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linux-stable-mirror/drivers/ata/libata.h
Damien Le Moal ce22aaed01 ata: libata-scsi: avoid Non-NCQ command starvation 
[ Upstream commit 0ea84089db ]

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 <yangxingui@huawei.com>
Reported-by: Igor Pylypiv <ipylypiv@google.com>
Fixes: bdb01301f3 ("scsi: Add host and host template flag 'host_tagset'")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Tested-by: Igor Pylypiv <ipylypiv@google.com>
Tested-by: Xingui Yang <yangxingui@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2026-03-13 17:20:23 +01:00

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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* libata.h - helper library for ATA
*
* Copyright 2003-2004 Red Hat, Inc. All rights reserved.
* Copyright 2003-2004 Jeff Garzik
*
* libata documentation is available via 'make {ps|pdf}docs',
* as Documentation/driver-api/libata.rst
*/
#ifndef __LIBATA_H__
#define __LIBATA_H__
#define DRV_NAME "libata"
#define DRV_VERSION "3.00" /* must be exactly four chars */
/* libata-core.c */
enum {
/* flags for ata_dev_read_id() */
ATA_READID_POSTRESET = (1 << 0), /* reading ID after reset */
/* selector for ata_down_xfermask_limit() */
ATA_DNXFER_PIO = 0, /* speed down PIO */
ATA_DNXFER_DMA = 1, /* speed down DMA */
ATA_DNXFER_40C = 2, /* apply 40c cable limit */
ATA_DNXFER_FORCE_PIO = 3, /* force PIO */
ATA_DNXFER_FORCE_PIO0 = 4, /* force PIO0 */
ATA_DNXFER_QUIET = (1 << 31),
};
#define ATA_PORT_TYPE_NAME "ata_port"
extern int atapi_passthru16;
extern int libata_fua;
extern int libata_noacpi;
extern int libata_allow_tpm;
extern const struct device_type ata_port_type;
extern struct ata_link *ata_dev_phys_link(struct ata_device *dev);
static inline bool ata_sstatus_online(u32 sstatus)
{
return (sstatus & 0xf) == 0x3;
}
static inline bool ata_dev_is_zac(struct ata_device *dev)
{
/* Host managed device or host aware device */
return dev->class == ATA_DEV_ZAC ||
ata_id_zoned_cap(dev->id) == 0x01;
}
static inline bool ata_port_eh_scheduled(struct ata_port *ap)
{
return ap->pflags & (ATA_PFLAG_EH_PENDING | ATA_PFLAG_EH_IN_PROGRESS);
}
#ifdef CONFIG_ATA_FORCE
extern void ata_force_cbl(struct ata_port *ap);
#else
static inline void ata_force_cbl(struct ata_port *ap) { }
#endif
extern u64 ata_tf_to_lba(const struct ata_taskfile *tf);
extern u64 ata_tf_to_lba48(const struct ata_taskfile *tf);
extern int ata_build_rw_tf(struct ata_queued_cmd *qc, u64 block, u32 n_block,
unsigned int tf_flags, int dld, int class);
extern u64 ata_tf_read_block(const struct ata_taskfile *tf,
struct ata_device *dev);
unsigned int ata_exec_internal(struct ata_device *dev, struct ata_taskfile *tf,
const u8 *cdb, enum dma_data_direction dma_dir,
void *buf, unsigned int buflen,
unsigned int timeout);
extern int ata_wait_ready(struct ata_link *link, unsigned long deadline,
int (*check_ready)(struct ata_link *link));
extern int ata_dev_read_id(struct ata_device *dev, unsigned int *p_class,
unsigned int flags, u16 *id);
extern int ata_dev_reread_id(struct ata_device *dev, unsigned int readid_flags);
extern int ata_dev_revalidate(struct ata_device *dev, unsigned int new_class,
unsigned int readid_flags);
extern int ata_dev_configure(struct ata_device *dev);
extern bool ata_dev_power_init_tf(struct ata_device *dev,
struct ata_taskfile *tf, bool set_active);
extern void ata_dev_power_set_standby(struct ata_device *dev);
extern void ata_dev_power_set_active(struct ata_device *dev);
void ata_dev_free_resources(struct ata_device *dev);
extern int ata_down_xfermask_limit(struct ata_device *dev, unsigned int sel);
extern unsigned int ata_dev_set_feature(struct ata_device *dev,
u8 subcmd, u8 action);
extern void ata_qc_free(struct ata_queued_cmd *qc);
extern void ata_qc_issue(struct ata_queued_cmd *qc);
extern void __ata_qc_complete(struct ata_queued_cmd *qc);
