From: mingzhe <mingzhe.zou@xxxxxxxxxxxx>
Bcache allows multiple flash devices to be created on the same cache.
We can create multiple flash devices, and the total size larger than
cache device's actual size.
```
[root@zou ~]# lsblk /dev/vdd
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdd 252:48 0 100G 0 disk
[root@zou ~]# echo 50G > /sys/block/vdd/bcache/set/flash_vol_create
[root@zou ~]# lsblk /dev/vdd
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdd 252:48 0 100G 0 disk
└─bcache1 251:128 0 50G 0 disk
[root@zou ~]# echo 50G > /sys/block/vdd/bcache/set/flash_vol_create
[root@zou ~]# lsblk /dev/vdd
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdd 252:48 0 100G 0 disk
├─bcache2 251:256 0 50G 0 disk
└─bcache1 251:128 0 50G 0 disk
[root@zou ~]# echo 50G > /sys/block/vdd/bcache/set/flash_vol_create
[root@zou ~]# lsblk /dev/vdd
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdd 252:48 0 100G 0 disk
├─bcache3 251:256 0 50G 0 disk
├─bcache2 251:256 0 50G 0 disk
└─bcache1 251:128 0 50G 0 disk
```
This patch will limit the total size of multi-flash device, until no
free space to create a new flash device with an error.
```
[root@zou ~]# lsblk /dev/vdd
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdd 252:48 0 100G 0 disk
[root@zou ~]# echo 50G > /sys/block/vdd/bcache/set/flash_vol_create
[root@zou ~]# lsblk /dev/vdd
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdd 252:48 0 100G 0 disk
└─bcache1 251:128 0 50G 0 disk
[root@zou ~]# echo 50G > /sys/block/vdd/bcache/set/flash_vol_create
[root@zou ~]# lsblk /dev/vdd
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdd 252:48 0 100G 0 disk
├─bcache2 251:256 0 39.9G 0 disk
└─bcache1 251:128 0 50G 0 disk
[root@zou ~]# echo 50G > /sys/block/vdd/bcache/set/flash_vol_create
-bash: echo: write error: No space left on device
[root@zou ~]# lsblk /dev/vdd
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vdd 252:48 0 100G 0 disk
├─bcache2 251:256 0 39.9G 0 disk
└─bcache1 251:128 0 50G 0 disk
```
Signed-off-by: mingzhe <mingzhe.zou@xxxxxxxxxxxx>
---
drivers/md/bcache/super.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 214a384dc1d7..d4b3ab078ad3 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1581,13 +1581,32 @@ static int flash_devs_run(struct cache_set *c)
static inline sector_t flash_dev_max_sectors(struct cache_set *c)
{
+ sector_t sectors;
+ struct uuid_entry *u;
+ struct bcache_device *d;
size_t avail_nbuckets;
struct cache *ca = c->cache;
size_t first_bucket = ca->sb.first_bucket;
size_t njournal_buckets = ca->sb.njournal_buckets;
avail_nbuckets = c->nbuckets - first_bucket - njournal_buckets;
- return bucket_to_sector(c, avail_nbuckets / 100 * FLASH_DEV_AVAILABLE_RATIO);
+ sectors = bucket_to_sector(c, avail_nbuckets / 100 * FLASH_DEV_AVAILABLE_RATIO);
+
+ /*
+ * Although 10% of buckets are forced to reserve, it should
+ * be able to meet the needs of gc and btree node allocation.
+ * But the remaining buckets are not necessarily allocatable
+ * free buckets. Because some of the buckets might be cached
+ * dirty data. At the same time, the space that has been
+ * allocated to other flash devices must be considered.
+ */
+ for (u = c->uuids; u < c->uuids + c->nr_uuids && sectors > 0; u++) {
+ if (!(d = c->devices[u - c->uuids]))
+ continue;
+ sectors -= min(UUID_FLASH_ONLY(u) ? u->sectors :
+ bcache_dev_sectors_dirty(d), sectors);
+ }
+ return sectors;
}
int bch_flash_dev_create(struct cache_set *c, uint64_t size)
@@ -1612,6 +1631,10 @@ int bch_flash_dev_create(struct cache_set *c, uint64_t size)
SET_UUID_FLASH_ONLY(u, 1);
u->sectors = min(flash_dev_max_sectors(c), size >> 9);
+ if (!u->sectors) {
+ pr_err("Can't create volume, no free space");
+ return -ENOSPC;
+ }
bch_uuid_write(c);
--
2.17.1
