Re: [PATCH v11 14/16] xfs: add xfs_calc_atomic_write_unit_max()

John Garry
2025-05-05T08:02:52Z

On 05/05/2025 07:08, John Garry wrote:
> On 05/05/2025 06:25, Darrick J. Wong wrote:
>> Ok so I even attached the reply to the WRONG VERSION.  Something in
>> these changes cause xfs/289 to barf up this UBSAN warning, even on a
>> realtime + rtgroups volume:

Could this just be from another mount (of not a realtime + rtgroups xfs
instance)?

>>
>> [ 1160.539004] ------------[ cut here ]------------
>> [ 1160.540701] UBSAN: shift-out-of-bounds in /storage/home/djwong/
>> cdev/work/linux-djw/include/linux/log2.h:67:13
>> [ 1160.544597] shift exponent 4294967295 is too large for 64-bit type
>> 'long unsigned int'
>> [ 1160.547038] CPU: 3 UID: 0 PID: 288421 Comm: mount Not tainted
>> 6.15.0-rc5-djwx #rc5 PREEMPT(lazy)
>> 6f606c17703b80ffff7378e7041918eca24b3e68
>> [ 1160.547045] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>> BIOS 1.16.0-4.module+el8.8.0+21164+ed375313 04/01/2014
>> [ 1160.547047] Call Trace:
>> [ 1160.547049]  <TASK>
>> [ 1160.547051]  dump_stack_lvl+0x4f/0x60
>> [ 1160.547060]  __ubsan_handle_shift_out_of_bounds+0x1bc/0x380
>> [ 1160.547066]  xfs_set_max_atomic_write_opt.cold+0x22d/0x252 [xfs
>> 1f657532c3dee9b1d567597a31645929273d3283]
>> [ 1160.547249]  xfs_mountfs+0xa5c/0xb50 [xfs
>> 1f657532c3dee9b1d567597a31645929273d3283]
>> [ 1160.547434]  xfs_fs_fill_super+0x7eb/0xb30 [xfs
>> 1f657532c3dee9b1d567597a31645929273d3283]
>> [ 1160.547616]  ? xfs_open_devices+0x240/0x240 [xfs
>> 1f657532c3dee9b1d567597a31645929273d3283]
>> [ 1160.547797]  get_tree_bdev_flags+0x132/0x1d0
>> [ 1160.547801]  vfs_get_tree+0x17/0xa0
>> [ 1160.547803]  path_mount+0x720/0xa80
>> [ 1160.547807]  __x64_sys_mount+0x10c/0x140
>> [ 1160.547810]  do_syscall_64+0x47/0x100
>> [ 1160.547814]  entry_SYSCALL_64_after_hwframe+0x4b/0x53
>> [ 1160.547817] RIP: 0033:0x7fde55d62e0a
>> [ 1160.547820] Code: 48 8b 0d f9 7f 0c 00 f7 d8 64 89 01 48 83 c8 ff
>> c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00
>> 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d c6 7f 0c 00 f7 d8 64 89
>> 01 48
>> [ 1160.547823] RSP: 002b:00007fff11920ce8 EFLAGS: 00000246 ORIG_RAX:
>> 00000000000000a5
>> [ 1160.547826] RAX: ffffffffffffffda RBX: 0000556a10cd1de0 RCX:
>> 00007fde55d62e0a
>> [ 1160.547828] RDX: 0000556a10cd2010 RSI: 0000556a10cd2090 RDI:
>> 0000556a10ce2590
>> [ 1160.547829] RBP: 0000000000000000 R08: 0000000000000000 R09:
>> 00007fff11920d50
>> [ 1160.547830] R10: 0000000000000000 R11: 0000000000000246 R12:
>> 0000556a10ce2590
>> [ 1160.547832] R13: 0000556a10cd2010 R14: 00007fde55eca264 R15:
>> 0000556a10cd1ef8
>> [ 1160.547834]  </TASK>
>> [ 1160.547835] ---[ end trace ]---
>>
>> John, can you please figure this one out, seeing as it's 10:30pm on
>> Sunday night here?

I could recreate this.

>

I think that we need this change:

@@ -715,6 +716,9 @@ static inline xfs_extlen_t
xfs_calc_rtgroup_awu_max(struct xfs_mount *mp)
{
struct xfs_groups *rgs = &mp->m_groups[XG_TYPE_RTG];

+ if (rgs->blocks == 0)
+ return 0;
if (mp->m_rtdev_targp && mp->m_rtdev_targp->bt_bdev_awu_min > 0)
return max_pow_of_two_factor(rgs->blocks);
return rounddown_pow_of_two(rgs->blocks);

My xfs/289 problem goes away with this change.

>