[PATCH 3/5] st: get rid of scsi_tapes array

From: Lee Duncan
Date: Wed May 16 2012 - 23:56:40 EST

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.

Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>
Reviewed-by: Lee Duncan <lduncan@xxxxxxxx>
---
drivers/scsi/st.c | 172 ++++++++++++++++++++---------------------------------
drivers/scsi/st.h | 2 +
2 files changed, 65 insertions(+), 109 deletions(-)

diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index 40f9d47..9c2c9d9 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;
-
extern struct class st_sysfs_class;
extern 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 +4101,30 @@ 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)) {
+ printk(KERN_WARNING "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) {
+ printk(KERN_WARNING "st: idr allocation failed: %d\n", error);
+ goto out_put_disk;
+ }
+
+ if (dev_num > ST_MAX_TAPES) {
+ printk(KERN_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 +4167,10 @@ 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 +4180,8 @@ 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:
+ idr_remove(&st_index_idr, dev_num);
out_put_disk:
put_disk(disk);
kfree(tpnt);
@@ -4218,38 +4194,29 @@ 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;
- }
- }
+ struct scsi_tape *tpnt = dev_get_drvdata(dev);
+ int rew, mode;
+ dev_t cdev_devno;
+ struct cdev *cdev;

- mutex_lock(&st_ref_mutex);
- kref_put(&tpnt->kref, scsi_tape_release);
- mutex_unlock(&st_ref_mutex);
- return 0;
+ scsi_autopm_get_device(tpnt->device);
+
+ 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);
return 0;
}

@@ -4336,7 +4303,6 @@ 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 +4425,10 @@ 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;
diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index ea35632..4456735 100644
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -66,6 +66,7 @@ struct st_modedef {
unsigned char default_compression; /* 0 = don't touch, etc */
short default_density; /* Forced density, -1 = no value */
int default_blksize; /* Forced blocksize, -1 = no value */
+ struct scsi_tape *tape;
struct cdev *cdevs[2]; /* Auto-rewind and non-rewind devices */
};

@@ -99,6 +100,7 @@ struct scsi_tape {
struct mutex lock; /* For serialization */
struct completion wait; /* For SCSI commands */
struct st_buffer *buffer;
+ int index;

/* Drive characteristics */
unsigned char omit_blklims;
--
1.7.9.2

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