Merge patch series "libsas: rediscover improvements for linkrate/sas_addr"

Xingui Yang <yangxingui@huawei.com> says:

When a device attached to an expander phy experiences a linkrate change
(e.g., due to cable reconnection or negotiation), the current code in
sas_rediscover_dev() treats it as "broadcast flutter" and takes no action
if the SAS address and device type remain unchanged.

This series is based on John Garry's suggestion [1] to check the linkrate
and mark the device as gone and rediscover when flutter occurs, replacing
the previous v2 patch series that used lldd callbacks.

The previous v2 approach added lldd_dev_info_update callback which John
commented as "seem fragile and too specialized" [2]. This series adopts
a simpler approach that directly checks linkrate/sas_addr changes in
sas_rediscover_dev() and triggers rediscovery using libsas's standard
async discovery pattern.

This aligns with Jason Yan's earlier work [3] which was verified to
solve the linkrate change issue.

Additionally, per the discussion in v3 [4], the existing replace code
path also suffers from the same sysfs duplication issue:
sas_unregister_devs_sas_addr() only marks the device as gone, but the
actual sysfs cleanup happens later in sas_destruct_devices(). Calling
sas_discover_new() immediately after unregister causes sysfs_warn_dup()
errors. This series also optimizes the replace path to use the async
pattern, ensuring proper ordering for both flutter and replace cases.

[1] https://lore.kernel.org/linux-scsi/c4e4c99f-a13c-4e28-8650-48be1f96d7cf@oracle.com/
[2] https://lore.kernel.org/linux-scsi/28bd9d5b-f597-0aae-5340-bd951b2083aa@huawei.com/
[3] https://lore.kernel.org/linux-scsi/20190130082412.9357-6-yanaijie@huawei.com/
[4] https://lore.kernel.org/linux-scsi/b99cd59f-b986-432e-aaf1-3b757e1c4c34@oracle.com/
[5] https://lore.kernel.org/linux-scsi/11581a25-caa6-4ea3-9aa0-2a4dacb7f34e@oracle.com/
[6] https://lore.kernel.org/linux-scsi/20260624063230.3264029-1-yangxingui@huawei.com/

Link: https://patch.msgid.link/20260811040334.4184911-1-yangxingui@huawei.com
Signed-off-by: Martin K. Petersen (Oracle) <mkp@kernel.org>

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