Re: [PATCH] erofs-utils: mkfs: also handle last compacted 2B pack in z_erofs_drop_inline_pcluster

version:
erofs-utils: 1.8.3
lz4:1.10.0
Android:17

cmd:
mkfs.erofs -z lz4hc,9 --compress-hints
./output/META/erofs_default_compress_hints.txt -d9 -b 4096
--mount-point product --fs-config-file
./output/META/product_filesystem_config.txt --file-contexts
./output/META/framework_file_contexts.bin -T 1230768000 -U
ad34a95d-293d-5e91-9234-c253209e9c71 -E dedupe,ztailpacking
./output/PRODUCT/tmp ./output/PRODUCT2/ 1>mkfs.log 2>&1
./fsck.erofs --extract -d9 output/PRODUCT/2sofiximage

error case:
mkfs 2 source files: libmsc.so.salsa, libmsc.so

erofs: failed to full decompress -3066 in[4096, 0] out[6121]
dump extent:
1192:  7765862.. 7770924 |    5062 :    9687040..   9691136 |    4096
1193:  7770924.. 7777021 |    6097 :    9691136..   9695232 |    4096
1194:  7777021.. 7784118 |    7097 :    9695232..   9699328 |    4096
1195:  7784118.. 7789918 |    5800 :    9699328..   9703424 |    4096
1196:  7789918.. 7797526 |    7608 :    9703424..   9707520 |    4096
1197:  7797526.. 7803647 |    6121 :    9707520..   9711616 |    4096
1198:  7803647.. 7806972 |    3325 :    9711616..   9715712 |    4096
mkfs debug log:
compacted_2b=1904  compacted_4b_initial=2 compacted_4b_end=0
write di_clusterof=2815 type=1 di_u.blkaddr=2371 d1=0 clusterofs=2815
//last pcluster
last 8 bytes in compacted pack:
6bfe0016 00000938
after drop inline operation:
0bfe0016 00000938

good case :
mkfs 1 source file:libmsc.so.salsa
dump extent:
1192:  7765862.. 7770924 |    5062 :    4886528..   4890624 |    4096
1193:  7770924.. 7777021 |    6097 :    4890624..   4894720 |    4096
1194:  7777021.. 7784118 |    7097 :    4894720..   4898816 |    4096
1195:  7784118.. 7789918 |    5800 :    4898816..   4902912 |    4096
1196:  7789918.. 7797526 |    7608 :    4902912..   4907008 |    4096
1197:  7797526.. 7805695 |    8169 :    4907008..   4911104 |    4096
1198:  7805695.. 7806972 |    1277 :    4911104..   4915200 |    4096
mkfs debug log:
compacted_2b=1904  compacted_4b_initial=0 compacted_4b_end=2
write di_clusterof=2815 type=1 di_u.blkaddr=1199 d1=0 clusterofs=2815
//last pcluster
last 8 bytes in compacted pack:
1aff2001 000004ae
after drop inline operation:
0aff2001 000004ae

Zhiguo Niu <[email protected]> 于2026年4月29日周三 16:00写道：
>
> With ztailpacking enabled, the current process assumes that a compacted_4b_end
> always exists in the compacted pack. However, in some specific files, the
> compacted pack may not have a compacted_4b_end. This leads to an incorrect
> modification of the last compacted_2B entry, resulting in incorrect modification
> of its clusterofs. In subsequent fsck operations, incorrect parameters will
> affect the decompression of the penultimate pcluster.
>
> This patch determines whether the last entry of the current compacted pack
> belongs to compacted 2B or 4B and then updates the correct bits accordingly.
>
> Fixes: a7c1f0575ef8 ("erofs-utils: lib: refine tailpcluster compression approach")
> Signed-off-by: Zhiguo Niu <[email protected]>
> ---
>  lib/compress.c | 38 +++++++++++++++++++++++++++-----------
>  1 file changed, 27 insertions(+), 11 deletions(-)
>
> diff --git a/lib/compress.c b/lib/compress.c
> index 62d2672..0eb464b 100644
> --- a/lib/compress.c
> +++ b/lib/compress.c
> @@ -1223,19 +1223,35 @@ void z_erofs_drop_inline_pcluster(struct erofs_inode *inode)
>
>                 di->di_advise = cpu_to_le16(type);
>         } else if (inode->datalayout == EROFS_INODE_COMPRESSED_COMPACT) {
> -               /* handle the last compacted 4B pack */
> +               /* handle the last compacted pack */
>                 unsigned int eofs, base, pos, v, lo;
>                 u8 *out;
> -
> -               eofs = inode->extent_isize -
> -                       (4 << (BLK_ROUND_UP(sbi, inode->i_size) & 1));
> -               base = round_down(eofs, 8);
> -               pos = 16 /* encodebits */ * ((eofs - base) / 4);
> -               out = inode->compressmeta + base;
> -               lo = erofs_blkoff(sbi, get_unaligned_le32(out + pos / 8));
> -               v = (type << sbi->blkszbits) | lo;
> -               out[pos / 8] = v & 0xff;
> -               out[pos / 8 + 1] = v >> 8;
> +               unsigned int compacted_4b_initial, compacted_2b, compacted_4b_end;
> +               unsigned int totalidx = BLK_ROUND_UP(sbi, inode->i_size);
> +               const erofs_off_t ebase = sizeof(struct z_erofs_map_header) +
> +                       round_up(erofs_iloc(inode) + inode->inode_isize +
> +                                       inode->xattr_isize, 8);
> +
> +               compacted_4b_initial = ((32 - ebase % 32) / 4) & 7;
> +               compacted_2b = 0;
> +               if ((le16_to_cpu(h->h_advise) & Z_EROFS_ADVISE_COMPACTED_2B) &&
> +                       compacted_4b_initial < totalidx)
> +                       compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
> +               compacted_4b_end = totalidx - compacted_4b_initial - compacted_2b;
> +               if (!compacted_2b || compacted_4b_end) {
> +                       eofs = inode->extent_isize - (4 << (totalidx & 1));
> +                       base = round_down(eofs, 8);
> +                       pos = 16 /* encodebits */ * ((eofs - base) / 4);
> +                       out = inode->compressmeta + base;
> +                       lo = erofs_blkoff(sbi, get_unaligned_le32(out + pos / 8));
> +                       v = (type << sbi->blkszbits) | lo;
> +                       out[pos / 8] = v & 0xff;
> +                       out[pos / 8 + 1] = v >> 8;
> +               } else {
> +                       eofs = inode->extent_isize - (4 + 1);
> +                       out = inode->compressmeta + eofs;
> +                       *out = (*out & 0x3f) | (type << 6);
> +               }
>         } else {
>                 DBG_BUGON(1);
>                 return;
> --
> 1.9.1
>