commit 7abfabaf5f805f5171d133ce6af9b65ab766e76a upstream.
Reading /proc/mdstat with a read buffer size that would not
fit the unused status line in the first read will skip this
line from the output.
So 'dd if=/proc/mdstat bs=64 2>/dev/null' will not print something
like: unused devices: <none>
Don't return NULL immediately in start() for v=2 but call
show() once to print the status line also for multiple reads.
Cc: stable@vger.kernel.org
Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface")
Signed-off-by: Jan Glauber <jglauber@digitalocean.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 6a4db2a60306eb65bfb14ccc9fde035b74a4b4e7 upstream.
commit d3374825ce57 ("md: make devices disappear when they are no longer
needed.") introduced protection between mddev creating & removing. The
md_open shouldn't create mddev when all_mddevs list doesn't contain
mddev. With currently code logic, there will be very easy to trigger
soft lockup in non-preempt env.
This patch changes md_open returning from -ERESTARTSYS to -EBUSY, which
will break the infinitely retry when md_open enter racing area.
This patch is partly fix soft lockup issue, full fix needs mddev_find
is split into two functions: mddev_find & mddev_find_or_alloc. And
md_open should call new mddev_find (it only does searching job).
For more detail, please refer with Christoph's "split mddev_find" patch
in later commits.
*** env ***
kvm-qemu VM 2C1G with 2 iscsi luns
kernel should be non-preempt
*** script ***
about trigger every time with below script
```
1 node1="mdcluster1"
2 node2="mdcluster2"
3
4 mdadm -Ss
5 ssh ${node2} "mdadm -Ss"
6 wipefs -a /dev/sda /dev/sdb
7 mdadm -CR /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sda \
/dev/sdb --assume-clean
8
9 for i in {1..10}; do
10 echo ==== $i ====;
11
12 echo "test ...."
13 ssh ${node2} "mdadm -A /dev/md0 /dev/sda /dev/sdb"
14 sleep 1
15
16 echo "clean ....."
17 ssh ${node2} "mdadm -Ss"
18 done
```
I use mdcluster env to trigger soft lockup, but it isn't mdcluster
speical bug. To stop md array in mdcluster env will do more jobs than
non-cluster array, which will leave enough time/gap to allow kernel to
run md_open.
*** stack ***
```
[ 884.226509] mddev_put+0x1c/0xe0 [md_mod]
[ 884.226515] md_open+0x3c/0xe0 [md_mod]
[ 884.226518] __blkdev_get+0x30d/0x710
[ 884.226520] ? bd_acquire+0xd0/0xd0
[ 884.226522] blkdev_get+0x14/0x30
[ 884.226524] do_dentry_open+0x204/0x3a0
[ 884.226531] path_openat+0x2fc/0x1520
[ 884.226534] ? seq_printf+0x4e/0x70
[ 884.226536] do_filp_open+0x9b/0x110
[ 884.226542] ? md_release+0x20/0x20 [md_mod]
[ 884.226543] ? seq_read+0x1d8/0x3e0
[ 884.226545] ? kmem_cache_alloc+0x18a/0x270
[ 884.226547] ? do_sys_open+0x1bd/0x260
[ 884.226548] do_sys_open+0x1bd/0x260
[ 884.226551] do_syscall_64+0x5b/0x1e0
[ 884.226554] entry_SYSCALL_64_after_hwframe+0x44/0xa9
```
*** rootcause ***
"mdadm -A" (or other array assemble commands) will start a daemon "mdadm
--monitor" by default. When "mdadm -Ss" is running, the stop action will
wakeup "mdadm --monitor". The "--monitor" daemon will immediately get
info from /proc/mdstat. This time mddev in kernel still exist, so
/proc/mdstat still show md device, which makes "mdadm --monitor" to open
/dev/md0.
The previously "mdadm -Ss" is removing action, the "mdadm --monitor"
open action will trigger md_open which is creating action. Racing is
happening.
