kernel/linux.git/include/linux/libata.h, branch v6.12.80

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

2026-03-13T16:20:23+00:00

[ Upstream commit 0ea84089dbf62a92dc7889c79e6b18fc89260808 ] 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: Sasha Levin

ata: libata: Remove ATA_DFLAG_ZAC device flag

2026-03-13T16:20:23+00:00

[ Upstream commit a0f26fcc383965e0522b81269062a9278bc802fe ] The ATA device flag ATA_DFLAG_ZAC is used to indicate if a devie is a host managed or host aware zoned device. However, this flag is not used in the hot path and only used during device scanning/revalidation and for inquiry and sense SCSI command translation. Save one bit from struct ata_device flags field by replacing this flag with the internal helper function ata_dev_is_zac(). This function returns true if the device class is ATA_DEV_ZAC (host managed ZAC device case) or if its identify data reports it supports the zoned command set (host aware ZAC device case). Signed-off-by: Damien Le Moal Reviewed-by: Hannes Reinecke Reviewed-by: Niklas Cassel Stable-dep-of: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Signed-off-by: Sasha Levin

ata: libata-sata: Add link_power_management_supported sysfs attribute

2025-08-20T16:30:57+00:00

commit 0060beec0bfa647c4b510df188b1c4673a197839 upstream. A port link power management (LPM) policy can be controlled using the link_power_management_policy sysfs host attribute. However, this attribute exists also for hosts that do not support LPM and in such case, attempting to change the LPM policy for the host (port) will fail with -EOPNOTSUPP. Introduce the new sysfs link_power_management_supported host attribute to indicate to the user if a the port and the devices connected to the port for the host support LPM, which implies that the link_power_management_policy attribute can be used. Since checking that a port and its devices support LPM is common between the new ata_scsi_lpm_supported_show() function and the existing ata_scsi_lpm_store() function, the new helper ata_scsi_lpm_supported() is introduced. Fixes: 413e800cadbf ("ata: libata-sata: Disallow changing LPM state if not supported") Reported-by: Borah, Chaitanya Kumar Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202507251014.a5becc3b-lkp@intel.com Signed-off-by: Damien Le Moal Reviewed-by: Martin K. Petersen Signed-off-by: Greg Kroah-Hartman

ata: libata-acpi: Do not assume 40 wire cable if no devices are enabled

2025-07-10T14:05:06+00:00

[ Upstream commit 33877220b8641b4cde474a4229ea92c0e3637883 ] On at least an ASRock 990FX Extreme 4 with a VIA VT6330, the devices have not yet been enabled by the first time ata_acpi_cbl_80wire() is called. This means that the ata_for_each_dev loop is never entered, and a 40 wire cable is assumed. The VIA controller on this board does not report the cable in the PCI config space, thus having to fall back to ACPI even though no SATA bridge is present. The _GTM values are correctly reported by the firmware through ACPI, which has already set up faster transfer modes, but due to the above the controller is forced down to a maximum of UDMA/33. Resolve this by modifying ata_acpi_cbl_80wire() to directly return the cable type. First, an unknown cable is assumed which preserves the mode set by the firmware, and then on subsequent calls when the devices have been enabled, an 80 wire cable is correctly detected. Since the function now directly returns the cable type, it is renamed to ata_acpi_cbl_pata_type(). Signed-off-by: Tasos Sahanidis Link: https://lore.kernel.org/r/20250519085945.1399466-1-tasos@tasossah.com Signed-off-by: Niklas Cassel Signed-off-by: Sasha Levin

ata: libata-core: Add ATA_QUIRK_NO_LPM_ON_ATI for certain Samsung SSDs

2025-03-28T21:03:27+00:00

[ Upstream commit f2aac4c73c9945cce156fd58a9a2f31f2c8a90c7 ] Before commit 7627a0edef54 ("ata: ahci: Drop low power policy board type") the ATI AHCI controllers specified board type 'board_ahci' rather than board type 'board_ahci'. This means that LPM was historically not enabled for the ATI AHCI controllers. By looking at commit 7a8526a5cd51 ("libata: Add ATA_HORKAGE_NO_NCQ_ON_ATI for Samsung 860 and 870 SSD."), it is clear that, for some unknown reason, that Samsung SSDs do not play nice with ATI AHCI controllers. (When using other AHCI controllers, NCQ can be enabled on these Samsung SSDs without issues.) In a similar way, from user reports, it is clear the ATI AHCI controllers can enable LPM on e.g. Maxtor HDDs perfectly fine, but when enabling LPM on certain Samsung SSDs, things break. (E.g. the SSDs will not get detected by the ATI AHCI controller even after a COMRESET.) Yet, when using LPM on these Samsung SSDs with other AHCI controllers, e.g. Intel AHCI controllers, these Samsung drives appear to work perfectly fine. Considering that the combination of ATI + Samsung, for some unknown reason, does not seem to work well, disable LPM when detecting an ATI AHCI controller with a problematic Samsung SSD. Apply this new ATA_QUIRK_NO_LPM_ON_ATI quirk for all Samsung SSDs that have already been reported to not play nice with ATI (ATA_QUIRK_NO_NCQ_ON_ATI). Fixes: 7627a0edef54 ("ata: ahci: Drop low power policy board type") Suggested-by: Hans de Goede Reported-by: Eric Closes: https://lore.kernel.org/linux-ide/Z8SBZMBjvVXA7OAK@eldamar.lan/ Tested-by: Eric Reviewed-by: Damien Le Moal Link: https://lore.kernel.org/r/20250317170348.1748671-2-cassel@kernel.org Signed-off-by: Niklas Cassel Signed-off-by: Sasha Levin

