zram: remove the claim mechanism

The zram claim mechanism was added to ensure no new opens come in
during teardown.  But the proper way to archive that is to call
del_gendisk first, which takes care of all that.  Once del_gendisk
is called in the right place, the reset side can also be simplified
as no I/O can be outstanding on a block device that is not open.

Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 6d15d51cee2b7e89411e221475d35c101a3c9e13..3641434a9b154d247bb242834bfd9d8fa4029ce7 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1756,64 +1756,33 @@ out_unlock:
 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;
+       struct zram *zram = dev_to_zram(dev);
        struct block_device *bdev;
+       unsigned short do_reset;
+       int ret = 0;
 
        ret = kstrtou16(buf, 10, &do_reset);
        if (ret)
                return ret;
-
        if (!do_reset)
                return -EINVAL;
 
-       zram = dev_to_zram(dev);
        bdev = bdget_disk(zram->disk, 0);
        if (!bdev)
                return -ENOMEM;
 
        mutex_lock(&bdev->bd_mutex);
-       /* Do not reset an active device or claimed device */
-       if (bdev->bd_openers || zram->claim) {
-               mutex_unlock(&bdev->bd_mutex);
-               bdput(bdev);
-               return -EBUSY;
-       }
-
-       /* From now on, anyone can't open /dev/zram[0-9] */
-       zram->claim = true;
+       if (bdev->bd_openers)
+               ret = -EBUSY;
+       else
+               zram_reset_device(zram);
        mutex_unlock(&bdev->bd_mutex);
-
-       /* Make sure all the pending I/O are finished */
-       fsync_bdev(bdev);
-       zram_reset_device(zram);
        bdput(bdev);
 
-       mutex_lock(&bdev->bd_mutex);
-       zram->claim = false;
-       mutex_unlock(&bdev->bd_mutex);
-
-       return len;
-}
-
-static int zram_open(struct block_device *bdev, fmode_t mode)
-{
-       int ret = 0;
-       struct zram *zram;
-
-       WARN_ON(!mutex_is_locked(&bdev->bd_mutex));
-
-       zram = bdev->bd_disk->private_data;
-       /* zram was claimed to reset so open request fails */
-       if (zram->claim)
-               ret = -EBUSY;
-
-       return ret;
+       return ret ? ret : len;
 }
 
 static const struct block_device_operations zram_devops = {
-       .open = zram_open,
        .submit_bio = zram_submit_bio,
        .swap_slot_free_notify = zram_slot_free_notify,
        .rw_page = zram_rw_page,
@@ -1821,7 +1790,6 @@ static const struct block_device_operations zram_devops = {
 };
 
 static const struct block_device_operations zram_wb_devops = {
-       .open = zram_open,
        .submit_bio = zram_submit_bio,
        .swap_slot_free_notify = zram_slot_free_notify,
        .owner = THIS_MODULE
@@ -1972,34 +1940,32 @@ out_free_dev:
        return ret;
 }
 
-static int zram_remove(struct zram *zram)
+static bool zram_busy(struct zram *zram)
 {
        struct block_device *bdev;
+       bool busy = false;
 
        bdev = bdget_disk(zram->disk, 0);
-       if (!bdev)
-               return -ENOMEM;
-
-       mutex_lock(&bdev->bd_mutex);
-       if (bdev->bd_openers || zram->claim) {
-               mutex_unlock(&bdev->bd_mutex);
+       if (bdev) {
+               if (bdev->bd_openers)
+                       busy = true;
                bdput(bdev);
-               return -EBUSY;
        }
 
-       zram->claim = true;
-       mutex_unlock(&bdev->bd_mutex);
+       return busy;
+}
 
-       zram_debugfs_unregister(zram);
+static int zram_remove(struct zram *zram)
+{
+       if (zram_busy(zram))
+               return -EBUSY;
 
-       /* Make sure all the pending I/O are finished */
-       fsync_bdev(bdev);
+       del_gendisk(zram->disk);
+       zram_debugfs_unregister(zram);
        zram_reset_device(zram);
-       bdput(bdev);
 
        pr_info("Removed device: %s\n", zram->disk->disk_name);
 
-       del_gendisk(zram->disk);
        blk_cleanup_queue(zram->disk->queue);
        put_disk(zram->disk);
        kfree(zram);