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-rw-r--r--pkg/sentry/fs/ext/disklayout/superblock.go471
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diff --git a/pkg/sentry/fs/ext/disklayout/superblock.go b/pkg/sentry/fs/ext/disklayout/superblock.go
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-// Copyright 2019 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package disklayout
-
-const (
- // SbOffset is the absolute offset at which the superblock is placed.
- SbOffset = 1024
-)
-
-// SuperBlock should be implemented by structs representing the ext superblock.
-// The superblock holds a lot of information about the enclosing filesystem.
-// This interface aims to provide access methods to important information held
-// by the superblock. It does NOT expose all fields of the superblock, only the
-// ones necessary. This can be expanded when need be.
-//
-// Location and replication:
-// - The superblock is located at offset 1024 in block group 0.
-// - Redundant copies of the superblock and group descriptors are kept in
-// all groups if SbSparse feature flag is NOT set. If it is set, the
-// replicas only exist in groups whose group number is either 0 or a
-// power of 3, 5, or 7.
-// - There is also a sparse superblock feature v2 in which there are just
-// two replicas saved in the block groups pointed by sb.s_backup_bgs.
-//
-// Replicas should eventually be updated if the superblock is updated.
-//
-// See https://www.kernel.org/doc/html/latest/filesystems/ext4/globals.html#super-block.
-type SuperBlock interface {
- // InodesCount returns the total number of inodes in this filesystem.
- InodesCount() uint32
-
- // BlocksCount returns the total number of data blocks in this filesystem.
- BlocksCount() uint64
-
- // FreeBlocksCount returns the number of free blocks in this filesystem.
- FreeBlocksCount() uint64
-
- // FreeInodesCount returns the number of free inodes in this filesystem.
- FreeInodesCount() uint32
-
- // MountCount returns the number of mounts since the last fsck.
- MountCount() uint16
-
- // MaxMountCount returns the number of mounts allowed beyond which a fsck is
- // needed.
- MaxMountCount() uint16
-
- // FirstDataBlock returns the absolute block number of the first data block,
- // which contains the super block itself.
- //
- // If the filesystem has 1kb data blocks then this should return 1. For all
- // other configurations, this typically returns 0.
- FirstDataBlock() uint32
-
- // BlockSize returns the size of one data block in this filesystem.
- // This can be calculated by 2^(10 + sb.s_log_block_size). This ensures that
- // the smallest block size is 1kb.
- BlockSize() uint64
-
- // BlocksPerGroup returns the number of data blocks in a block group.
- BlocksPerGroup() uint32
-
- // ClusterSize returns block cluster size (set during mkfs time by admin).
- // This can be calculated by 2^(10 + sb.s_log_cluster_size). This ensures that
- // the smallest cluster size is 1kb.
- //
- // sb.s_log_cluster_size must equal sb.s_log_block_size if bigalloc feature
- // is NOT set and consequently BlockSize() = ClusterSize() in that case.
- ClusterSize() uint64
-
- // ClustersPerGroup returns:
- // - number of clusters per group if bigalloc is enabled.
- // - BlocksPerGroup() otherwise.
- ClustersPerGroup() uint32
-
- // InodeSize returns the size of the inode disk record size in bytes. Use this
- // to iterate over inode arrays on disk.
- //
- // In ext2 and ext3:
- // - Each inode had a disk record of 128 bytes.
- // - The inode struct size was fixed at 128 bytes.
- //
- // In ext4 its possible to allocate larger on-disk inodes:
- // - Inode disk record size = sb.s_inode_size (function return value).
- // = 256 (default)
- // - Inode struct size = 128 + inode.i_extra_isize.
- // = 128 + 32 = 160 (default)
- InodeSize() uint16
-
- // InodesPerGroup returns the number of inodes in a block group.
- InodesPerGroup() uint32
-
- // BgDescSize returns the size of the block group descriptor struct.
- //
- // In ext2, ext3, ext4 (without 64-bit feature), the block group descriptor
- // is only 32 bytes long.
