Re: [bug report] raid0 array mkfs.xfs hang

[John Garry <john.g.garry@oracle.com>]

This looks to resolve the issue:

------>8------

Author: John Garry <john.g.garry@oracle.com>
Date:   Wed Aug 14 12:15:26 2024 +0100

block: Read max write zeroes once for __blkdev_issue_write_zeroes()

As reported in [0], we may get a hang when formatting a XFS FS on a 
RAID0 disk.

Commit 73a768d5f955 ("block: factor out a blk_write_zeroes_limit 
helper") changed __blkdev_issue_write_zeroes() to read the max write 
zeroes value in a loop. This is not safe in case max write zeroes 
changes, which it seems to do. For case of [0], the value goes to 0, and 
we get an infinite loop.

Lift the limit reading out of the loop.

[0] 
https://lore.kernel.org/linux-xfs/4d31268f-310b-4220-88a2-e191c3932a82@oracle.com/T/#t
Signed-off-by: John Garry <john.g.garry@oracle.com>

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 9f735efa6c94..f65fb083c25d 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -113,11 +113,11 @@ static sector_t bio_write_zeroes_limit(struct 
block_device *bdev)

  static void __blkdev_issue_write_zeroes(struct block_device *bdev,
                 sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
-               struct bio **biop, unsigned flags)
+               struct bio **biop, unsigned flags, sector_t limit)
  {
+
         while (nr_sects) {
-               unsigned int len = min_t(sector_t, nr_sects,
-                               bio_write_zeroes_limit(bdev));
+               unsigned int len = min_t(sector_t, nr_sects, limit);
                 struct bio *bio;

                 if ((flags & BLKDEV_ZERO_KILLABLE) &&
@@ -144,9 +144,10 @@ static int blkdev_issue_write_zeroes(struct 
block_device *bdev, sector_t sector,
         struct bio *bio = NULL;
         struct blk_plug plug;
         int ret = 0;
+       sector_t limit = bio_write_zeroes_limit(bdev);

         blk_start_plug(&plug);
-       __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp, &bio, 
flags);
+       __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp, &bio, 
flags, limit);
         if (bio) {
                 if ((flags & BLKDEV_ZERO_KILLABLE) &&
                     fatal_signal_pending(current)) {
@@ -165,7 +166,7 @@ static int blkdev_issue_write_zeroes(struct 
block_device *bdev, sector_t sector,
          * on an I/O error, in which case we'll turn any error into
          * "not supported" here.
          */
-       if (ret && !bdev_write_zeroes_sectors(bdev))
+       if (ret && !limit)
                 return -EOPNOTSUPP;
         return ret;
  }
@@ -265,12 +266,14 @@ int __blkdev_issue_zeroout(struct block_device 
*bdev, sector_t sector,
                 sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
                 unsigned flags)
  {
+
+       sector_t limit = bio_write_zeroes_limit(bdev);
         if (bdev_read_only(bdev))
                 return -EPERM;

-       if (bdev_write_zeroes_sectors(bdev)) {
+       if (limit) {
                 __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
-                               gfp_mask, biop, flags);
+                               gfp_mask, biop, flags, limit);
         } else {
                 if (flags & BLKDEV_ZERO_NOFALLBACK)
                         return -EOPNOTSUPP;
ubuntu@jgarry-instance-20240809-1141-3:~/linux$



-----8<------

The value max write zeroes value is changing in raid0_map_submit_bio() 
-> mddev_check_write_zeroes()


