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loop: replace linked list of allocated devices with an idr index
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Replace the linked list, that keeps track of allocated devices, with an
idr index to allow a more efficient lookup of devices.

Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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Kay Sievers authored and Jens Axboe committed Jul 31, 2011
1 parent aa387cc commit 34dd82a
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Showing 2 changed files with 80 additions and 73 deletions.
152 changes: 80 additions & 72 deletions drivers/block/loop.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -78,8 +78,8 @@

#include <asm/uaccess.h>

static LIST_HEAD(loop_devices);
static DEFINE_MUTEX(loop_devices_mutex);
static DEFINE_IDR(loop_index_idr);
static DEFINE_MUTEX(loop_index_mutex);

static int max_part;
static int part_shift;
Expand Down Expand Up @@ -722,17 +722,10 @@ static inline int is_loop_device(struct file *file)
static ssize_t loop_attr_show(struct device *dev, char *page,
ssize_t (*callback)(struct loop_device *, char *))
{
struct loop_device *l, *lo = NULL;

mutex_lock(&loop_devices_mutex);
list_for_each_entry(l, &loop_devices, lo_list)
if (disk_to_dev(l->lo_disk) == dev) {
lo = l;
break;
}
mutex_unlock(&loop_devices_mutex);
struct gendisk *disk = dev_to_disk(dev);
struct loop_device *lo = disk->private_data;

return lo ? callback(lo, page) : -EIO;
return callback(lo, page);
}

#define LOOP_ATTR_RO(_name) \
Expand Down Expand Up @@ -1557,40 +1550,64 @@ int loop_register_transfer(struct loop_func_table *funcs)
return 0;
}

static int unregister_transfer_cb(int id, void *ptr, void *data)
{
struct loop_device *lo = ptr;
struct loop_func_table *xfer = data;

mutex_lock(&lo->lo_ctl_mutex);
if (lo->lo_encryption == xfer)
loop_release_xfer(lo);
mutex_unlock(&lo->lo_ctl_mutex);
return 0;
}

int loop_unregister_transfer(int number)
{
unsigned int n = number;
struct loop_device *lo;
struct loop_func_table *xfer;

if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
return -EINVAL;

xfer_funcs[n] = NULL;

list_for_each_entry(lo, &loop_devices, lo_list) {
mutex_lock(&lo->lo_ctl_mutex);

if (lo->lo_encryption == xfer)
loop_release_xfer(lo);

mutex_unlock(&lo->lo_ctl_mutex);
}

idr_for_each(&loop_index_idr, &unregister_transfer_cb, xfer);
return 0;
}

EXPORT_SYMBOL(loop_register_transfer);
EXPORT_SYMBOL(loop_unregister_transfer);

static struct loop_device *loop_alloc(int i)
static int loop_add(struct loop_device **l, int i)
{
struct loop_device *lo;
struct gendisk *disk;
int err;

lo = kzalloc(sizeof(*lo), GFP_KERNEL);
if (!lo)
if (!lo) {
err = -ENOMEM;
goto out;
}

err = idr_pre_get(&loop_index_idr, GFP_KERNEL);
if (err < 0)
goto out_free_dev;

if (i >= 0) {
int m;

/* create specific i in the index */
err = idr_get_new_above(&loop_index_idr, lo, i, &m);
if (err >= 0 && i != m) {
idr_remove(&loop_index_idr, m);
err = -EEXIST;
}
} else {
err = -EINVAL;
}
if (err < 0)
goto out_free_dev;

lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
if (!lo->lo_queue)
Expand All @@ -1611,56 +1628,54 @@ static struct loop_device *loop_alloc(int i)
disk->private_data = lo;
disk->queue = lo->lo_queue;
sprintf(disk->disk_name, "loop%d", i);
return lo;
add_disk(disk);
*l = lo;
return lo->lo_number;

