kernel/linux.git/drivers/ata/libata-eh.c, branch v6.19.11

ata: libata-eh: Fix detection of deferred qc timeouts

2026-03-12T11:10:01+00:00

[ Upstream commit ee0e6e69a772d601e152e5368a1da25d656122a8 ] If the ata_qc_for_each_raw() loop finishes without finding a matching SCSI command for any QC, the variable qc will hold a pointer to the last element examined, which has the tag i == ATA_MAX_QUEUE - 1. This qc can match the port deferred QC (ap->deferred_qc). If that happens, the condition qc == ap->deferred_qc evaluates to true despite the loop not breaking with a match on the SCSI command for this QC. In that case, the error handler mistakenly intercepts a command that has not been issued yet and that has not timed out, and thus erroneously returning a timeout error. Fix the problem by checking for i < ATA_MAX_QUEUE in addition to qc == ap->deferred_qc. The problem was found by an experimental code review agent based on gemini-3.1-pro while reviewing backports into v6.18.y. Assisted-by: Gemini:gemini-3.1-pro Fixes: eddb98ad9364 ("ata: libata-eh: correctly handle deferred qc timeouts") Signed-off-by: Guenter Roeck [cassel: modified commit log as suggested by Damien] Reviewed-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Sasha Levin

ata: libata: cancel pending work after clearing deferred_qc

2026-03-12T11:09:54+00:00

[ Upstream commit aac9b27f7c1f2b2cf7f50a9ca633ecbbcaf22af9 ] Syzbot reported a WARN_ON() in ata_scsi_deferred_qc_work(), caused by ap->ops->qc_defer() returning non-zero before issuing the deferred qc. ata_scsi_schedule_deferred_qc() is called during each command completion. This function will check if there is a deferred QC, and if ap->ops->qc_defer() returns zero, meaning that it is possible to queue the deferred qc at this time (without being deferred), then it will queue the work which will issue the deferred qc. Once the work get to run, which can potentially be a very long time after the work was scheduled, there is a WARN_ON() if ap->ops->qc_defer() returns non-zero. While we hold the ap->lock both when assigning and clearing deferred_qc, and the work itself holds the ap->lock, the code currently does not cancel the work after clearing the deferred qc. This means that the following scenario can happen: 1) One or several NCQ commands are queued. 2) A non-NCQ command is queued, gets stored in ap->deferred_qc. 3) Last NCQ command gets completed, work is queued to issue the deferred qc. 4) Timeout or error happens, ap->deferred_qc is cleared. The queued work is currently NOT canceled. 5) Port is reset. 6) One or several NCQ commands are queued. 7) A non-NCQ command is queued, gets stored in ap->deferred_qc. 8) Work is finally run. Yet at this time, there is still NCQ commands in flight. The work in 8) really belongs to the non-NCQ command in 2), not to the non-NCQ command in 7). The reason why the work is executed when it is not supposed to, is because it was never canceled when ap->deferred_qc was cleared in 4). Thus, ensure that we always cancel the work after clearing ap->deferred_qc. Another potential fix would have been to let ata_scsi_deferred_qc_work() do nothing if ap->ops->qc_defer() returns non-zero. However, canceling the work when clearing ap->deferred_qc seems slightly more logical, as we hold the ap->lock when clearing ap->deferred_qc, so we know that the work cannot be holding the lock. (The function could be waiting for the lock, but that is okay since it will do nothing if ap->deferred_qc is not set.) Reported-by: syzbot+bcaf842a1e8ead8dfb89@syzkaller.appspotmail.com Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Fixes: eddb98ad9364 ("ata: libata-eh: correctly handle deferred qc timeouts") Reviewed-by: Igor Pylypiv Reviewed-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Sasha Levin

ata: libata: avoid long timeouts on hot-unplugged SATA DAS

2026-03-04T12:20:34+00:00

[ Upstream commit 151cabd140322205e27dae5c4bbf261ede0056e3 ] 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 Signed-off-by: Henry Tseng Signed-off-by: Damien Le Moal Signed-off-by: Sasha Levin

