3f33992017
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> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.