kernel/linux.git/include/linux/libata.h, branch v6.18.34

ata: libata-scsi: do not needlessly defer commands when using PMP with FBS

2026-06-01T15:50:38+00:00

commit 759e8756da00aa115d504a18155b1d1ee1cc12e8 upstream. The ACS specification does not allow a non-NCQ command to be issued while an NCQ command is outstanding. Commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") introduced a feature where a deferred non-NCQ command gets issued from a workqueue. The design stores a single non-NCQ command per port. However, when using Port Multipliers (PMPs), specifically PMPs that support FIS-Based Switching (FBS), non-NCQ and NCQ commands can be mixed on the same port, just not for the same link, see e.g. ata_std_qc_defer() which is, and always has operated on a per-link basis. Therefore, move the deferred_qc from struct ata_port to struct ata_link. This way, when using a PMP with FBS, we will not needlessly defer commands to all other links, just because one link issued a non-NCQ command while having an NCQ command outstanding. Only commands for that specific link will be deferred. This is in line with how PMPs with FBS worked before commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation"). Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Tested-by: Tommy Kelly Reviewed-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Greg Kroah-Hartman

ata: libata-scsi: do not use the deferred QC feature on PMPs with CBS

2026-06-01T15:50:38+00:00

commit f233124fb36cd57ef09f96d517a38ab4b902e15e upstream. When using Port Multipliers (PMPs) with Command-Based Switching (CBS), you can only issue commands to one link at a time. For PMPs with CBS, there is already code to handle commands being sent to different links in sata_pmp_qc_defer_cmd_switch() using ap->excl_link. sata_sil24 also makes use of ap->excl_link. A user on the list reported that commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") broke PMPs with CBS. The commit introduced code that stores a deferred qc in ap->deferred_qc, to later be issued via a workqueue. It turns out that this change is incompatible with the existing ap->excl_link handling used by PMPs with CBS. Thus, modify sata_pmp_qc_defer_cmd_switch() and sil24_qc_defer() to return ATA_DEFER_LINK_EXCL, and make sure that the deferred QC handling via workqueue is not used for this return value. This way, PMPs with CBS will work once again. Note that the starvation referenced in commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") can only happen on libsas ports, and libsas does not support Port Multipliers, thus there is no harm of reverting back to the previous way of deferring commands for PMPs with CBS. Non-libsas ports connected to anything but a PMP with CBS (e.g. a normal drive or a PMP with FBS) will continue using the deferred workqueue, since it does result in lower completion latencies for non-NCQ commands, even though the workqueue is not strictly needed to avoid starvation for non-libsas ports. If we want to modify the scope of the workqueue issuing to also handle PMPs with CBS, then we should ensure that we can save both NCQ and non-NCQ commands in ap->deferred_qc, while also removing the existing PMP CBS handling using ap->excl_link, such that we don't duplicate features. While at it, also add a comment explaining how the ap->excl_link mechanism works. Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Tested-by: Tommy Kelly Reported-by: Tommy Kelly Closes: https://lore.kernel.org/linux-ide/ce09cc21-a8e9-4845-b205-35411e22fba9@tkel.ly/ Reviewed-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Greg Kroah-Hartman

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

2026-02-26T22:59:46+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-core: relax checks in ata_read_log_directory()

2025-10-13T07:12:36+00:00

Commit 6d4405b16d37 ("ata: libata-core: Cache the general purpose log directory") introduced caching of a device general purpose log directory to avoid repeated access to this log page during device scan. This change also added a check on this log page to verify that the log page version is 0x0001 as mandated by the ACS specifications. And it turns out that some devices do not bother reporting this version, instead reporting a version 0, resulting in error messages such as: ata6.00: Invalid log directory version 0x0000 and to the device being marked as not supporting the general purpose log directory log page. Since before commit 6d4405b16d37 the log page version check did not exist and things were still working correctly for these devices, relax ata_read_log_directory() version check and only warn about the invalid log page version number without disabling access to the log directory page. Fixes: 6d4405b16d37 ("ata: libata-core: Cache the general purpose log directory") Cc: stable@vger.kernel.org Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220635 Signed-off-by: Damien Le Moal Signed-off-by: Niklas Cassel

