[SCSI] st: get rid of scsi_tapes array

st currently allocates an array to store pointers to all of the
scsi_tape objects. It's used to discover available indexes to use as the
base for the minor number selection and later to look up scsi_tape
devices for character devices.

We switch to using an IDR for minor selection and a pointer from
st_modedef back to scsi_tape for the lookups.

Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Acked-by: Kai Mäkisara <kai.makisara@kolumbus.fi>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 68 insertions, 110 deletions

diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index 492b53b6e51d..052622fdba02 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -37,6 +37,7 @@ static const char *verstr = "20101219";
 #include <linux/blkdev.h>
 #include <linux/moduleparam.h>
 #include <linux/cdev.h>
+#include <linux/idr.h>
 #include <linux/delay.h>
 #include <linux/mutex.h>
 
@@ -81,9 +82,6 @@ static int try_direct_io = TRY_DIRECT_IO;
 static int try_rdio = 1;
 static int try_wdio = 1;
 
-static int st_dev_max;
-static int st_nr_dev;
-
 static struct class st_sysfs_class;
 static struct device_attribute st_dev_attrs[];
 
@@ -174,13 +172,9 @@ static int debugging = DEBUG;
    24 bits) */
 #define SET_DENS_AND_BLK 0x10001
 
-static DEFINE_RWLOCK(st_dev_arr_lock);
-
 static int st_fixed_buffer_size = ST_FIXED_BUFFER_SIZE;
 static int st_max_sg_segs = ST_MAX_SG;
 
-static struct scsi_tape **scsi_tapes = NULL;
-
 static int modes_defined;
 
 static int enlarge_buffer(struct st_buffer *, int, int);
@@ -222,6 +216,10 @@ static void scsi_tape_release(struct kref *);
 #define to_scsi_tape(obj) container_of(obj, struct scsi_tape, kref)
 
 static DEFINE_MUTEX(st_ref_mutex);
+static DEFINE_SPINLOCK(st_index_lock);
+static DEFINE_SPINLOCK(st_use_lock);
+static DEFINE_IDR(st_index_idr);
+
 
 
 #include "osst_detect.h"
@@ -239,10 +237,9 @@ static struct scsi_tape *scsi_tape_get(int dev)
         struct scsi_tape *STp = NULL;
 
         mutex_lock(&st_ref_mutex);
-        write_lock(&st_dev_arr_lock);
+        spin_lock(&st_index_lock);
 
-        if (dev < st_dev_max && scsi_tapes != NULL)
-                STp = scsi_tapes[dev];
+        STp = idr_find(&st_index_idr, dev);
         if (!STp) goto out;
 
         kref_get(&STp->kref);
@@ -259,7 +256,7 @@ out_put:
         kref_put(&STp->kref, scsi_tape_release);
         STp = NULL;
 out:
-        write_unlock(&st_dev_arr_lock);
+        spin_unlock(&st_index_lock);
         mutex_unlock(&st_ref_mutex);
         return STp;
 }
@@ -1202,12 +1199,12 @@ static int st_open(struct inode *inode, struct file *filp)
                 return -ENXIO;
         }
 
-        write_lock(&st_dev_arr_lock);
         filp->private_data = STp;
         name = tape_name(STp);
 
+        spin_lock(&st_use_lock);
         if (STp->in_use) {
-                write_unlock(&st_dev_arr_lock);
+                spin_unlock(&st_use_lock);
                 scsi_tape_put(STp);
                 mutex_unlock(&st_mutex);
                 DEB( printk(ST_DEB_MSG "%s: Device already in use.\n", name); )
@@ -1215,7 +1212,7 @@ static int st_open(struct inode *inode, struct file *filp)
         }
 
         STp->in_use = 1;
-        write_unlock(&st_dev_arr_lock);
+        spin_unlock(&st_use_lock);
         STp->rew_at_close = STp->autorew_dev = (iminor(inode) & 0x80) == 0;
 
         if (scsi_autopm_get_device(STp->device) < 0) {
@@ -1404,9 +1401,9 @@ static int st_release(struct inode *inode, struct file *filp)
                 do_door_lock(STp, 0);
 
         normalize_buffer(STp->buffer);
-        write_lock(&st_dev_arr_lock);
+        spin_lock(&st_use_lock);
         STp->in_use = 0;
-        write_unlock(&st_dev_arr_lock);
+        spin_unlock(&st_use_lock);
         scsi_autopm_put_device(STp->device);
         scsi_tape_put(STp);
 
@@ -4029,58 +4026,16 @@ static int st_probe(struct device *dev)
                 goto out_buffer_free;
         }
 
