On Fri, 11 Aug 2023, Jan Kara wrote:
> Convert bcache to use bdev_open_by_path() and pass the handle around.
>
> CC: linux-bcache@xxxxxxxxxxxxxxx
> CC: Coly Li <colyli@xxxxxxx
> CC: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> Acked-by: Coly Li <colyli@xxxxxxx>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> drivers/md/bcache/bcache.h | 2 +
> drivers/md/bcache/super.c | 78 ++++++++++++++++++++------------------
> 2 files changed, 43 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
> index 5a79bb3c272f..2aa3f2c1f719 100644
> --- a/drivers/md/bcache/bcache.h
> +++ b/drivers/md/bcache/bcache.h
> @@ -299,6 +299,7 @@ struct cached_dev {
> struct list_head list;
> struct bcache_device disk;
> struct block_device *bdev;
> + struct bdev_handle *bdev_handle;
It looks like you've handled most if not all of the `block_device *bdev`
refactor. Can we drop `block_device *bdev` and fixup any remaining
references? More below.
>
> struct cache_sb sb;
> struct cache_sb_disk *sb_disk;
> @@ -421,6 +422,7 @@ struct cache {
>
> struct kobject kobj;
> struct block_device *bdev;
> + struct bdev_handle *bdev_handle;
ditto.
>
> struct task_struct *alloc_thread;
>
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index 0ae2b3676293..c11ac86be72b 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -1368,8 +1368,8 @@ static void cached_dev_free(struct closure *cl)
> if (dc->sb_disk)
> put_page(virt_to_page(dc->sb_disk));
>
> - if (!IS_ERR_OR_NULL(dc->bdev))
> - blkdev_put(dc->bdev, dc);
> + if (dc->bdev_handle)
> + bdev_release(dc->bdev_handle);
bdev_release does not reset dc->bdev, which could leave a hanging
reference.
>
> wake_up(&unregister_wait);
>
> @@ -1444,7 +1444,7 @@ static int cached_dev_init(struct cached_dev *dc, unsigned int block_size)
> /* Cached device - bcache superblock */
>
> static int register_bdev(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
> - struct block_device *bdev,
> + struct bdev_handle *bdev_handle,
> struct cached_dev *dc)
> {
> const char *err = "cannot allocate memory";
> @@ -1452,14 +1452,15 @@ static int register_bdev(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
> int ret = -ENOMEM;
>
> memcpy(&dc->sb, sb, sizeof(struct cache_sb));
> - dc->bdev = bdev;
> + dc->bdev_handle = bdev_handle;
> + dc->bdev = bdev_handle->bdev;
If I understand correctly, this patch duplicates the dc->bdev reference to
exist as dc->bdev_handle->bdev _and_ dc->bdev. (Same for changes related
to `struct cache`.)
This would mean future developers have to understand they are the same
thing, and someone may not manage it correctly.
If block core is moving to `struct bdev_handle`, then can we drop
`dc->bdev` and replace all occurances of `dc->bdev` with
`bdev_handle->bdev`? Or make an accessor macro/function like
bdev_handle_get_bdev(dc->bdev_handle)?
Unless I misunderstand something here, I would NACK this as written
because it increases the liklihood of future developer error.
I've added a few other comments below, but my comments are not exhaustive:
> dc->sb_disk = sb_disk;
>
> if (cached_dev_init(dc, sb->block_size << 9))
> goto err;
>
> err = "error creating kobject";
> - if (kobject_add(&dc->disk.kobj, bdev_kobj(bdev), "bcache"))
> + if (kobject_add(&dc->disk.kobj, bdev_kobj(dc->bdev), "bcache"))
> goto err;
> if (bch_cache_accounting_add_kobjs(&dc->accounting, &dc->disk.kobj))
> goto err;
> @@ -2216,8 +2217,8 @@ void bch_cache_release(struct kobject *kobj)
> if (ca->sb_disk)
> put_page(virt_to_page(ca->sb_disk));
>
> - if (!IS_ERR_OR_NULL(ca->bdev))
> - blkdev_put(ca->bdev, ca);
> + if (ca->bdev_handle)
> + bdev_release(ca->bdev_handle);
>
ca->bdev is not cleaned up
> kfree(ca);
> module_put(THIS_MODULE);
> @@ -2337,16 +2338,18 @@ static int cache_alloc(struct cache *ca)
> }
>
> static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
> - struct block_device *bdev, struct cache *ca)
> + struct bdev_handle *bdev_handle,
> + struct cache *ca)
> {
> const char *err = NULL; /* must be set for any error case */
> int ret = 0;
>
> memcpy(&ca->sb, sb, sizeof(struct cache_sb));
> - ca->bdev = bdev;
> + ca->bdev_handle = bdev_handle;
> + ca->bdev = bdev_handle->bdev;
> ca->sb_disk = sb_disk;
>
> - if (bdev_max_discard_sectors((bdev)))
> + if (bdev_max_discard_sectors((bdev_handle->bdev)))
> ca->discard = CACHE_DISCARD(&ca->sb);
>
> ret = cache_alloc(ca);
> @@ -2354,10 +2357,10 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
> /*
> * If we failed here, it means ca->kobj is not initialized yet,
> * kobject_put() won't be called and there is no chance to
> - * call blkdev_put() to bdev in bch_cache_release(). So we
> - * explicitly call blkdev_put() here.
> + * call bdev_release() to bdev in bch_cache_release(). So
> + * we explicitly call bdev_release() here.
