[PATCHv6 RFC 0/3] Add visibility for native NVMe multipath using sysfs

[Keith Busch]

On Wed, Jan 08, 2025 at 09:47:48AM -0700, Keith Busch wrote:
> On Fri, Dec 13, 2024 at 09:48:33AM +0530, Nilay Shroff wrote:
> > This RFC propose adding new sysfs attributes for adding visibility of
> > nvme native multipath I/O.
> > 
> > The changes are divided into three patches.
> > The first patch adds visibility for round-robin io-policy.
> > The second patch adds visibility for numa io-policy.
> > The third patch adds the visibility for queue-depth io-policy.
> 
> Thanks, applied to nvme-6.14.

I think I have to back this out of nvme-6.14 for now. This appears to be
causing a problem with blktests, test case trtype = loop nvme/058, as
reported by Chaitanya.

Here's a snippet of the kernel messages related to this:

[ 9031.706759] sysfs: cannot create duplicate filename '/devices/virtual/nvme-subsystem/nvme-subsys1/nvme1n2/multipath/nvme1c4n2'
[ 9031.706767] CPU: 41 UID: 0 PID: 52494 Comm: kworker/u192:61 Tainted:G        W  O     N 6.13.0-rc4nvme+ #109
[ 9031.706775] Tainted: [W]=WARN, [O]=OOT_MODULE, [N]=TEST
[ 9031.706777] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 9031.706781] Workqueue: async async_run_entry_fn
[ 9031.706790] Call Trace:
[ 9031.706795]  <TASK>
[ 9031.706798]  dump_stack_lvl+0x94/0xb0
[ 9031.706806]  sysfs_warn_dup+0x5b/0x70
[ 9031.706812]  sysfs_do_create_link_sd+0xce/0xe0
[ 9031.706817]  sysfs_add_link_to_group+0x35/0x60
[ 9031.706823]  nvme_mpath_add_sysfs_link+0xc3/0x160 [nvme_core]
[ 9031.706848]  nvme_mpath_set_live+0xb9/0x1f0 [nvme_core]
[ 9031.706865]  nvme_mpath_add_disk+0x10b/0x130 [nvme_core]
[ 9031.706883]  nvme_alloc_ns+0x8d5/0xc80 [nvme_core]
[ 9031.706904]  nvme_scan_ns+0x280/0x350 [nvme_core]
[ 9031.706920]  ? do_raw_spin_unlock+0x4e/0xc0
[ 9031.706929]  async_run_entry_fn+0x31/0x130
[ 9031.706934]  process_one_work+0x1f9/0x630
[ 9031.706943]  worker_thread+0x191/0x330
[ 9031.706948]  ? __pfx_worker_thread+0x10/0x10
[ 9031.706952]  kthread+0xe1/0x120
[ 9031.706956]  ? __pfx_kthread+0x10/0x10
[ 9031.706959]  ret_from_fork+0x31/0x50
[ 9031.706965]  ? __pfx_kthread+0x10/0x10
[ 9031.706968]  ret_from_fork_asm+0x1a/0x30
[ 9031.706980]  </TASK>
[ 9031.707062] block nvme1n2: failed to create link to nvme1c4n2