| Message ID | 20220908233600.3043271-3-bvanassche@acm.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Prepare for constifying SCSI host templates | expand |
On 9/8/22 6:35 PM, Bart Van Assche wrote: > Instead of using scsi_host_template members to track the SCSI proc > directory entries, track these entries in a list. This patch changes the > time needed for looking up the proc dir pointer from O(1) into O(n). I > think this is acceptable since the number of SCSI host adapter types per > host is usually small (less than ten). > > This patch has been tested by attaching two USB storage devices to a > qemu host: > Reviewed-by: Mike Christie <michael.christie@oracle.com>
On 09/09/2022 00:35, Bart Van Assche wrote: > Instead of using scsi_host_template members to track the SCSI proc > directory entries, track these entries in a list. This patch changes the > time needed for looking up the proc dir pointer from O(1) into O(n). I > think this is acceptable since the number of SCSI host adapter types per > host is usually small (less than ten). > > This patch has been tested by attaching two USB storage devices to a > qemu host: > > $ grep -aH . /proc/scsi/usb-storage/* > /proc/scsi/usb-storage/7: Host scsi7: usb-storage > /proc/scsi/usb-storage/7: Vendor: QEMU > /proc/scsi/usb-storage/7: Product: QEMU USB HARDDRIVE > /proc/scsi/usb-storage/7:Serial Number: 1-0000:00:02.1:00.0-6 > /proc/scsi/usb-storage/7: Protocol: Transparent SCSI > /proc/scsi/usb-storage/7: Transport: Bulk > /proc/scsi/usb-storage/7: Quirks: SANE_SENSE > /proc/scsi/usb-storage/8: Host scsi8: usb-storage > /proc/scsi/usb-storage/8: Vendor: QEMU > /proc/scsi/usb-storage/8: Product: QEMU USB HARDDRIVE > /proc/scsi/usb-storage/8:Serial Number: 1-0000:00:02.1:00.0-7 > /proc/scsi/usb-storage/8: Protocol: Transparent SCSI > /proc/scsi/usb-storage/8: Transport: Bulk > /proc/scsi/usb-storage/8: Quirks: SANE_SENSE > > This patch prepares for constifying most SCSI host templates. > > Cc: Christoph Hellwig <hch@lst.de> > Cc: Ming Lei <ming.lei@redhat.com> > Cc: Hannes Reinecke <hare@suse.de> > Cc: John Garry <john.garry@huawei.com> > Cc: Mike Christie <michael.christie@oracle.com> > Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> > Signed-off-by: Bart Van Assche <bvanassche@acm.org> > --- > drivers/scsi/scsi_priv.h | 4 +- > drivers/scsi/scsi_proc.c | 110 +++++++++++++++++++++++++++++++++------ > include/scsi/scsi_host.h | 12 ----- > 3 files changed, 95 insertions(+), 31 deletions(-) > > diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h > index f385b3f04d6e..be5d7c9b7f39 100644 > --- a/drivers/scsi/scsi_priv.h > +++ b/drivers/scsi/scsi_priv.h > @@ -100,8 +100,8 @@ extern void scsi_evt_thread(struct work_struct *work); > > /* scsi_proc.c */ > #ifdef CONFIG_SCSI_PROC_FS > -extern void scsi_proc_hostdir_add(struct scsi_host_template *); > -extern void scsi_proc_hostdir_rm(struct scsi_host_template *); > +extern void scsi_proc_hostdir_add(const struct scsi_host_template *); > +extern void scsi_proc_hostdir_rm(const struct scsi_host_template *); > extern void scsi_proc_host_add(struct Scsi_Host *); > extern void scsi_proc_host_rm(struct Scsi_Host *); > extern int scsi_init_procfs(void); > diff --git a/drivers/scsi/scsi_proc.c b/drivers/scsi/scsi_proc.c > index eeb9261c93f7..e04db652a81e 100644 > --- a/drivers/scsi/scsi_proc.c > +++ b/drivers/scsi/scsi_proc.c > @@ -43,8 +43,23 @@ > > static struct proc_dir_entry *proc_scsi; > > -/* Protect sht->present and sht->proc_dir */ > +/* Protects scsi_proc_list */ > static DEFINE_MUTEX(global_host_template_mutex); > +static LIST_HEAD(scsi_proc_list); > + > +/** > + * struct scsi_proc_entry - (host template, SCSI proc dir) association > + * @entry: entry in scsi_proc_list. > + * @sht: SCSI host template associated with the procfs directory. > + * @proc_dir: procfs directory associated with the SCSI host template. > + * @present: Number of SCSI hosts instantiated for @sht. > + */ > +struct scsi_proc_entry { > + struct list_head entry; > + const struct scsi_host_template *sht; > + struct proc_dir_entry *proc_dir; > + unsigned char present; is there really a hard limit of 255 hosts? > +}; > > static ssize_t proc_scsi_host_write(struct file *file, const char __user *buf, > size_t count, loff_t *ppos) > @@ -83,6 +98,32 @@ static int proc_scsi_host_open(struct inode *inode, struct file *file) > 4 * PAGE_SIZE); > } > > +static struct scsi_proc_entry * > +__scsi_lookup_proc_entry(const struct scsi_host_template *sht) > +{ > + struct scsi_proc_entry *e; > + > + lockdep_assert_held(&global_host_template_mutex); I'm not sure we really need this - maybe a comment would be better. I don't care too much either way. > + > + list_for_each_entry(e, &scsi_proc_list, entry) > + if (e->sht == sht) > + return e; > + > + return NULL; > +} > + > +static struct scsi_proc_entry * > +scsi_lookup_proc_entry(const struct scsi_host_template *sht) > +{ > + struct scsi_proc_entry *e; > + > + mutex_lock(&global_host_template_mutex); > + e = __scsi_lookup_proc_entry(sht); > + mutex_unlock(&global_host_template_mutex); > + > + return e; > +} > + > /** > * scsi_template_proc_dir() - returns the procfs dir for a SCSI host template > * @sht: SCSI host template pointer. > @@ -90,7 +131,9 @@ static int proc_scsi_host_open(struct inode *inode, struct file *file) > struct proc_dir_entry * > scsi_template_proc_dir(const struct scsi_host_template *sht) > { > - return sht->proc_dir; > + struct scsi_proc_entry *e = scsi_lookup_proc_entry(sht); > + > + return e ? e->proc_dir : NULL; > } > EXPORT_SYMBOL(scsi_template_proc_dir); > > @@ -109,34 +152,56 @@ static const struct proc_ops proc_scsi_ops = { > * Sets sht->proc_dir to the new directory. > */ > > -void scsi_proc_hostdir_add(struct scsi_host_template *sht) > +void scsi_proc_hostdir_add(const struct scsi_host_template *sht) > { > + struct scsi_proc_entry *e; > + > if (!sht->show_info) > return; > > mutex_lock(&global_host_template_mutex); > - if (!sht->present++) { > - sht->proc_dir = proc_mkdir(sht->proc_name, proc_scsi); > - if (!sht->proc_dir) > - printk(KERN_ERR "%s: proc_mkdir failed for %s\n", > - __func__, sht->proc_name); > + e = __scsi_lookup_proc_entry(sht); > + if (!e) { > + e = kzalloc(sizeof(*e), GFP_KERNEL); > + if (!e) > + goto unlock; > } > + if (e->present++) { > + e = NULL; > + goto unlock; > + } > + e->proc_dir = proc_mkdir(sht->proc_name, proc_scsi); > + if (!e->proc_dir) { > + printk(KERN_ERR "%s: proc_mkdir failed for %s\n", __func__, > + sht->proc_name); > + goto unlock; hmmm... in this case we don't add e to the list. As unlikely as it seems, if a subsequent attempt to create the proc dir passes for another host with the same sht, then e->present would be incorrect, right? > + } > + e->sht = sht; > + list_add_tail(&e->entry, &scsi_proc_list); > + e = NULL; > +unlock: > mutex_unlock(&global_host_template_mutex); > + > + kfree(e); > } > > /** > * scsi_proc_hostdir_rm - remove directory in /proc for a scsi host > * @sht: owner of directory > */ > -void scsi_proc_hostdir_rm(struct scsi_host_template *sht) > +void scsi_proc_hostdir_rm(const struct scsi_host_template *sht) > { > + struct scsi_proc_entry *e; > + > if (!sht->show_info) > return; > > mutex_lock(&global_host_template_mutex); > - if (!--sht->present && sht->proc_dir) { > + e = __scsi_lookup_proc_entry(sht); > + if (e && !