- // In ext4 with 64-bit feature, the block group descriptor expands to AT LEAST
- // 64 bytes. It might be bigger than that.
- BgDescSize() uint16
-
- // CompatibleFeatures returns the CompatFeatures struct which holds all the
- // compatible features this fs supports.
- CompatibleFeatures() CompatFeatures
-
- // IncompatibleFeatures returns the CompatFeatures struct which holds all the
- // incompatible features this fs supports.
- IncompatibleFeatures() IncompatFeatures
-
- // ReadOnlyCompatibleFeatures returns the CompatFeatures struct which holds all the
- // readonly compatible features this fs supports.
- ReadOnlyCompatibleFeatures() RoCompatFeatures
-
- // Magic() returns the magic signature which must be 0xef53.
- Magic() uint16
-
- // Revision returns the superblock revision. Superblock struct fields from
- // offset 0x54 till 0x150 should only be used if superblock has DynamicRev.
- Revision() SbRevision
-}
-
-// SbRevision is the type for superblock revisions.
-type SbRevision uint32
-
-// Super block revisions.
-const (
- // OldRev is the good old (original) format.
- OldRev SbRevision = 0
-
- // DynamicRev is v2 format w/ dynamic inode sizes.
- DynamicRev SbRevision = 1
-)
-
-// Superblock compatible features.
-// This is not exhaustive, unused features are not listed.
-const (
- // SbDirPrealloc indicates directory preallocation.
- SbDirPrealloc = 0x1
-
- // SbHasJournal indicates the presence of a journal. jbd2 should only work
- // with this being set.
- SbHasJournal = 0x4
-
- // SbExtAttr indicates extended attributes support.
- SbExtAttr = 0x8
-
- // SbResizeInode indicates that the fs has reserved GDT blocks (right after
- // group descriptors) for fs expansion.
- SbResizeInode = 0x10
-
- // SbDirIndex indicates that the fs has directory indices.
- SbDirIndex = 0x20
-
- // SbSparseV2 stands for Sparse superblock version 2.
- SbSparseV2 = 0x200
-)
-
-// CompatFeatures represents a superblock's compatible feature set. If the
-// kernel does not understand any of these feature, it can still read/write
-// to this fs.
-type CompatFeatures struct {
- DirPrealloc bool
- HasJournal bool
- ExtAttr bool
- ResizeInode bool
- DirIndex bool
- SparseV2 bool
-}
-
-// ToInt converts superblock compatible features back to its 32-bit rep.
-func (f CompatFeatures) ToInt() uint32 {
- var res uint32
-
- if f.DirPrealloc {
- res |= SbDirPrealloc
- }
- if f.HasJournal {
- res |= SbHasJournal
- }
- if f.ExtAttr {
- res |= SbExtAttr
- }
- if f.ResizeInode {
- res |= SbResizeInode
- }
- if f.DirIndex {
- res |= SbDirIndex
- }
- if f.SparseV2 {
- res |= SbSparseV2
- }
-
- return res
-}
-
-// CompatFeaturesFromInt converts the integer representation of superblock
-// compatible features to CompatFeatures struct.
-func CompatFeaturesFromInt(f uint32) CompatFeatures {
- return CompatFeatures{
- DirPrealloc: f&SbDirPrealloc > 0,
- HasJournal: f&SbHasJournal > 0,
- ExtAttr: f&SbExtAttr > 0,
- ResizeInode: f&SbResizeInode > 0,
- DirIndex: f&SbDirIndex > 0,
- SparseV2: f&SbSparseV2 > 0,
- }
-}
-
-// Superblock incompatible features.
-// This is not exhaustive, unused features are not listed.
-const (
- // SbDirentFileType indicates that directory entries record the file type.
- // We should use struct DirentNew for dirents then.
- SbDirentFileType = 0x2
-
- // SbRecovery indicates that the filesystem needs recovery.
- SbRecovery = 0x4
-
- // SbJournalDev indicates that the filesystem has a separate journal device.
