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

[Michael Chang]

The zstd support in btrfs has dependenciy to zstd module and core.img
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
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
landed upstream.

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
        {
          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;
 
-- 
2.16.4