bcache-tools: 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 incompat feature set. It indicates bucket_size_hi is
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,
bcache-tools only display "obso_large_bucket" for cache device created
with BCH_FEATURE_INCOMPAT_LARGE_BUCKET, kernel driver will make bcache
device as read-only if BCH_FEATURE_INCOMPAT_LARGE_BUCKET is set.
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: 8c063851990a ("bcache-tools: add large_bucket incompat feature")
Signed-off-by: Coly Li <colyli@suse.de>
diff --git a/bcache.h b/bcache.h
index 58e973c..6dcdbb7 100644
--- a/bcache.h
+++ b/bcache.h
@@ -100,7 +100,7 @@
__le16 keys;
};
__le64 d[SB_JOURNAL_BUCKETS]; /* journal buckets */
- __le16 bucket_size_hi;
+ __le16 obso_bucket_size_hi; /* obsoleted */
};
/*
@@ -202,7 +202,8 @@
#define BCH_FEATURE_COMPAT_SUPP 0
#define BCH_FEATURE_RO_COMPAT_SUPP 0
-#define BCH_FEATURE_INCOMPAT_SUPP BCH_FEATURE_INCOMPAT_LARGE_BUCKET
+#define BCH_FEATURE_INCOMPAT_SUPP (BCH_FEATURE_INCOMPAT_OBSO_LARGE_BUCKET| \
+ BCH_FEATURE_INCOMPAT_LOG_LARGE_BUCKET_SIZE)
#define BCH_HAS_COMPAT_FEATURE(sb, mask) \
((sb)->feature_compat & (mask))
@@ -214,7 +215,10 @@
/* Feature set definition */
/* Incompat feature set */
-#define BCH_FEATURE_INCOMPAT_LARGE_BUCKET 0x0001 /* 32bit bucket size */
+/* 32bit bucket size, obsoleted */
+#define BCH_FEATURE_INCOMPAT_OBSO_LARGE_BUCKET 0x0001
+/* real bucket size is (1 << bucket_size) */
+#define BCH_FEATURE_INCOMPAT_LOG_LARGE_BUCKET_SIZE 0x0002
#define BCH_FEATURE_COMPAT_FUNCS(name, flagname) \
static inline int bch_has_feature_##name(struct cache_sb *sb) \
@@ -267,6 +271,7 @@
~BCH##_FEATURE_INCOMPAT_##flagname; \
}
-BCH_FEATURE_INCOMPAT_FUNCS(large_bucket, LARGE_BUCKET);
+BCH_FEATURE_INCOMPAT_FUNCS(obso_large_bucket, OBSO_LARGE_BUCKET);
+BCH_FEATURE_INCOMPAT_FUNCS(large_bucket, LOG_LARGE_BUCKET_SIZE);
#endif
diff --git a/features.c b/features.c
index 181e348..f7f6224 100644
--- a/features.c
+++ b/features.c
@@ -20,7 +20,9 @@
};
static struct feature feature_list[] = {
- {BCH_FEATURE_INCOMPAT, BCH_FEATURE_INCOMPAT_LARGE_BUCKET,
+ {BCH_FEATURE_INCOMPAT, BCH_FEATURE_INCOMPAT_OBSO_LARGE_BUCKET,
+ "obso_large_bucket"},
+ {BCH_FEATURE_INCOMPAT, BCH_FEATURE_INCOMPAT_LOG_LARGE_BUCKET_SIZE,
"large_bucket"},
{0, 0, 0 },
};
diff --git a/lib.c b/lib.c
index a529ad3..8e7da8b 100644
--- a/lib.c
+++ b/lib.c
@@ -21,6 +21,19 @@
* utils function
*/
+static unsigned int log2_u32(uint32_t n)
+{
+ int r = 0;
+
+ n = n >> 1;
+ while (n) {
+ n = n >> 1;
+ r++;
+ }
+
+ return r;
+}
+
static void trim_prefix(char *dest, char *src, int num)
{
strcpy(dest, src + num);
@@ -772,7 +785,7 @@
if (sb->version >= BCACHE_SB_VERSION_CDEV_WITH_FEATURES &&
bch_has_feature_large_bucket(sb))
- sb->bucket_size += le16_to_cpu(sb_disk->bucket_size_hi) << 16;
+ sb->bucket_size = 1 << le16_to_cpu(sb_disk->bucket_size);
return sb;
}
@@ -824,7 +837,7 @@
if (sb->version >= BCACHE_SB_VERSION_CDEV_WITH_FEATURES &&
bch_has_feature_large_bucket(sb))
- sb_disk->bucket_size_hi = cpu_to_le16(sb->bucket_size >> 16);
+ sb_disk->bucket_size = cpu_to_le16(log2_u32(sb->bucket_size));
return sb_disk;
}
diff --git a/lib.h b/lib.h
index 9b5ed02..0357a11 100644
--- a/lib.h
+++ b/lib.h
@@ -13,7 +13,7 @@
char label[SB_LABEL_SIZE + 1];
char uuid[40];
uint16_t sectors_per_block;
- uint16_t sectors_per_bucket;
+ uint32_t sectors_per_bucket;
char cset[40];
char state[40];
char bname[40];
