Re: [PATCH 3/8] zram: factor out device reset from reset_store()

Minchan Kim
2015-03-05T02:28:18Z

On Tue, Mar 03, 2015 at 09:49:45PM +0900, Sergey Senozhatsky wrote:
> Device reset currently consists of two steps:
> a) holding ->bd_mutex we ensure that there are no device users
> (bdev->bd_openers)
>
> b) and internal part (executed under bdev->bd_mutex and partially
> under zram->init_lock) that resets the device - frees allocated
> memory and returns the device back to its initial (un-init) state.
>
> Dynamic device removal requires the same amount of work and checks.
> We can reuse internal cleanup part (b) zram_reset_device(), but step (a)
> is done in sysfs ATTR reset_store() handler.
>
> Rename step (b) from zram_reset_device() to zram_reset_device_internal()

Nitpick:
Usually, we have used double underbar for internal functions(ie, __zram_reset_device).

> and factor out step (a) to zram_reset_device(). Both reset_store() and
> dynamic device removal will use zram_reset_device().
>
> For readability let's keep them separated.
>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> ---
> drivers/block/zram/zram_drv.c | 135 +++++++++++++++++++++---------------------
> 1 file changed, 67 insertions(+), 68 deletions(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 6707b7b..59662dc 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -729,48 +729,6 @@ static void zram_bio_discard(struct zram *zram, u32 index,
> }
> }
>
> -static void zram_reset_device(struct zram *zram)
> -{
> - struct zram_meta *meta;
> - struct zcomp *comp;
> - u64 disksize;
> -
> - down_write(&zram->init_lock);
> -
> - zram->limit_pages = 0;
> -
> - if (!init_done(zram)) {
> - up_write(&zram->init_lock);
> - return;
> - }
> -
> - meta = zram->meta;
> - comp = zram->comp;
> - disksize = zram->disksize;
> - /*
> - * Refcount will go down to 0 eventually and r/w handler
> - * cannot handle further I/O so it will bail out by
> - * check zram_meta_get.
> - */
> - zram_meta_put(zram);
> - /*
> - * We want to free zram_meta in process context to avoid
> - * deadlock between reclaim path and any other locks.
> - */
> - wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
> -
> - /* Reset stats */
> - memset(&zram->stats, 0, sizeof(zram->stats));
> - zram->disksize = 0;
> - zram->max_comp_streams = 1;
> - set_capacity(zram->disk, 0);
> -
> - up_write(&zram->init_lock);
> - /* I/O operation under all of CPU are done so let's free */
> - zram_meta_free(meta, disksize);
> - zcomp_destroy(comp);
> -}
> -
> static ssize_t disksize_store(struct device *dev,
> struct device_attribute *attr, const char *buf, size_t len)
> {
> @@ -829,16 +787,54 @@ out_free_meta:
> return err;
> }
>
> -static ssize_t reset_store(struct device *dev,
> - struct device_attribute *attr, const char *buf, size_t len)
> +/* internal device reset part -- cleanup allocated memory and
> + * return back to initial state */
> +static void zram_reset_device_internal(struct zram *zram)
> {
> - int ret;
> - unsigned short do_reset;
> - struct zram *zram;
> - struct block_device *bdev;
> + struct zram_meta *meta;
> + struct zcomp *comp;
> + u64 disksize;
>
> - zram = dev_to_zram(dev);
> - bdev = bdget_disk(zram->disk, 0);
> + down_write(&zram->init_lock);
> +
> + zram->limit_pages = 0;
> +
> + if (!init_done(zram)) {
> + up_write(&zram->init_lock);
> + return;
> + }
> +
> + meta = zram->meta;
> + comp = zram->comp;
> + disksize = zram->disksize;
> + /*
> + * Refcount will go down to 0 eventually and r/w handler
> + * cannot handle further I/O so it will bail out by
> + * check zram_meta_get.
> + */
> + zram_meta_put(zram);
> + /*
> + * We want to free zram_meta in process context to avoid
> + * deadlock between reclaim path and any other locks.
> + */
> + wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
> +
> + /* Reset stats */
> + memset(&zram->stats, 0, sizeof(zram->stats));
> + zram->disksize = 0;
> + zram->max_comp_streams = 1;
> + set_capacity(zram->disk, 0);
> +
> + up_write(&zram->init_lock);
> + /* I/O operation under all of CPU are done so let's free */
> + zram_meta_free(meta, disksize);
> + zcomp_destroy(comp);
> +}
> +
> +static int zram_reset_device(struct zram *zram)
> +{
> + int ret = 0;
> + struct block_device *bdev = bdget_disk(zram->disk, 0);
>
> if (!bdev)
> return -ENOMEM;
> @@ -850,31 +846,34 @@ static ssize_t reset_store(struct device *dev,
> goto out;
> }
>
> - ret = kstrtou16(buf, 10, &do_reset);
> - if (ret)
> - goto out;
> -
> - if (!do_reset) {
> - ret = -EINVAL;
> - goto out;
> - }
> -
> /* Make sure all pending I/O is finished */
> fsync_bdev(bdev);
> - zram_reset_device(zram);
> -
> - mutex_unlock(&bdev->bd_mutex);
> - revalidate_disk(zram->disk);
> - bdput(bdev);
> -
> - return len;
> -
> + zram_reset_device_internal(zram);
> out:
> mutex_unlock(&bdev->bd_mutex);
> bdput(bdev);
> return ret;
> }
>
> +static ssize_t reset_store(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t len)
> +{
> + int ret;
> + unsigned short do_reset;
> + struct zram *zram;
> +
> + zram = dev_to_zram(dev);
> + ret = kstrtou16(buf, 10, &do_reset);
> + if (ret)
> + return ret;
> +
> + if (!do_reset)
> + return -EINVAL;
> +
> + ret = zram_reset_device(zram);
> + return ret ? ret : len;
> +}
> +
> static void __zram_make_request(struct zram *zram, struct bio *bio)
> {
> int offset, rw;
> @@ -1167,7 +1166,7 @@ static void zram_remove(struct zram *zram)
> sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
> &zram_disk_attr_group);
>
> - zram_reset_device(zram);
> + zram_reset_device_internal(zram);
> idr_remove(&zram_index_idr, zram->disk->first_minor);
> blk_cleanup_queue(zram->disk->queue);
> del_gendisk(zram->disk);
> --
> 2.3.1.167.g7f4ba4b
>

--
Kind regards,
Minchan Kim