ata: libata-eh: correctly handle deferred qc timeouts

2026-02-26T23:01:41+00:00

commit eddb98ad9364b4e778768785d46cfab04ce52100 upstream. A deferred qc may timeout while waiting for the device queue to drain to be submitted. In such case, since the qc is not active, ata_scsi_cmd_error_handler() ends up calling scsi_eh_finish_cmd(), which frees the qc. But as the port deferred_qc field still references this finished/freed qc, the deferred qc work may eventually attempt to call ata_qc_issue() against this invalid qc, leading to errors such as reported by UBSAN (syzbot run): UBSAN: shift-out-of-bounds in drivers/ata/libata-core.c:5166:24 shift exponent 4210818301 is too large for 64-bit type 'long long unsigned int' ... Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 ubsan_epilogue+0xa/0x30 lib/ubsan.c:233 __ubsan_handle_shift_out_of_bounds+0x279/0x2a0 lib/ubsan.c:494 ata_qc_issue.cold+0x38/0x9f drivers/ata/libata-core.c:5166 ata_scsi_deferred_qc_work+0x154/0x1f0 drivers/ata/libata-scsi.c:1679 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275 process_scheduled_works kernel/workqueue.c:3358 [inline] worker_thread+0x5da/0xe40 kernel/workqueue.c:3439 kthread+0x370/0x450 kernel/kthread.c:467 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Fix this by checking if the qc of a timed out SCSI command is a deferred one, and in such case, clear the port deferred_qc field and finish the SCSI command with DID_TIME_OUT. Reported-by: syzbot+1f77b8ca15336fff21ff@syzkaller.appspotmail.com Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Signed-off-by: Damien Le Moal Reviewed-by: Hannes Reinecke Reviewed-by: Igor Pylypiv Signed-off-by: Greg Kroah-Hartman

ata: libata-scsi: avoid Non-NCQ command starvation

2026-02-26T23:01:40+00:00

commit 0ea84089dbf62a92dc7889c79e6b18fc89260808 upstream. When a non-NCQ command is issued while NCQ commands are being executed, ata_scsi_qc_issue() indicates to the SCSI layer that the command issuing should be deferred by returning SCSI_MLQUEUE_XXX_BUSY. This command deferring is correct and as mandated by the ACS specifications since NCQ and non-NCQ commands cannot be mixed. However, in the case of a host adapter using multiple submission queues, when the target device is under a constant load of NCQ commands, there are no guarantees that requeueing the non-NCQ command will be executed later and it may be deferred again repeatedly as other submission queues can constantly issue NCQ commands from different CPUs ahead of the non-NCQ command. This can lead to very long delays for the execution of non-NCQ commands, and even complete starvation for these commands in the worst case scenario. Since the block layer and the SCSI layer do not distinguish between queueable (NCQ) and non queueable (non-NCQ) commands, libata-scsi SAT implementation must ensure forward progress for non-NCQ commands in the presence of NCQ command traffic. This is similar to what SAS HBAs with a hardware/firmware based SAT implementation do. Implement such forward progress guarantee by limiting requeueing of non-NCQ commands from ata_scsi_qc_issue(): when a non-NCQ command is received and NCQ commands are in-flight, do not force a requeue of the non-NCQ command by returning SCSI_MLQUEUE_XXX_BUSY and instead return 0 to indicate that the command was accepted but hold on to the qc using the new deferred_qc field of struct ata_port. This deferred qc will be issued using the work item deferred_qc_work running the function ata_scsi_deferred_qc_work() once all in-flight commands complete, which is checked with the port qc_defer() callback return value indicating that no further delay is necessary. This check is done using the helper function ata_scsi_schedule_deferred_qc() which is called from ata_scsi_qc_complete(). This thus excludes this mechanism from all internal non-NCQ commands issued by ATA EH. When a port deferred_qc is non NULL, that is, the port has a command waiting for the device queue to drain, the issuing of all incoming commands (both NCQ and non-NCQ) is deferred using the regular busy mechanism. This simplifies the code and also avoids potential denial of service problems if a user issues too many non-NCQ commands. Finally, whenever ata EH is scheduled, regardless of the reason, a deferred qc is always requeued so that it can be retried once EH completes. This is done by calling the function ata_scsi_requeue_deferred_qc() from ata_eh_set_pending(). This avoids the need for any special processing for the deferred qc in case of NCQ error, link or device reset, or device timeout. Reported-by: Xingui Yang Reported-by: Igor Pylypiv Fixes: bdb01301f3ea ("scsi: Add host and host template flag 'host_tagset'") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel Reviewed-by: Martin K. Petersen Reviewed-by: John Garry Tested-by: Igor Pylypiv Tested-by: Xingui Yang Signed-off-by: Greg Kroah-Hartman

