Re: [PATCH v3 2/2] scsi: libsas: Add linkrate and sas_addr change detection in rediscover

[yangxingui <yangxingui@huawei.com>]

On 2026/5/27 17:42, John Garry wrote:
> On 25/05/2026 03:25, yangxingui wrote:
>>>>
>>>> Hi, John
>>>> As the commit log. The existing pattern (unregister + 
>>>> sas_discover_new) handles the "replace" case where the SAS address 
>>>> changes completely, implying a different device.
>>>> For the flutter case where we detect linkrate/sas_addr changes,
>>>
>>> Can you please clarify this: you say that the existing pattern 
>>> handles "replace" case where the SAS address changes completely, and 
>>> then flutter case covers sas_addr changes.
>>>
>>> What is the difference in the SAS address changes between the two cases?
>>>
>> Hi, John
>>
>> The difference is in when the SAS address change is detected:
>> Replace case:
>> - Detected immediately by the initial SMP DISCOVER response
>> - New SAS address differs from stored phy->attached_sas_addr
>>
>> Flutter case:
>> - Initial SMP DISCOVER shows SAS address matching stored phy- 
>>  >attached_sas_addr
>> - Linkrate may change
>> - After sas_ex_phy_discover() refreshes phy info, child device address 
>> and linkrate may mismatched with refreshed phy info
>>
>> Additional issue with Replace flow:
>> The existing replace code path also suffers from the same 
>> sysfs_warn_dup issue I mentioned earlier. 
>> sas_unregister_devs_sas_addr() only marks the device as gone and adds 
>> it to destroy_list. The actual sysfs cleanup happens later in 
>> sas_destruct_devices(). Calling sas_discover_new() immediately after 
>> unregister causes sysfs duplicate directory errors.
>>
> 
> So can you actually recreate this issue? Or is it just theoretical?
Yes, it can recreate, such as quickly replacing a disk or swapping two 
disk. However, during normal use, we recommend that customers wait for 
one minute before inserting a new disk when replacing a disk to avoid 
this issue.

The following are example of similar exception logs:
log1：

[ 7957.283194][T67794] sas: ex 500e004aaaaaaa1f phy19 replace 
5001882016000000
[ 7957.290960][T67794] sysfs: cannot create duplicate filename 
'/devices/pci0000:74/0000:74:02.0/host1/port-1:2/expander-1:2/port-1:2:19'
[ 7957.317973][T67794] Hardware name: Huawei Technologies Co., Ltd. 
EVBCS/EVBCS, BIOS CS B055 2P TA 02/19/2020
[ 7957.328900][T67794] Workqueue: 0000:74:02.0_disco_q 
sas_revalidate_domain [libsas]
[ 7957.337636][T67794] Call trace:
[ 7957.341419][T67794]  dump_backtrace+0x0/0x200
[ 7957.346317][T67794]  show_stack+0x20/0x30
[ 7957.350887][T67794]  dump_stack+0xf0/0x138
[ 7957.355511][T67794]  sysfs_warn_dup+0x6c/0x90
[ 7957.360410][T67794]  sysfs_create_dir_ns+0xf8/0x11c
[ 7957.365795][T67794]  create_dir+0x30/0x18c
[ 7957.370416][T67794]  kobject_add_internal+0x5c/0x190
[ 7957.375877][T67794]  kobject_add+0x98/0x110
[ 7957.380566][T67794]  device_add+0x100/0x4a0
[ 7957.385255][T67794]  sas_port_add+0x30/0x74 [scsi_transport_sas]
[ 7957.391722][T67794]  sas_ex_discover_end_dev+0x328/0x630 [libsas]
[ 7957.398328][T67794]  sas_ex_discover_dev+0x230/0x320 [libsas]
[ 7957.404599][T67794]  sas_ex_discover_devices+0x60/0x100 [libsas]
[ 7957.411116][T67794]  sas_discover_new+0xa4/0x150 [libsas]
[ 7957.416986][T67794]  sas_rediscover_dev+0x198/0x260 [libsas]
[ 7957.423125][T67794]  sas_rediscover+0xb8/0x100 [libsas]
[ 7957.428854][T67794]  sas_ex_revalidate_domain+0x5c/0xe0 [libsas]
[ 7957.435320][T67794]  sas_revalidate_domain+0x1ac/0x1b4 [libsas]
[ 7957.441714][T67794]  process_one_work+0x1d8/0x4cc
[ 7957.446884][T67794]  worker_thread+0x158/0x410
[ 7957.451769][T67794]  kthread+0x108/0x13c
[ 7957.456089][T67794]  ret_from_fork+0x10/0x18
[ 7957.460800][T67794] kobject_add_internal failed for port-1:2:19 with 
-EEXIST, don't try to register things with the same name in the same 
directory.
[ 7957.474864][T67794] sas: ex 500e004aaaaaaa1f phy19 failed to discover

