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Henry Tseng 9443fe6d05 ata: libata: avoid long timeouts on hot-unplugged SATA DAS 
[ Upstream commit 151cabd140 ]

When a SATA DAS enclosure is connected behind a Thunderbolt PCIe
switch, hot-unplugging the whole enclosure causes pciehp to tear down
the PCI hierarchy before the SCSI layer issues SYNCHRONIZE CACHE and
START STOP UNIT for the disks.

libata still queues these commands and the AHCI driver tries to access
the HBA registers even though the PCI channel is already offline. This
results in a series of timeouts and error recovery attempts, e.g.:

  [  824.778346] pcieport 0000:00:07.0: pciehp: Slot(14): Link Down
  [  891.612720] ata8.00: qc timeout after 5000 msecs (cmd 0xec)
  [  902.876501] ata8.00: qc timeout after 10000 msecs (cmd 0xec)
  [  934.107998] ata8.00: qc timeout after 30000 msecs (cmd 0xec)
  [  936.206431] sd 7:0:0:0: [sda] Synchronize Cache(10) failed:
      Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
  ...
  [ 1006.298356] ata1.00: qc timeout after 5000 msecs (cmd 0xec)
  [ 1017.561926] ata1.00: qc timeout after 10000 msecs (cmd 0xec)
  [ 1048.791790] ata1.00: qc timeout after 30000 msecs (cmd 0xec)
  [ 1050.890035] sd 0:0:0:0: [sdb] Synchronize Cache(10) failed:
      Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK

With this patch applied, the same hot-unplug looks like:

  [   59.965496] pcieport 0000:00:07.0: pciehp: Slot(14): Link Down
  [   60.002502] sd 7:0:0:0: [sda] Synchronize Cache(10) failed:
      Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
  ...
  [   60.103050] sd 0:0:0:0: [sdb] Synchronize Cache(10) failed:
      Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK

In this test setup with two disks, the hot-unplug sequence shrinks from
about 226 seconds (~3.8 minutes) between the Link Down event and the
last SYNCHRONIZE CACHE failure to under a second. Without this patch the
total delay grows roughly with the number of disks, because each disk
gets its own SYNCHRONIZE CACHE and qc timeout series.

If the underlying PCI device is already gone, these commands cannot
succeed anyway. Avoid issuing them by introducing
ata_adapter_is_online(), which checks pci_channel_offline() for
PCI-based hosts. It is used from ata_scsi_find_dev() to return NULL,
causing the SCSI layer to fail new commands with DID_BAD_TARGET
immediately, and from ata_qc_issue() to bail out before touching the
HBA registers.

Since such failures would otherwise trigger libata error handling,
ata_adapter_is_online() is also consulted from ata_scsi_port_error_handler().
When the adapter is offline, libata skips ap->ops->error_handler(ap) and
completes error handling using the existing path, rather than running
a full EH sequence against a dead adapter.

With this change, SYNCHRONIZE CACHE and START STOP UNIT commands
issued during hot-unplug fail quickly once the PCI channel is offline,
without qc timeout spam or long libata EH delays.

Suggested-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Henry Tseng <henrytseng@qnap.com>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-04 07:20:28 -05:00
arch um: Preserve errno within signal handler 2026-03-04 07:20:28 -05:00
block block: decouple secure erase size limit from discard size limit 2026-03-04 07:19:38 -05:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation hwmon: (nct6683) Add customer ID for ASRock Z590 Taichi 2026-03-04 07:20:06 -05:00
drivers ata: libata: avoid long timeouts on hot-unplugged SATA DAS 2026-03-04 07:20:28 -05:00
fs ext4: propagate flags to convert_initialized_extent() 2026-03-04 07:20:21 -05:00
include PCI/bwctrl: Disable BW controller on Intel P45 using a quirk 2026-03-04 07:20:27 -05:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/timeout: annotate data race in io_flush_timeouts() 2026-03-04 07:19:36 -05:00
ipc ipc: don't audit capability check in ipc_permissions() 2026-02-26 14:59:19 -08:00
kernel cgroup/cpuset: Don't fail cpuset.cpus change in v2 2026-03-04 07:19:56 -05:00
lib objpool: fix the overestimation of object pooling metadata size 2026-02-26 14:59:36 -08:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/slab: fix false lockdep warning in __kfree_rcu_sheaf() 2026-02-26 14:59:14 -08:00
net net/rds: Clear reconnect pending bit 2026-03-04 07:20:26 -05:00
rust rust: cpufreq: always inline functions using build_assert with arguments 2026-03-04 07:19:37 -05:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts modpost: Amend ppc64 save/restfpr symnames for -Os build 2026-03-04 07:20:07 -05:00
security apparmor: fix aa_label to return state from compount and component match 2026-02-26 14:59:42 -08:00
sound ALSA: usb-audio: Add iface reset and delay quirk for AB13X USB Audio 2026-03-04 07:20:09 -05:00
tools rtla: Fix NULL pointer dereference in actions_parse 2026-03-04 07:20:13 -05:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:41:44 +01:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.15 2026-02-27 16:05:10 -05:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.