[EROFS] Add support for xattr reservation of the base layer rootdir

Set the minimum inline xattr size for the root directory of the base
layer, as there may not be enough room for xattr during the incremental
build process.

Signed-off-by: Hongzhen Luo <hongzhen@linux.alibaba.com>

Author: Hongzhen Luo

src/overlaybd/tar/erofs/CMakeLists.txt

@@ -3,7 +3,7 @@ include(FetchContent)
 FetchContent_Declare(
     erofs-utils
     GIT_REPOSITORY git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git
-    GIT_TAG        617d708925b3c5d1dd132853e47d9d9f51443e6f
+    GIT_TAG        ac0997ea32a465a6b0db7b782bb8d4d07952365a
 )
 
 FetchContent_MakeAvailable(erofs-utils)

src/overlaybd/tar/erofs/liberofs.cpp

@@ -17,6 +17,7 @@
 #define round_down_blk(addr) ((addr) & (~(SECTOR_SIZE - 1)))
 #define round_up_blk(addr) (round_down_blk((addr) + SECTOR_SIZE - 1))
 #define min(a, b) (a) < (b) ? (a) : (b)
+#define EROFS_ROOT_XATTR_SZ (16 * 1024)
 
 #define EROFS_UNIMPLEMENTED 1
 
@@ -641,6 +642,10 @@ int LibErofs::extract_tar(photon::fs::IFile *source, bool meta_only, bool first_
     cfg.incremental = !first_layer;
     erofs_cfg = erofs_get_configure();
     erofs_cfg->c_ovlfs_strip = true;
+    if (first_layer)
+        erofs_cfg->c_root_xattr_isize = EROFS_ROOT_XATTR_SZ;
+    else
+        erofs_cfg->c_root_xattr_isize = 0;
     cfg.mp_fp = std::tmpfile();
 
     err = erofs_mkfs(&cfg);