Christopher Haster
9d322741ca
TLDR: This drops the idea of different bmap strategies/modes, and sorts
out most of the compile-time/runtime conditional bmap interactions.
---
Motivation: Benchmarking (at least up to the 32-bit word limit) has
shown the bmap will unlikely be a significant bottleneck, even on large
disks. The largest disks tend to be NAND, and NAND's ridiculous block
size limits pressure on block allocation.
There are still concerns for areas I haven't measured yet:
- SD/eMMC/FTL - Small blocks, so more pressure on block allocation. In
theory the logical block size can be artificially increased, but this
comes with a granularity tradeoff.
- I've only measured throughput, latency is a whole other story.
However, users have reported lfs3_fs_gc is useful for mitigating this,
so maybe latency is less of a concern now?
But while there may still be room for improvement via alternative bmap
strategies, the risk a concerning amount of complexity. Yes,
configuration gets more complicated, but the real issue is any bmap
strategies that try to track _deallocations_ (the original idea being
treediffing) risk falling leaking blocks if all cases aren't covered.
The current "bmap cache" strategy strikes a really nice balance where it
reduces _amortized_ block allocation -> ~O(log n) without RAM, while
retaining the safe, bug-resistant, single-source-of-truth properties
that come with lookahead-based allocation.
---
So, long story short, dropping other strategies, and now the presence of
the bmap is a boolean flag.
This is also the first format-specific flag:
- Define LFS3_BMAP to enable the bmap logic, but note by default the
bmap will still not be used.
- Define LFS3_YES_BMAP to force the bmap to be used.
- With LFS3_BMAP, passing LFS3_F_GBMAP to lfs3_format will include the
on-disk block-map.
- No flag is needed during mount, the presence of the bmap is determined
by the on-disk wcompat flags (LFS3_WCOMPAT_GBMAP). This also prevents
rw mounting if the bmap is not supported, but rdonly mounting is
allowed.
- Users can check if the bmap is in use via lfs3_fs_stat, which reports
LFS3_I_GBMAP in the flags field.
There's still some missing pieces, but these will be a bit more
involved:
- lfs3_fs_grow needs to be made bmap aware!
- We probably want something like lfs3_fs_mkgbmap and lfs3_fs_rmgbmap to
allow converting between bmap backed/not-backed filesystem images.
Code changes minimal:
code stack ctx
before: 37172 2352 684
after: 37172 (+0.0%) 2352 (+0.0%) 684 (+0.0%)
code stack ctx
bmap before: 38844 2456 800
bmap after: 38852 (+0.0%) 2456 (+0.0%) 800 (+0.0%)
333 lines
17 KiB
Python
Executable File
333 lines
17 KiB
Python
Executable File
#!/usr/bin/env python3
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# prevent local imports
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if __name__ == "__main__":
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__import__('sys').path.pop(0)
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import collections as co
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FILTERS = [
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(['--o', '--open'], 'O', "Filter by LFS3_O_* flags."),
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(['--a', '--attr'], 'A', "Filter by LFS3_A_* flags."),
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(['--f', '--format'], 'F', "Filter by LFS3_F_* flags."),
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(['--m', '--mount'], 'M', "Filter by LFS3_M_* flags."),
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('--gc', 'GC', "Filter by LFS3_GC_* flags."),
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(['--i', '--info'], 'I', "Filter by LFS3_I_* flags."),
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(['--t', '--traversal'], 'T', "Filter by LFS3_T_* flags."),
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('--alloc', 'ALLOC', "Filter by LFS3_ALLOC_* flags."),
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(['--rc', '--rcompat'], 'RCOMPAT', "Filter by LFS3_RCOMPAT_* flags."),
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(['--wc', '--wcompat'], 'WCOMPAT', "Filter by LFS3_WCOMPAT_* flags."),
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(['--oc', '--ocompat'], 'OCOMPAT', "Filter by LFS3_OCOMPAT_* flags."),
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]
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FLAGS = [
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# File open flags
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('O_MODE', 3, "The file's access mode" ),
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('^_RDONLY', 0, "Open a file as read only" ),
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('^_WRONLY', 1, "Open a file as write only" ),
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('^_RDWR', 2, "Open a file as read and write" ),
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('O_CREAT', 0x00000004, "Create a file if it does not exist" ),
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('O_EXCL', 0x00000008, "Fail if a file already exists" ),
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('O_TRUNC', 0x00000010, "Truncate the existing file to zero size" ),
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('O_APPEND', 0x00000020, "Move to end of file on every write" ),
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('O_FLUSH', 0x00000040, "Flush data on every write" ),
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('O_SYNC', 0x00000080, "Sync metadata on every write" ),
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('O_DESYNC', 0x04000000, "Do not sync or recieve file updates" ),
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('O_CKMETA', 0x00001000, "Check metadata checksums" ),
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('O_CKDATA', 0x00002000, "Check metadata + data checksums" ),
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('o_WRSET', 3, "Open a file as an atomic write" ),
