user/sven/linux.git/drivers/md, branch v4.10.3

md linear: fix a race between linear_add() and linear_congested()

2017-03-12T05:44:20Z

commit 03a9e24ef2aaa5f1f9837356aed79c860521407a upstream. Recently I receive a bug report that on Linux v3.0 based kerenl, hot add disk to a md linear device causes kernel crash at linear_congested(). From the crash image analysis, I find in linear_congested(), mddev->raid_disks contains value N, but conf->disks[] only has N-1 pointers available. Then a NULL pointer deference crashes the kernel. There is a race between linear_add() and linear_congested(), RCU stuffs used in these two functions cannot avoid the race. Since Linuv v4.0 RCU code is replaced by introducing mddev_suspend(). After checking the upstream code, it seems linear_congested() is not called in generic_make_request() code patch, so mddev_suspend() cannot provent it from being called. The possible race still exists. Here I explain how the race still exists in current code. For a machine has many CPUs, on one CPU, linear_add() is called to add a hard disk to a md linear device; at the same time on other CPU, linear_congested() is called to detect whether this md linear device is congested before issuing an I/O request onto it. Now I use a possible code execution time sequence to demo how the possible race happens, seq linear_add() linear_congested() 0 conf=mddev->private 1 oldconf=mddev->private 2 mddev->raid_disks++ 3 for (i=0; iraid_disks;i++) 4 bdev_get_queue(conf->disks[i].rdev->bdev) 5 mddev->private=newconf In linear_add() mddev->raid_disks is increased in time seq 2, and on another CPU in linear_congested() the for-loop iterates conf->disks[i] by the increased mddev->raid_disks in time seq 3,4. But conf with one more element (which is a pointer to struct dev_info type) to conf->disks[] is not updated yet, accessing its structure member in time seq 4 will cause a NULL pointer deference fault. To fix this race, there are 2 parts of modification in the patch, 1) Add 'int raid_disks' in struct linear_conf, as a copy of mddev->raid_disks. It is initialized in linear_conf(), always being consistent with pointers number of 'struct dev_info disks[]'. When iterating conf->disks[] in linear_congested(), use conf->raid_disks to replace mddev->raid_disks in the for-loop, then NULL pointer deference will not happen again. 2) RCU stuffs are back again, and use kfree_rcu() in linear_add() to free oldconf memory. Because oldconf may be referenced as mddev->private in linear_congested(), kfree_rcu() makes sure that its memory will not be released until no one uses it any more. Also some code comments are added in this patch, to make this modification to be easier understandable. This patch can be applied for kernels since v4.0 after commit: 3be260cc18f8 ("md/linear: remove rcu protections in favour of suspend/resume"). But this bug is reported on Linux v3.0 based kernel, for people who maintain kernels before Linux v4.0, they need to do some back back port to this patch. Changelog: - V3: add 'int raid_disks' in struct linear_conf, and use kfree_rcu() to replace rcu_call() in linear_add(). - v2: add RCU stuffs by suggestion from Shaohua and Neil. - v1: initial effort. Signed-off-by: Coly Li Cc: Shaohua Li Cc: Neil Brown Signed-off-by: Shaohua Li Signed-off-by: Greg Kroah-Hartman

dm raid: fix data corruption on reshape request

2017-03-12T05:44:11Z

commit d36a19541fe8f392778ac137d60f9be8dfdd8f9d upstream. The lvm2 sequence to manage dm-raid constructor flags that trigger a rebuild or a reshape is defined as: 1) load table with flags (e.g. rebuild/delta_disks/data_offset) 2) clear out the flags in lvm2 metadata 3) store the lvm2 metadata, reload the table to reset the flags previously established during the initial load (1) -- in order to prevent repeatedly requesting a rebuild or a reshape on activation Currently, loading an inactive table with rebuild/reshape flags specified will cause dm-raid to rebuild/reshape on resume and thus start updating the raid metadata (about the progress). When the second table reload, to reset the flags, occurs the constructor accesses the volatile progress state kept in the raid superblocks. Because the active mapping is still processing the rebuild/reshape, that position will be stale by the time the device is resumed. In the reshape case, this causes data corruption by processing already reshaped stripes again. In the rebuild case, it does _not_ cause data corruption but instead involves superfluous rebuilds. Fix by keeping the raid set frozen during the first resume and then allow the rebuild/reshape during the second resume. Fixes: 9dbd1aa3a ("dm raid: add reshaping support to the target") Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm round robin: revert "use percpu 'repeat_count' and 'current_path'"

2017-03-12T05:44:11Z

commit 37a098e9d10db6e2efc05fe61e3a6ff2e9802c53 upstream. The sloppy nature of lockless access to percpu pointers (s->current_path) in rr_select_path(), from multiple threads, is causing some paths to used more than others -- which results in less IO performance being observed. Revert these upstream commits to restore truly symmetric round-robin IO submission in DM multipath: b0b477c dm round robin: use percpu 'repeat_count' and 'current_path' 802934b dm round robin: do not use this_cpu_ptr() without having preemption disabled There is no benefit to all this complexity if repeat_count = 1 (which is the recommended default). Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm stats: fix a leaked s->histogram_boundaries array

2017-03-12T05:44:11Z

commit 6085831883c25860264721df15f05bbded45e2a2 upstream. Fixes: dfcfac3e4cd9 ("dm stats: collect and report histogram of IO latencies") Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm cache: fix corruption seen when using cache > 2TB