--e->present) { > remove_proc_entry(sht->proc_name, proc_scsi); > - sht->proc_dir = NULL; > + list_del(&e->entry); > + kfree(e); > } > mutex_unlock(&global_host_template_mutex); > } > @@ -148,16 +213,21 @@ void scsi_proc_hostdir_rm(struct scsi_host_template *sht) > */ > void scsi_proc_host_add(struct Scsi_Host *shost) > { > - struct scsi_host_template *sht = shost->hostt; > + const struct scsi_host_template *sht = shost->hostt; > + struct scsi_proc_entry *e; > struct proc_dir_entry *p; > char name[10]; > > - if (!sht->proc_dir) > + if (!sht->show_info) > + return; > + > + e = scsi_lookup_proc_entry(sht); > + if (!e) > return; > > sprintf(name,"%d", shost->host_no); > - p = proc_create_data(name, S_IRUGO | S_IWUSR, > - sht->proc_dir, &proc_scsi_ops, shost); > + p = proc_create_data(name, S_IRUGO | S_IWUSR, e->proc_dir, > + &proc_scsi_ops, shost); > if (!p) > printk(KERN_ERR "%s: Failed to register host %d in" > "%s\n", __func__, shost->host_no, > @@ -170,13 +240,19 @@ void scsi_proc_host_add(struct Scsi_Host *shost) > */ > void scsi_proc_host_rm(struct Scsi_Host *shost) > { > + const struct scsi_host_template *sht = shost->hostt; > + struct scsi_proc_entry *e; > char name[10]; > > - if (!shost->hostt->proc_dir) > + if (!sht->show_info) > + return; > + > + e = scsi_lookup_proc_entry(sht); > + if (!e) > return; > > sprintf(name,"%d", shost->host_no); > - remove_proc_entry(name, shost->hostt->proc_dir); > + remove_proc_entry(name, e->proc_dir); > } > /** > * proc_print_scsidevice - return data about this host > diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h > index 030faca947d2..fb8184d87384 100644 > --- a/include/scsi/scsi_host.h > +++ b/include/scsi/scsi_host.h > @@ -357,12 +357,6 @@ struct scsi_host_template { > */ > const char *proc_name; > > - /* > - * Used to store the procfs directory if a driver implements the > - * show_info method. > - */ > - struct proc_dir_entry *proc_dir; > - > /* > * This determines if we will use a non-interrupt driven > * or an interrupt driven scheme. It is set to the maximum number > @@ -423,12 +417,6 @@ struct scsi_host_template { > */ > short cmd_per_lun; > > - /* > - * present contains counter indicating how many boards of this > - * type were found when we did the scan. > - */ > - unsigned char present; > - > /* If use block layer to manage tags, this is tag allocation policy */ > int tag_alloc_policy; > > .
On 9/13/22 07:26, John Garry wrote: > On 09/09/2022 00:35, Bart Van Assche wrote: >> +struct scsi_proc_entry { >> + struct list_head entry; >> + const struct scsi_host_template *sht; >> + struct proc_dir_entry *proc_dir; >> + unsigned char present; > > is there really a hard limit of 255 hosts? Apparently that limit exists today. I can use a wider data type for the 'present' member if you want. >> +static struct scsi_proc_entry * >> +__scsi_lookup_proc_entry(const struct scsi_host_template *sht) >> +{ >> + struct scsi_proc_entry *e; >> + >> + lockdep_assert_held(&global_host_template_mutex); > > I'm not sure we really need this - maybe a comment would be better. I > don't care too much either way. lockdep_assert_held() statements get verified at runtime if lockdep is enabled but comments not. This is why I prefer lockdep_assert_held() over a comment. >> + if (e->present++) { >> + e = NULL; >> + goto unlock; >> + } >> + e->proc_dir = proc_mkdir(sht->proc_name, proc_scsi); >> + if (!e->proc_dir) { >> + printk(KERN_ERR "%s: proc_mkdir failed for %s\n", __func__, >> + sht->proc_name); >> + goto unlock; > > hmmm... in this case we don't add e to the list. As unlikely as it > seems, if a subsequent attempt to create the proc dir passes for another > host with the same sht, then e->present would be incorrect, right? Right, this needs to be fixed. Thanks, Bart.