-        write_lock(&st_dev_arr_lock);
-        if (st_nr_dev >= st_dev_max) {
-                struct scsi_tape **tmp_da;
-                int tmp_dev_max;
-
-                tmp_dev_max = max(st_nr_dev * 2, 8);
-                if (tmp_dev_max > ST_MAX_TAPES)
-                        tmp_dev_max = ST_MAX_TAPES;
-                if (tmp_dev_max <= st_nr_dev) {
-                        write_unlock(&st_dev_arr_lock);
-                        printk(KERN_ERR "st: Too many tape devices (max. %d).\n",
-                               ST_MAX_TAPES);
-                        goto out_put_disk;
-                }
-
-                tmp_da = kzalloc(tmp_dev_max * sizeof(struct scsi_tape *), GFP_ATOMIC);
-                if (tmp_da == NULL) {
-                        write_unlock(&st_dev_arr_lock);
-                        printk(KERN_ERR "st: Can't extend device array.\n");
-                        goto out_put_disk;
-                }
-
-                if (scsi_tapes != NULL) {
-                        memcpy(tmp_da, scsi_tapes,
-                               st_dev_max * sizeof(struct scsi_tape *));
-                        kfree(scsi_tapes);
-                }
-                scsi_tapes = tmp_da;
-
-                st_dev_max = tmp_dev_max;
-        }
-
-        for (i = 0; i < st_dev_max; i++)
-                if (scsi_tapes[i] == NULL)
-                        break;
-        if (i >= st_dev_max)
-                panic("scsi_devices corrupt (st)");
-
         tpnt = kzalloc(sizeof(struct scsi_tape), GFP_ATOMIC);
         if (tpnt == NULL) {
-                write_unlock(&st_dev_arr_lock);
                 printk(KERN_ERR "st: Can't allocate device descriptor.\n");
                 goto out_put_disk;
         }
         kref_init(&tpnt->kref);
         tpnt->disk = disk;
-        sprintf(disk->disk_name, "st%d", i);
         disk->private_data = &tpnt->driver;
         disk->queue = SDp->request_queue;
         tpnt->driver = &st_template;
-        scsi_tapes[i] = tpnt;
-        dev_num = i;
 
         tpnt->device = SDp;
         if (SDp->scsi_level <= 2)
@@ -4126,6 +4081,7 @@ static int st_probe(struct device *dev)
                 STm->default_compression = ST_DONT_TOUCH;
                 STm->default_blksize = (-1);    /* No forced size */
                 STm->default_density = (-1);    /* No forced density */
+                STm->tape = tpnt;
         }
 
         for (i = 0; i < ST_NBR_PARTITIONS; i++) {
@@ -4145,8 +4101,29 @@ static int st_probe(struct device *dev)
             tpnt->blksize_changed = 0;
         mutex_init(&tpnt->lock);
 
-        st_nr_dev++;
-        write_unlock(&st_dev_arr_lock);
+        if (!idr_pre_get(&st_index_idr, GFP_KERNEL)) {
+                pr_warn("st: idr expansion failed\n");
+                error = -ENOMEM;
+                goto out_put_disk;
+        }
+
+        spin_lock(&st_index_lock);
+        error = idr_get_new(&st_index_idr, tpnt, &dev_num);
+        spin_unlock(&st_index_lock);
+        if (error) {
+                pr_warn("st: idr allocation failed: %d\n", error);
+                goto out_put_disk;
+        }
+
+        if (dev_num > ST_MAX_TAPES) {
+                pr_err("st: Too many tape devices (max. %d).\n", ST_MAX_TAPES);
+                goto out_put_index;
+        }
+
+        tpnt->index = dev_num;
+        sprintf(disk->disk_name, "st%d", dev_num);
+
+        dev_set_drvdata(dev, tpnt);
 
         for (mode = 0; mode < ST_NBR_MODES; ++mode) {
                 STm = &(tpnt->modes[mode]);
@@ -4189,10 +4166,10 @@ static int st_probe(struct device *dev)
         return 0;
 
