[libata] locking rewrite (== fix)

A lot of power packed into a little patch.

This change eliminates the sharing between our controller-wide spinlock
and the SCSI core's Scsi_Host lock.  As the locking in libata was
already highly compartmentalized, always referencing our own lock, and
never scsi_host::host_lock.

As a side effect, this change eliminates a deadlock from calling
scsi_finish_command() while inside our spinlock.

2 files changed, 8 insertions, 3 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index a17e12032f65..ff18fa7044c5 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -4089,8 +4089,6 @@ static void ata_host_init(struct ata_port *ap, struct Scsi_Host *host,
         host->unique_id = ata_unique_id++;
         host->max_cmd_len = 12;
 
-        scsi_assign_lock(host, &host_set->lock);
-
         ap->flags = ATA_FLAG_PORT_DISABLED;
         ap->id = host->unique_id;
         ap->host = host;
diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 1e3792f86fcf..248baae96486 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -39,6 +39,7 @@
 #include <scsi/scsi.h>
 #include "scsi.h"
 #include <scsi/scsi_host.h>
+#include <scsi/scsi_device.h>
 #include <linux/libata.h>
 #include <linux/hdreg.h>
 #include <asm/uaccess.h>
@@ -2405,8 +2406,12 @@ int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
         struct ata_port *ap;
         struct ata_device *dev;
         struct scsi_device *scsidev = cmd->device;
+        struct Scsi_Host *shost = scsidev->host;
 
-        ap = (struct ata_port *) &scsidev->host->hostdata[0];
+        ap = (struct ata_port *) &shost->hostdata[0];
+
+        spin_unlock(shost->host_lock);
+        spin_lock(&ap->host_set->lock);
 
         ata_scsi_dump_cdb(ap, cmd);
 
@@ -2429,6 +2434,8 @@ int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
                 ata_scsi_translate(ap, dev, cmd, done, atapi_xlat);
 
 out_unlock:
+        spin_unlock(&ap->host_set->lock);
+        spin_lock(shost->host_lock);
         return 0;
 }