ata: libata-eh: Fix link state check for IDE/PATA ports

2025-08-14T09:42:16+00:00

Commit 4371fe1ba400 ("ata: libata-eh: Avoid unnecessary resets when revalidating devices") replaced the call to ata_phys_link_offline() in ata_eh_revalidate_and_attach() with the new function ata_eh_link_established() which relaxes the checks on a device link state to account for low power mode transitions. However, this change assumed that the device port has a valid scr_read method to obtain the SStatus register for the port. This is not always the case, especially with older IDE/PATA adapters (e.g. PATA/IDE devices emulated with QEMU). For such adapter, ata_eh_link_established() will always return false, causing ata_eh_revalidate_and_attach() to go into its error path and ultimately to the device being disabled. Avoid this by restoring the previous behavior, which is to assume that the link is online if reading the port SStatus register fails. While at it, also fix the spelling of SStatus in the comment describing the function ata_eh_link_established(). Reported-by: Shin'ichiro Kawasaki Fixes: 4371fe1ba400 ("ata: libata-eh: Avoid unnecessary resets when revalidating devices") Signed-off-by: Damien Le Moal Tested-by: Shin'ichiro Kawasaki Reviewed-by: Niklas Cassel

ata: libata-eh: Simplify reset operation management

2025-07-16T07:31:43+00:00

Introduce struct ata_reset_operations to aggregate in a single structure the definitions of the 4 reset methods (prereset, softreset, hardreset and postreset) for a port. This new structure is used in struct ata_port to define the reset methods for a regular port (reset field) and for a port-multiplier port (pmp_reset field). A pointer to either of these fields replaces the 4 reset method arguments passed to ata_eh_recover() and ata_eh_reset(). The definition of the reset methods for all drivers is changed to use the reset and pmp_reset fields in struct ata_port_operations. A large number of files is modifed, but no functional changes are introduced. Suggested-by: Niklas Cassel Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel Reviewed-by: Martin K. Petersen Reviewed-by: Hannes Reinecke Link: https://lore.kernel.org/r/20250716020315.235457-3-dlemoal@kernel.org Signed-off-by: Niklas Cassel

ata: libata-eh: Remove ata_do_eh()

2025-07-16T07:31:43+00:00

The only reason for ata_do_eh() to exist is that the two caller sites, ata_std_error_handler() and ata_sff_error_handler() may pass it a NULL hardreset operation so that the built-in (generic) hardreset operation for a driver is ignored if the adapter SCR access is not available. However, ata_std_error_handler() and ata_sff_error_handler() modifications of the hardreset port operation can easily be combined as they are mutually exclusive. That is, a driver using sata_std_hardreset() as its hardreset operation cannot use sata_sff_hardreset() and vice-versa. With this observation, ata_do_eh() can be removed and its code moved to ata_std_error_handler(). The condition used to ignore the built-in hardreset port operation is modified to be the one that was used in ata_sff_error_handler(). This requires defining a stub for the function sata_sff_hardreset() to avoid compilation errors when CONFIG_ATA_SFF is not enabled. Furthermore, instead of modifying the local hardreset operation definition, set the ATA_LFLAG_NO_HRST link flag to prevent the use of built-in hardreset methods for ports without a valid scr_read function. This flag is checked in ata_eh_reset() and if set, the hardreset method is ignored. This change simplifies ata_sff_error_handler() as this function now only needs to call ata_std_error_handler(). No functional changes. Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel Reviewed-by: Martin K. Petersen Reviewed-by: Hannes Reinecke Link: https://lore.kernel.org/r/20250716020315.235457-2-dlemoal@kernel.org Signed-off-by: Niklas Cassel

ata: libata-eh: Make ata_eh_followup_srst_needed() return a bool

2025-07-11T08:32:51+00:00

ata_eh_followup_srst_needed() returns an integer used as a boolean. So change this function to return that type. No functional changes. Signed-off-by: Damien Le Moal Reviewed-by: Hannes Reinecke Reviewed-by: Niklas Cassel Link: https://lore.kernel.org/r/20250711082158.220047-1-dlemoal@kernel.org Signed-off-by: Niklas Cassel

ata: libata-eh: use bool for fastdrain in ata_eh_set_pending()

2025-07-07T10:41:33+00:00

Use the bool type for the fastdrain argument of ata_eh_set_pending(), as it should be. No functional changes. Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel Link: https://lore.kernel.org/r/20250704104552.310630-1-dlemoal@kernel.org Signed-off-by: Niklas Cassel