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Since bcache code was merged into mainline kerrnel, each cache set only
as one single cache in it. The multiple caches framework is here but the
code is far from completed. Considering the multiple copies of cached
data can also be stored on e.g. md raid1 devices, it is unnecessary to
support multiple caches in one cache set indeed.
The previous preparation patches fix the dependencies of explicitly
making a cache set only have single cache. Now we don't have to maintain
an embedded partial super block in struct cache_set, the in-memory super
block can be directly referenced from struct cache.
This patch removes the embedded struct cache_sb from struct cache_set,
and fixes all locations where the superb lock was referenced from this
removed super block by referencing the in-memory super block of struct
cache.
Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The following three sysfs files are created to display according feature
set information of bcache:
/sys/fs/bcache/<cache set UUID>/internal/feature_compat
/sys/fs/bcache/<cache set UUID>/internal/feature_ro_compat
/sys/fs/bcache/<cache set UUID>/internal/feature_incompat
is added by this patch, to display feature sets information of the cache
set.
Now only an incompat feature 'large_bucket' added in bcache, the sysfs
file content is:
[large_bucket]
string large_bucket means the running bcache drive supports incompat
feature 'large_bucket', the wrapping [] means the 'large_bucket' feature
is currently enabled on this cache set.
This patch is ready to display compat and ro_compat features, in future
once bcache code implements such feature sets, the according feature
strings will be displayed in their sysfs files too.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The large bucket feature is to extend bucket_size from 16bit to 32bit.
When create cache device on zoned device (e.g. zoned NVMe SSD), making
a single bucket cover one or more zones of the zoned device is the
simplest way to support zoned device as cache by bcache.
But current maximum bucket size is 16MB and a typical zone size of zoned
device is 256MB, this is the major motiviation to extend bucket size to
a larger bit width.
This patch is the basic and first change to support large bucket size,
the major changes it makes are,
- Add BCH_FEATURE_INCOMPAT_LARGE_BUCKET for the large bucket feature,
INCOMPAT means it introduces incompatible on-disk format change.
- Add BCH_FEATURE_INCOMPAT_FUNCS(large_bucket, LARGE_BUCKET) routines.
- Adds __le16 bucket_size_hi into struct cache_sb_disk at offset 0x8d0
for the on-disk super block format.
- For the in-memory super block struct cache_sb, member bucket_size is
extended from __u16 to __32.
- Add get_bucket_size() to combine the bucket_size and bucket_size_hi
from struct cache_sb_disk into an unsigned int value.
Since we already have large bucket size helpers meta_bucket_pages(),
meta_bucket_bytes() and alloc_meta_bucket_pages(), they make sure when
bucket size > 8MB, the memory allocation for bcache meta data bucket
won't fail no matter how large the bucket size extended. So these meta
data buckets are handled properly when the bucket size width increase
from 16bit to 32bit, we don't need to worry about them.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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