From 3e082a910d217b2e7b186077ebf5a1126a68c62f Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Thu, 28 Sep 2006 15:19:20 -0600 Subject: [SCSI] Add ability to scan scsi busses asynchronously Since it often takes around 20-30 seconds to scan a scsi bus, it's highly advantageous to do this in parallel with other things. The bulk of this patch is ensuring that devices don't change numbering, and that all devices are discovered prior to trying to start init. For those who build SCSI as modules, there's a new scsi_wait_scan module that will ensure all bus scans are finished. This patch only handles drivers which call scsi_scan_host. Fibre Channel, SAS, SATA, USB and Firewire all need additional work. Signed-off-by: Matthew Wilcox Signed-off-by: James Bottomley --- drivers/scsi/scsi_scan.c | 203 +++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 197 insertions(+), 6 deletions(-) (limited to 'drivers/scsi/scsi_scan.c') diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index fd9e281c3bfe..148e24cc3222 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -29,7 +29,9 @@ #include #include #include -#include +#include +#include +#include #include #include @@ -87,6 +89,11 @@ module_param_named(max_luns, max_scsi_luns, int, S_IRUGO|S_IWUSR); MODULE_PARM_DESC(max_luns, "last scsi LUN (should be between 1 and 2^32-1)"); +static char scsi_scan_type[6] = "sync"; + +module_param_string(scan, scsi_scan_type, sizeof(scsi_scan_type), S_IRUGO); +MODULE_PARM_DESC(scan, "sync, async or none"); + /* * max_scsi_report_luns: the maximum number of LUNS that will be * returned from the REPORT LUNS command. 8 times this value must @@ -108,6 +115,68 @@ MODULE_PARM_DESC(inq_timeout, "Timeout (in seconds) waiting for devices to answer INQUIRY." " Default is 5. Some non-compliant devices need more."); +static DEFINE_SPINLOCK(async_scan_lock); +static LIST_HEAD(scanning_hosts); + +struct async_scan_data { + struct list_head list; + struct Scsi_Host *shost; + struct completion prev_finished; +}; + +/** + * scsi_complete_async_scans - Wait for asynchronous scans to complete + * + * Asynchronous scans add themselves to the scanning_hosts list. Once + * that list is empty, we know that the scans are complete. Rather than + * waking up periodically to check the state of the list, we pretend to be + * a scanning task by adding ourselves at the end of the list and going to + * sleep. When the task before us wakes us up, we take ourselves off the + * list and return. + */ +int scsi_complete_async_scans(void) +{ + struct async_scan_data *data; + + do { + if (list_empty(&scanning_hosts)) + return 0; + /* If we can't get memory immediately, that's OK. Just + * sleep a little. Even if we never get memory, the async + * scans will finish eventually. + */ + data = kmalloc(sizeof(*data), GFP_KERNEL); + if (!data) + msleep(1); + } while (!data); + + data->shost = NULL; + init_completion(&data->prev_finished); + + spin_lock(&async_scan_lock); + /* Check that there's still somebody else on the list */ + if (list_empty(&scanning_hosts)) + goto done; + list_add_tail(&data->list, &scanning_hosts); + spin_unlock(&async_scan_lock); + + printk(KERN_INFO "scsi: waiting for bus probes to complete ...\n"); + wait_for_completion(&data->prev_finished); + + spin_lock(&async_scan_lock); + list_del(&data->list); + done: + spin_unlock(&async_scan_lock); + + kfree(data); + return 0; +} + +#ifdef MODULE +/* Only exported for the benefit of scsi_wait_scan */ +EXPORT_SYMBOL_GPL(scsi_complete_async_scans); +#endif + /** * scsi_unlock_floptical - unlock device via a special MODE SENSE command * @sdev: scsi device to send command to @@ -619,7 +688,7 @@ static int scsi_probe_lun(struct scsi_device *sdev, unsigned char *inq_result, * SCSI_SCAN_LUN_PRESENT: a new scsi_device was allocated and initialized **/ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result, - int *bflags) + int *bflags, int async) { /* * XXX do not save the inquiry, since it can change underneath us, @@ -795,7 +864,7 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result, * register it and tell the rest of the kernel * about it. */ - if (scsi_sysfs_add_sdev(sdev) != 0) + if (!async && scsi_sysfs_add_sdev(sdev) != 0) return SCSI_SCAN_NO_RESPONSE; return SCSI_SCAN_LUN_PRESENT; @@ -964,7 +1033,7 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget, goto out_free_result; } - res = scsi_add_lun(sdev, result, &bflags); + res = scsi_add_lun(sdev, result, &bflags, shost->async_scan); if (res == SCSI_SCAN_LUN_PRESENT) { if (bflags & BLIST_KEY) { sdev->lockable = 0; @@ -1464,6 +1533,9 @@ void scsi_scan_target(struct device *parent, unsigned int channel, { struct Scsi_Host *shost = dev_to_shost(parent); + if (!shost->async_scan) + scsi_complete_async_scans(); + mutex_lock(&shost->scan_mutex); if (scsi_host_scan_allowed(shost)) __scsi_scan_target(parent, channel, id, lun, rescan); @@ -1509,6 +1581,9 @@ int scsi_scan_host_selected(struct Scsi_Host *shost, unsigned int channel, "%s: <%u:%u:%u>\n", __FUNCTION__, channel, id, lun)); + if (!shost->async_scan) + scsi_complete_async_scans(); + if (((channel != SCAN_WILD_CARD) && (channel > shost->max_channel)) || ((id != SCAN_WILD_CARD) && (id >= shost->max_id)) || ((lun != SCAN_WILD_CARD) && (lun > shost->max_lun))) @@ -1529,14 +1604,130 @@ int scsi_scan_host_selected(struct Scsi_Host *shost, unsigned int channel, return 0; } +static void scsi_sysfs_add_devices(struct Scsi_Host *shost) +{ + struct scsi_device *sdev; + shost_for_each_device(sdev, shost) { + if (scsi_sysfs_add_sdev(sdev) != 0) + scsi_destroy_sdev(sdev); + } +} + +/** + * scsi_prep_async_scan - prepare for an async scan + * @shost: the host which will be scanned + * Returns: a cookie to be passed to scsi_finish_async_scan() + * + * Tells the midlayer this host is going to do an asynchronous scan. + * It reserves the host's position in the scanning list and ensures + * that other asynchronous scans started after this one won't affect the + * ordering of the discovered devices. + */ +struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) +{ + struct async_scan_data *data; + + if (strncmp(scsi_scan_type, "sync", 4) == 0) + return NULL; + + if (shost->async_scan) { + printk("%s called twice for host %d", __FUNCTION__, + shost->host_no); + dump_stack(); + return NULL; + } + + data = kmalloc(sizeof(*data), GFP_KERNEL); + if (!data) + goto err; + data->shost = scsi_host_get(shost); + if (!data->shost) + goto err; + init_completion(&data->prev_finished); + + spin_lock(&async_scan_lock); + shost->async_scan = 1; + if (list_empty(&scanning_hosts)) + complete(&data->prev_finished); + list_add_tail(&data->list, &scanning_hosts); + spin_unlock(&async_scan_lock); + + return data; + + err: + kfree(data); + return NULL; +} + +/** + * scsi_finish_async_scan - asynchronous scan has finished + * @data: cookie returned from earlier call to scsi_prep_async_scan() + * + * All the devices currently attached to this host have been found. + * This function announces all the devices it has found to the rest + * of the system. + */ +void scsi_finish_async_scan(struct async_scan_data *data) +{ + struct Scsi_Host *shost; + + if (!data) + return; + + shost = data->shost; + if (!shost->async_scan) { + printk("%s called twice for host %d", __FUNCTION__, + shost->host_no); + dump_stack(); + return; + } + + wait_for_completion(&data->prev_finished); + + scsi_sysfs_add_devices(shost); + + spin_lock(&async_scan_lock); + shost->async_scan = 0; + list_del(&data->list); + if (!list_empty(&scanning_hosts)) { + struct async_scan_data *next = list_entry(scanning_hosts.next, + struct async_scan_data, list); + complete(&next->prev_finished); + } + spin_unlock(&async_scan_lock); + + scsi_host_put(shost); + kfree(data); +} + +static int do_scan_async(void *_data) +{ + struct