```
<thread 1>: "mdadm -Ss"
md_release
mddev_put deletes mddev from all_mddevs
queue_work for mddev_delayed_delete
at this time, "/dev/md0" is still available for opening
<thread 2>: "mdadm --monitor ..."
md_open
+ mddev_find can't find mddev of /dev/md0, and create a new mddev and
| return.
+ trigger "if (mddev->gendisk != bdev->bd_disk)" and return
-ERESTARTSYS.
```
In non-preempt kernel, <thread 2> is occupying on current CPU. and
mddev_delayed_delete which was created in <thread 1> also can't be
schedule.
In preempt kernel, it can also trigger above racing. But kernel doesn't
allow one thread running on a CPU all the time. after <thread 2> running
some time, the later "mdadm -A" (refer above script line 13) will call
md_alloc to alloc a new gendisk for mddev. it will break md_open
statement "if (mddev->gendisk != bdev->bd_disk)" and return 0 to caller,
the soft lockup is broken.
Cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zhao Heming <heming.zhao@suse.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 8b57251f9a91f5e5a599de7549915d2d226cc3af upstream. Factor out a self-contained helper to just lookup a mddev by the dev_t "unit". Cc: stable@vger.kernel.org Reviewed-by: Heming Zhao <heming.zhao@suse.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 65aa97c4d2bfd76677c211b9d03ef05a98c6d68e upstream.
Split mddev_find into a simple mddev_find that just finds an existing
mddev by the unit number, and a more complicated mddev_find that deals
with find or allocating a mddev.
This turns out to fix this bug reported by Zhao Heming.
----------------------------- snip ------------------------------
commit d3374825ce57 ("md: make devices disappear when they are no longer
needed.") introduced protection between mddev creating & removing. The
md_open shouldn't create mddev when all_mddevs list doesn't contain
mddev. With currently code logic, there will be very easy to trigger
soft lockup in non-preempt env.
commit f7c7a2f9a23e5b6e0f5251f29648d0238bb7757e upstream.
md_kick_rdev_from_array will remove rdev, so we should
use rdev_for_each_safe to search list.
How to trigger:
env: Two nodes on kvm-qemu x86_64 VMs (2C2G with 2 iscsi luns).
```
node2=192.168.0.3
for i in {1..20}; do
echo ==== $i `date` ====;
mdadm -Ss && ssh ${node2} "mdadm -Ss"
wipefs -a /dev/sda /dev/sdb
mdadm -CR /dev/md0 -b clustered -e 1.2 -n 2 -l 1 /dev/sda \
/dev/sdb --assume-clean
ssh ${node2} "mdadm -A /dev/md0 /dev/sda /dev/sdb"
mdadm --wait /dev/md0
ssh ${node2} "mdadm --wait /dev/md0"
mdadm --manage /dev/md0 --fail /dev/sda --remove /dev/sda
sleep 1
done
```
Crash stack:
```
stack segment: 0000 [#1] SMP
... ...
RIP: 0010:md_check_recovery+0x1e8/0x570 [md_mod]
... ...
RSP: 0018:ffffb149807a7d68 EFLAGS: 00010207
RAX: 0000000000000000 RBX: ffff9d494c180800 RCX: ffff9d490fc01e50
RDX: fffff047c0ed8308 RSI: 0000000000000246 RDI: 0000000000000246
RBP: 6b6b6b6b6b6b6b6b R08: ffff9d490fc01e40 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
R13: ffff9d494c180818 R14: ffff9d493399ef38 R15: ffff9d4933a1d800
FS: 0000000000000000(0000) GS:ffff9d494f700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe68cab9010 CR3: 000000004c6be001 CR4: 00000000003706e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
raid1d+0x5c/0xd40 [raid1]
? finish_task_switch+0x75/0x2a0
? lock_timer_base+0x67/0x80
? try_to_del_timer_sync+0x4d/0x80
? del_timer_sync+0x41/0x50
? schedule_timeout+0x254/0x2d0
? md_start_sync+0xe0/0xe0 [md_mod]
? md_thread+0x127/0x160 [md_mod]
md_thread+0x127/0x160 [md_mod]
? wait_woken+0x80/0x80
kthread+0x10d/0x130
? kthread_park+0xa0/0xa0
ret_from_fork+0x1f/0x40
```
Fixes: dbb64f8635f5d ("md-cluster: Fix adding of new disk with new reload code")
Fixes: 659b254fa7392 ("md-cluster: remove a disk asynchronously from cluster environment")
Cc: stable@vger.kernel.org
Reviewed-by: Gang He <ghe@suse.com>
Signed-off-by: Heming Zhao <heming.zhao@suse.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
One customer reports a crash problem which causes by flush request. It
triggers a warning before crash.
