Messages in this thread | | | Date | Thu, 5 Mar 2015 09:59:02 +0900 | From | Minchan Kim <> | Subject | Re: [PATCH 2/8] zram: use idr instead of `zram_devices' array |
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On Wed, Mar 04, 2015 at 04:49:13PM +0900, Sergey Senozhatsky wrote: > 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.
About memory footprint, sizeof(list_head) might be win if we create zram dyamically and there is few zram device in the system because IDR uses own metadata and bitmap and so. But I don't think it's not too much if there is few device, either. However, automatic id generation appeals more rather than memory footprint so I hope you add it in description for someone to know why we decided idr in future.
Thanks.
> > -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 > >
-- Kind regards, Minchan Kim
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