async_scan_data *data = _data; + scsi_scan_host_selected(data->shost, SCAN_WILD_CARD, SCAN_WILD_CARD, + SCAN_WILD_CARD, 0); + + scsi_finish_async_scan(data); + return 0; +} + /** * scsi_scan_host - scan the given adapter * @shost: adapter to scan **/ void scsi_scan_host(struct Scsi_Host *shost) { - scsi_scan_host_selected(shost, SCAN_WILD_CARD, SCAN_WILD_CARD, - SCAN_WILD_CARD, 0); + struct async_scan_data *data; + + if (strncmp(scsi_scan_type, "none", 4) == 0) + return; + + data = scsi_prep_async_scan(shost); + if (!data) { + scsi_scan_host_selected(shost, SCAN_WILD_CARD, SCAN_WILD_CARD, + SCAN_WILD_CARD, 0); + return; + } + kthread_run(do_scan_async, data, "scsi_scan_%d", shost->host_no); } EXPORT_SYMBOL(scsi_scan_host); -- cgit v1.2.3 From 21db1882f79a1ad5977cae6766376a63f60ec414 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Wed, 22 Nov 2006 13:24:52 -0700 Subject: [SCSI] Add Kconfig option for asynchronous SCSI scanning Without this patch, the user has to add a kernel command line parameter to get asynchronous SCSI scanning. Now they can select the default at compile time and still override it at boot time if they need to. Signed-off-by: Matthew Wilcox Signed-off-by: James Bottomley --- drivers/scsi/Kconfig | 17 +++++++++++++++++ drivers/scsi/scsi_scan.c | 8 +++++++- 2 files changed, 24 insertions(+), 1 deletion(-) (limited to 'drivers/scsi/scsi_scan.c') diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig index 5881464a938d..8442be1bb162 100644 --- a/drivers/scsi/Kconfig +++ b/drivers/scsi/Kconfig @@ -216,6 +216,23 @@ config SCSI_LOGGING there should be no noticeable performance impact as long as you have logging turned off. +config SCSI_SCAN_ASYNC + bool "Asynchronous SCSI scanning" + depends on SCSI + help + The SCSI subsystem can probe for devices while the rest of the + system continues booting, and even probe devices on different + busses in parallel, leading to a significant speed-up. + If you have built SCSI as modules, enabling this option can + be a problem as the devices may not have been found by the + time your system expects them to have been. You can load the + scsi_wait_scan module to ensure that all scans have completed. + If you build your SCSI drivers into the kernel, then everything + will work fine if you say Y here. + + You can override this choice by specifying scsi_mod.scan="sync" + or "async" on the kernel's command line. + menu "SCSI Transports" depends on SCSI diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index aa1b1e0e9d22..d91d268dd331 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -89,7 +89,13 @@ module_param_named(max_luns, max_scsi_luns, int, S_IRUGO|S_IWUSR); MODULE_PARM_DESC(max_luns, "last scsi LUN (should be between 1 and 2^32-1)"); -static char scsi_scan_type[6] = "sync"; +#ifdef CONFIG_SCSI_SCAN_ASYNC +#define SCSI_SCAN_TYPE_DEFAULT "async" +#else +#define SCSI_SCAN_TYPE_DEFAULT "sync" +#endif + +static char scsi_scan_type[6] = SCSI_SCAN_TYPE_DEFAULT; module_param_string(scan, scsi_scan_type, sizeof(scsi_scan_type), S_IRUGO); MODULE_PARM_DESC(scan, "sync, async or none"); -- cgit v1.2.3 From 93b45af5c6b9d41bbe9da11442291ac4eefc15b4 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Wed, 22 Nov 2006 13:24:53 -0700 Subject: [SCSI] fix missing check for no scanning Drivers that called scsi_scan_target() instead of scsi_scan_host() were still adding devices; this needs to be under the control of userspace, not the driver. Signed-off-by: Matthew Wilcox Signed-off-by: James Bottomley --- drivers/scsi/scsi_scan.