/* new request after previous flush is completed */
if (ktime_after(req_start, mddev->prev_flush_start)) {
WARN_ON(mddev->flush_bio);
mddev->flush_bio = bio;
bio = NULL;
}
The WARN_ON is triggered. We use spin lock to protect prev_flush_start and
flush_bio in md_flush_request. But there is no lock protection in
md_submit_flush_data. It can set flush_bio to NULL first because of
compiler reordering write instructions.
For example, flush bio1 sets flush bio to NULL first in
md_submit_flush_data. An interrupt or vmware causing an extended stall
happen between updating flush_bio and prev_flush_start. Because flush_bio
is NULL, flush bio2 can get the lock and submit to underlayer disks. Then
flush bio1 updates prev_flush_start after the interrupt or extended stall.
Then flush bio3 enters in md_flush_request. The start time req_start is
behind prev_flush_start. The flush_bio is not NULL(flush bio2 hasn't
finished). So it can trigger the WARN_ON now. Then it calls INIT_WORK
again. INIT_WORK() will re-initialize the list pointers in the
work_struct, which then can result in a corrupted work list and the
work_struct queued a second time. With the work list corrupted, it can
lead in invalid work items being used and cause a crash in
process_one_work.
We need to make sure only one flush bio can be handled at one same time.
So add spin lock in md_submit_flush_data to protect prev_flush_start and
flush_bio in an atomic way.
Reviewed-by: David Jeffery <djeffery@redhat.com>
Signed-off-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Pull block driver updates from Jens Axboe:
"Nothing major in here:
- NVMe pull request from Christoph:
- nvmet passthrough improvements (Chaitanya Kulkarni)
- fcloop error injection support (James Smart)
- read-only support for zoned namespaces without Zone Append
(Javier González)
- improve some error message (Minwoo Im)
- reject I/O to offline fabrics namespaces (Victor Gladkov)
- PCI queue allocation cleanups (Niklas Schnelle)
- remove an unused allocation in nvmet (Amit Engel)
- a Kconfig spelling fix (Colin Ian King)
- nvme_req_qid simplication (Baolin Wang)
- MD pull request from Song:
- Fix race condition in md_ioctl() (Dae R. Jeong)
- Initialize read_slot properly for raid10 (Kevin Vigor)
- Code cleanup (Pankaj Gupta)
- md-cluster resync/reshape fix (Zhao Heming)
- Move null_blk into its own directory (Damien Le Moal)
- null_blk zone and discard improvements (Damien Le Moal)
- bcache race fix (Dongsheng Yang)
- Set of rnbd fixes/improvements (Gioh Kim, Guoqing Jiang, Jack Wang,
Lutz Pogrell, Md Haris Iqbal)
- lightnvm NULL pointer deref fix (tangzhenhao)
- sr in_interrupt() removal (Sebastian Andrzej Siewior)
- FC endpoint security support for s390/dasd (Jan Höppner, Sebastian
Ott, Vineeth Vijayan). From the s390 arch guys, arch bits included
as it made it easier for them to funnel the feature through the
block driver tree.
