libext2fs: optimize ext2fs_bg_has_super()
Reduce the CPU time needed when checking whether a block group has a
sparse superblock.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/lib/ext2fs/closefs.c b/lib/ext2fs/closefs.c
index 973c2a2..3582a0c 100644
--- a/lib/ext2fs/closefs.c
+++ b/lib/ext2fs/closefs.c
@@ -20,12 +20,12 @@
#include "ext2_fs.h"
#include "ext2fsP.h"
-static int test_root(int a, int b)
+static int test_root(unsigned int a, unsigned int b)
{
- if (a == 0)
- return 1;
while (1) {
- if (a == 1)
+ if (a < b)
+ return 0;
+ if (a == b)
return 1;
if (a % b)
return 0;
@@ -33,14 +33,15 @@
}
}
-int ext2fs_bg_has_super(ext2_filsys fs, int group_block)
+int ext2fs_bg_has_super(ext2_filsys fs, dgrp_t group)
{
if (!(fs->super->s_feature_ro_compat &
- EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER))
+ EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER) || group <= 1)
return 1;
-
- if (test_root(group_block, 3) || (test_root(group_block, 5)) ||
- test_root(group_block, 7))
+ if (!(group & 1))
+ return 0;
+ if (test_root(group, 3) || (test_root(group, 5)) ||
+ test_root(group, 7))
return 1;
return 0;
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 93c8360..326d5c1 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -911,7 +911,7 @@
extern errcode_t ext2fs_close2(ext2_filsys fs, int flags);
extern errcode_t ext2fs_flush(ext2_filsys fs);
extern errcode_t ext2fs_flush2(ext2_filsys fs, int flags);
-extern int ext2fs_bg_has_super(ext2_filsys fs, int group_block);
+extern int ext2fs_bg_has_super(ext2_filsys fs, dgrp_t group_block);
extern errcode_t ext2fs_super_and_bgd_loc2(ext2_filsys fs,
dgrp_t group,
blk64_t *ret_super_blk,