From fd47d3e1c2949838e858379aaf2bc20647be2912 Mon Sep 17 00:00:00 2001
From: Behan Webster <behanw@converseincode.com>
Date: Thu, 8 Nov 2012 11:24:46 -0500
Subject: [PATCH] jbd2: remove VLAIS usage from JBD2 code
The use of variable length arrays in structs (VLAIS) in the Linux Kernel code
precludes the use of compilers which don't implement VLAIS (for instance the
Clang compiler). Since ctx is always a 32-bit CRC, hard coding a size of 4
bytes accomplishes the same thing without the use of VLAIS. This is the same
technique already employed in fs/ext4/ext4.h
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
include/linux/jbd2.h | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index de7f55682088..1be23d9fdacb 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1302,15 +1302,21 @@ static inline int jbd_space_needed(journal_t *journal)
extern int jbd_blocks_per_page(struct inode *inode);
+/* JBD uses a CRC32 checksum */
+#define JBD_MAX_CHECKSUM_SIZE 4
+
static inline u32 jbd2_chksum(journal_t *journal, u32 crc,
const void *address, unsigned int length)
{
struct {
struct shash_desc shash;
- char ctx[crypto_shash_descsize(journal->j_chksum_driver)];
+ char ctx[JBD_MAX_CHECKSUM_SIZE];
} desc;
int err;
+ BUG_ON(crypto_shash_descsize(journal->j_chksum_driver) >
+ JBD_MAX_CHECKSUM_SIZE);
+
desc.shash.tfm = journal->j_chksum_driver;
desc.shash.flags = 0;
*(u32 *)desc.ctx = crc;