2017-03-12T05:44:11Z

commit ca763d0a53b264a650342cee206512bc92ac7050 upstream. A rounding bug due to compiler generated temporary being 32bit was found in remap_to_cache(). A localized cast in remap_to_cache() fixes the corruption but this preferred fix (changing from uint32_t to sector_t) eliminates potential for future rounding errors elsewhere. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm crypt: replace RCU read-side section with rwsem

2017-02-03T15:26:14Z

The lockdep splat below hints at a bug in RCU usage in dm-crypt that was introduced with commit c538f6ec9f56 ("dm crypt: add ability to use keys from the kernel key retention service"). The kernel keyring function user_key_payload() is in fact a wrapper for rcu_dereference_protected() which must not be called with only rcu_read_lock() section mark. Unfortunately the kernel keyring subsystem doesn't currently provide an interface that allows the use of an RCU read-side section. So for now we must drop RCU in favour of rwsem until a proper function is made available in the kernel keyring subsystem. =============================== [ INFO: suspicious RCU usage. ] 4.10.0-rc5 #2 Not tainted ------------------------------- ./include/keys/user-type.h:53 suspicious rcu_dereference_protected() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 2 locks held by cryptsetup/6464: #0: (&md->type_lock){+.+.+.}, at: [] dm_lock_md_type+0x12/0x20 [dm_mod] #1: (rcu_read_lock){......}, at: [] crypt_set_key+0x1d8/0x4b0 [dm_crypt] stack backtrace: CPU: 1 PID: 6464 Comm: cryptsetup Not tainted 4.10.0-rc5 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014 Call Trace: dump_stack+0x67/0x92 lockdep_rcu_suspicious+0xc5/0x100 crypt_set_key+0x351/0x4b0 [dm_crypt] ? crypt_set_key+0x1d8/0x4b0 [dm_crypt] crypt_ctr+0x341/0xa53 [dm_crypt] dm_table_add_target+0x147/0x330 [dm_mod] table_load+0x111/0x350 [dm_mod] ? retrieve_status+0x1c0/0x1c0 [dm_mod] ctl_ioctl+0x1f5/0x510 [dm_mod] dm_ctl_ioctl+0xe/0x20 [dm_mod] do_vfs_ioctl+0x8e/0x690 ? ____fput+0x9/0x10 ? task_work_run+0x7e/0xa0 ? trace_hardirqs_on_caller+0x122/0x1b0 SyS_ioctl+0x3c/0x70 entry_SYSCALL_64_fastpath+0x18/0xad RIP: 0033:0x7f392c9a4ec7 RSP: 002b:00007ffef6383378 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007ffef63830a0 RCX: 00007f392c9a4ec7 RDX: 000000000124fcc0 RSI: 00000000c138fd09 RDI: 0000000000000005 RBP: 00007ffef6383090 R08: 00000000ffffffff R09: 00000000012482b0 R10: 2a28205d34383336 R11: 0000000000000246 R12: 00007f392d803a08 R13: 00007ffef63831e0 R14: 0000000000000000 R15: 00007f392d803a0b Fixes: c538f6ec9f56 ("dm crypt: add ability to use keys from the kernel key retention service") Reported-by: Milan Broz Signed-off-by: Ondrej Kozina Reviewed-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm rq: cope with DM device destruction while in dm_old_request_fn()

2017-02-03T15:18:43Z

Fixes a crash in dm_table_find_target() due to a NULL struct dm_table being passed from dm_old_request_fn() that races with DM device destruction. Reported-by: artem@flashgrid.io Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org

dm mpath: cleanup -Wbool-operation warning in choose_pgpath()

2017-02-03T15:18:37Z

Reported-by: David Binderman Signed-off-by: Mike Snitzer

md/r5cache: disable write back for degraded array

2017-01-24T19:26:06Z

write-back cache in degraded mode introduces corner cases to the array. Although we try to cover all these corner cases, it is safer to just disable write-back cache when the array is in degraded mode. In this patch, we disable writeback cache for degraded mode: 1. On device failure, if the array enters degraded mode, raid5_error() will submit async job r5c_disable_writeback_async to disable writeback; 2. In r5c_journal_mode_store(), it is invalid to enable writeback in degraded mode; 3. In r5c_try_caching_write(), stripes with s->failed>0 will be handled in write-through mode. Signed-off-by: Song Liu Signed-off-by: Shaohua Li

md/r5cache: shift complex rmw from read path to write path

2017-01-24T19:20:15Z

Write back cache requires a complex RMW mechanism, where old data is read into dev->orig_page for prexor, and then xor is done with dev->page. This logic is already implemented in the write path. However, current read path is not awared of this requirement. When the array is optimal, the RMW is not required, as the data are read from raid disks. However, when the target stripe is degraded, complex RMW is required to generate right data. To keep read path as clean as possible, we handle read path by flushing degraded, in-journal stripes before processing reads to missing dev. Specifically, when there is read requests to a degraded stripe with data in journal, handle_stripe_fill() calls r5c_make_stripe_write_out() and exits. Then handle_stripe_dirtying() will do the complex RMW and flush the stripe to RAID disks. After that, read requests are handled. There is one more corner case when there is non-overwrite bio for the missing (or out of sync) dev. handle_stripe_dirtying() will not be able to process the non-overwrite bios without constructing the data in handle_stripe_fill(). This is fixed by delaying non-overwrite bios in handle_stripe_dirtying(). So handle_stripe_fill() works on these bios after the stripe is flushed to raid disks. Signed-off-by: Song Liu Signed-off-by: Shaohua Li