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('o_TYPE', 0xf0000000, "The file's type" ),
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('^_REG', 0x10000000, "Type = regular-file" ),
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('^_DIR', 0x20000000, "Type = directory" ),
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('^_STICKYNOTE', 0x30000000, "Type = stickynote" ),
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('^_BOOKMARK', 0x40000000, "Type = bookmark" ),
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('^_ORPHAN', 0x50000000, "Type = orphan" ),
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('^_TRAVERSAL', 0x60000000, "Type = traversal" ),
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('^_UNKNOWN', 0x70000000, "Type = unknown" ),
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('o_ZOMBIE', 0x08000000, "File has been removed" ),
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('o_UNCREAT', 0x02000000, "File does not exist yet" ),
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('o_UNSYNC', 0x01000000, "File's metadata does not match disk" ),
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('o_UNCRYST', 0x00800000, "File's leaf not fully crystallized" ),
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('o_UNGRAFT', 0x00400000, "File's leaf does not match disk" ),
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('o_UNFLUSH', 0x00200000, "File's cache does not match disk" ),
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# Custom attribute flags
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('A_MODE', 3, "The attr's access mode" ),
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('^_RDONLY', 0, "Open an attr as read only" ),
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('^_WRONLY', 1, "Open an attr as write only" ),
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('^_RDWR', 2, "Open an attr as read and write" ),
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('A_LAZY', 0x04, "Only write attr if file changed" ),
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# Filesystem format flags
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('F_MODE', 1, "Format's access mode" ),
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('^_RDWR', 0, "Format the filesystem as read and write" ),
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('F_REVDBG', 0x00000010, "Add debug info to revision counts" ),
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('F_REVNOISE', 0x00000020, "Add noise to revision counts" ),
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('F_CKPROGS', 0x00080000, "Check progs by reading back progged data" ),
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('F_CKFETCHES', 0x00100000, "Check block checksums before first use" ),
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('F_CKMETAPARITY', 0x00200000, "Check metadata tag parity bits" ),
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('F_CKDATACKSUMS', 0x00800000, "Check data checksums on reads" ),
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('F_CKMETA', 0x00001000, "Check metadata checksums" ),
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('F_CKDATA', 0x00002000, "Check metadata + data checksums" ),
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('F_GBMAP', 0x01000000, "Use the global on-disk block-map" ),
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# Filesystem mount flags
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('M_MODE', 1, "Mount's access mode" ),
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('^_RDWR', 0, "Mount the filesystem as read and write" ),
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('^_RDONLY', 1, "Mount the filesystem as read only" ),
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('M_FLUSH', 0x00000040, "Open all files with LFS3_O_FLUSH" ),
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('M_SYNC', 0x00000080, "Open all files with LFS3_O_SYNC" ),
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('M_REVDBG', 0x00000010, "Add debug info to revision counts" ),
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('M_REVNOISE', 0x00000020, "Add noise to revision counts" ),
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('M_CKPROGS', 0x00080000, "Check progs by reading back progged data" ),
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('M_CKFETCHES', 0x00100000, "Check block checksums before first use" ),
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('M_CKMETAPARITY', 0x00200000, "Check metadata tag parity bits" ),
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('M_CKDATACKSUMS', 0x00800000, "Check data checksums on reads" ),
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('M_MKCONSISTENT', 0x00000100, "Make the filesystem consistent" ),
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('M_LOOKAHEAD', 0x00000200, "Populate lookahead buffer" ),
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('M_COMPACT', 0x00000800, "Compact metadata logs" ),
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('M_CKMETA', 0x00001000, "Check metadata checksums" ),
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('M_CKDATA', 0x00002000, "Check metadata + data checksums" ),
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# GC flags
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('GC_MKCONSISTENT',0x00000100, "Make the filesystem consistent" ),
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('GC_LOOKAHEAD', 0x00000200, "Populate lookahead buffer" ),
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('GC_COMPACT', 0x00000800, "Compact metadata logs" ),
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('GC_CKMETA', 0x00001000, "Check metadata checksums" ),
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('GC_CKDATA', 0x00002000, "Check metadata + data checksums" ),
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# Filesystem info flags
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('I_RDONLY', 0x00000001, "Mounted read only" ),
