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SubjectRe: [PATCH v2 7/7] scsi: libsas: fix issue of swapping two sas disks
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Date
On 30/01/2019 08:24, Jason Yan wrote:
> The work flow of revalidation now is scanning expander phy by the
> sequence of the phy and check if the phy have changed. This will leads
> to an issue of swapping two sas disks on one expander.
>
> Assume we have two sas disks, connected with expander phy10 and phy11:
>
> phy10: 5000cca04eb1001d port-0:0:10
> phy11: 5000cca04eb043ad port-0:0:11
>
> Swap these two disks, and imaging the following scenario:
>
> revalidation 1:

What does "revalidation 1" actually mean?

> -->phy10: 0 --> delete phy10 domain device
> -->phy11: 5000cca04eb043ad (no change)

so is disk 11 still inserted at this stage?

> revalidation done
>
> revalidation 2:

is port-0:0:10 deleted now?

> -->step 1, check phy10:
> -->phy10: 5000cca04eb043ad --> add to wide port(port-0:0:11) (phy11
> address is still 5000cca04eb043ad now)

So this should not happen. How are you physcially swapping them such
that phy11 address is still 5000cca04eb043ad? I don't see how this would
be true at revalidation 1.

>
> -->step 2, check phy11:
> -->phy11: 0 --> phy11 address is 0 now, but it's part of wide
> port(port-0:0:11), the domain device will not be deleted.
> revalidation done
>
> revalidation 3:
> -->phy10, 5000cca04eb043ad (no change)
> -->phy11: 5000cca04eb1001d --> try to add port-0:0:11 but failed,
> port-0:0:11 already exist, trigger a warning as follows
> revalidation done
>
> [14790.189699] sysfs: cannot create duplicate filename
> '/devices/pci0000:74/0000:74:02.0/host0/port-0:0/expander-0:0/port-0:0:11'
> [14790.201081] CPU: 25 PID: 5031 Comm: kworker/u192:3 Not tainted
> 4.16.0-rc1-191134-g138f084-dirty #228
> [14790.210199] Hardware name: Huawei D06/D06, BIOS Hisilicon D06 EC UEFI
> Nemo 2.0 RC0 - B303 05/16/2018
> [14790.219323] Workqueue: 0000:74:02.0_disco_q sas_revalidate_domain
> [14790.225404] Call trace:
> [14790.227842] dump_backtrace+0x0/0x18c
> [14790.231492] show_stack+0x14/0x1c
> [14790.234798] dump_stack+0x88/0xac
> [14790.238101] sysfs_warn_dup+0x64/0x7c
> [14790.241751] sysfs_create_dir_ns+0x90/0xa0
> [14790.245835] kobject_add_internal+0xa0/0x284
> [14790.250092] kobject_add+0xb8/0x11c
> [14790.253570] device_add+0xe8/0x598
> [14790.256960] sas_port_add+0x24/0x50
> [14790.260436] sas_ex_discover_devices+0xb10/0xc30
> [14790.265040] sas_ex_revalidate_domain+0x1d8/0x518
> [14790.269731] sas_revalidate_domain+0x12c/0x154
> [14790.274163] process_one_work+0x128/0x2b0
> [14790.278160] worker_thread+0x14c/0x408
> [14790.281897] kthread+0xfc/0x128
> [14790.285026] ret_from_fork+0x10/0x18
> [14790.288598] ------------[ cut here ]------------
>
> At last, the disk 5000cca04eb1001d is lost.
>
> The basic idea of fix this issue is to let the revalidation first scan
> all phys, and then unregisterring devices. Only when no devices need to
> be unregisterred, go to the next step to discover new devices. If there
> are devices need unregister, unregister those devices and tell the
> revalidation event processor to retry again. The next revalidation will
> process the discovering of the new devices.
>
> Tested-by: Chen Liangfei <chenliangfei1@huawei.com>
> Signed-off-by: Jason Yan <yanaijie@huawei.com>
> CC: Xiaofei Tan <tanxiaofei@huawei.com>
> CC: chenxiang <chenxiang66@hisilicon.com>
> CC: John Garry <john.garry@huawei.com>
> CC: Johannes Thumshirn <jthumshirn@suse.de>
> CC: Ewan Milne <emilne@redhat.com>
> CC: Christoph Hellwig <hch@lst.de>
> CC: Tomas Henzl <thenzl@redhat.com>
> CC: Dan Williams <dan.j.williams@intel.com>
> CC: Hannes Reinecke <hare@suse.com>
> ---
> drivers/scsi/libsas/sas_expander.c | 146 +++++++++++++++++++++++++------------
> 1 file changed, 100 insertions(+), 46 deletions(-)
>
> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> index e781941a7088..073bb5c6e353 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -2056,7 +2056,7 @@ static bool sas_process_flutter(struct domain_device *dev, struct ex_phy *phy,
> return true;
> }
>
> -static int sas_unregister(struct domain_device *dev, int phy_id, bool last,
> +static int sas_ex_unregister(struct domain_device *dev, int phy_id, bool last,
> bool *retry)
> {
> struct expander_device *ex = &dev->ex_dev;
> @@ -2108,21 +2108,8 @@ static int sas_unregister(struct domain_device *dev, int phy_id, bool last,
> return 0;
> }
>
> -/**
> - * sas_rediscover - revalidate the domain.
> - * @dev:domain device to be detect.
> - * @phy_id: the phy id will be detected.
> - *
> - * NOTE: this process _must_ quit (return) as soon as any connection