extern int atapi_check_dma(struct ata_queued_cmd *qc);
extern void swap_buf_le16(u16 *buf, unsigned int buf_words);
extern bool ata_phys_link_online(struct ata_link *link);
extern bool ata_phys_link_offline(struct ata_link *link);
bool ata_adapter_is_online(struct ata_port *ap);
extern void ata_dev_init(struct ata_device *dev);
extern void ata_link_init(struct ata_port *ap, struct ata_link *link, int pmp);
extern int sata_link_init_spd(struct ata_link *link);
extern int ata_task_ioctl(struct scsi_device *scsidev, void __user *arg);
extern int ata_cmd_ioctl(struct scsi_device *scsidev, void __user *arg);
extern const char *sata_spd_string(unsigned int spd);
extern unsigned int ata_read_log_page(struct ata_device *dev, u8 log,
u8 page, void *buf, unsigned int sectors);
void ata_dev_cleanup_cdl_resources(struct ata_device *dev);
#define to_ata_port(d) container_of(d, struct ata_port, tdev)
/* libata-sata.c */
#ifdef CONFIG_SATA_HOST
int sata_down_spd_limit(struct ata_link *link, u32 spd_limit);
int ata_eh_get_ncq_success_sense(struct ata_link *link);
#else
static inline int sata_down_spd_limit(struct ata_link *link, u32 spd_limit)
{
return -EOPNOTSUPP;
}
static inline int ata_eh_get_ncq_success_sense(struct ata_link *link)
{
return -EOPNOTSUPP;
}
#endif
/* libata-acpi.c */
#ifdef CONFIG_ATA_ACPI
extern unsigned int ata_acpi_gtf_filter;
extern void ata_acpi_dissociate(struct ata_host *host);
extern void ata_acpi_on_resume(struct ata_port *ap);
extern int ata_acpi_on_devcfg(struct ata_device *dev);
extern void ata_acpi_on_disable(struct ata_device *dev);
extern void ata_acpi_set_state(struct ata_port *ap, pm_message_t state);
extern void ata_acpi_bind_port(struct ata_port *ap);
extern void ata_acpi_bind_dev(struct ata_device *dev);
extern acpi_handle ata_dev_acpi_handle(struct ata_device *dev);
#else
static inline void ata_acpi_dissociate(struct ata_host *host) { }
static inline void ata_acpi_on_resume(struct ata_port *ap) { }
static inline int ata_acpi_on_devcfg(struct ata_device *dev) { return 0; }
static inline void ata_acpi_on_disable(struct ata_device *dev) { }
static inline void ata_acpi_set_state(struct ata_port *ap,
pm_message_t state) { }
static inline void ata_acpi_bind_port(struct ata_port *ap) {}
static inline void ata_acpi_bind_dev(struct ata_device *dev) {}
#endif
/* libata-scsi.c */
extern struct ata_device *ata_scsi_find_dev(struct ata_port *ap,
const struct scsi_device *scsidev);
extern int ata_scsi_add_hosts(struct ata_host *host,
const struct scsi_host_template *sht);
extern void ata_scsi_scan_host(struct ata_port *ap, int sync);
extern int ata_scsi_offline_dev(struct ata_device *dev);
extern bool ata_scsi_sense_is_valid(u8 sk, u8 asc, u8 ascq);
extern void ata_scsi_set_sense(struct ata_device *dev,
struct scsi_cmnd *cmd, u8 sk, u8 asc, u8 ascq);
extern void ata_scsi_set_sense_information(struct ata_device *dev,
struct scsi_cmnd *cmd,
const struct ata_taskfile *tf);
extern void ata_scsi_media_change_notify(struct ata_device *dev);
extern void ata_scsi_hotplug(struct work_struct *work);
extern void ata_scsi_dev_rescan(struct work_struct *work);
extern int ata_scsi_user_scan(struct Scsi_Host *shost, unsigned int channel,
unsigned int id, u64 lun);
void ata_scsi_sdev_config(struct scsi_device *sdev);
int ata_scsi_dev_config(struct scsi_device *sdev, struct queue_limits *lim,
struct ata_device *dev);
int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev);
void ata_scsi_deferred_qc_work(struct work_struct *work);
void ata_scsi_requeue_deferred_qc(struct ata_port *ap);
/* libata-eh.c */
extern unsigned int ata_internal_cmd_timeout(struct ata_device *dev, u8 cmd);
extern void ata_internal_cmd_timed_out(struct ata_device *dev, u8 cmd);
extern void ata_eh_acquire(struct ata_port *ap);
extern void ata_eh_release(struct ata_port *ap);