> 
> xfsprogs 5.3.0 does not have this issue for v6.11-rc. xfsprogs 5.15.0 
> and later does.
> 
> For xfsprogs on my modestly recent baseline, mkfs.xfs is getting stuck 
> in prepare_devices() -> libxfs_log_clear() -> libxfs_device_zero() -> 
> libxfs_device_zero() -> platform_zero_range() -> 
> fallocate(start=2198746472448 len=2136997888), and this never returns 
> AFAICS. With v6.10 kernel, that fallocate with same args returns promptly.
> 
> That code path is just not in xfsprogs 5.3.0
> 
>> After upgrading from v6.10 to v6.11-rc1/2, I am seeing a hang when 
>> attempting to format a software raid0 array:
>>
>> $sudo mkfs.xfs -f -K  /dev/md127
>> meta-data=/dev/md127             isize=512    agcount=32, 
>> agsize=33550272 blks
>>           =                       sectsz=4096  attr=2, projid32bit=1
>>           =                       crc=1        finobt=1, sparse=1, 
>> rmapbt=0
>>           =                       reflink=1    bigtime=0 inobtcount=0
>> data     =                       bsize=4096   blocks=1073608704, 
>> imaxpct=5
>>           =                       sunit=64     swidth=256 blks
>> naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
>> log      =internal log           bsize=4096   blocks=521728, version=2
>>           =                       sectsz=4096  sunit=1 blks, lazy-count=1
>> realtime =none                   extsz=4096   blocks=0, rtextents=0
>> ^C^C^C^C
>>
>>
>> I'm using mkfs.xfs -K to avoid discard-related lock-up issues which I 
>> have seen reported when googling - maybe this is just another similar 
>> issue.
>>
>> The kernel lockup callstack is at the bottom.
>>
>> Some array details:
>> $sudo mdadm --detail /dev/md127
>> /dev/md127:
>>             Version : 1.2
>>       Creation Time : Thu Aug  8 13:23:59 2024
>>          Raid Level : raid0
>>          Array Size : 4294438912 (4.00 TiB 4.40 TB)
>>        Raid Devices : 4
>>       Total Devices : 4
>>         Persistence : Superblock is persistent
>>
>>         Update Time : Thu Aug  8 13:23:59 2024
>>               State : clean
>>      Active Devices : 4
>>     Working Devices : 4
>>      Failed Devices : 0
>>       Spare Devices : 0
>>
>>              Layout : -unknown-
>>          Chunk Size : 256K
>>
>> Consistency Policy : none
>>
>>                Name : 0
>>                UUID : 3490e53f:36d0131b:7c7eb913:0fd62deb
>>              Events : 0
>>
>>      Number   Major   Minor   RaidDevice State
>>         0       8       16        0      active sync   /dev/sdb
>>         1       8       64        1      active sync   /dev/sde
>>         2       8       48        2      active sync   /dev/sdd
>>         3       8       80        3      active sync   /dev/sdf
>>
>>
>>
>> $lsblk
>> NAME               MAJ:MIN RM  SIZE RO TYPE  MOUNTPOINT
>> sda                  8:0    0 46.6G  0 disk
>> ├─sda1               8:1    0  100M  0 part  /boot/efi
>> ├─sda2               8:2    0    1G  0 part  /boot
>> └─sda3               8:3    0 45.5G  0 part
>>    ├─ocivolume-root 252:0    0 35.5G  0 lvm   /
>>    └─ocivolume-oled 252:1    0   10G  0 lvm   /var/oled
>> sdb                  8:16   0    1T  0 disk
>> └─md127              9:127  0    4T  0 raid0
>> sdc                  8:32   0    1T  0 disk
>> sdd                  8:48   0    1T  0 disk
