From patchwork Tue Oct 30 21:50:08 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [V2] Remove VLAIS usage from JBD2 code Date: Tue, 30 Oct 2012 11:50:08 -0000 From: Behan Webster X-Patchwork-Id: 195631 Message-Id: <1351633808-8720-1-git-send-email-behanw@converseincode.com> To: tytso@mit.edu Cc: linux-ext4@vger.kernel.org, Mark Charlebois , Behan Webster From: Mark Charlebois 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 [Used a #define to specify the fixed size of ctx] Signed-off-by: Behan Webster --- 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 3efc43f..93b323f 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -1303,15 +1303,21 @@ 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;