From: Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>
If we want to build a bcache device with backing device of a bcache flash device,
we will fail with creating a duplicated sysfs filename.
E.g:
(1) we create bcache0 with vdc, then there is "/sys/block/bcache0/bcache" as a link to "/sys/block/vdc/bcache"
$ readlink /sys/block/bcache0/bcache
../../../pci0000:00/0000:00:0b.0/virtio4/block/vdc/bcache
(2) if we continue to create bcache1 with bcache0:
$ make-bcache -B /dev/bcache0
We will fail to register bdev with "sysfs: cannot create duplicate filename '/devices/virtual/block/bcache0/bcache'"
How this commit solving this problem?
E.g:
we have vdf as cache disk, vdc as backing disk.
$ make-bcache -C /dev/vdf -B /dev/vdc --wipe-bcache
$ echo 100G > /sys/block/vdf/bcache_cache/set/flash_vol_create
$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdf 252:80 0 50G 0 disk
├─bcache0 251:0 0 100G 0 disk
└─bcache1 251:128 0 100G 0 disk
vdc 252:32 0 100G 0 disk
└─bcache0 251:0 0 100G 0 disk
(a) rename sysfs file to more meaningful name:
(a.2) bcahce_cache -> sysfs filename under cache disk (/sys/block/vdf/bcache_cache)
(a.1) bcache_fdev -> flash bcache device (/sys/block/bcache1/bcache_fdev)
(a.4) bcache_bdev -> sysfs filename for backing disk (/sys/block/vdc/bcache_bdev)
(a.3) bcache_cdev -> link to /sys/block/vdc/bcache_bdev (/sys/block/bcache0/bcache_cdev)
(b) create ->bcache lagacy link file for backward compatability
$ ll /sys/block/vdc/bcache
lrwxrwxrwx 1 root root 0 Oct 26 11:21 /sys/block/vdc/bcache -> bcache_bdev
$ ll /sys/block/bcache0/bcache
lrwxrwxrwx 1 root root 0 Oct 26 11:21 /sys/block/bcache0/bcache -> ../../../pci0000:00/0000:00:0b.0/virtio4/block/vdc/bcache_bdev
$ ll /sys/block/bcache1/bcache
lrwxrwxrwx 1 root root 0 Oct 26 11:19 /sys/block/bcache1/bcache -> bcache_fdev
$ ll /sys/block/vdf/bcache
lrwxrwxrwx 1 root root 0 Oct 26 11:17 /sys/block/vdf/bcache -> bcache_cache
These link are created with sysfs_create_link_nowarn(), that means, we dont
care about the failure when creating if these links are already created.
Because these lagacy sysfile are only for backwards compatability in no-overlay usecase
of bcache, in the no-overlay use, bcache will never create duplicated link.
In overlay usecase after this commit, please dont use bcache link any more, instead
use bcache_cdev, bcache_fdev, bcache_bdev or bcache_cache.
Then we can create a cached_dev with bcache1 (flash dev) as backing dev.
$ make-bcache -B /dev/bcache1
$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdf 252:80 0 50G 0 disk
├─bcache0 251:0 0 100G 0 disk
└─bcache1 251:128 0 100G 0 disk
└─bcache2 251:256 0 100G 0 disk
As a result there is a cached device bcache2 with backing device of a flash device bcache1.
----------------------------
| bcache2 (cached_dev) |
| ------------------------ |
| | sdb (cache_dev) | |
| ------------------------ |
| ------------------------ |
| | bcache1 (flash_dev)| |
| ------------------------ |
----------------------------
Signed-off-by: Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>
Signed-off-by: mingzhe <mingzhe.zou@xxxxxxxxxxxx>
---
drivers/md/bcache/super.c | 38 ++++++++++++++++++++++++++++++++++----
1 file changed, 34 insertions(+), 4 deletions(-)
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index ba3909bb6bea..8a922ce91d1e 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1087,12 +1087,19 @@ int bch_cached_dev_run(struct cached_dev *dc)
if (sysfs_create_link(&d->kobj, &disk_to_dev(d->disk)->kobj, "dev") ||
sysfs_create_link(&disk_to_dev(d->disk)->kobj,
- &d->kobj, "bcache")) {
+ &d->kobj, "bcache_cdev")) {
pr_err("Couldn't create bcache dev <-> disk sysfs symlinks\n");
ret = -ENOMEM;
goto out;
}
+ ret = sysfs_create_link_nowarn(&disk_to_dev(d->disk)->kobj,
+ &d->kobj, "bcache");
+ if (ret && ret != -EEXIST) {
+ pr_err("Couldn't create lagacy disk sysfs ->bcache symlinks\n");
+ goto out;
+ }
+
dc->status_update_thread = kthread_run(cached_dev_status_update,
dc, "bcache_status_update");
if (IS_ERR(dc->status_update_thread)) {
@@ -1461,8 +1468,16 @@ static int register_bdev(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
goto err;
err = "error creating kobject";
- if (kobject_add(&dc->disk.kobj, bdev_kobj(bdev), "bcache"))
+ if (kobject_add(&dc->disk.kobj, bdev_kobj(bdev), "bcache_bdev"))
goto err;
+
+ err = "error creating lagacy sysfs link";
+ ret = sysfs_create_link_nowarn(bdev_kobj(bdev), &dc->disk.kobj, "bcache");
+ if (ret && ret != -EEXIST) {
+ pr_err("Couldn't create lagacy disk sysfs ->bcache");
+ goto err;
+ }
+
if (bch_cache_accounting_add_kobjs(&dc->accounting, &dc->disk.kobj))
goto err;
@@ -1524,6 +1539,7 @@ static void flash_dev_flush(struct closure *cl)
static int flash_dev_run(struct cache_set *c, struct uuid_entry *u)
{
+ int ret;
int err = -ENOMEM;
struct bcache_device *d = kzalloc(sizeof(struct bcache_device),
GFP_KERNEL);
@@ -1546,10 +1562,17 @@ static int flash_dev_run(struct cache_set *c, struct uuid_entry *u)
if (err)
goto err;
- err = kobject_add(&d->kobj, &disk_to_dev(d->disk)->kobj, "bcache");
+ err = kobject_add(&d->kobj, &disk_to_dev(d->disk)->kobj, "bcache_fdev");
if (err)
goto err;
+ ret = sysfs_create_link_nowarn(&disk_to_dev(d->disk)->kobj,
+ &d->kobj, "bcache");
+ if (ret && ret != -EEXIST) {
+ pr_err("Couldn't create lagacy flash dev ->bcache");
+ goto err;
+ }
+
bcache_device_link(d, c, "volume");
if (bch_has_feature_obso_large_bucket(&c->cache->sb)) {
@@ -2370,12 +2393,19 @@ 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), "bcache_cache")) {
err = "error calling kobject_add";
ret = -ENOMEM;
goto out;
}
+ ret = sysfs_create_link_nowarn(bdev_kobj(bdev), &ca->kobj, "bcache");
+ if (ret && ret != -EEXIST) {
+ pr_err("Couldn't create lagacy disk sysfs ->cache symlinks\n");
+ goto out;
+ } else
+ ret = 0;
+
mutex_lock(&bch_register_lock);
err = register_cache_set(ca);
mutex_unlock(&bch_register_lock);
--
2.17.1