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('I_FLUSH', 0x00000040, "Mounted with LFS3_M_FLUSH" ),
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('I_SYNC', 0x00000080, "Mounted with LFS3_M_SYNC" ),
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('I_REVDBG', 0x00000010, "Mounted with LFS3_M_REVDBG" ),
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('I_REVNOISE', 0x00000020, "Mounted with LFS3_M_REVNOISE" ),
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('I_CKPROGS', 0x00080000, "Mounted with LFS3_M_CKPROGS" ),
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('I_CKFETCHES', 0x00100000, "Mounted with LFS3_M_CKFETCHES" ),
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('I_CKMETAPARITY', 0x00200000, "Mounted with LFS3_M_CKMETAPARITY" ),
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('I_CKDATACKSUMS', 0x00800000, "Mounted with LFS3_M_CKDATACKSUMS" ),
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('I_MKCONSISTENT', 0x00000100, "Filesystem needs mkconsistent to write" ),
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('I_LOOKAHEAD', 0x00000200, "Lookahead buffer is not full" ),
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('I_COMPACT', 0x00000800, "Filesystem may have uncompacted metadata" ),
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('I_CKMETA', 0x00001000, "Metadata checksums not checked recently" ),
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('I_CKDATA', 0x00002000, "Data checksums not checked recently" ),
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('I_GBMAP', 0x01000000, "Global on-disk block-map in use" ),
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('i_INMODE', 0x00030000, "Btree commit mode" ),
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('^_INMTREE', 0x00010000, "Committing to mtree" ),
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('^_INGBMAP', 0x00020000, "Committing to gbmap" ),
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# Traversal flags
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('T_MODE', 1, "The traversal's access mode" ),
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('^_RDWR', 0, "Open traversal as read and write" ),
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('^_RDONLY', 1, "Open traversal as read only" ),
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('T_MTREEONLY', 0x00000002, "Only traverse the mtree" ),
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('T_MKCONSISTENT',
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0x00000100, "Make the filesystem consistent" ),
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('T_LOOKAHEAD', 0x00000200, "Populate lookahead buffer" ),
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('T_COMPACT', 0x00000800, "Compact metadata logs" ),
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('T_CKMETA', 0x00001000, "Check metadata checksums" ),
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('T_CKDATA', 0x00002000, "Check metadata + data checksums" ),
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('t_TYPE', 0xf0000000, "The traversal's type" ),
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('^_REG', 0x10000000, "Type = regular-file" ),
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('^_DIR', 0x20000000, "Type = directory" ),
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('^_STICKYNOTE', 0x30000000, "Type = stickynote" ),
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('^_BOOKMARK', 0x40000000, "Type = bookmark" ),
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('^_ORPHAN', 0x50000000, "Type = orphan" ),
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('^_TRAVERSAL', 0x60000000, "Type = traversal" ),
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('^_UNKNOWN', 0x70000000, "Type = unknown" ),
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('t_TSTATE', 0x000f0000, "The current traversal state" ),
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('^_MROOTANCHOR',
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0x00000000, "Tstate = mroot-anchor" ),
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('^_MROOTCHAIN', 0x00010000, "Tstate = mroot-chain" ),
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('^_MTREE', 0x00020000, "Tstate = mtree" ),
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('^_BMAP', 0x00030000, "Tstate = bmap" ),
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('^_MDIRS', 0x00040000, "Tstate = mtree-mdirs" ),
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('^_MDIR', 0x00050000, "Tstate = mdir" ),
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('^_BTREE', 0x00060000, "Tstate = btree" ),
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('^_HANDLES', 0x00070000, "Tstate = open-mdirs" ),
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('^_HBTREE', 0x00080000, "Tstate = open-btree" ),
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('^_DONE', 0x00090000, "Tstate = done" ),
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('t_BTYPE', 0x00f00000, "The current block type" ),
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('^_MDIR', 0x00100000, "Btype = mdir" ),
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('^_BTREE', 0x00200000, "Btype = btree" ),
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('^_DATA', 0x00300000, "Btype = data" ),
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('t_ZOMBIE', 0x08000000, "File has been removed" ),
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('t_DIRTY', 0x02000000, "Filesystem modified during traversal" ),
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('t_MUTATED', 0x01000000, "Filesystem modified by traversal" ),
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# Block allocator flags
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('alloc_ERASE', 0x00000001, "Please erase the block" ),
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# Read-compat flags
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('RCOMPAT_NONSTANDARD',