> */
> - blkdev_put(bdev, ca);
> + bdev_release(bdev_handle);
ca->bdev is not cleaned up
> if (ret == -ENOMEM)
> err = "cache_alloc(): -ENOMEM";
> else if (ret == -EPERM)
> @@ -2367,7 +2370,7 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
> goto err;
> }
>
> - if (kobject_add(&ca->kobj, bdev_kobj(bdev), "bcache")) {
> + if (kobject_add(&ca->kobj, bdev_kobj(bdev_handle->bdev), "bcache")) {
> err = "error calling kobject_add";
> ret = -ENOMEM;
> goto out;
> @@ -2382,14 +2385,14 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
> goto out;
> }
>
> - pr_info("registered cache device %pg\n", ca->bdev);
> + pr_info("registered cache device %pg\n", ca->bdev_handle->bdev);
>
> out:
> kobject_put(&ca->kobj);
>
> err:
> if (err)
> - pr_notice("error %pg: %s\n", ca->bdev, err);
> + pr_notice("error %pg: %s\n", ca->bdev_handle->bdev, err);
>
> return ret;
> }
> @@ -2445,7 +2448,7 @@ struct async_reg_args {
> char *path;
> struct cache_sb *sb;
> struct cache_sb_disk *sb_disk;
> - struct block_device *bdev;
> + struct bdev_handle *bdev_handle;
> void *holder;
> };
>
> @@ -2456,8 +2459,8 @@ static void register_bdev_worker(struct work_struct *work)
> container_of(work, struct async_reg_args, reg_work.work);
>
> mutex_lock(&bch_register_lock);
> - if (register_bdev(args->sb, args->sb_disk, args->bdev, args->holder)
> - < 0)
> + if (register_bdev(args->sb, args->sb_disk, args->bdev_handle,
> + args->holder) < 0)
> fail = true;
> mutex_unlock(&bch_register_lock);
>
> @@ -2477,7 +2480,8 @@ static void register_cache_worker(struct work_struct *work)
> container_of(work, struct async_reg_args, reg_work.work);
>
> /* blkdev_put() will be called in bch_cache_release() */
> - if (register_cache(args->sb, args->sb_disk, args->bdev, args->holder))
> + if (register_cache(args->sb, args->sb_disk, args->bdev_handle,
> + args->holder))
> fail = true;
>
> if (fail)
> @@ -2514,7 +2518,7 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
> char *path = NULL;
> struct cache_sb *sb;
> struct cache_sb_disk *sb_disk;
> - struct block_device *bdev, *bdev2;
> + struct bdev_handle *bdev_handle, *bdev_handle2;
> void *holder = NULL;
> ssize_t ret;
> bool async_registration = false;
> @@ -2547,15 +2551,15 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
>
> ret = -EINVAL;
> err = "failed to open device";
> - bdev = blkdev_get_by_path(strim(path), BLK_OPEN_READ, NULL, NULL);
> - if (IS_ERR(bdev))
> + bdev_handle = bdev_open_by_path(strim(path), BLK_OPEN_READ, NULL, NULL);
> + if (IS_ERR(bdev_handle))
> goto out_free_sb;
>
> err = "failed to set blocksize";
> - if (set_blocksize(bdev, 4096))
> + if (set_blocksize(bdev_handle->bdev, 4096))
> goto out_blkdev_put;
>
> - err = read_super(sb, bdev, &sb_disk);
> + err = read_super(sb, bdev_handle->bdev, &sb_disk);
> if (err)
> goto out_blkdev_put;
>
> @@ -2567,13 +2571,13 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
> }
>
> /* Now reopen in exclusive mode with proper holder */
> - bdev2 = blkdev_get_by_dev(bdev->bd_dev, BLK_OPEN_READ | BLK_OPEN_WRITE,
> - holder, NULL);
> - blkdev_put(bdev, NULL);
> - bdev = bdev2;
> - if (IS_ERR(bdev)) {
> - ret = PTR_ERR(bdev);
> - bdev = NULL;
> + bdev_handle2 = bdev_open_by_dev(bdev_handle->bdev->bd_dev,
> + BLK_OPEN_READ | BLK_OPEN_WRITE, holder, NULL);
> + bdev_release(bdev_handle);
> + bdev_handle = bdev_handle2;
> + if (IS_ERR(bdev_handle)) {
> + ret = PTR_ERR(bdev_handle);
> + bdev_handle = NULL;
> if (ret == -EBUSY) {
> dev_t dev;
>
> @@ -2608,7 +2612,7 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
> args->path = path;
> args->sb = sb;
> args->sb_disk = sb_disk;
> - args->bdev = bdev;
> + args->bdev_handle = bdev_handle;
> args->holder = holder;
> register_device_async(args);
> /* No wait and returns to user space */
> @@ -2617,14 +2621,14 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
>
> if (SB_IS_BDEV(sb)) {
> mutex_lock(&bch_register_lock);
> - ret = register_bdev(sb, sb_disk, bdev, holder);
> + ret = register_bdev(sb, sb_disk, bdev_handle, holder);
> mutex_unlock(&bch_register_lock);
> /* blkdev_put() will be called in cached_dev_free() */
> if (ret < 0)
> goto out_free_sb;
> } else {
> /* blkdev_put() will be called in bch_cache_release() */
> - ret = register_cache(sb, sb_disk, bdev, holder);
> + ret = register_cache(sb, sb_disk, bdev_handle, holder);
> if (ret)
> goto out_free_sb;
> }
> @@ -2640,8 +2644,8 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
> out_put_sb_page:
> put_page(virt_to_page(sb_disk));
> out_blkdev_put:
> - if (bdev)
> - blkdev_put(bdev, holder);
> + if (bdev_handle)
> + bdev_release(bdev_handle);
> out_free_sb:
> kfree(sb);
> out_free_path:
> --
> 2.35.3
>
>
--
Eric Wheeler