extern void ata_scsi_error(struct Scsi_Host *host);
extern void ata_eh_fastdrain_timerfn(struct timer_list *t);
extern void ata_qc_schedule_eh(struct ata_queued_cmd *qc);
extern void ata_dev_disable(struct ata_device *dev);
extern void ata_eh_detach_dev(struct ata_device *dev);
extern void ata_eh_about_to_do(struct ata_link *link, struct ata_device *dev,
unsigned int action);
extern void ata_eh_done(struct ata_link *link, struct ata_device *dev,
unsigned int action);
extern void ata_eh_autopsy(struct ata_port *ap);
const char *ata_get_cmd_name(u8 command);
extern void ata_eh_report(struct ata_port *ap);
extern int ata_eh_reset(struct ata_link *link, int classify,
ata_prereset_fn_t prereset, ata_reset_fn_t softreset,
ata_reset_fn_t hardreset, ata_postreset_fn_t postreset);
extern int ata_set_mode(struct ata_link *link, struct ata_device **r_failed_dev);
extern int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
ata_reset_fn_t softreset, ata_reset_fn_t hardreset,
ata_postreset_fn_t postreset,
struct ata_link **r_failed_disk);
extern void ata_eh_finish(struct ata_port *ap);
extern int ata_ering_map(struct ata_ering *ering,
int (*map_fn)(struct ata_ering_entry *, void *),
void *arg);
enum scsi_disposition ata_eh_decide_disposition(struct ata_queued_cmd *qc);
extern unsigned int atapi_eh_tur(struct ata_device *dev, u8 *r_sense_key);
extern unsigned int atapi_eh_request_sense(struct ata_device *dev,
u8 *sense_buf, u8 dfl_sense_key);
/* libata-pmp.c */
#ifdef CONFIG_SATA_PMP
extern int sata_pmp_scr_read(struct ata_link *link, int reg, u32 *val);
extern int sata_pmp_scr_write(struct ata_link *link, int reg, u32 val);
extern int sata_pmp_set_lpm(struct ata_link *link, enum ata_lpm_policy policy,
unsigned hints);
extern int sata_pmp_attach(struct ata_device *dev);
#else /* CONFIG_SATA_PMP */
static inline int sata_pmp_scr_read(struct ata_link *link, int reg, u32 *val)
{
return -EINVAL;
}
static inline int sata_pmp_scr_write(struct ata_link *link, int reg, u32 val)
{
return -EINVAL;
}
static inline int sata_pmp_set_lpm(struct ata_link *link,
enum ata_lpm_policy policy, unsigned hints)
{
return -EINVAL;
}
static inline int sata_pmp_attach(struct ata_device *dev)
{
return -EINVAL;
}
#endif /* CONFIG_SATA_PMP */
/* libata-sff.c */
#ifdef CONFIG_ATA_SFF
extern void ata_sff_flush_pio_task(struct ata_port *ap);
extern void ata_sff_port_init(struct ata_port *ap);
extern int ata_sff_init(void);
extern void ata_sff_exit(void);
#else /* CONFIG_ATA_SFF */
static inline void ata_sff_flush_pio_task(struct ata_port *ap)
{ }
static inline void ata_sff_port_init(struct ata_port *ap)
{ }
static inline int ata_sff_init(void)
{ return 0; }
static inline void ata_sff_exit(void)
{ }
#endif /* CONFIG_ATA_SFF */
/* libata-zpodd.c */
#ifdef CONFIG_SATA_ZPODD
void zpodd_init(struct ata_device *dev);
void zpodd_exit(struct ata_device *dev);
static inline bool zpodd_dev_enabled(struct ata_device *dev)
{
return dev->zpodd != NULL;
}
void zpodd_on_suspend(struct ata_device *dev);
bool zpodd_zpready(struct ata_device *dev);
void zpodd_enable_run_wake(struct ata_device *dev);
void zpodd_disable_run_wake(struct ata_device *dev);
void zpodd_post_poweron(struct ata_device *dev);
#else /* CONFIG_SATA_ZPODD */
static inline void zpodd_init(struct ata_device *dev) {}
static inline void zpodd_exit(struct ata_device *dev) {}
static inline bool zpodd_dev_enabled(struct ata_device *dev) { return false; }
static inline void zpodd_on_suspend(struct ata_device *dev) {}
static inline bool zpodd_zpready(struct ata_device *dev) { return false; }
static inline void zpodd_enable_run_wake(struct ata_device *dev) {}
static inline void zpodd_disable_run_wake(struct ata_device *dev) {}
static inline void zpodd_post_poweron(struct ata_device *dev) {}
#endif /* CONFIG_SATA_ZPODD */
#endif /* __LIBATA_H__ */
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