 out_free_tape:
+        sysfs_remove_link(&tpnt->device->sdev_gendev.kobj,
+                          "tape");
         for (mode=0; mode < ST_NBR_MODES; mode++) {
                 STm = &(tpnt->modes[mode]);
-                sysfs_remove_link(&tpnt->device->sdev_gendev.kobj,
-                                  "tape");
                 for (j=0; j < 2; j++) {
                         if (STm->cdevs[j]) {
                                 device_destroy(&st_sysfs_class,
@@ -4202,10 +4179,10 @@ out_free_tape:
                         }
                 }
         }
-        write_lock(&st_dev_arr_lock);
-        scsi_tapes[dev_num] = NULL;
-        st_nr_dev--;
-        write_unlock(&st_dev_arr_lock);
+out_put_index:
+        spin_lock(&st_index_lock);
+        idr_remove(&st_index_idr, dev_num);
+        spin_unlock(&st_index_lock);
 out_put_disk:
         put_disk(disk);
         kfree(tpnt);
@@ -4218,38 +4195,32 @@ out:
 
 static int st_remove(struct device *dev)
 {
-        struct scsi_device *SDp = to_scsi_device(dev);
-        struct scsi_tape *tpnt;
-        int i, j, mode;
-
-        scsi_autopm_get_device(SDp);
-        write_lock(&st_dev_arr_lock);
-        for (i = 0; i < st_dev_max; i++) {
-                tpnt = scsi_tapes[i];
-                if (tpnt != NULL && tpnt->device == SDp) {
-                        scsi_tapes[i] = NULL;
-                        st_nr_dev--;
-                        write_unlock(&st_dev_arr_lock);
-                        sysfs_remove_link(&tpnt->device->sdev_gendev.kobj,
-                                          "tape");
-                        for (mode = 0; mode < ST_NBR_MODES; ++mode) {
-                                for (j=0; j < 2; j++) {
-                                        device_destroy(&st_sysfs_class,
-                                                       MKDEV(SCSI_TAPE_MAJOR,
-                                                             TAPE_MINOR(i, mode, j)));
-                                        cdev_del(tpnt->modes[mode].cdevs[j]);
-                                        tpnt->modes[mode].cdevs[j] = NULL;
-                                }
-                        }
-
-                        mutex_lock(&st_ref_mutex);
-                        kref_put(&tpnt->kref, scsi_tape_release);
-                        mutex_unlock(&st_ref_mutex);
-                        return 0;
+        struct scsi_tape *tpnt = dev_get_drvdata(dev);
+        int rew, mode;
+        dev_t cdev_devno;
+        struct cdev *cdev;
+        int index = tpnt->index;
+
+        scsi_autopm_get_device(to_scsi_device(dev));
+        sysfs_remove_link(&tpnt->device->sdev_gendev.kobj, "tape");
+        for (mode = 0; mode < ST_NBR_MODES; ++mode) {
+                for (rew = 0; rew < 2; rew++) {
+                        cdev = tpnt->modes[mode].cdevs[rew];
+                        if (!cdev)
+                                continue;
+                        cdev_devno = cdev->dev;
+                        device_destroy(&st_sysfs_class, cdev_devno);
+                        cdev_del(tpnt->modes[mode].cdevs[rew]);
+                        tpnt->modes[mode].cdevs[rew] = NULL;
                 }
         }
 
-        write_unlock(&st_dev_arr_lock);
+        mutex_lock(&st_ref_mutex);
+        kref_put(&tpnt->kref, scsi_tape_release);
+        mutex_unlock(&st_ref_mutex);
+        spin_lock(&st_index_lock);
+        idr_remove(&st_index_idr, index);
+        spin_unlock(&st_index_lock);
         return 0;
 }
 
@@ -4336,7 +4307,6 @@ static void __exit exit_st(void)
         unregister_chrdev_region(MKDEV(SCSI_TAPE_MAJOR, 0),
                                  ST_MAX_TAPE_ENTRIES);
         class_unregister(&st_sysfs_class);
-        kfree(scsi_tapes);
         printk(KERN_INFO "st: Unloaded.\n");
 }
 
@@ -4459,22 +4429,10 @@ static ssize_t
 options_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
         struct st_modedef *STm = dev_get_drvdata(dev);
-        struct scsi_tape *STp;
-        int i, j, options;
+        struct scsi_tape *STp = STm->tape;
+        int options;
         ssize_t l = 0;
 
-        for (i=0; i < st_dev_max; i++) {
-                for (j=0; j < ST_NBR_MODES; j++)
-                        if (&scsi_tapes[i]->modes[j] == STm)
-                                break;
-                if (j < ST_NBR_MODES)
-                        break;
-        }
-        if (i == st_dev_max)
-                return 0;  /* should never happen */
-
-        STp = scsi_tapes[i];
-
         options = STm->do_buffer_writes ? MT_ST_BUFFER_WRITES : 0;
         options |= STm->do_async_writes ? MT_ST_ASYNC_WRITES : 0;
         options |= STm->do_read_ahead ? MT_ST_READ_AHEAD : 0;