- Follow up fixes (Colin Ian King)"
* tag 'for-5.11/drivers-2020-12-14' of git://git.kernel.dk/linux-block: (64 commits)
block: drop dead assignments in loop_init()
sr: Remove in_interrupt() usage in sr_init_command().
sr: Switch the sector size back to 2048 if sr_read_sector() changed it.
cdrom: Reset sector_size back it is not 2048.
drivers/lightnvm: fix a null-ptr-deref bug in pblk-core.c
null_blk: Move driver into its own directory
null_blk: Allow controlling max_hw_sectors limit
null_blk: discard zones on reset
null_blk: cleanup discard handling
null_blk: Improve implicit zone close
null_blk: improve zone locking
block: Align max_hw_sectors to logical blocksize
null_blk: Fail zone append to conventional zones
null_blk: Fix zone size initialization
bcache: fix race between setting bdev state to none and new write request direct to backing
block/rnbd: fix a null pointer dereference on dev->blk_symlink_name
block/rnbd-clt: Dynamically alloc buffer for pathname & blk_symlink_name
block/rnbd: call kobject_put in the failure path
Documentation/ABI/rnbd-srv: add document for force_close
block/rnbd-srv: close a mapped device from server side.
...
Pull block updates from Jens Axboe:
"Another series of killing more code than what is being added, again
thanks to Christoph's relentless cleanups and tech debt tackling.
This contains:
- blk-iocost improvements (Baolin Wang)
- part0 iostat fix (Jeffle Xu)
- Disable iopoll for split bios (Jeffle Xu)
- block tracepoint cleanups (Christoph Hellwig)
- Merging of struct block_device and hd_struct (Christoph Hellwig)
- Rework/cleanup of how block device sizes are updated (Christoph
Hellwig)
- Simplification of gendisk lookup and removal of block device
aliasing (Christoph Hellwig)
- Block device ioctl cleanups (Christoph Hellwig)
- Removal of bdget()/blkdev_get() as exported API (Christoph Hellwig)
- Disk change rework, avoid ->revalidate_disk() (Christoph Hellwig)
- sbitmap improvements (Pavel Begunkov)
- Hybrid polling fix (Pavel Begunkov)
- bvec iteration improvements (Pavel Begunkov)
- Zone revalidation fixes (Damien Le Moal)
- blk-throttle limit fix (Yu Kuai)
- Various little fixes"
* tag 'for-5.11/block-2020-12-14' of git://git.kernel.dk/linux-block: (126 commits)
blk-mq: fix msec comment from micro to milli seconds
blk-mq: update arg in comment of blk_mq_map_queue
blk-mq: add helper allocating tagset->tags
Revert "block: Fix a lockdep complaint triggered by request queue flushing"
nvme-loop: use blk_mq_hctx_set_fq_lock_class to set loop's lock class
blk-mq: add new API of blk_mq_hctx_set_fq_lock_class
block: disable iopoll for split bio
block: Improve blk_revalidate_disk_zones() checks
sbitmap: simplify wrap check
sbitmap: replace CAS with atomic and
sbitmap: remove swap_lock
sbitmap: optimise sbitmap_deferred_clear()
blk-mq: skip hybrid polling if iopoll doesn't spin
blk-iocost: Factor out the base vrate change into a separate function
blk-iocost: Factor out the active iocgs' state check into a separate function
blk-iocost: Move the usage ratio calculation to the correct place
blk-iocost: Remove unnecessary advance declaration
blk-iocost: Fix some typos in comments
blktrace: fix up a kerneldoc comment
block: remove the request_queue to argument request based tracepoints
...
This reverts commit 2628089b74d5a64bd0bcb5d247a18f78d7b6f4d0. Matthew Ruffell reported data corruption in raid10 due to the changes in discard handling [1]. Revert these changes before we find a proper fix. [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1907262/ Cc: Matthew Ruffell <matthew.ruffell@canonical.com> Cc: Xiao Ni <xni@redhat.com> Signed-off-by: Song Liu <songliubraving@fb.com>
The request_queue can trivially be derived from the bio. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>