> - * errors are encountered. Connection recovery is done elsewhere.
> - * Discover process only interrogates devices in order to discover the
> - * domain.For plugging out, we un-register the device only when it is
> - * the last phy in the port, for other phys in this port, we just delete it
> - * from the port.For inserting, we do discovery when it is the
> - * first phy,for other phys in this port, we add it to the port to
> - * forming the wide-port.
> - */
> -static void sas_rediscover(struct domain_device *dev, const int phy_id,
> +
> +static void sas_ex_unregister_device(struct domain_device *dev, const int phy_id,
> bool *retry)
> {
> struct expander_device *ex = &dev->ex_dev;
> @@ -2131,31 +2118,70 @@ static void sas_rediscover(struct domain_device *dev, const int phy_id,
> int i;
> bool last = true; /* is this the last phy of the port */
>
> - pr_debug("ex %016llx phy%d originated BROADCAST(CHANGE)\n",
> - SAS_ADDR(dev->sas_addr), phy_id);
> -
> - if (SAS_ADDR(changed_phy->attached_sas_addr) != 0) {
> - for (i = 0; i < ex->num_phys; i++) {
> - struct ex_phy *phy = &ex->ex_phy[i];
> + for (i = 0; i < ex->num_phys; i++) {
> + struct ex_phy *phy = &ex->ex_phy[i];
>
> - if (i == phy_id)
> - continue;
> - if (SAS_ADDR(phy->attached_sas_addr) ==
> - SAS_ADDR(changed_phy->attached_sas_addr)) {
> - pr_debug("phy%d part of wide port with phy%d\n",
> - phy_id, i);
> - last = false;
> - break;
> - }
> + if (i == phy_id)
> + continue;
> + if (SAS_ADDR(phy->attached_sas_addr) ==
> + SAS_ADDR(changed_phy->attached_sas_addr)) {
> + pr_debug("phy%d part of wide port with phy%d\n",
> + phy_id, i);
> + last = false;
> + break;
> }
> - res = sas_unregister(dev, phy_id, last, retry);
> - } else
> - res = sas_discover_new(dev, phy_id);
> + }
> + res = sas_ex_unregister(dev, phy_id, last, retry);
>
> pr_debug("ex %016llx phy%d discover returned 0x%x\n",
> SAS_ADDR(dev->sas_addr), phy_id, res);
> }
>
> +static int sas_ex_try_unregister(struct domain_device *dev, u8 *changed_phy,
> + int nr, bool *retry)
> +{
> + struct expander_device *ex = &dev->ex_dev;
> + int unregistered = 0;
> + struct ex_phy *phy;
> + int i;
> +
> + for (i = 0; i < nr; i++) {
> + pr_debug("ex %016llx phy%d originated BROADCAST(CHANGE)\n",
> + SAS_ADDR(dev->sas_addr), changed_phy[i]);
> +
> + phy = &ex->ex_phy[changed_phy[i]];
> +
> + if (SAS_ADDR(phy->attached_sas_addr) == 0)
> + continue;
> +
> + sas_ex_unregister_device(dev, changed_phy[i], retry);
> + changed_phy[i] = 0xff;
> + unregistered++;
> + }
> + return unregistered;
> +}
> +
> +static void sas_ex_register(struct domain_device *dev, u8 *changed_phy,
> + int nr)
> +{
> + struct expander_device *ex = &dev->ex_dev;
> + struct ex_phy *phy;
> + int res = 0;
> + int i;
> +
> + for (i = 0; i < nr; i++) {
> + if (changed_phy[i] == 0xff)
> + continue;
> +
> + phy = &ex->ex_phy[changed_phy[i]];
> +
> + res = sas_discover_new(dev, changed_phy[i]);
> +
> + pr_debug("ex %016llx phy%d register returned 0x%x\n",
> + SAS_ADDR(dev->sas_addr), changed_phy[i], res);
> + }
> +}
> +
> /**
> * sas_ex_revalidate_domain - revalidate the domain
> * @port_dev: port domain device.
> @@ -2170,21 +2196,49 @@ void sas_ex_revalidate_domain(struct domain_device *port_dev, bool *retry)
> {
> int res;
> struct domain_device *dev = NULL;
> + u8 changed_phy[MAX_EXPANDER_PHYS];
> + struct expander_device *ex;
> + int unregistered = 0;
> + int phy_id;
> + int nr = 0;
> + int i = 0;
>
> res = sas_find_bcast_dev(port_dev, &dev);
> - if (res == 0 && dev) {
> - struct expander_device *ex = &dev->ex_dev;
> - int i = 0, phy_id;
> -
> - do {
> - phy_id = -1;
> - res = sas_find_bcast_phy(dev, &phy_id, i, true);
> - if (phy_id == -1)
> - break;
> - sas_rediscover(dev, phy_id, retry);
> - i = phy_id + 1;
> - } while (i < ex->num_phys);
> + if (res || !dev)
> + return;
> +
> + memset(changed_phy, 0xff, MAX_EXPANDER_PHYS);
> + ex = &dev->ex_dev;
> +
> + do {
> + phy_id = -1;
> + res = sas_find_bcast_phy(dev, &phy_id, i, true);
> + if (phy_id == -1)
> + break;
> + changed_phy[nr++] = phy_id;
> + i = phy_id + 1;
> + } while (i < dev->ex_dev.num_phys);
> +
> + if (nr == 0)
> + return;
> +
> + unregistered = sas_ex_try_unregister(dev, changed_phy, nr, retry);
> +
> + if (unregistered > 0) {
> + struct ex_phy *phy;
> +
> + for (i = 0; i < nr; i++) {
> + if (changed_phy[i] == 0xff)
> + continue;
> + phy = &ex->ex_phy[changed_phy[i]];
> + phy->phy_change_count = -1;
> + }
> + ex->ex_change_count = -1;
> + *retry = true;
> + return;
> }
> +
> + sas_ex_register(dev, changed_phy, nr);
> }
>
> void sas_smp_handler(struct bsg_job *job, struct Scsi_Host *shost,
>


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