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authorJingbo Xu <jefflexu@linux.alibaba.com>2023-07-22 11:45:37 +0200
committerGao Xiang <hsiangkao@linux.alibaba.com>2023-08-11 06:11:44 +0200
commit3f339920175c871ac63b4ea179117da7518618fd (patch)
treeebb1d11e0d394435bbd4b57923c5458abb30bd97
parenterofs: DEFLATE compression support (diff)
downloadlinux-3f339920175c871ac63b4ea179117da7518618fd.tar.xz
linux-3f339920175c871ac63b4ea179117da7518618fd.zip
erofs: update on-disk format for xattr name filter
The xattr name 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. There are some commonly used extended attributes (n) and the total number of these is approximately 30. trusted.overlay.opaque trusted.overlay.redirect trusted.overlay.origin trusted.overlay.impure trusted.overlay.nlink trusted.overlay.upper trusted.overlay.metacopy trusted.overlay.protattr user.overlay.opaque user.overlay.redirect user.overlay.origin user.overlay.impure user.overlay.nlink user.overlay.upper user.overlay.metacopy user.overlay.protattr security.evm security.ima security.selinux security.SMACK64 security.SMACK64IPIN security.SMACK64IPOUT security.SMACK64EXEC security.SMACK64TRANSMUTE security.SMACK64MMAP security.apparmor security.capability system.posix_acl_access system.posix_acl_default user.mime_type Given the number of bits of the bloom filter (m) is 32, the optimal value for the number of the hash functions (k) is 1 (ln2 * m/n = 0.74). The single hash function is implemented as: xxh32(name, strlen(name), EROFS_XATTR_FILTER_SEED + index) where `index` represents the index of corresponding predefined short name prefix, while `name` represents the name string after stripping the above predefined name prefix. The constant magic number EROFS_XATTR_FILTER_SEED, i.e. 0x25BBE08F, is used to give a better spread when mapping these 30 extended attributes into 32-bit bloom filter as: bit 0: security.ima bit 1: bit 2: trusted.overlay.nlink bit 3: bit 4: user.overlay.nlink bit 5: trusted.overlay.upper bit 6: user.overlay.origin bit 7: trusted.overlay.protattr bit 8: security.apparmor bit 9: user.overlay.protattr bit 10: user.overlay.opaque bit 11: security.selinux bit 12: security.SMACK64TRANSMUTE bit 13: security.SMACK64 bit 14: security.SMACK64MMAP bit 15: user.overlay.impure bit 16: security.SMACK64IPIN bit 17: trusted.overlay.redirect bit 18: trusted.overlay.origin bit 19: security.SMACK64IPOUT bit 20: trusted.overlay.opaque bit 21: system.posix_acl_default bit 22: bit 23: user.mime_type bit 24: trusted.overlay.impure bit 25: security.SMACK64EXEC bit 26: user.overlay.redirect bit 27: user.overlay.upper bit 28: security.evm bit 29: security.capability bit 30: system.posix_acl_access bit 31: trusted.overlay.metacopy, user.overlay.metacopy h_name_filter is introduced to the on-disk per-inode xattr header to place the corresponding xattr name filter, where bit value 1 indicates non-existence for compatibility. This feature is indicated by EROFS_FEATURE_COMPAT_XATTR_FILTER compatible feature bit. Reserve one byte in on-disk superblock as the on-disk format for xattr name filter may change in the future. With this flag we don't need bothering these compatible bits again at that time. Suggested-by: Alexander Larsson <alexl@redhat.com> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com> Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com> Reviewed-by: Chao Yu <chao@kernel.org> Link: https://lore.kernel.org/r/20230722094538.11754-2-jefflexu@linux.alibaba.com Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
-rw-r--r--fs/erofs/erofs_fs.h10
1 files changed, 8 insertions, 2 deletions
diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
index 364f51171c13..a03ec70ba6f2 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_FILTER 0x00000004
/*
* Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
@@ -81,7 +82,8 @@ struct erofs_super_block {
__u8 xattr_prefix_count; /* # of long xattr name prefixes */
__le32 xattr_prefix_start; /* start of long xattr prefixes */
__le64 packed_nid; /* nid of the special packed inode */
- __u8 reserved2[24];
+ __u8 xattr_filter_reserved; /* reserved for xattr name filter */
+ __u8 reserved2[23];
};
/*
@@ -200,7 +202,7 @@ struct erofs_inode_extended {
* for read-only fs, no need to introduce h_refcount
*/
struct erofs_xattr_ibody_header {
- __le32 h_reserved;
+ __le32 h_name_filter; /* bit value 1 indicates not-present */
__u8 h_shared_count;
__u8 h_reserved2[7];
__le32 h_shared_xattrs[]; /* shared xattr id array */
@@ -221,6 +223,10 @@ struct erofs_xattr_ibody_header {
#define EROFS_XATTR_LONG_PREFIX 0x80
#define EROFS_XATTR_LONG_PREFIX_MASK 0x7f
+#define EROFS_XATTR_FILTER_BITS 32
+#define EROFS_XATTR_FILTER_DEFAULT UINT32_MAX
+#define EROFS_XATTR_FILTER_SEED 0x25BBE08F
+
/* xattr entry (for both inline & shared xattrs) */
struct erofs_xattr_entry {
__u8 e_name_len; /* length of name */