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h index f385b3f04d6e..be5d7c9b7f39 100644 --- a/drivers/scsi/scsi_priv.h +++ b/drivers/scsi/scsi_priv.h @@ -100,8 +100,8 @@ extern void scsi_evt_thread(struct work_struct *work); /* scsi_proc.c */ #ifdef CONFIG_SCSI_PROC_FS -extern void scsi_proc_hostdir_add(struct scsi_host_template *); -extern void scsi_proc_hostdir_rm(struct scsi_host_template *); +extern void scsi_proc_hostdir_add(const struct scsi_host_template *); +extern void scsi_proc_hostdir_rm(const struct scsi_host_template *); extern void scsi_proc_host_add(struct Scsi_Host *); extern void scsi_proc_host_rm(struct Scsi_Host *); extern int scsi_init_procfs(void); diff --git a/drivers/scsi/scsi_proc.c b/drivers/scsi/scsi_proc.c index eeb9261c93f7..e04db652a81e 100644 --- a/drivers/scsi/scsi_proc.c +++ b/drivers/scsi/scsi_proc.c @@ -43,8 +43,23 @@ static struct proc_dir_entry *proc_scsi; -/* Protect sht->present and sht->proc_dir */ +/* Protects scsi_proc_list */ static DEFINE_MUTEX(global_host_template_mutex); +static LIST_HEAD(scsi_proc_list); + +/** + * struct scsi_proc_entry - (host template, SCSI proc dir) association + * @entry: entry in scsi_proc_list. + * @sht: SCSI host template associated with the procfs directory. + * @proc_dir: procfs directory associated with the SCSI host template. + * @present: Number of SCSI hosts instantiated for @sht. + */ +struct scsi_proc_entry { + struct list_head entry; + const struct scsi_host_template *sht; + struct proc_dir_entry *proc_dir; + unsigned char present; +}; static ssize_t proc_scsi_host_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) @@ -83,6 +98,32 @@ static int proc_scsi_host_open(struct inode *inode, struct file *file) 4 * PAGE_SIZE); } +static struct scsi_proc_entry * +__scsi_lookup_proc_entry(const struct scsi_host_template *sht) +{ + struct scsi_proc_entry *e; + + lockdep_assert_held(&global_host_template_mutex); + + list_for_each_entry(e, &scsi_proc_list, entry) + if (e->sht == sht) + return e; + + return NULL; +} + +static struct scsi_proc_entry * +scsi_lookup_proc_entry(const struct scsi_host_template *sht) +{ + struct scsi_proc_entry *e; + + mutex_lock(&global_host_template_mutex); + e = __scsi_lookup_proc_entry(sht); + mutex_unlock(&global_host_template_mutex); + + return e; +} + /** * scsi_template_proc_dir() - returns the procfs dir for a SCSI host template * @sht: SCSI host template pointer. @@ -90,7 +131,9 @@ static int proc_scsi_host_open(struct inode *inode, struct file *file) struct proc_dir_entry * scsi_template_proc_dir(const struct scsi_host_template *sht) { - return sht->proc_dir; + struct scsi_proc_entry *e = scsi_lookup_proc_entry(sht); + + return e ? e->proc_dir : NULL; } EXPORT_SYMBOL(scsi_template_proc_dir); @@ -109,34 +152,56 @@ static const struct proc_ops proc_scsi_ops = { * Sets sht->proc_dir to the new directory. */ -void scsi_proc_hostdir_add(struct scsi_host_template *sht) +void scsi_proc_hostdir_add(const struct scsi_host_template *sht) { + struct scsi_proc_entry *e; + if (!sht->show_info) return; mutex_lock(&global_host_template_mutex); - if (!sht->present++) { - sht->proc_dir = proc_mkdir(sht->proc_name, proc_scsi); - if (!sht->proc_dir) - printk(KERN_ERR "%s: proc_mkdir failed for %s\n", - __func__, sht->proc_name); + e = __scsi_lookup_proc_entry(sht); + if (!e) { + e = kzalloc(sizeof(*e), GFP_KERNEL); + if (!e) + goto unlock; } + if (e->present++) { + e = NULL; + goto unlock; + } + e->proc_dir = proc_mkdir(sht->proc_name, proc_scsi); + if (!e->proc_dir) { + printk(KERN_ERR "%s: proc_mkdir failed for %s\n", __func__, + sht->proc_name); + goto unlock; + } + e->sht = sht; + list_add_tail(&e->entry, &scsi_proc_list); + e = NULL; +unlock: mutex_unlock(&global_host_template_mutex); + + kfree(e); } /** * scsi_proc_hostdir_rm - remove directory in /proc for a scsi host * @sht: owner of directory */ -void scsi_proc_hostdir_rm(struct scsi_host_template *sht) +void scsi_proc_hostdir_rm(const struct scsi_host_template *sht) { + struct scsi_proc_entry *e; + if (!sht->show_info) return; mutex_lock(&global_host_template_mutex); - if (!