- SbJournalDev = 0x8
-
- // SbMetaBG indicates that the filesystem is using Meta block groups. Moves
- // the group descriptors from the congested first block group into the first
- // group of each metablock group to increase the maximum block groups limit
- // and hence support much larger filesystems.
- //
- // See https://www.kernel.org/doc/html/latest/filesystems/ext4/overview.html#meta-block-groups.
- SbMetaBG = 0x10
-
- // SbExtents indicates that the filesystem uses extents. Must be set in ext4
- // filesystems.
- SbExtents = 0x40
-
- // SbIs64Bit indicates that this filesystem addresses blocks with 64-bits.
- // Hence can support 2^64 data blocks.
- SbIs64Bit = 0x80
-
- // SbMMP indicates that this filesystem has multiple mount protection.
- //
- // See https://www.kernel.org/doc/html/latest/filesystems/ext4/globals.html#multiple-mount-protection.
- SbMMP = 0x100
-
- // SbFlexBg indicates that this filesystem has flexible block groups. Several
- // block groups are tied into one logical block group so that all the metadata
- // for the block groups (bitmaps and inode tables) are close together for
- // faster loading. Consequently, large files will be continuous on disk.
- // However, this does not affect the placement of redundant superblocks and
- // group descriptors.
- //
- // See https://www.kernel.org/doc/html/latest/filesystems/ext4/overview.html#flexible-block-groups.
- SbFlexBg = 0x200
-
- // SbLargeDir shows that large directory enabled. Directory htree can be 3
- // levels deep. Directory htrees are allowed to be 2 levels deep otherwise.
- SbLargeDir = 0x4000
-
- // SbInlineData allows inline data in inodes for really small files.
- SbInlineData = 0x8000
-
- // SbEncrypted indicates that this fs contains encrypted inodes.
- SbEncrypted = 0x10000
-)
-
-// IncompatFeatures represents a superblock's incompatible feature set. If the
-// kernel does not understand any of these feature, it should refuse to mount.
-type IncompatFeatures struct {
- DirentFileType bool
- Recovery bool
- JournalDev bool
- MetaBG bool
- Extents bool
- Is64Bit bool
- MMP bool
- FlexBg bool
- LargeDir bool
- InlineData bool
- Encrypted bool
-}
-
-// ToInt converts superblock incompatible features back to its 32-bit rep.
-func (f IncompatFeatures) ToInt() uint32 {
- var res uint32
-
- if f.DirentFileType {
- res |= SbDirentFileType
- }
- if f.Recovery {
- res |= SbRecovery
- }
- if f.JournalDev {
- res |= SbJournalDev
- }
- if f.MetaBG {
- res |= SbMetaBG
- }
- if f.Extents {
- res |= SbExtents
- }
- if f.Is64Bit {
- res |= SbIs64Bit
- }
- if f.MMP {
- res |= SbMMP
- }
- if f.FlexBg {
- res |= SbFlexBg
- }
- if f.LargeDir {
- res |= SbLargeDir
- }
- if f.InlineData {
- res |= SbInlineData
- }
- if f.Encrypted {
- res |= SbEncrypted
- }
-
- return res
-}
-
-// IncompatFeaturesFromInt converts the integer representation of superblock
-// incompatible features to IncompatFeatures struct.
-func IncompatFeaturesFromInt(f uint32) IncompatFeatures {
- return IncompatFeatures{
- DirentFileType: f&SbDirentFileType > 0,
- Recovery: f&SbRecovery > 0,
- JournalDev: f&SbJournalDev > 0,
- MetaBG: f&SbMetaBG > 0,
- Extents: f&SbExtents > 0,
- Is64Bit: f&SbIs64Bit > 0,
- MMP: f&SbMMP > 0,
- FlexBg: f&SbFlexBg > 0,
- LargeDir: f&SbLargeDir > 0,
- InlineData: f&SbInlineData > 0,
- Encrypted: f&SbEncrypted > 0,
- }
-}
-
-// Superblock readonly compatible features.
-// This is not exhaustive, unused features are not listed.
