Re: [PATCH] btrfs: disable zstd support for i386-pc

[Paul Menzel]

Dear Michael,


Thank you for your patch.

On 2019-11-05 10:19, Michael Chang wrote:
> The zstd support in btrfs has dependenciy to zstd module and core.img

dependency

> grows its size significantly to 75KB on my system. The resulted image
> cannot be installed into btrfs bootloader area in the size of 64KB and
> eventually fails with following message.
> 
> /usr/sbin/grub-install: warning: your core.img is unusually large.  It won't 
> fit in the embedding area.
> /usr/sbin/grub-install: error: filesystem `btrfs' doesn't support blocklists.
> 
> The patch disabled the zstd support of btrfs in pc-bios platform to

disables (present tense)

Maybe:

So, disable the zstd support of btrfs for the PC BIOS platform to …

> avoid the regression. The resulting size is 56KB, albeit a bit too close
> to the 64KB but works. This is simple workaround until a proper fix

is *a* simple

> landed upstream.

lands

Is there a feature request/bug report for this? Maybe reference it heare?

> Signed-off-by: Michael Chang <address@hidden>
> ---
>  grub-core/fs/btrfs.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index 48bd3d04a..8f98892d3 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -17,6 +17,7 @@
>   *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
>   */
>  
> +#ifndef GRUB_MACHINE_PCBIOS
>  /*
>   * Tell zstd to expose functions that aren't part of the stable API, which
>   * aren't safe to use when linking against a dynamic library. We vendor in a
> @@ -24,6 +25,7 @@
>   * functions to provide our own allocator, which uses grub_malloc(), to zstd.
>   */
>  #define ZSTD_STATIC_LINKING_ONLY
> +#endif
>  
>  #include <grub/err.h>
>  #include <grub/file.h>
> @@ -35,7 +37,9 @@
>  #include <grub/lib/crc.h>
>  #include <grub/deflate.h>
>  #include <minilzo.h>
> +#ifndef GRUB_MACHINE_PCBIOS
>  #include <zstd.h>
> +#endif
>  #include <grub/i18n.h>
>  #include <grub/btrfs.h>
>  #include <grub/crypto.h>
> @@ -56,8 +60,10 @@ GRUB_MOD_LICENSE ("GPLv3+");
>  #define GRUB_BTRFS_LZO_BLOCK_MAX_CSIZE (GRUB_BTRFS_LZO_BLOCK_SIZE + \
>                                    (GRUB_BTRFS_LZO_BLOCK_SIZE / 16) + 64 + 3)
>  
> +#ifndef GRUB_MACHINE_PCBIOS
>  #define ZSTD_BTRFS_MAX_WINDOWLOG 17
>  #define ZSTD_BTRFS_MAX_INPUT     (1 << ZSTD_BTRFS_MAX_WINDOWLOG)
> +#endif
>  
>  typedef grub_uint8_t grub_btrfs_checksum_t[0x20];
>  typedef grub_uint16_t grub_btrfs_uuid_t[8];
> @@ -229,7 +235,9 @@ struct grub_btrfs_extent_data
>  #define GRUB_BTRFS_COMPRESSION_NONE 0
>  #define GRUB_BTRFS_COMPRESSION_ZLIB 1
>  #define GRUB_BTRFS_COMPRESSION_LZO  2
> +#ifndef GRUB_MACHINE_PCBIOS
>  #define GRUB_BTRFS_COMPRESSION_ZSTD 3
> +#endif
>  
>  #define GRUB_BTRFS_OBJECT_ID_CHUNK 0x100
>  
> @@ -1229,6 +1237,7 @@ grub_btrfs_read_inode (struct grub_btrfs_data *data,
>    return grub_btrfs_read_logical (data, elemaddr, inode, sizeof (*inode), 0);
>  }
>  
> +#ifndef GRUB_MACHINE_PCBIOS
>  static void *grub_zstd_malloc (void *state __attribute__((unused)), size_t 
> size)
>  {
>    return grub_malloc (size);
> @@ -1318,6 +1327,7 @@ err:
>  
>    return ret;
>  }
> +#endif
>  
>  static grub_ssize_t
>  grub_btrfs_lzo_decompress(char *ibuf, grub_size_t isize, grub_off_t off,
> @@ -1494,8 +1504,12 @@ grub_btrfs_extent_read (struct grub_btrfs_data *data,
>  
>        if (data->extent->compression != GRUB_BTRFS_COMPRESSION_NONE
>         && data->extent->compression != GRUB_BTRFS_COMPRESSION_ZLIB
> +#ifndef GRUB_MACHINE_PCBIOS
>         && data->extent->compression != GRUB_BTRFS_COMPRESSION_LZO
>         && data->extent->compression != GRUB_BTRFS_COMPRESSION_ZSTD)
> +#else
> +       && data->extent->compression != GRUB_BTRFS_COMPRESSION_LZO)
> +#endif

Why not just guard the ZSTD line by switching the order of LZO and ZSTD for
the closing bracket?

>       {
>         grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
>                     "compression type 0x%x not supported",
> @@ -1535,6 +1549,7 @@ grub_btrfs_extent_read (struct grub_btrfs_data *data,
>                 != (grub_ssize_t) csize)
>               return -1;
>           }
> +#ifndef GRUB_MACHINE_PCBIOS
>         else if (data->extent->compression == GRUB_BTRFS_COMPRESSION_ZSTD)
>           {
>             if (grub_btrfs_zstd_decompress (data->extent->inl, data->extsize -
> @@ -1544,6 +1559,7 @@ grub_btrfs_extent_read (struct grub_btrfs_data *data,
>                 != (grub_ssize_t) csize)
>               return -1;
>           }
> +#endif
>         else
>           grub_memcpy (buf, data->extent->inl + extoff, csize);
>         break;
> @@ -1581,10 +1597,12 @@ grub_btrfs_extent_read (struct grub_btrfs_data *data,
>               ret = grub_btrfs_lzo_decompress (tmp, zsize, extoff
>                                   + grub_le_to_cpu64 (data->extent->offset),
>                                   buf, csize);
> +#ifndef GRUB_MACHINE_PCBIOS
>             else if (data->extent->compression == GRUB_BTRFS_COMPRESSION_ZSTD)
>               ret = grub_btrfs_zstd_decompress (tmp, zsize, extoff
>                                   + grub_le_to_cpu64 (data->extent->offset),
>                                   buf, csize);
> +#endif
>             else
>               ret = -1;

Does some documentation need to be updated?


Kind regards,

Paul

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