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0x00000001, "Non-standard filesystem format" ),
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('RCOMPAT_WRONLY', 0x00000002, "Reading is disallowed" ),
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('RCOMPAT_BMOSS', 0x00000010, "Files may use inlined data" ),
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('RCOMPAT_BSPROUT',0x00000020, "Files may use block pointers" ),
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('RCOMPAT_BSHRUB', 0x00000040, "Files may use inlined btrees" ),
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('RCOMPAT_BTREE', 0x00000080, "Files may use btrees" ),
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('RCOMPAT_MMOSS', 0x00000100, "May use an inlined mdir" ),
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('RCOMPAT_MSPROUT',0x00000200, "May use an mdir pointer" ),
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('RCOMPAT_MSHRUB', 0x00000400, "May use an inlined mtree" ),
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('RCOMPAT_MTREE', 0x00000800, "May use an mdir btree" ),
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('RCOMPAT_GRM', 0x00001000, "Global-remove in use" ),
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('rcompat_OVERFLOW',
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0x80000000, "Can't represent all flags" ),
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# Write-compat flags
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('WCOMPAT_NONSTANDARD',
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0x00000001, "Non-standard filesystem format" ),
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('WCOMPAT_RDONLY', 0x00000002, "Writing is disallowed" ),
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('WCOMPAT_DIR', 0x00000010, "Directory file types in use" ),
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('WCOMPAT_GCKSUM', 0x00001000, "Global-checksum in use" ),
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('WCOMPAT_GBMAP', 0x00002000, "Global on-disk block-map in use" ),
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('wcompat_OVERFLOW',
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0x80000000, "Can't represent all flags" ),
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# Optional-compat flags
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('OCOMPAT_NONSTANDARD',
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0x00000001, "Non-standard filesystem format" ),
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('ocompat_OVERFLOW',
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0x80000000, "Can't represent all flags" ),
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]
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def main(flags, *,
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list=False,
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all=False,
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filter=[]):
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import builtins
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list_, list = list, builtins.list
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all_, all = all, builtins.all
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filter_, filter = filter, builtins.filter
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# filter by prefix if there are any filters
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filter__ = set(filter_)
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flags__ = []
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types__ = co.defaultdict(lambda: set())
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for n, f, h in FLAGS:
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p, n = n.split('_', 1)
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if p == '^':
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p = last_p
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t = last_t
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types__[p].add(t)
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else:
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t = None
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last_p = p
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last_t = f
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if not filter__ or p.upper() in filter__:
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flags__.append((p, t, n, f, h))
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lines = []
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# list all known flags
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if list_:
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for p, t, n, f, h in flags__:
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if not all_ and (t is not None or p[0].islower()):
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continue
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lines.append(('LFS3_%s_%s' % (p, n), '0x%08x' % f, h))
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# find flags by name or value
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else:
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for f_ in flags:
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found = False
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# find by LFS3_+prefix+_+name
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for p, t, n, f, h in flags__:
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if 'LFS3_%s_%s' % (p, n) == f_.upper():
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lines.append(('LFS3_%s_%s' % (p, n), '0x%08x' % f, h))
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found = True
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if found:
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continue
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# find by prefix+_+name
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for p, t, n, f, h in flags__:
