Al Viro complained of a ton of bogosity with regards to the jbd2 block tag
header checksum.  This one checksum is 16 bits, so cut off the upper 16 bits
and treat it as a 16-bit value and don't mess around with be32* conversions.
Fortunately metadata checksumming is still "experimental" and not in a shipping
e2fsprogs, so there should be few users affected by this.

v2: Eliminate unnecessary variables and make it clear(er) which values are 32
bits wide.

Reported-by: Al Viro <v...@zeniv.linux.org.uk>
Signed-off-by: Darrick J. Wong <darrick.w...@oracle.com>
---
 fs/jbd2/commit.c   |   12 ++++++------
 fs/jbd2/recovery.c |   11 +++++------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 750c701..67a8a2f 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -343,20 +343,20 @@ static void jbd2_block_tag_csum_set(journal_t *j, 
journal_block_tag_t *tag,
 {
        struct page *page = bh->b_page;
        __u8 *addr;
-       __u32 csum;
+       __u32 csum32;
 
        if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2))
                return;
 
        sequence = cpu_to_be32(sequence);
        addr = kmap_atomic(page);
-       csum = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence,
-                         sizeof(sequence));
-       csum = jbd2_chksum(j, csum, addr + offset_in_page(bh->b_data),
-                         bh->b_size);
+       csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence,
+                            sizeof(sequence));
+       csum32 = jbd2_chksum(j, csum32, addr + offset_in_page(bh->b_data),
+                            bh->b_size);
        kunmap_atomic(addr);
 
-       tag->t_checksum = cpu_to_be32(csum);
+       tag->t_checksum = cpu_to_be16(csum32);
 }
 /*
  * jbd2_journal_commit_transaction
diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
index 626846b..d4851464 100644
--- a/fs/jbd2/recovery.c
+++ b/fs/jbd2/recovery.c
@@ -399,18 +399,17 @@ static int jbd2_commit_block_csum_verify(journal_t *j, 
void *buf)
 static int jbd2_block_tag_csum_verify(journal_t *j, journal_block_tag_t *tag,
                                      void *buf, __u32 sequence)
 {
-       __u32 provided, calculated;
+       __u32 csum32;
 
        if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2))
                return 1;
 
        sequence = cpu_to_be32(sequence);
-       calculated = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence,
-                                sizeof(sequence));
-       calculated = jbd2_chksum(j, calculated, buf, j->j_blocksize);
-       provided = be32_to_cpu(tag->t_checksum);
+       csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence,
+                            sizeof(sequence));
+       csum32 = jbd2_chksum(j, csum32, buf, j->j_blocksize);
 
-       return provided == cpu_to_be32(calculated);
+       return tag->t_checksum == cpu_to_be16(csum32);
 }
 
 static int do_one_pass(journal_t *journal,
--
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