scsi: switch ->bios_param() to passing gendisk

2025-08-13T06:59:28+00:00

Instances are passed struct block_device *bdev argument; the only thing it is used for (if it's used in the first place) is bdev->bd_disk. Might as well pass that in the first place... Reviewed-by: Martin K. Petersen Reviewed-by: Christoph Hellwig Acked-by: Jens Axboe Signed-off-by: Al Viro

ata: libata-sata: Add link_power_management_supported sysfs attribute

2025-07-31T03:56:21+00:00

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

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-core: Rename ata_do_set_mode()

2025-07-04T08:36:00+00:00

With the renaming of libata-eh ata_set_mode() function to ata_eh_set_mode(), libata-core function ata_do_set_mode() can now be renamed to the simpler ata_set_mode(). All the call sites of the former ata_do_set_mode() are updated to use the new function name. No functional changes. Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel Link: https://lore.kernel.org/r/20250703103622.291272-5-dlemoal@kernel.org Signed-off-by: Niklas Cassel

ata: libata-core: Cache the general purpose log directory

2025-07-04T08:36:00+00:00

The function ata_log_supported() tests if a log page is supported by a device using the General Purpose Log Directory log page, which lists the size of all surported log pages. However, this log page is read from the device using ata_read_log_page() every time ata_log_supported() is called. That is not necessary. Avoid reading the General Purpose Log Directory log page by caching its content in the gp_log_dir buffer defined as part of struct ata_device. The functions ata_read_log_directory() and ata_clear_log_directory() are introduced to manage this buffer. ata_clear_log_directory() zero-fill the gp_log_dir buffer every time ata_dev_configure() is called, that is, when the device is first scanned and when it is being revalidated. The function ata_log_supported() is modified to call ata_read_log_directory() instead of ata_read_log_page(). The function ata_read_log_directory() calls ata_read_log_page() to read the General Purpose Log Directory log page from the device only if the first 16-bits word of the log is not equal to 0x0001, that is, it is not equal to the ACS mandated value for the log version. With this, the log page is read from the device only once for every ata_dev_configure() call. For instance, with pr_debug enabled, a call to ata_dev_configure() before this patch generates the following log page accesses: ata3.00: read log page - log 0x0, page 0x0 ata3.00: read log page - log 0x13, page 0x0 ata3.00: read log page - log 0x0, page 0x0 ata3.00: read log page - log 0x12, page 0x0 ata3.00: read log page - log 0x0, page 0x0 ata3.00: read log page - log 0x30, page 0x0 ata3.00: read log page - log 0x30, page 0x8 ata3.00: read log page - log 0x0, page 0x0 ata3.00: read log page - log 0x0, page 0x0 ata3.00: read log page - log 0x0, page 0x0 ata3.00: read log page - log 0x30, page 0x0 ata3.00: read log page - log 0x0, page 0x0 ata3.00: read log page - log 0x30, page 0x0 ata3.00: read log page - log 0x30, page 0x3 ata3.00: read log page - log 0x30, page 0x4 ata3.00: read log page - log 0x18, page 0x0 That is, the general purpose log directory page is read 7 times. With this patch applied, the number of accesses to this log page is reduced to one: ata3.00: read log page - log 0x0, page 0x0 ata3.00: read log page - log 0x13, page 0x0 ata3.00: read log page - log 0x12, page 0x0 ata3.00: read log page - log 0x30, page 0x0 ata3.00: read log page - log 0x30, page 0x8 ata3.00: read log page - log 0x30, page 0x0 ata3.00: read log page - log 0x30, page 0x0 ata3.00: read log page - log 0x30, page 0x3 ata3.00: read log page - log 0x30, page 0x4 ata3.00: read log page - log 0x18, page 0x0 Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel Link: https://lore.kernel.org/r/20250703103622.291272-2-dlemoal@kernel.org Signed-off-by: Niklas Cassel