st: get rid of scsi_tapes array

From: Jeff Mahoney <[email protected]>

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.

---
 drivers/scsi/st.c |  172 ++++++++++++++++++++---------------------------------
 drivers/scsi/st.h |    2 +
 2 files changed, 65 insertions(+), 109 deletions(-)

index f437b7f..a3718a5 100644
@@ -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 +4101,30 @@ 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;

index ea35632..4456735 100644
@@ -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

... patch removed

I have finally had time to review and test this patch set. I am sorry this has taken so long.

I have found one change of behaviour and a theoretical problem:
The new code does not re-use the tape numbers when freed and re-scanned. The current code does re-use the freed numbers. Are there any reasons for this changed behaviour? (The theoretical problem is that the new code frees the tape structure but leaves the pointer in the idr tree.)

The patch at the end of this message (applies after the whole series) is an attempt to implement re-use of tape numbers. I am not completely sure that the change is correctly placed but it seems to work.

Another minor thing is that the documentation should be updated :-)

The patch at the end also updates the version code. I am not sure if the version code is useful, but it should be either updated or removed.

Otherwise no problems found. I am ready to ack the patch set after the re-use thing has been resolved (one way or another).

Thanks,
Kai

-----------------------------8<--------------------------------------------

@@ -17,7 +17,7 @@
    Last modified: 18-JAN-1998 Richard Gooch <[email protected]> Devfs support
  */
 
-static const char *verstr = "20101219";
+static const char *verstr = "20120701";
 
 #include <linux/module.h>
 

@@ -4273,6 +4273,9 @@ static void scsi_tape_release(struct kre
 
 	disk->private_data = NULL;
 	put_disk(disk);
+	spin_lock(&st_index_lock);
+	idr_remove(&st_index_idr, tpnt->index);
+	spin_unlock(&st_index_lock);
 	kfree(tpnt);
 	return;
 }

@@ -2,7 +2,7 @@ This file contains brief information abo
 The driver is currently maintained by Kai Mäkisara (email
 [email protected])
 
-Last modified: Sun Aug 29 18:25:47 2010 by kai.makisara
+Last modified: Sun Jul  1 11:41:27 2012 by kai.makisara
 
 
 BASICS

@@ -112,10 +112,8 @@ attempted).
 
 MINOR NUMBERS
 
-The tape driver currently supports 128 drives by default. This number
-can be increased by editing st.h and recompiling the driver if
-necessary. The upper limit is 2^17 drives if 4 modes for each drive
-are used.
+The upper limit is 2^17 drives if 4 modes for each drive are used. The
+tape driver currently supports drives up to this limit.
 
 The minor numbers consist of the following bit fields:
 

Thanks for the review, and good catch. I'll look over your added patch and give feedback as soon as I can.

Of course.

The Lee-Man

Kai:

Your added patch looks great, and I see you fixed the documentation as well. Thanks for your help.

- Lee

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Actually, we've run into a hiccup here. Using cdev as the target of the link doesn't work, the tape symlink isn't created, and we end up with lsscsi not listing tape device nodes.

I'll work up a fix.

- -Jeff

- --
Jeff Mahoney
SUSE Labs

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