On 10/19/23 02:54, Bart Van Assche wrote:
> Introduce the .eh_needs_prepare_resubmit and the .eh_prepare_resubmit
> function pointers in struct scsi_driver. Make the error handler call
> .eh_prepare_resubmit() before resubmitting commands if any of the
> .eh_needs_prepare_resubmit() invocations return true. A later patch
> will use this functionality to sort SCSI commands by LBA from inside
> the SCSI disk driver before these are resubmitted by the error handler.
>
> Cc: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
> Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Ming Lei <ming.lei@xxxxxxxxxx>
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
> drivers/scsi/scsi_error.c | 72 ++++++++++++++++++++++++++++++++++++++
> drivers/scsi/scsi_priv.h | 1 +
> include/scsi/scsi_driver.h | 2 ++
> 3 files changed, 75 insertions(+)
>
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index c67cdcdc3ba8..c877db23a72d 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -27,6 +27,7 @@
> #include <linux/blkdev.h>
> #include <linux/delay.h>
> #include <linux/jiffies.h>
> +#include <linux/list_sort.h>
>
> #include <scsi/scsi.h>
> #include <scsi/scsi_cmnd.h>
> @@ -2186,6 +2187,75 @@ void scsi_eh_ready_devs(struct Scsi_Host *shost,
> }
> EXPORT_SYMBOL_GPL(scsi_eh_ready_devs);
>
> +/*
> + * Returns true if .eh_prepare_resubmit should be called for the commands in
> + * @done_q.
> + */
> +static bool scsi_needs_preparation(struct list_head *done_q)
> +{
> + struct scsi_cmnd *scmd;
> +
> + list_for_each_entry(scmd, done_q, eh_entry) {
> + struct scsi_driver *uld;
> + bool (*npr)(struct scsi_cmnd *scmd);
> +
> + if (!scmd->device)
> + continue;
> + uld = scsi_cmd_to_driver(scmd);
> + if (!uld)
> + continue;
> + npr = uld->eh_needs_prepare_resubmit;
> + if (npr && npr(scmd))
> + return true;
> + }
> +
> + return false;
> +}
> +
> +/*
> + * Comparison function that allows to sort SCSI commands by ULD driver.
> + */
> +static int scsi_cmp_uld(void *priv, const struct list_head *_a,
> + const struct list_head *_b)
> +{
> + struct scsi_cmnd *a = list_entry(_a, typeof(*a), eh_entry);
> + struct scsi_cmnd *b = list_entry(_b, typeof(*b), eh_entry);
> +
> + /* See also the comment above the list_sort() definition. */
> + return scsi_cmd_to_driver(a) > scsi_cmd_to_driver(b);
> +}
> +
> +void scsi_call_prepare_resubmit(struct list_head *done_q)
> +{
> + struct scsi_cmnd *scmd, *next;
> +
> + if (!scsi_needs_preparation(done_q))
> + return;
This function will always go through the list of commands in done_q. That could
hurt performance for scsi hosts that do not need this prepare resubmit, which I
think is UFS only for now. So can't we just add a flag or something to avoid that ?
> +
> + /* Sort pending SCSI commands by ULD. */
> + list_sort(NULL, done_q, scsi_cmp_uld);
> +
> + /*
> + * Call .eh_prepare_resubmit for each range of commands with identical
> + * ULD driver pointer.
> + */
> + list_for_each_entry_safe(scmd, next, done_q, eh_entry) {
> + struct scsi_driver *uld =
> + scmd->device ? scsi_cmd_to_driver(scmd) : NULL;
> + struct list_head *prev, uld_cmd_list;
> +
> + while (&next->eh_entry != done_q &&
> + scsi_cmd_to_driver(next) == uld)
> + next = list_next_entry(next, eh_entry);
> + if (!uld->eh_prepare_resubmit)
> + continue;
> + prev = scmd->eh_entry.prev;
> + list_cut_position(&uld_cmd_list, prev, next->eh_entry.prev);
> + uld->eh_prepare_resubmit(&uld_cmd_list);
> + list_splice(&uld_cmd_list, prev);
> + }
> +}
> +
> /**
> * scsi_eh_flush_done_q - finish processed commands or retry them.
> * @done_q: list_head of processed commands.
> @@ -2194,6 +2264,8 @@ void scsi_eh_flush_done_q(struct list_head *done_q)
> {
> struct scsi_cmnd *scmd, *next;
>
> + scsi_call_prepare_resubmit(done_q);
> +
> list_for_each_entry_safe(scmd, next, done_q, eh_entry) {
> list_del_init(&scmd->eh_entry);
> if (scsi_device_online(scmd->device) &&
> diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
> index 3f0dfb97db6b..64070e530c4d 100644
> --- a/drivers/scsi/scsi_priv.h
> +++ b/drivers/scsi/scsi_priv.h
> @@ -101,6 +101,7 @@ int scsi_eh_get_sense(struct list_head *work_q,
> struct list_head *done_q);
> bool scsi_noretry_cmd(struct scsi_cmnd *scmd);
> void scsi_eh_done(struct scsi_cmnd *scmd);
> +void scsi_call_prepare_resubmit(struct list_head *done_q);
>
> /* scsi_lib.c */
> extern void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd);
> diff --git a/include/scsi/scsi_driver.h b/include/scsi/scsi_driver.h
> index 4ce1988b2ba0..00ffa470724a 100644
> --- a/include/scsi/scsi_driver.h
> +++ b/include/scsi/scsi_driver.h
> @@ -18,6 +18,8 @@ struct scsi_driver {
> int (*done)(struct scsi_cmnd *);
> int (*eh_action)(struct scsi_cmnd *, int);
> void (*eh_reset)(struct scsi_cmnd *);
> + bool (*eh_needs_prepare_resubmit)(struct scsi_cmnd *cmd);
> + void (*eh_prepare_resubmit)(struct list_head *cmd_list);
> };
> #define to_scsi_driver(drv) \
> container_of((drv), struct scsi_driver, gendrv)
--
Damien Le Moal
Western Digital Research