-const (
- // SbSparse indicates sparse superblocks. Only groups with number either 0 or
- // a power of 3, 5, or 7 will have redundant copies of the superblock and
- // block descriptors.
- SbSparse = 0x1
-
- // SbLargeFile indicates that this fs has been used to store a file >= 2GiB.
- SbLargeFile = 0x2
-
- // SbHugeFile indicates that this fs contains files whose sizes are
- // represented in units of logicals blocks, not 512-byte sectors.
- SbHugeFile = 0x8
-
- // SbGdtCsum indicates that group descriptors have checksums.
- SbGdtCsum = 0x10
-
- // SbDirNlink indicates that the new subdirectory limit is 64,999. Ext3 has a
- // 32,000 subdirectory limit.
- SbDirNlink = 0x20
-
- // SbExtraIsize indicates that large inodes exist on this filesystem.
- SbExtraIsize = 0x40
-
- // SbHasSnapshot indicates the existence of a snapshot.
- SbHasSnapshot = 0x80
-
- // SbQuota enables usage tracking for all quota types.
- SbQuota = 0x100
-
- // SbBigalloc maps to the bigalloc feature. When set, the minimum allocation
- // unit becomes a cluster rather than a data block. Then block bitmaps track
- // clusters, not data blocks.
- //
- // See https://www.kernel.org/doc/html/latest/filesystems/ext4/overview.html#bigalloc.
- SbBigalloc = 0x200
-
- // SbMetadataCsum indicates that the fs supports metadata checksumming.
- SbMetadataCsum = 0x400
-
- // SbReadOnly marks this filesystem as readonly. Should refuse to mount in
- // read/write mode.
- SbReadOnly = 0x1000
-)
-
-// RoCompatFeatures represents a superblock's readonly compatible feature set.
-// If the kernel does not understand any of these feature, it can still mount
-// readonly. But if the user wants to mount read/write, the kernel should
-// refuse to mount.
-type RoCompatFeatures struct {
- Sparse bool
- LargeFile bool
- HugeFile bool
- GdtCsum bool
- DirNlink bool
- ExtraIsize bool
- HasSnapshot bool
- Quota bool
- Bigalloc bool
- MetadataCsum bool
- ReadOnly bool
-}
-
-// ToInt converts superblock readonly compatible features to its 32-bit rep.
-func (f RoCompatFeatures) ToInt() uint32 {
- var res uint32
-
- if f.Sparse {
- res |= SbSparse
- }
- if f.LargeFile {
- res |= SbLargeFile
- }
- if f.HugeFile {
- res |= SbHugeFile
- }
- if f.GdtCsum {
- res |= SbGdtCsum
- }
- if f.DirNlink {
- res |= SbDirNlink
- }
- if f.ExtraIsize {
- res |= SbExtraIsize
- }
- if f.HasSnapshot {
- res |= SbHasSnapshot
- }
- if f.Quota {
- res |= SbQuota
- }
- if f.Bigalloc {
- res |= SbBigalloc
- }
- if f.MetadataCsum {
- res |= SbMetadataCsum
- }
- if f.ReadOnly {
- res |= SbReadOnly
- }
-
- return res
-}
-
-// RoCompatFeaturesFromInt converts the integer representation of superblock
-// readonly compatible features to RoCompatFeatures struct.
-func RoCompatFeaturesFromInt(f uint32) RoCompatFeatures {
- return RoCompatFeatures{
- Sparse: f&SbSparse > 0,
- LargeFile: f&SbLargeFile > 0,
- HugeFile: f&SbHugeFile > 0,
- GdtCsum: f&SbGdtCsum > 0,
- DirNlink: f&SbDirNlink > 0,
- ExtraIsize: f&SbExtraIsize > 0,
- HasSnapshot: f&SbHasSnapshot > 0,
- Quota: f&SbQuota > 0,
- Bigalloc: f&SbBigalloc > 0,
- MetadataCsum: f&SbMetadataCsum > 0,
- ReadOnly: f&SbReadOnly > 0,
- }
-}