log2：
[ 8608.766031][T66335] sas: ex 500e004aaaaaaa1f phy17 change count has 
changed
[ 8608.774390][T66335] sysfs: cannot create duplicate filename 
'/devices/pci0000:74/0000:74:02.0/host1/port-1:2/expander-1:3/port-1:3:17'
[ 8608.800667][T66335] Hardware name: Huawei Technologies Co., Ltd. 
EVBCS/EVBCS, BIOS CS B055 2P TA 02/19/2020
[ 8608.811270][T66335] Workqueue: 0000:74:02.0_disco_q 
sas_revalidate_domain [libsas]
[ 8608.819685][T66335] Call trace:
[ 8608.823235][T66335]  dump_backtrace+0x0/0x200
[ 8608.827990][T66335]  show_stack+0x20/0x30
[ 8608.832387][T66335]  dump_stack+0xf0/0x138
[ 8608.836858][T66335]  sysfs_warn_dup+0x6c/0x90
[ 8608.841580][T66335]  sysfs_create_dir_ns+0xf8/0x11c
[ 8608.846814][T66335]  create_dir+0x30/0x18c
[ 8608.851257][T66335]  kobject_add_internal+0x5c/0x190
[ 8608.856566][T66335]  kobject_add+0x98/0x110
[ 8608.861083][T66335]  device_add+0x100/0x4a0
[ 8608.865588][T66335]  sas_port_add+0x30/0x74 [scsi_transport_sas]
[ 8608.871919][T66335]  sas_ex_discover_end_dev+0x328/0x630 [libsas]
[ 8608.878345][T66335]  sas_ex_discover_dev+0x230/0x320 [libsas]
[ 8608.884430][T66335]  sas_ex_discover_devices+0x60/0x100 [libsas]
[ 8608.890768][T66335]  sas_discover_new+0xa4/0x150 [libsas]
[ 8608.896506][T66335]  sas_rediscover+0xd8/0x100 [libsas]
[ 8608.902075][T66335]  sas_ex_revalidate_domain+0x5c/0xe0 [libsas]
[ 8608.908438][T66335]  sas_revalidate_domain+0x1ac/0x1b4 [libsas]
[ 8608.914708][T66335]  process_one_work+0x1d8/0x4cc
[ 8608.919757][T66335]  worker_thread+0x158/0x410
[ 8608.924533][T66335]  kthread+0x108/0x13c
[ 8608.928778][T66335]  ret_from_fork+0x10/0x18
[ 8608.933377][T66335] kobject_add_internal failed for port-1:3:17 with 
-EEXIST, don't try to register things with the same name in the same 
directory.
[ 8608.947364][T66335] sas: ex 500e004aaaaaaa1f phy17 failed to discover


> About this following code:
> 
> +        if (need_rediscover) {
> +            set_bit(SAS_DEV_GONE, &child_dev->state);
> +            phy->phy_change_count = -1;
> +            ex->ex_change_count = -1;
> +            sas_unregister_devs_sas_addr(dev, phy_id, true);
> +            sas_discover_event(dev->port, DISCE_REVALIDATE_DOMAIN);
> +        } else {
> 
> 
> Can we factor it out with other code? AFAICR, this can pattern can be 
> seen elsewhere.

Yes, in the updated v4 version, I refined it into a function.