out_free_queue:
blk_cleanup_queue(lo->lo_queue);
out_free_dev:
kfree(lo);
out:
return NULL;
return err;
}

static void loop_free(struct loop_device *lo)
static void loop_remove(struct loop_device *lo)
{
del_gendisk(lo->lo_disk);
blk_cleanup_queue(lo->lo_queue);
put_disk(lo->lo_disk);
list_del(&lo->lo_list);
kfree(lo);
}

static struct loop_device *loop_init_one(int i)
static int loop_lookup(struct loop_device **l, int i)
{
struct loop_device *lo;
int ret = -ENODEV;

list_for_each_entry(lo, &loop_devices, lo_list) {
if (lo->lo_number == i)
return lo;
}

lo = loop_alloc(i);
lo = idr_find(&loop_index_idr, i);
if (lo) {
add_disk(lo->lo_disk);
list_add_tail(&lo->lo_list, &loop_devices);
*l = lo;
ret = lo->lo_number;
}
return lo;
}

static void loop_del_one(struct loop_device *lo)
{
del_gendisk(lo->lo_disk);
loop_free(lo);
return ret;
}

static struct kobject *loop_probe(dev_t dev, int *part, void *data)
{
struct loop_device *lo;
struct kobject *kobj;
int err;

mutex_lock(&loop_devices_mutex);
lo = loop_init_one(MINOR(dev) >> part_shift);
kobj = lo ? get_disk(lo->lo_disk) : ERR_PTR(-ENOMEM);
mutex_unlock(&loop_devices_mutex);
mutex_lock(&loop_index_mutex);
err = loop_lookup(&lo, MINOR(dev) >> part_shift);
if (err < 0)
err = loop_add(&lo, MINOR(dev) >> part_shift);
if (err < 0)
kobj = ERR_PTR(err);
else
kobj = get_disk(lo->lo_disk);
mutex_unlock(&loop_index_mutex);

*part = 0;
return kobj;
Expand All @@ -1670,7 +1685,7 @@ static int __init loop_init(void)
{
int i, nr;
unsigned long range;
struct loop_device *lo, *next;
struct loop_device *lo;

/*
* loop module now has a feature to instantiate underlying device
Expand Down Expand Up @@ -1719,43 +1734,36 @@ static int __init loop_init(void)
if (register_blkdev(LOOP_MAJOR, "loop"))
return -EIO;

for (i = 0; i < nr; i++) {
lo = loop_alloc(i);
if (!lo)
goto Enomem;
list_add_tail(&lo->lo_list, &loop_devices);
}

/* point of no return */

list_for_each_entry(lo, &loop_devices, lo_list)
add_disk(lo->lo_disk);

blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
THIS_MODULE, loop_probe, NULL, NULL);

/* pre-create number devices of devices given by config or max_loop */
mutex_lock(&loop_index_mutex);
for (i = 0; i < nr; i++)
loop_add(&lo, i);
mutex_unlock(&loop_index_mutex);

printk(KERN_INFO "loop: module loaded\n");
return 0;
}

Enomem:
printk(KERN_INFO "loop: out of memory\n");

list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
loop_free(lo);
static int loop_exit_cb(int id, void *ptr, void *data)
{
struct loop_device *lo = ptr;

unregister_blkdev(LOOP_MAJOR, "loop");
return -ENOMEM;
loop_remove(lo);
return 0;
}

static void __exit loop_exit(void)
{
unsigned long range;
struct loop_device *lo, *next;

range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;

list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
loop_del_one(lo);
idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
idr_remove_all(&loop_index_idr);
idr_destroy(&loop_index_idr);

blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
unregister_blkdev(LOOP_MAJOR, "loop");
Expand Down
1 change: 0 additions & 1 deletion include/linux/loop.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,6 @@ struct loop_device {

struct request_queue *lo_queue;
struct gendisk *lo_disk;
struct list_head lo_list;
};

#endif /* __KERNEL__ */
Expand Down

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