--sht->present && sht->proc_dir) { + e = __scsi_lookup_proc_entry(sht); + if (e && !--e->present) { remove_proc_entry(sht->proc_name, proc_scsi); - sht->proc_dir = NULL; + list_del(&e->entry); + kfree(e); } mutex_unlock(&global_host_template_mutex); } @@ -148,16 +213,21 @@ void scsi_proc_hostdir_rm(struct scsi_host_template *sht) */ void scsi_proc_host_add(struct Scsi_Host *shost) { - struct scsi_host_template *sht = shost->hostt; + const struct scsi_host_template *sht = shost->hostt; + struct scsi_proc_entry *e; struct proc_dir_entry *p; char name[10]; - if (!sht->proc_dir) + if (!sht->show_info) + return; + + e = scsi_lookup_proc_entry(sht); + if (!e) return; sprintf(name,"%d", shost->host_no); - p = proc_create_data(name, S_IRUGO | S_IWUSR, - sht->proc_dir, &proc_scsi_ops, shost); + p = proc_create_data(name, S_IRUGO | S_IWUSR, e->proc_dir, + &proc_scsi_ops, shost); if (!p) printk(KERN_ERR "%s: Failed to register host %d in" "%s\n", __func__, shost->host_no, @@ -170,13 +240,19 @@ void scsi_proc_host_add(struct Scsi_Host *shost) */ void scsi_proc_host_rm(struct Scsi_Host *shost) { + const struct scsi_host_template *sht = shost->hostt; + struct scsi_proc_entry *e; char name[10]; - if (!shost->hostt->proc_dir) + if (!sht->show_info) + return; + + e = scsi_lookup_proc_entry(sht); + if (!e) return; sprintf(name,"%d", shost->host_no); - remove_proc_entry(name, shost->hostt->proc_dir); + remove_proc_entry(name, e->proc_dir); } /** * proc_print_scsidevice - return data about this host diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index 030faca947d2..fb8184d87384 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h @@ -357,12 +357,6 @@ struct scsi_host_template { */ const char *proc_name; - /* - * Used to store the procfs directory if a driver implements the - * show_info method. - */ - struct proc_dir_entry *proc_dir; - /* * This determines if we will use a non-interrupt driven * or an interrupt driven scheme. It is set to the maximum number @@ -423,12 +417,6 @@ struct scsi_host_template { */ short cmd_per_lun; - /* - * present contains counter indicating how many boards of this - * type were found when we did the scan. - */ - unsigned char present; - /* If use block layer to manage tags, this is tag allocation policy */ int tag_alloc_policy;
Instead of using scsi_host_template members to track the SCSI proc directory entries, track these entries in a list. This patch changes the time needed for looking up the proc dir pointer from O(1) into O(n). I think this is acceptable since the number of SCSI host adapter types per host is usually small (less than ten). This patch has been tested by attaching two USB storage devices to a qemu host: $ grep -aH . /proc/scsi/usb-storage/* /proc/scsi/usb-storage/7: Host scsi7: usb-storage /proc/scsi/usb-storage/7: Vendor: QEMU /proc/scsi/usb-storage/7: Product: QEMU USB HARDDRIVE /proc/scsi/usb-storage/7:Serial Number: 1-0000:00:02.1:00.0-6 /proc/scsi/usb-storage/7: Protocol: Transparent SCSI /proc/scsi/usb-storage/7: Transport: Bulk /proc/scsi/usb-storage/7: Quirks: SANE_SENSE /proc/scsi/usb-storage/8: Host scsi8: usb-storage /proc/scsi/usb-storage/8: Vendor: QEMU /proc/scsi/usb-storage/8: Product: QEMU USB HARDDRIVE /proc/scsi/usb-storage/8:Serial Number: 1-0000:00:02.1:00.0-7 /proc/scsi/usb-storage/8: Protocol: Transparent SCSI /proc/scsi/usb-storage/8: Transport: Bulk /proc/scsi/usb-storage/8: Quirks: SANE_SENSE This patch prepares for constifying most SCSI host templates. Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@redhat.com> Cc: Hannes Reinecke <hare@suse.de> Cc: John Garry <john.garry@huawei.com> Cc: Mike Christie <michael.christie@oracle.com> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Signed-off-by: Bart Van Assche <bvanassche@acm.org> --- drivers/scsi/scsi_priv.h | 4 +- drivers/scsi/scsi_proc.c | 110 +++++++++++++++++++++++++++++++++------ include/scsi/scsi_host.h | 12 ----- 3 files changed, 95 insertions(+), 31 deletions(-)