From 6b7f123f378743d739377871c0cbfbaf28c7d25a Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Tue, 26 Jun 2007 15:18:51 -0600 Subject: [PATCH] [SCSI] Fix async scanning double-add problems Stress-testing and some thought has revealed some places where asynchronous scanning needs some more attention to locking. - Since async_scan is a bit, we need to hold the host_lock while modifying it to prevent races against other CPUs modifying the word that bit is in. This is probably a theoretical race for the moment, but other patches may change that. - The async_scan bit means not only that this host is being scanned asynchronously, but that all the devices attached to this host are not yet added to sysfs. So we must ensure that this bit is always in sync. I've chosen to do this with the scan_mutex since it's already acquired in most of the right places. - If the host changes state to deleted while we're in the middle of a scan, we'll end up with some devices on the host's list which must be deleted. Add a check to scsi_sysfs_add_devices() to ensure the host is still running. - To avoid the async_scan bit being protected by three locks, the async_scan_lock now only protects the scanning_list. Signed-off-by: Matthew Wilcox Signed-off-by: James Bottomley --- drivers/scsi/scsi_scan.c | 37 +++++++++++++++++++++++++++---------- 1 file changed, 27 insertions(+), 10 deletions(-) diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index a86e62f4b3b..309b2246d2d 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -121,6 +121,7 @@ MODULE_PARM_DESC(inq_timeout, "Timeout (in seconds) waiting for devices to answer INQUIRY." " Default is 5. Some non-compliant devices need more."); +/* This lock protects only this list */ static DEFINE_SPINLOCK(async_scan_lock); static LIST_HEAD(scanning_hosts); @@ -1466,14 +1467,14 @@ struct scsi_device *__scsi_add_device(struct Scsi_Host *shost, uint channel, if (strncmp(scsi_scan_type, "none", 4) == 0) return ERR_PTR(-ENODEV); - if (!shost->async_scan) - scsi_complete_async_scans(); - starget = scsi_alloc_target(parent, channel, id); if (!starget) return ERR_PTR(-ENOMEM); mutex_lock(&shost->scan_mutex); + if (!shost->async_scan) + scsi_complete_async_scans(); + if (scsi_host_scan_allowed(shost)) scsi_probe_and_add_lun(starget, lun, NULL, &sdev, 1, hostdata); mutex_unlock(&shost->scan_mutex); @@ -1586,10 +1587,10 @@ void scsi_scan_target(struct device *parent, unsigned int channel, if (strncmp(scsi_scan_type, "none", 4) == 0) return; + mutex_lock(&shost->scan_mutex); 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); mutex_unlock(&shost->scan_mutex); @@ -1634,15 +1635,15 @@ 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))) return -EINVAL; mutex_lock(&shost->scan_mutex); + if (!shost->async_scan) + scsi_complete_async_scans(); + if (scsi_host_scan_allowed(shost)) { if (channel == SCAN_WILD_CARD) for (channel = 0; channel <= shost->max_channel; @@ -1661,7 +1662,8 @@ 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) + if (!scsi_host_scan_allowed(shost) || + scsi_sysfs_add_sdev(sdev) != 0) scsi_destroy_sdev(sdev); } } @@ -1679,6 +1681,7 @@ static void scsi_sysfs_add_devices(struct Scsi_Host *shost) static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) { struct async_scan_data *data; + unsigned long flags; if (strncmp(scsi_scan_type, "sync", 4) == 0) return NULL; @@ -1698,8 +1701,13 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) goto err; init_completion(&data->prev_finished); - spin_lock(&async_scan_lock); + mutex_lock(&shost->scan_mutex); + spin_lock_irqsave(shost->host_lock, flags); shost->async_scan = 1; + spin_unlock_irqrestore(shost->host_lock, flags); + mutex_unlock(&shost->scan_mutex); + + spin_lock(&async_scan_lock); if (list_empty(&scanning_hosts)) complete(&data->prev_finished); list_add_tail(&data->list, &scanning_hosts); @@ -1723,11 +1731,15 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) static void scsi_finish_async_scan(struct async_scan_data *data) { struct Scsi_Host *shost; + unsigned long flags; if (!data) return; shost = data->shost; + + mutex_lock(&shost->scan_mutex); + if (!shost->async_scan) { printk("%s called twice for host %d", __FUNCTION__, shost->host_no); @@ -1739,8 +1751,13 @@ static void scsi_finish_async_scan(struct async_scan_data *data) scsi_sysfs_add_devices(shost); - spin_lock(&async_scan_lock); + spin_lock_irqsave(shost->host_lock, flags); shost->async_scan = 0; + spin_unlock_irqrestore(shost->host_lock, flags); + + mutex_unlock(&shost->scan_mutex); + + spin_lock(&async_scan_lock); list_del(&data->list); if (!list_empty(&scanning_hosts)) { struct async_scan_data *next = list_entry(scanning_hosts.next, -- 2.41.1