iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

bcache: reserve never used bits from bkey.high

Browse Source 
There sre 3 bits in member high of struct bkey are never used, and no
plan to support them in future,
- HEADER_SIZE, start at bit 58, length 2 bits
- KEY_PINNED,  start at bit 55, length 1 bit

No any kernel code, or user space tool references or accesses the three
bits. Therefore it is possible and feasible to reserve the valuable bits
from bkey.high. They can be used in future for other purpose.

Signed-off-by: Coly Li <colyli@suse.de>
Link: https://lore.kernel.org/r/20211020143812.6403-3-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Coly Li 2021-10-20 22:38:06 +08:00 committed by Jens Axboe
parent a307e2abfc
commit 0a2b3e3635
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/uapi/linux/bcache.h
View File

@ -43,9 +43,9 @@ static inline void SET_##name(struct bkey *k, unsigned int i, __u64 v) \
#define KEY_MAX_U64S 8
KEY_FIELD(KEY_PTRS, high, 60, 3)
KEY_FIELD(HEADER_SIZE, high, 58, 2)
KEY_FIELD(__PAD0, high, 58, 2)
KEY_FIELD(KEY_CSUM, high, 56, 2)
KEY_FIELD(KEY_PINNED, high, 55, 1)
KEY_FIELD(__PAD1, high, 55, 1)
KEY_FIELD(KEY_DIRTY, high, 36, 1)
KEY_FIELD(KEY_SIZE, high, 20, KEY_SIZE_BITS)