Re: [PATCH 2/8] zram: use idr instead of `zram_devices' array

Sergey Senozhatsky
2015-03-04T07:49:32Z

On (03/04/15 16:06), Minchan Kim wrote:
> So are you claiming using of idr is smaller memory footprint than zram included
> list_head?
> I hope why you want to use idr for dynamic device management.
>

and idr handles auto device_id generation for us, all we need to do in zram code
is to pass '0, 0' to idr_alloc(), instead of 'device_id, device_id + 1'.
hoping that automatic id generation will be there one day.

-ss

> > still provides ability to match the device_id with the device pointer.
> > No user-space visible changes.
> >
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> > ---
> > drivers/block/zram/zram_drv.c | 81 ++++++++++++++++++++++++-------------------
> > 1 file changed, 46 insertions(+), 35 deletions(-)
> >
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index 8fc2566..6707b7b 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -32,12 +32,12 @@
> > #include <linux/string.h>
> > #include <linux/vmalloc.h>
> > #include <linux/err.h>
> > +#include <linux/idr.h>
> >
> > #include "zram_drv.h"
> >
> > -/* Globals */
> > +static DEFINE_IDR(zram_index_idr);
> > static int zram_major;
> > -static struct zram *zram_devices;
> > static const char *default_compressor = "lzo";
> >
> > /* Module params (documentation at end) */
> > @@ -1061,18 +1061,28 @@ static struct attribute_group zram_disk_attr_group = {
> > .attrs = zram_disk_attrs,
> > };
> >
> > -static int create_device(struct zram *zram, int device_id)
> > +static int zram_add(int device_id)
> > {
> > + struct zram *zram;
> > struct request_queue *queue;
> > int ret = -ENOMEM;
> >
> > + zram = kzalloc(sizeof(struct zram), GFP_KERNEL);
> > + if (!zram)
> > + return ret;
> > +
> > + ret = idr_alloc(&zram_index_idr, zram, device_id,
> > + device_id + 1, GFP_KERNEL);
> > + if (ret < 0)
> > + goto out_free_dev;
> > +
> > init_rwsem(&zram->init_lock);
> >
> > queue = blk_alloc_queue(GFP_KERNEL);
> > if (!queue) {
> > pr_err("Error allocating disk queue for device %d\n",
> > device_id);
> > - goto out;
> > + goto out_free_idr;
> > }
> >
> > blk_queue_make_request(queue, zram_make_request);
> > @@ -1141,34 +1151,42 @@ out_free_disk:
> > put_disk(zram->disk);
> > out_free_queue:
> > blk_cleanup_queue(queue);
> > -out:
> > +out_free_idr:
> > + idr_remove(&zram_index_idr, device_id);
> > +out_free_dev:
> > + kfree(zram);
> > return ret;
> > }
> >
> > -static void destroy_devices(unsigned int nr)
> > +static void zram_remove(struct zram *zram)
> > {
> > - struct zram *zram;
> > - unsigned int i;
> > -
> > - for (i = 0; i < nr; i++) {
> > - zram = &zram_devices[i];
> > - /*
> > - * Remove sysfs first, so no one will perform a disksize
> > - * store while we destroy the devices
> > - */
> > - sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
> > - &zram_disk_attr_group);
> > + /*
> > + * Remove sysfs first, so no one will perform a disksize
> > + * store while we destroy the devices
> > + */
> > + sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
> > + &zram_disk_attr_group);
> >
> > - zram_reset_device(zram);
> > + zram_reset_device(zram);
> > + idr_remove(&zram_index_idr, zram->disk->first_minor);
> > + blk_cleanup_queue(zram->disk->queue);
> > + del_gendisk(zram->disk);
> > + put_disk(zram->disk);
> > + kfree(zram);
> > +}
> >
> > - blk_cleanup_queue(zram->disk->queue);
> > - del_gendisk(zram->disk);
> > - put_disk(zram->disk);
> > - }
> > +static int zram_exit_cb(int id, void *ptr, void *data)
> > +{
> > + zram_remove(ptr);
> > + return 0;
> > +}
> >
> > - kfree(zram_devices);
> > +static void destroy_devices(void)
> > +{
> > + idr_for_each(&zram_index_idr, &zram_exit_cb, NULL);
> > + idr_destroy(&zram_index_idr);
> > unregister_blkdev(zram_major, "zram");
> > - pr_info("Destroyed %u device(s)\n", nr);
> > + pr_info("Destroyed device(s)\n");
> > }
> >
> > static int __init zram_init(void)
> > @@ -1187,16 +1205,9 @@ static int __init zram_init(void)
> > return -EBUSY;
> > }
> >
> > - /* Allocate the device array and initialize each one */
> > - zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
> > - if (!zram_devices) {
> > - unregister_blkdev(zram_major, "zram");
> > - return -ENOMEM;
> > - }
> > -
> > for (dev_id = 0; dev_id < num_devices; dev_id++) {
> > - ret = create_device(&zram_devices[dev_id], dev_id);
> > - if (ret)
> > + ret = zram_add(dev_id);
> > + if (ret != 0)
> > goto out_error;
> > }
> >
> > @@ -1204,13 +1215,13 @@ static int __init zram_init(void)
> > return 0;
> >
> > out_error:
> > - destroy_devices(dev_id);
> > + destroy_devices();
> > return ret;
> > }
> >
> > static void __exit zram_exit(void)
> > {
> > - destroy_devices(num_devices);
> > + destroy_devices();
> > }
> >
> > module_init(zram_init);
> > --
> > 2.3.1.167.g7f4ba4b
> >
>
> --
> Kind regards,
> Minchan Kim
>