Messages in this thread Patch in this message | | | Date | Tue, 27 Jun 2023 10:12:58 +0800 | Subject | Re: [RFC 1/2] erofs: update on-disk format for xattr bloom filter | From | Gao Xiang <> |
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On 2023/6/21 16:32, Jingbo Xu wrote: > The xattr bloom filter feature is going to be introduced to speed up the > negative xattr lookup, e.g. system.posix_acl_[access|default] lookup > when running "ls -lR" workload. > > The number of common used xattr (n) is approximately 8, including > system.[posix_acl_access|posix_acl_default], security.[capability|selinux] > and security.[SMACK64|SMACK64TRANSMUTE|SMACK64EXEC|SMACK64MMAP]. Given the > number of bits of the bloom filter (m) is 32, the optimal value for the > number of the hash functions (k) is 2 (ln2 * m/n = 2.7). > > Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com> > --- > fs/erofs/erofs_fs.h | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h > index 2c7b16e340fe..9daea86cdb52 100644 > --- a/fs/erofs/erofs_fs.h > +++ b/fs/erofs/erofs_fs.h > @@ -13,6 +13,7 @@ > > #define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001 > #define EROFS_FEATURE_COMPAT_MTIME 0x00000002 > +#define EROFS_FEATURE_COMPAT_XATTR_BLOOM 0x00000003
#define EROFS_FEATURE_COMPAT_XATTR_BLOOM 0x00000004
> > /* > * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should > @@ -200,7 +201,7 @@ struct erofs_inode_extended { > * for read-only fs, no need to introduce h_refcount > */ > struct erofs_xattr_ibody_header { > - __le32 h_reserved; > + __le32 h_map; /* bloom filter, bit value 1 indicates not-present */
`map` here is too ambiguous, could we rename it as "h_name_filter"?
> __u8 h_shared_count; > __u8 h_reserved2[7]; > __le32 h_shared_xattrs[]; /* shared xattr id array */ > @@ -221,6 +222,11 @@ struct erofs_xattr_ibody_header { > #define EROFS_XATTR_LONG_PREFIX 0x80 > #define EROFS_XATTR_LONG_PREFIX_MASK 0x7f > > +#define EROFS_XATTR_BLOOM_BITS 32 > +#define EROFS_XATTR_BLOOM_MASK (EROFS_XATTR_BLOOM_BITS - 1) > +#define EROFS_XATTR_BLOOM_DEFAULT UINT32_MAX > +#define EROFS_XATTR_BLOOM_COUNTS 2
could we rename them as EROFS_XATTR_NAME_FILTER_xxx?
Thanks, Gao Xiang
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