ata: libata: Improve CDL resource management

2024-09-07T01:16:56+00:00

The ncq_sense_buf buffer field of struct ata_port is allocated and used only for devices that support the Command Duration Limits (CDL) feature. However, the cdl buffer of struct ata_device, which is used to cache the command duration limits log page for devices supporting CDL is always allocated as part of struct ata_device, which is wasteful of memory for devices that do not support this feature. Clean this up by defining both buffers as part of the new ata_cdl structure and allocating this structure only for devices that support the CDL feature. This new structure is attached to struct ata_device using the cdl pointer. The functions ata_dev_init_cdl_resources() and ata_dev_cleanup_cdl_resources() are defined to manage this new structure allocation, initialization and freeing when a port is removed or a device disabled. ata_dev_init_cdl_resources() is called from ata_dev_config_cdl() only for devices that support CDL. ata_dev_cleanup_cdl_resources() is called from ata_dev_free_resources() to free the ata_cdl structure when a device is being disabled by EH. Note that the name of the former cdl log buffer of struct ata_device is changed to desc_log_buf to make it clearer that it is a buffer for the limit descriptors log page. This change reduces the size of struct ata_device, thus reducing memory usage for ATA devices that do not support the CDL feature. Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel

ata: libata: Move sector_buf from struct ata_port to struct ata_device

2024-09-07T01:16:55+00:00

The 512B buffer sector_buf field of struct ata_port is used for scanning devices as well as during error recovery with ata EH. This buffer is thus useless if a port does not have a device connected to it. And also given that commands using this buffer are issued to devices, and not to ports, move this buffer definition from struct ata_port to struct ata_device. This change slightly increases system memory usage for systems using a port-multiplier as in that case we do not need a per-device buffer for scanning devices (PMP does not allow parallel scanning) nor for EH (as when entering EH we are guaranteed that all commands to all devices connected to the PMP have completed or have been aborted). However, this change reduces memory usage on systems that have many ports with only few devices rives connected, which is a much more common use case than the PMP use case. Suggested-by: Niklas Cassel Signed-off-by: Damien Le Moal Reviewed-by: Hannes Reinecke Reviewed-by: Niklas Cassel

ata: libata: Rename ata_eh_read_sense_success_ncq_log()

2024-09-07T01:16:55+00:00

The function ata_eh_read_sense_success_ncq_log() does more that just reading the sense data for successful NCQ commands log page as it also sets the sense data for all commands listed in the log page. Rename this function to ata_eh_get_ncq_success_sense() to better describe what the function does. Furthermore, since this function is only called from ata_eh_get_success_sense() in libata-eh.c, there is no need to export it and its declaration can be moved to drivers/ata/libata.h. To be consistent with this change, the function ata_eh_read_sense_success_non_ncq() is also renamed to ata_eh_get_non_ncq_success_sense(). Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel Reviewed-by: Hannes Reinecke

ata: libata: Move sata_std_hardreset() definition to libata-sata.c

2024-09-07T01:16:55+00:00

Unlike ata_std_prereset() and ata_std_postreset(), the function sata_std_hardreset() applies only to SATA devices, as its name implies. So move its definition to libata-sata.c. Together with this, also move the definition of sata_port_ops to libata-sata.c, where it belongs. Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel Reviewed-by: Hannes Reinecke

ata: libata: Remove obsolete function declarations

2024-08-26T23:04:53+00:00

The function ata_schedule_scsi_eh() was removed with commit f8bbfc247efb ("[PATCH] SCSI: make scsi_implement_eh() generic API for SCSI transports"), and the function ata_sff_irq_clear() was removed with commit 37f65b8bc262("libata-sff: ata_sff_irq_clear() is BMDMA specific"). Remove the now useless declarations of these functions in drivers/ata/libata.h and include/linux/libata.h. Signed-off-by: Gaosheng Cui Signed-off-by: Damien Le Moal