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Subject[PATCHv2 04/10] zram: factor out device reset from reset_store()
Date
Device reset currently includes 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 state.

Up until now it worked just fine. But there will be yet another device
reset user soon -- on-demand device removal. We currently can reuse (b),
but step (a) is done in sysfs ATTR reset_store() handler, which makes it
hard to use it in on-demand device reset path.

Rename step (b) from zram_reset_device() to zram_reset_device_internal()
and factor out step (a) to zram_reset_device().

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 4511830..14ec8f2 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -750,48 +750,6 @@ 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)
{
@@ -850,16 +808,54 @@ 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;
@@ -871,31 +867,34 @@ 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;
@@ -1264,7 +1263,7 @@ 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);
--
2.4.0.rc2


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