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author | Coly Li <colyli@suse.de> | 2021-01-04 15:41:21 +0800 |
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committer | Jens Axboe <axboe@kernel.dk> | 2021-01-09 09:21:03 -0700 |
commit | b16671e8f493e3df40b1fb0dff4078f391c5099a (patch) | |
tree | e3757bcd8199f9dea6915e68be2b77480573637c /include/uapi/linux/bcache.h | |
parent | 1dfc0686c29a9bbd3a446a29f9ccde3dec3bc75a (diff) | |
download | linux-stable-b16671e8f493e3df40b1fb0dff4078f391c5099a.tar.gz linux-stable-b16671e8f493e3df40b1fb0dff4078f391c5099a.tar.bz2 linux-stable-b16671e8f493e3df40b1fb0dff4078f391c5099a.zip |
bcache: introduce BCH_FEATURE_INCOMPAT_LOG_LARGE_BUCKET_SIZE for large bucket
When large bucket feature was added, BCH_FEATURE_INCOMPAT_LARGE_BUCKET
was introduced into the incompat feature set. It used bucket_size_hi
(which was added at the tail of struct cache_sb_disk) to extend current
16bit bucket size to 32bit with existing bucket_size in struct
cache_sb_disk.
This is not a good idea, there are two obvious problems,
- Bucket size is always value power of 2, if store log2(bucket size) in
existing bucket_size of struct cache_sb_disk, it is unnecessary to add
bucket_size_hi.
- Macro csum_set() assumes d[SB_JOURNAL_BUCKETS] is the last member in
struct cache_sb_disk, bucket_size_hi was added after d[] which makes
csum_set calculate an unexpected super block checksum.
To fix the above problems, this patch introduces a new incompat feature
bit BCH_FEATURE_INCOMPAT_LOG_LARGE_BUCKET_SIZE, when this bit is set, it
means bucket_size in struct cache_sb_disk stores the order of power-of-2
bucket size value. When user specifies a bucket size larger than 32768
sectors, BCH_FEATURE_INCOMPAT_LOG_LARGE_BUCKET_SIZE will be set to
incompat feature set, and bucket_size stores log2(bucket size) more
than store the real bucket size value.
The obsoleted BCH_FEATURE_INCOMPAT_LARGE_BUCKET won't be used anymore,
it is renamed to BCH_FEATURE_INCOMPAT_OBSO_LARGE_BUCKET and still only
recognized by kernel driver for legacy compatible purpose. The previous
bucket_size_hi is renmaed to obso_bucket_size_hi in struct cache_sb_disk
and not used in bcache-tools anymore.
For cache device created with BCH_FEATURE_INCOMPAT_LARGE_BUCKET feature,
bcache-tools and kernel driver still recognize the feature string and
display it as "obso_large_bucket".
With this change, the unnecessary extra space extend of bcache on-disk
super block can be avoided, and csum_set() may generate expected check
sum as well.
Fixes: ffa470327572 ("bcache: add bucket_size_hi into struct cache_sb_disk for large bucket")
Signed-off-by: Coly Li <colyli@suse.de>
Cc: stable@vger.kernel.org # 5.9+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/uapi/linux/bcache.h')
-rw-r--r-- | include/uapi/linux/bcache.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h index 52e8bcb33981..cf7399f03b71 100644 --- a/include/uapi/linux/bcache.h +++ b/include/uapi/linux/bcache.h @@ -213,7 +213,7 @@ struct cache_sb_disk { __le16 keys; }; __le64 d[SB_JOURNAL_BUCKETS]; /* journal buckets */ - __le16 bucket_size_hi; + __le16 obso_bucket_size_hi; /* obsoleted */ }; /* |