[PATCH] erofs-utils: mkfs: fix CPU spin using --tar=f when stdin is closed

[Gao Xiang]

On 2026/3/3 03:01, David Scott wrote:
> On my Mac I saw a CPU spin which looked like this:
> ```
> Call graph:
>      2192 Thread_132504   DispatchQueue_1: com.apple.main-thread  (serial)
>        2192 start  (in dyld) + 6992  [0x185bcbda4]
>          2192 main  (in mkfs.erofs) + 7916  [0x10253a6d0]
>            2192 tarerofs_parse_tar  (in mkfs.erofs) + 5492  [0x102551d48]
>              2187 tarerofs_write_file_data  (in mkfs.erofs) + 140  [0x102551fe0]
>              + 2187 write  (in libsystem_kernel.dylib) + 8  [0x185f47834]
>              4 tarerofs_write_file_data  (in mkfs.erofs) + 116  [0x102551fc8]
>              + 4 erofs_iostream_read  (in mkfs.erofs) + 16,36,...  [0x10254fa28,0x10254fa3c,...]
>              1 tarerofs_write_file_data  (in mkfs.erofs) + 140  [0x102551fe0]
> ```
> 
> The input stream was closed prematurely, so the reads returned 0 (EOF),
> which wasn't considered an error.
> 
> Treat return of 0 (EOF) as an error.
> 
> Reproduce by:
> ```
> dd if=/dev/zero bs=1024 count=4 2>/dev/null > /tmp/testfile
> COPYFILE_DISABLE=1 tar cf - -C /tmp testfile | head -c 2048 > /tmp/truncated.tar
> ./mkfs/mkfs.erofs --tar=f output.erofs < /tmp/truncated.tar
> ```
> Before the patch this will hang, after it should fail as expected.
> 
> (COPYFILE_DISABLE tells mac to avoid putting extra stuff in the tar)
> 
> Closes: https://github.com/erofs/erofs-utils/issues/43
> Signed-off-by: David Scott <dave at recoil.org>

LGTM, will apply.

Thanks,
Gao Xiang