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Date: Mon, 4 Dec 2023 18:05:27 +0000
From: John Garry <john.g.garry@...cle.com>
To: Xingui Yang <yangxingui@...wei.com>, yanaijie@...wei.com,
jejb@...ux.ibm.com, martin.petersen@...cle.com,
damien.lemoal@...nsource.wdc.com
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
linuxarm@...wei.com, prime.zeng@...ilicon.com,
chenxiang66@...ilicon.com, kangfenglong@...wei.com
Subject: Re: [PATCH v5 3/3] scsi: libsas: Fix the failure of adding phy with
zero-address to port
On 04/12/2023 12:29, Xingui Yang wrote:
> When the expander device which attached many SATA disks is connected to
> the host, first disable and then enable the local phy. The following BUG()
> will be triggered with a small probability:
>
> [562240.051046] sas: phy19 part of wide port with phy16
Please use code from latest kernel. This again seems to be the old
comment format.
> [562240.051197] sas: ex 500e004aaaaaaa1f phy19:U:0 attached: 0000000000000000 (no device)
The log at 562240.051046 tells that phy19 formed a wideport with phy16,
but then here we see that phy19 has attached SAS address 0. How did we
form a wideport with a phy with sas address 0? Sorry if I asked this
before, but I looked through the thread and it is not clear.
> [562240.051203] sas: done REVALIDATING DOMAIN on port 0, pid:435909, res 0x0
> <...>
> [562240.062536] sas: ex 500e004aaaaaaa1f phy0 new device attached
> [562240.062616] sas: ex 500e004aaaaaaa1f phy00:U:5 attached: 0000000000000000 (stp)
> [562240.062680] port-7:7:0: trying to add phy phy-7:7:19 fails: it's already part of another port
> [562240.085064] ------------[ cut here ]------------
> [562240.096612] kernel BUG at drivers/scsi/scsi_transport_sas.c:1083!
> [562240.109611] Internal error: Oops - BUG: 0 [#1] SMP
> [562240.343518] Process kworker/u256:3 (pid: 435909, stack limit = 0x0000000003bcbebf)
> [562240.421714] Workqueue: 0000:b4:02.0_disco_q sas_revalidate_domain [libsas]
> [562240.437173] pstate: 40c00009 (nZcv daif +PAN +UAO)
> [562240.450478] pc : sas_port_add_phy+0x13c/0x168 [scsi_transport_sas]
> [562240.465283] lr : sas_port_add_phy+0x13c/0x168 [scsi_transport_sas]
> [562240.479751] sp : ffff0000300cfa70
> [562240.674822] Call trace:
> [562240.682709] sas_port_add_phy+0x13c/0x168 [scsi_transport_sas]
> [562240.694013] sas_ex_get_linkrate.isra.5+0xcc/0x128 [libsas]
> [562240.704957] sas_ex_discover_end_dev+0xfc/0x538 [libsas]
> [562240.715508] sas_ex_discover_dev+0x3cc/0x4b8 [libsas]
> [562240.725634] sas_ex_discover_devices+0x9c/0x1a8 [libsas]
> [562240.735855] sas_ex_revalidate_domain+0x2f0/0x450 [libsas]
> [562240.746123] sas_revalidate_domain+0x158/0x160 [libsas]
> [562240.756014] process_one_work+0x1b4/0x448
> [562240.764548] worker_thread+0x54/0x468
> [562240.772562] kthread+0x134/0x138
> [562240.779989] ret_from_fork+0x10/0x18
>
> What causes this problem:
> 1. For phy19, when the phy is attached and added to the parent wide port,
> the path is:
> sas_rediscover()
> ->sas_discover_new()
> ->sas_ex_discover_devices()
> ->sas_ex_discover_dev()
> -> sas_add_parent_port()
>
> ex_phy->port was not set and when it is removed from parent wide port the
> path is:
> sas_rediscover()
> ->sas_unregister_devs_sas_addr()
Sorry, but that is not a callpath. Maybe you condensed it. Please expand it.