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if '%s_%s' % (p, n) == f_.upper():
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lines.append(('LFS3_%s_%s' % (p, n), '0x%08x' % f, h))
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found = True
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if found:
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continue
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# find by name
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for p, t, n, f, h in flags__:
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if n == f_.upper():
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lines.append(('LFS3_%s_%s' % (p, n), '0x%08x' % f, h))
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found = True
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if found:
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continue
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# find by value
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try:
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f__ = int(f_, 0)
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f___ = f__
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for p, t, n, f, h in flags__:
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# ignore type masks here
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if t is None and f in types__[p]:
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continue
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# matches flag?
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if t is None and (f__ & f) == f:
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lines.append(('LFS3_%s_%s' % (p, n), '0x%08x' % f, h))
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f___ &= ~f
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# matches type?
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elif t is not None and (f__ & t) == f:
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lines.append(('LFS3_%s_%s' % (p, n), '0x%08x' % f, h))
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f___ &= ~t
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if f___:
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lines.append(('?', '0x%08x' % f___, 'Unknown flags'))
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except ValueError:
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lines.append(('?', f_, 'Unknown flag'))
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# first find widths
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w = [0, 0]
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for l in lines:
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w[0] = max(w[0], len(l[0]))
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w[1] = max(w[1], len(l[1]))
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# then print results
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for l in lines:
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print('%-*s %-*s %s' % (
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w[0], l[0],
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w[1], l[1],
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l[2]))
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if __name__ == "__main__":
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import argparse
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import sys
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parser = argparse.ArgumentParser(
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description="Decode littlefs flags.",
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allow_abbrev=False)
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parser.add_argument(
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'flags',
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nargs='*',
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help="Flags or names of flags to decode.")
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parser.add_argument(
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'-l', '--list',
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action='store_true',
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help="List all known flags.")
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parser.add_argument(
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'-a', '--all',
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action='store_true',
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help="Also show internal flags and types.")
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class AppendFilter(argparse.Action):
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def __init__(self, nargs=None, **kwargs):
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super().__init__(nargs=0, **kwargs)
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def __call__(self, parser, namespace, value, option):
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if getattr(namespace, 'filter', None) is None:
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namespace.filter = []
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namespace.filter.append(self.const)
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for flag, prefix, help in FILTERS:
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parser.add_argument(
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*([flag] if isinstance(flag, str) else flag),
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action=AppendFilter,
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const=prefix,
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help=help)
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sys.exit(main(**{k: v
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for k, v in vars(parser.parse_intermixed_args()).items()
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if v is not None}))
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