>> └─md127              9:127  0    4T  0 raid0
>> sde                  8:64   0    1T  0 disk
>> └─md127              9:127  0    4T  0 raid0
>> sdf                  8:80   0    1T  0 disk
>> └─md127              9:127  0    4T  0 raid0
>>
>> I'll start to look deeper, but any suggestions on the problem are 
>> welcome.
>>
>> Thanks,
>> John
>>
>>
>> ort_iscsi aesni_intel crypto_simd cryptd
>> [  396.110305] CPU: 0 UID: 0 PID: 321 Comm: kworker/0:1H Not tainted 
>> 6.11.0-rc1-g8400291e289e #11
>> [  396.111020] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), 
>> BIOS 1.5.1 06/16/2021
>> [  396.111695] Workqueue: kblockd blk_mq_run_work_fn
>> [  396.112114] RIP: 0010:bio_endio+0xa0/0x1b0
>> [  396.112455] Code: 96 9a 02 00 48 8b 43 08 48 85 c0 74 09 0f b7 53 
>> 14 f6 c2 80 75 3b 48 8b 43 38 48 3d e0 a3 3c b2 75 44 0f b6 43 19 48 
>> 8b 6b 40 <84> c0 74 09 80 7d 19 00 75 03 88 45 19 48 89 df 48 89 eb e8 
>> 58 fe
>> [  396.113962] RSP: 0018:ffffa3fec19fbc38 EFLAGS: 00000246
>> [  396.114392] RAX: 0000000000000001 RBX: ffff97a284c3e600 RCX: 
>> 00000000002a0001
>> [  396.114974] RDX: 0000000000000000 RSI: ffffcfb0f1130f80 RDI: 
>> 0000000000020000
>> [  396.115546] RBP: ffff97a284c41bc0 R08: ffff97a284c3e3c0 R09: 
>> 00000000002a0001
>> [  396.116185] R10: 0000000000000000 R11: 0000000000000000 R12: 
>> ffff9798216ed000
>> [  396.116766] R13: ffff97975bf071c0 R14: ffff979751be4798 R15: 
>> 0000000000009000
>> [  396.117393] FS:  0000000000000000(0000) GS:ffff97b5ff600000(0000) 
>> knlGS:0000000000000000
>> [  396.118122] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [  396.118709] CR2: 00007f2477a45f68 CR3: 0000000107998005 CR4: 
>> 0000000000770ef0
>> [  396.119398] PKRU: 55555554
>> [  396.119627] Call Trace:
>> [  396.119905]  <IRQ>
>> [  396.120078]  ? watchdog_timer_fn+0x1e2/0x260
>> [  396.120457]  ? __pfx_watchdog_timer_fn+0x10/0x10
>> [  396.120900]  ? __hrtimer_run_queues+0x10c/0x270
>> [  396.121276]  ? hrtimer_interrupt+0x109/0x250
>> [  396.121663]  ? __sysvec_apic_timer_interrupt+0x55/0x120
>> [  396.122197]  ? sysvec_apic_timer_interrupt+0x6c/0x90
>> [  396.122640]  </IRQ>
>> [  396.122815]  <TASK>
>> [  396.123009]  ? asm_sysvec_apic_timer_interrupt+0x1a/0x20
>> [  396.123473]  ? bio_endio+0xa0/0x1b0
>> [  396.123794]  ? bio_endio+0xb8/0x1b0
>> [  396.124082]  md_end_clone_io+0x42/0xa0
>> [  396.124406]  blk_update_request+0x128/0x490
>> [  396.124745]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [  396.125554]  ? scsi_dec_host_busy+0x14/0x90
>> [  396.126290]  blk_mq_end_request+0x22/0x2e0
>> [  396.126965]  blk_mq_dispatch_rq_list+0x2b6/0x730
>> [  396.127660]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [  396.128386]  __blk_mq_sched_dispatch_requests+0x442/0x640
>> [  396.129152]  blk_mq_sched_dispatch_requests+0x2a/0x60
>> [  396.130005]  blk_mq_run_work_fn+0x67/0x80
>> [  396.130697]  process_scheduled_works+0xa6/0x3e0
>> [  396.131413]  worker_thread+0x117/0x260
>> [  396.132051]  ? __pfx_worker_thread+0x10/0x10
>> [  396.132697]  kthread+0xd2/0x100
>> [  396.133288]  ? __pfx_kthread+0x10/0x10
>> [  396.133977]  ret_from_fork+0x34/0x40
>> [  396.134613]  ? __pfx_kthread+0x10/0x10
>> [  396.135207]  ret_from_fork_asm+0x1a/0x30
>> [  396.135863]  </TASK>
>>
>