>
> Then the sas address of phy19 becomes 0, and since ex_phy->port is NULL,
> phy19 was not removed from the parent wide port's phy_list.
>
> 2. For phy0, it is connected to a new sata device and the path is:
> sas_rediscover()
> ->sas_discover_new()->sas_ex_phy_discover()
> ->sas_ex_phy_discover_helper()
> ->sas_set_ex_phy()
> ->sas_ex_discover_devices()
> ->sas_ex_discover_dev()
> ->sas_ex_discover_end_dev()
> ->sas_port_alloc() // Create port-7:7:0
> ->sas_ex_get_linkrate()
> ->sas_port_add_phy()
>
> The type of the newly connected device is stp, but the linkrate is 5 which
> less than 1.5G, then the sas address is set to 0 in sas_set_ex_phy().
I don't understand why we do anything when in this state. linkrate == 5
means phy reset in progress. Can we just bail out until the SATA phy is
in a decent shape? I assume that when the SATA phy is in "up" state that
we get a broadcast event and can re-evaluate.
> Subsequently, a new port port-7:7:0 was created and tried to add phy19 with
> the same zero-address to this new port. However, phy19 still belongs to
> another port, then a BUG() was triggered in sas_ex_get_linkrate().
>
> Fix the problem as follows:
> 1. Use sas_port_add_ex_phy() instead of sas_port_add_phy() when ex_phy is
> added to the parent port.
this seems ok
>
> 2. Set ex_dev->parent_port to NULL when the number of phy on the port
> becomes 0.
>
> 3. When phy->attached_dev_type != NO_DEVICE, do not set the zero address
> for phy->attached_sas_addr.
>
> Fixes: 2908d778ab3e ("[SCSI] aic94xx: new driver")
> Fixes: 7d1d86518118 ("[SCSI] libsas: fix false positive 'device attached' conditions")
> Signed-off-by: Xingui Yang <yangxingui@...wei.com>
> ---
> drivers/scsi/libsas/sas_expander.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> index 7aa968b85e1e..9152152d5e10 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -45,7 +45,7 @@ static void sas_add_parent_port(struct domain_device *dev, int phy_id)
> BUG_ON(sas_port_add(ex->parent_port));
> sas_port_mark_backlink(ex->parent_port);
> }
> - sas_port_add_phy(ex->parent_port, ex_phy->phy);
> + sas_port_add_ex_phy(ex->parent_port, ex_phy);
> }
>
> /* ---------- SMP task management ---------- */
> @@ -261,8 +261,7 @@ static void sas_set_ex_phy(struct domain_device *dev, int phy_id,
> /* help some expanders that fail to zero sas_address in the 'no
> * device' case
> */
Please pay attention to this comment. It seems that some expanders
require us to explicitly zero the SAS address.
> - if (phy->attached_dev_type == SAS_PHY_UNUSED ||
> - phy->linkrate < SAS_LINK_RATE_1_5_GBPS)
> + if (phy->attached_dev_type == SAS_PHY_UNUSED)
> memset(phy->attached_sas_addr, 0, SAS_ADDR_SIZE);
> else
> memcpy(phy->attached_sas_addr, dr->attached_sas_addr, SAS_ADDR_SIZE);
> @@ -1864,9 +1863,12 @@ static void sas_unregister_devs_sas_addr(struct domain_device *parent,
> if (phy->port) {
> sas_port_delete_phy(phy->port, phy->phy);
> sas_device_set_phy(found, phy->port);
> - if (phy->port->num_phys == 0)
> + if (phy->port->num_phys == 0) {
> list_add_tail(&phy->port->del_list,
> &parent->port->sas_port_del_list);
> + if (ex_dev->parent_port == phy->port)
> + ex_dev->parent_port = NULL;
This does not feel like the right place to do this. So the port which we
queue to free is the ex_dev->parent_port, right?
BTW, do you know why it's called ex_dev->parent_port and not
ex_dev->port? I find the name parent_port confusing...
Thanks,
John
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