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authorCarlos Maiolino <cmaiolino@redhat.com>2012-12-10 16:30:45 -0500
committerTheodore Ts'o <tytso@mit.edu>2012-12-10 16:30:45 -0500
commit9a4c8019471386c6fb039ae9e30f5216b6b55a9e (patch)
treedf7b86c60e1f32f793d85438f67e3c9f23ec165a /fs/ext4/ext4.h
parent939da1084458246d2e29dd921c2012c177000e96 (diff)
ext4: ensure Inode flags consistency are checked at build time
Flags being used by atomic operations in inode flags (e.g. ext4_test_inode_flag(), should be consistent with that actually stored in inodes, i.e.: EXT4_XXX_FL. It ensures that this consistency is checked at build-time, not at run-time. Currently, the flags consistency are being checked at run-time, but, there is no real reason to not do a build-time check instead of a run-time check. The code is comparing macro defined values with enum type variables, where both are constants, so, there is no problem in comparing constants at build-time. enum variables are treated as constants by the C compiler, according to the C99 specs (see www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf sec. 6.2.5, item 16), so, there is no real problem in comparing an enumeration type at build time Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/ext4.h')
-rw-r--r--fs/ext4/ext4.h29
1 files changed, 13 insertions, 16 deletions
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index e20dc38858d..b79d613091d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -463,25 +463,22 @@ enum {
EXT4_INODE_RESERVED = 31, /* reserved for ext4 lib */
};
-#define TEST_FLAG_VALUE(FLAG) (EXT4_##FLAG##_FL == (1 << EXT4_INODE_##FLAG))
-#define CHECK_FLAG_VALUE(FLAG) if (!TEST_FLAG_VALUE(FLAG)) { \
- printk(KERN_EMERG "EXT4 flag fail: " #FLAG ": %d %d\n", \
- EXT4_##FLAG##_FL, EXT4_INODE_##FLAG); BUG_ON(1); }
-
-/*
- * Since it's pretty easy to mix up bit numbers and hex values, and we
- * can't do a compile-time test for ENUM values, we use a run-time
- * test to make sure that EXT4_XXX_FL is consistent with respect to
- * EXT4_INODE_XXX. If all is well the printk and BUG_ON will all drop
- * out so it won't cost any extra space in the compiled kernel image.
- * But it's important that these values are the same, since we are
- * using EXT4_INODE_XXX to test for the flag values, but EXT4_XX_FL
- * must be consistent with the values of FS_XXX_FL defined in
- * include/linux/fs.h and the on-disk values found in ext2, ext3, and
- * ext4 filesystems, and of course the values defined in e2fsprogs.
+/*
+ * Since it's pretty easy to mix up bit numbers and hex values, we use a
+ * build-time check to make sure that EXT4_XXX_FL is consistent with respect to
+ * EXT4_INODE_XXX. If all is well, the macros will be dropped, so, it won't cost
+ * any extra space in the compiled kernel image, otherwise, the build will fail.
+ * It's important that these values are the same, since we are using
+ * EXT4_INODE_XXX to test for flag values, but EXT4_XXX_FL must be consistent
+ * with the values of FS_XXX_FL defined in include/linux/fs.h and the on-disk
+ * values found in ext2, ext3 and ext4 filesystems, and of course the values
+ * defined in e2fsprogs.
*
* It's not paranoia if the Murphy's Law really *is* out to get you. :-)
*/
+#define TEST_FLAG_VALUE(FLAG) (EXT4_##FLAG##_FL == (1 << EXT4_INODE_##FLAG))
+#define CHECK_FLAG_VALUE(FLAG) BUILD_BUG_ON(!TEST_FLAG_VALUE(FLAG))
+
static inline void ext4_check_flag_values(void)
{
CHECK_FLAG_VALUE(SECRM);