Re: [PATCH v2 0/3] ata,sd: Fix reading concurrent positioning ranges

Damien Le Moal
2022-06-03T01:31:15Z

On 6/3/22 07:51, Tyler Erickson wrote:
> This patch series fixes reading the concurrent positioning ranges.
>
> The first patch fixes reading this in libata, where it was reading
> more data than a drive necessarily supports, resulting in a
> command abort.
>
> The second patch fixes the SCSI translated data to put the VPD page
> length in the correct starting byte.
>
> The third patch in sd, the fix is adding 4 instead of 3 for the header
> length. Using 3 will always result in an error and was likely used
> incorrectly as T10 specifications list all tables starting at byte 0,
> and byte 3 is the page length, which would mean there are 4 total
> bytes before the remaining data that contains the ranges and other
> information.
>
> Tyler Erickson (3):
> libata: fix reading concurrent positioning ranges log
> libata: fix translation of concurrent positioning ranges
> scsi: sd: Fix interpretation of VPD B9h length
>
> drivers/ata/libata-core.c | 21 +++++++++++++--------
> drivers/ata/libata-scsi.c | 2 +-
> drivers/scsi/sd.c | 2 +-
> 3 files changed, 15 insertions(+), 10 deletions(-)
>
>
> base-commit: 700170bf6b4d773e328fa54ebb70ba444007c702

Looks all good to me. I tested this and really wonder how I did not catch
these mistakes earlier :)

Using a tcmu emulator for various concurrent positioning range configs to
test, I got a lockdep splat when unplugging the drive:

[ 760.702859] ======================================================
[ 760.702863] WARNING: possible circular locking dependency detected
[ 760.702868] 5.18.0+ #1509 Not tainted
[ 760.702875] ------------------------------------------------------
[...]
[ 760.702966] the existing dependency chain (in reverse order) is:
[ 760.702969]
[ 760.702969] -> #1 (&q->sysfs_lock){+.+.}-{3:3}:
[ 760.702982] __mutex_lock+0x15b/0x1480
[ 760.702998] blk_ia_range_sysfs_show+0x41/0xc0
[ 760.703010] sysfs_kf_seq_show+0x1f2/0x360
[ 760.703022] seq_read_iter+0x40f/0x1130
[ 760.703036] new_sync_read+0x2d8/0x520
[ 760.703049] vfs_read+0x31a/0x450
[ 760.703060] ksys_read+0xf7/0x1d0
[ 760.703070] do_syscall_64+0x34/0x80
[ 760.703081] entry_SYSCALL_64_after_hwframe+0x46/0xb0
[ 760.703093]
[ 760.703093] -> #0 (kn->active#385){++++}-{0:0}:
[ 760.703108] __lock_acquire+0x2ba6/0x6a20
[ 760.703125] lock_acquire+0x19f/0x510
[ 760.703136] __kernfs_remove+0x739/0x940
[ 760.703145] kernfs_remove_by_name_ns+0x90/0xe0
[ 760.703154] remove_files+0x8c/0x1a0
[ 760.703165] sysfs_remove_group+0x77/0x150
[ 760.703175] sysfs_remove_groups+0x4f/0x90
[ 760.703186] __kobject_del+0x7d/0x1b0
[ 760.703196] kobject_del+0x31/0x50
[ 760.703203] disk_unregister_independent_access_ranges+0x153/0x290
[ 760.703214] blk_unregister_queue+0x166/0x210
[ 760.703226] del_gendisk+0x2f8/0x7c0
[ 760.703233] sd_remove+0x5e/0xb0 [sd_mod]
[ 760.703252] device_release_driver_internal+0x3ad/0x750
[ 760.703262] bus_remove_device+0x2a6/0x570
[ 760.703269] device_del+0x48f/0xb50
[ 760.703280] __scsi_remove_device+0x21b/0x2b0 [scsi_mod]
[ 760.703339] scsi_remove_device+0x3a/0x50 [scsi_mod]
[ 760.703391] tcm_loop_port_unlink+0xca/0x160 [tcm_loop]
[ 760.703407] target_fabric_port_unlink+0xd5/0x120 [target_core_mod]
[ 760.703494] configfs_unlink+0x37f/0x7a0
[ 760.703502] vfs_unlink+0x295/0x800
[ 760.703514] do_unlinkat+0x2d9/0x560
[ 760.703520] __x64_sys_unlink+0xa5/0xf0
[ 760.703528] do_syscall_64+0x34/0x80
[ 760.703537] entry_SYSCALL_64_after_hwframe+0x46/0xb0
[ 760.703548]
[ 760.703548] other info that might help us debug this:
[ 760.703548]
[ 760.703551] Possible unsafe locking scenario:
[ 760.703551]
[ 760.703554] CPU0 CPU1
[ 760.703556] ---- ----
[ 760.703558] lock(&q->sysfs_lock);
[ 760.703565] lock(kn->active#385);
[ 760.703573] lock(&q->sysfs_lock);
[ 760.703579] lock(kn->active#385);
[ 760.703587]
[ 760.703587] *** DEADLOCK ***

This needs to be checked too, but that is not related to your fixes.

I will queue the libata patches for rc1 update.

Martin,

Do you want to take patch 3 or should I just take it ?

--
Damien Le Moal
Western Digital Research