Re: [PATCH v3 02/11] scsi: scsi_debug: Don't iter all shosts in clear_luns_changed_on_target()

Douglas Gilbert
2023-03-28T23:39:10Z

On 2023-03-27 03:43, John Garry wrote:
> In clear_luns_changed_on_target(), we iter all devices for all shosts to
> conditionally clear the SDEBUG_UA_LUNS_CHANGED flag in the per-device
> uas_bm.
>
> One condition to see whether we clear the flag is to test whether the host
> for the device under consideration is the same as the matching device's
> (devip) host. This check will only ever pass for devices for the same
> shost, so only iter the devices for the matching device shost.
>
> We can now drop the spinlock'ing of the sdebug_host_list_lock in the same
> function. This will allow us to use a mutex instead of the spinlock for
> the global shost lock, as clear_luns_changed_on_target() could be called
> in non-blocking context, in scsi_debug_queuecommand() -> make_ua() ->
> clear_luns_changed_on_target() (which is why required a spinlock).
>
> Signed-off-by: John Garry <john.g.garry@oracle.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com

Thanks.

> ---
> drivers/scsi/scsi_debug.c | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index 782515abca2c..eba6eca81e84 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -1063,18 +1063,15 @@ static void all_config_cdb_len(void)
>
> static void clear_luns_changed_on_target(struct sdebug_dev_info *devip)
> {
> - struct sdebug_host_info *sdhp;
> + struct sdebug_host_info *sdhp = devip->sdbg_host;
> struct sdebug_dev_info *dp;
>
> - spin_lock(&sdebug_host_list_lock);
> - list_for_each_entry(sdhp, &sdebug_host_list, host_list) {
> - list_for_each_entry(dp, &sdhp->dev_info_list, dev_list) {
> - if ((devip->sdbg_host == dp->sdbg_host) &&
> - (devip->target == dp->target))
> - clear_bit(SDEBUG_UA_LUNS_CHANGED, dp->uas_bm);
> + list_for_each_entry(dp, &sdhp->dev_info_list, dev_list) {
> + if ((devip->sdbg_host == dp->sdbg_host) &&
> + (devip->target == dp->target)) {
> + clear_bit(SDEBUG_UA_LUNS_CHANGED, dp->uas_bm);
> }
> }
> - spin_unlock(&sdebug_host_list_lock);
> }
>
> static int make_ua(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)