d0
[22613.237259]  vfs_read+0xa5/0x1a0
[22613.239229]  ksys_read+0x110/0x160
[22613.240590]  ? kernel_write+0xb0/0xb0
[22613.242040]  do_syscall_64+0x77/0x290
[22613.243625]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[22613.245450] RIP: 0033:0x7fc2c886ac61
[22613.246706] Code: fe ff ff 48 8d 3d c7 a0 09 00 48 83 ec 08 e8 46 03 02 00 66 0f 1f 44 00 00 8b 05 ca fb 2c 00 48 63 ff 85 c0 75 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 57 f3 c3 0f 1f 44 00 00 55 53 48 89 d5 48 89
[22613.253296] RSP: 002b:00007ffebe776d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[22613.255835] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007fc2c886ac61
[22613.258472] RDX: 0000000000020000 RSI: 00007fc2c8cca000 RDI: 0000000000000003
[22613.260807] RBP: 0000000000020000 R08: ffffffffffffffff R09: 0000000000000000
[22613.263188] R10: 000000000000038c R11: 0000000000000246 R12: 00007fc2c8cca000
[22613.265598] R13: 0000000000000003 R14: 00007fc2c8cca00f R15: 0000000000020000
[22613.268729] Modules linked in: scsi_transport_iscsi af_packet iscsi_ibft iscsi_boot_sysfs vmw_vsock_vmci_transport vsock fuse bnep kvm_intel kvm irqbypass crc32_pclmul crc32c_intel ghash_clmulni_intel snd_ens1371 snd_ac97_codec ac97_bus bcache snd_pcm btusb btrtl btbcm btintel crc64 aesni_intel glue_helper crypto_simd vmw_balloon cryptd bluetooth snd_timer snd_rawmidi snd joydev pcspkr e1000 rfkill vmw_vmci soundcore ecdh_generic ecc gameport i2c_piix4 mptctl ac button hid_generic usbhid sr_mod cdrom ata_generic ehci_pci vmwgfx uhci_hcd drm_kms_helper syscopyarea serio_raw sysfillrect sysimgblt fb_sys_fops ttm ehci_hcd mptspi scsi_transport_spi mptscsih ata_piix mptbase ahci usbcore libahci drm sg dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc scsi_dh_alua
[22613.292429] CR2: 0000000000000000
[22613.293563] ---[ end trace a074b26a8508f378 ]---
[22613.295138] RIP: 0010:sysfs_kf_seq_show+0x117/0x230
[22613.296769] Code: ff 48 8b 0b 48 8b 44 24 08 48 01 e9 eb a6 31 f6 48 89 cf ba 00 10 00 00 48 89 4c 24 10 e8 b1 e6 e9 ff 4c 89 ff e8 19 07 ea ff <49> 8b 07 48 85 c0 48 89 44 24 08 0f 84 91 00 00 00 49 8b 6d 00 48
[22613.303553] RSP: 0018:ffff8881d4f8fd78 EFLAGS: 00010246
[22613.305280] RAX: 0000000000000000 RBX: ffff8881eb99b180 RCX: ffffffff810d9ef6
[22613.307924] RDX: 0000000000000001 RSI: 0000000000000246 RDI: 0000000000000246
[22613.310272] RBP: 0000000000001000 R08: fffffbfff072ddcd R09: fffffbfff072ddcd
[22613.312685] R10: 0000000000000001 R11: fffffbfff072ddcc R12: ffff8881de5c0200
[22613.315076] R13: ffff8881ed175500 R14: ffff8881eb99b198 R15: 0000000000000000
[22613.318116] FS:  00007fc2c8d3d500(0000) GS:ffff8881f2a80000(0000) knlGS:0000000000000000
[22613.320743] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[22613.322628] CR2: 0000000000000000 CR3: 00000001ec89a004 CR4: 00000000003606e0

Here this patch fixes the following problem by explicity set all the 7
members to 0 in bch_cache_accounting_clear().

Reported-by: Сорокин Артем Сергеевич <a.sorokin@bank-hlynov.ru>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache: reap from tail of c->btree_cache in bch_mca_scan() 2020-01-23T18:40:02+00:00 Coly Li colyli@suse.de 2020-01-23T17:01:42+00:00 e3de04469a49ee09c89e80bf821508df458ccee6 When shrink btree node cache from c->btree_cache in bch_mca_scan(), no matter the selected node is reaped or not, it will be rotated from the head to the tail of c->btree_cache list. But in bcache journal code, when flushing the btree nodes with oldest journal entry, btree nodes are iterated and slected from the tail of c->btree_cache list in btree_flush_write(). The list_rotate_left() in bch_mca_scan() will make btree_flush_write() iterate more nodes in c->btree_list in reverse order. This patch just reaps the selected btree node cache, and not move it from the head to the tail of c->btree_cache list. Then bch_mca_scan() will not mess up c->btree_cache list to btree_flush_write(). Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
When shrink btree node cache from c->btree_cache in bch_mca_scan(),
no matter the selected node is reaped or not, it will be rotated from
the head to the tail of c->btree_cache list. But in bcache journal
code, when flushing the btree nodes with oldest journal entry, btree
nodes are iterated and slected from the tail of c->btree_cache list in
btree_flush_write(). The list_rotate_left() in bch_mca_scan() will
make btree_flush_write() iterate more nodes in c->btree_list in reverse
order.

This patch just reaps the selected btree node cache, and not move it
from the head to the tail of c->btree_cache list. Then bch_mca_scan()
will not mess up c->btree_cache list to btree_flush_write().

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>