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'drivers/scsi/scsi_scan.c') diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index d91d268dd331..3ccaa4be92d8 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -1549,6 +1549,9 @@ void scsi_scan_target(struct device *parent, unsigned int channel, { struct Scsi_Host *shost = dev_to_shost(parent); + if (strncmp(scsi_scan_type, "none", 4) == 0) + return; + if (!shost->async_scan) scsi_complete_async_scans(); -- cgit v1.2.3 From 1aa8fab2acf1cb8b341131b726773fcff0abc707 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Wed, 22 Nov 2006 13:24:54 -0700 Subject: [SCSI] Make scsi_scan_host work for drivers which find their own targets If a driver can find its own targets, it can now fill in scan_finished and (optionally) scan_start in the scsi_host_template. Then, when it calls scsi_scan_host(), it will be called back (from a thread if asynchronous discovery is enabled), first to start the scan, and then at intervals to check if the scan is completed. Also make scsi_prep_async_scan and scsi_finish_async_scan static. Signed-off-by: Matthew Wilcox Signed-off-by: James Bottomley --- drivers/scsi/scsi_scan.c | 27 ++++++++++++++++++++------- include/scsi/scsi_host.h | 18 ++++++++++++++++++ 2 files changed, 38 insertions(+), 7 deletions(-) (limited to 'drivers/scsi/scsi_scan.c') diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index 3ccaa4be92d8..4d656148bd67 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -1642,7 +1642,7 @@ static void scsi_sysfs_add_devices(struct Scsi_Host *shost) * that other asynchronous scans started after this one won't affect the * ordering of the discovered devices. */ -struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) +static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) { struct async_scan_data *data; @@ -1686,7 +1686,7 @@ struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) * This function announces all the devices it has found to the rest * of the system. */ -void scsi_finish_async_scan(struct async_scan_data *data) +static void scsi_finish_async_scan(struct async_scan_data *data) { struct Scsi_Host *shost; @@ -1719,12 +1719,25 @@ void scsi_finish_async_scan(struct async_scan_data *data) kfree(data); } -static int do_scan_async(void *_data) +static void do_scsi_scan_host(struct Scsi_Host *shost) { - struct async_scan_data *data = _data; - scsi_scan_host_selected(data->shost, SCAN_WILD_CARD, SCAN_WILD_CARD, + if (shost->hostt->scan_finished) { + unsigned long start = jiffies; + if (shost->hostt->scan_start) + shost->hostt->scan_start(shost); + + while (!shost->hostt->scan_finished(shost, jiffies - start)) + msleep(10); + } else { + scsi_scan_host_selected(shost, SCAN_WILD_CARD, SCAN_WILD_CARD, SCAN_WILD_CARD, 0); + } +} +static int do_scan_async(void *_data) +{ + struct async_scan_data *data = _data; + do_scsi_scan_host(data->shost); scsi_finish_async_scan(data); return 0; } @@ -1742,10 +1755,10 @@ void scsi_scan_host(struct Scsi_Host *shost) data = scsi_prep_async_scan(shost); if (!data) { - scsi_scan_host_selected(shost, SCAN_WILD_CARD, SCAN_WILD_CARD, - SCAN_WILD_CARD, 0); + do_scsi_scan_host(shost); return; } + kthread_run(do_scan_async, data, "scsi_scan_%d", shost->host_no); } EXPORT_SYMBOL(scsi_scan_host); diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index e618e711ea57..6d8945d71c65 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h @@ -240,6 +240,24 @@ struct scsi_host_template { */ void (* target_destroy)(struct scsi_target *); + /* + * If a host has the ability to discover targets on its own instead + * of scanning the entire bus, it can fill in this function and + * call scsi_scan_host(). This function will be called periodically + * until it returns 1 with the scsi_host and the elapsed time of + * the scan in jiffies. + * + * Status: OPTIONAL + */ + int (* scan_finished)(struct Scsi_Host *, unsigned long); + + /* + * If the host wants to be called before the scan starts, but + * after the midlayer has set up ready for the scan, it can fill + * in this function. + */ + void (* scan_start)(struct Scsi_Host *); + /* * fill in this function to allow the queue depth of this host * to be changeable (on a per device basis). returns either -- cgit v1.2.3