In the v4 test log, the disk is gone and then connected again.
test case:
phy=phy-10:0:0
echo 1.5 Gbit > /sys/class/sas_phy/$phy/maximum_linkrate

The details are as follows:

[  541.880156] sas: broadcast received: 0
[  541.880712] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  541.882509] sas: ex 500e004aaaaaaa1f phy00 change count has changed
[  541.883680] sas: ex 500e004aaaaaaa1f phy00 originated BROADCAST(CHANGE)
[  541.883703] sas: ex 500e004aaaaaaa1f rediscovering phy00
[  541.884838] sas: ex 500e004aaaaaaa1f phy00:U:8 attached: 
500e004aaaaaaa00 (stp pending)
[  541.884844] sas: ex 500e004aaaaaaa1f phy00 broadcast flutter, needs 
recovery
[  541.898893] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  541.899444] sas: broadcast received: 0
[  541.899506] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  541.899659] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  541.900213] sas: broadcast received: 0
[  541.900282] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  541.900367] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  541.900992] sas: broadcast received: 0
[  541.901041] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  541.901132] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  541.901160] sas: broadcast received: 0
[  541.901195] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  541.901278] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  541.901887] sas: broadcast received: 0
[  541.901948] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  541.902035] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  541.902673] sas: broadcast received: 0
[  541.902741] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  541.902836] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  541.903467] sas: broadcast received: 0
[  541.903536] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  541.903625] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  541.919967] sas: broadcast received: 0
[  541.920036] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  541.920385] sas: ex 500e004aaaaaaa1f phy00 change count has changed
[  541.920494] sas: ex 500e004aaaaaaa1f phy00 originated BROADCAST(CHANGE)
[  541.920504] sas: ex 500e004aaaaaaa1f rediscovering phy00
[  541.920687] sas: ex 500e004aaaaaaa1f phy00:U:8 attached: 
500e004aaaaaaa00 (stp)
[  541.920697] sas: ex 500e004aaaaaaa1f phy00 linkrate changed from 9 to 8
[  541.920710] sas: ex 500e004aaaaaaa1f phy00 replace 500e004aaaaaaa00
[  541.922648] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  542.007031] sd 10:0:0:0: [sdd] Stopping disk
[  542.007122] sd 10:0:0:0: [sdd] Start/Stop Unit failed: Result: 
hostbyte=0x04 driverbyte=DRIVER_OK
[  542.027347] hisi_sas_v3_hw 0000:70:04.0: dev[2:5] is gone
[  542.039000] sas: REVALIDATING DOMAIN on port 0, pid:8995
[  542.039358] sas: ex 500e004aaaaaaa1f phy00 change count has changed
[  542.039436] sas: broadcast received: 0
[  542.039470] sas: ex 500e004aaaaaaa1f phy00 originated BROADCAST(CHANGE)
[  542.039482] sas: ex 500e004aaaaaaa1f phy00 new device attached
[  542.039569] sas: ex 500e004aaaaaaa1f phy00:U:8 attached: 
500e004aaaaaaa00 (stp)
[  542.040152] hisi_sas_v3_hw 0000:70:04.0: dev[15:5] found
[  542.042112] sas: done REVALIDATING DOMAIN on port 0, pid:8995, res 0x0
[  542.153137] sas: Enter sas_scsi_recover_host busy: 0 failed: 0
[  542.153900] sas: ata10: end_device-10:0:1: dev error handler
[  542.153972] sas: ata11: end_device-10:0:2: dev error handler
[  542.153994] sas: ata12: end_device-10:0:5: dev error handler
[  542.154010] sas: ata13: end_device-10:0:6: dev error handler
[  542.154021] sas: ata14: end_device-10:0:9: dev error handler
[  542.154032] sas: ata15: end_device-10:0:10: dev error handler
[  542.154044] sas: ata9: end_device-10:0:0: dev error handler
[  542.519243] ata9.00: ATA-10: ST4000NM0035-1V4107, TN03, max UDMA/133
[  542.522538] ata9.00: 7814037168 sectors, multi 0: LBA48 NCQ (depth 32)
[  542.522561] ata9.00: Features: DIPM NCQ-sndrcv
[  542.527315] ata9.00: configured for UDMA/133
[  542.527976] sas: --- Exit sas_scsi_recover_host: busy: 0 failed: 0 
tries: 1
[  542.570193] scsi 10:0:13:0: Direct-Access     ATA 
ST4000NM0035-1V4 TN03 PQ: 0 ANSI: 5
[  542.571771] scsi 10:0:13:0: Attached scsi generic sg3 type 0


Thanks,
Xingui