Re: [PATCH] libext2fs: don't swap extent-based journal backup on read

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On 2009-11-10, at 13:45, Eric Sandeen wrote:
The f_illitable_flexbg test was failing on ppc, because
e2fsck_move_ext3_journal is doing a direct memcmp of i_block with
s_jnl_blocks, and failing.

This is because we don't swap extent data on read from disk; rather
we do it when we access the extents.  However, ext2fs_swap_super
was swapping s_jnl_blocks unconditionally, so these didn't match.

Looks like we need to treat s_jnl_blocks the same as i_block, and
swap it on access, not on read.  Except for the last i_size bit...

Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>

Makes sense:
Reviewed-by: Andreas Dilger <adilger@xxxxxxx>

---

diff --git a/lib/ext2fs/swapfs.c b/lib/ext2fs/swapfs.c
index 42bc01e..38f5f9b 100644
--- a/lib/ext2fs/swapfs.c
+++ b/lib/ext2fs/swapfs.c
@@ -73,9 +73,19 @@ void ext2fs_swap_super(struct ext2_super_block * sb)
	sb->s_kbytes_written = ext2fs_swab64(sb->s_kbytes_written);
	for (i=0; i < 4; i++)
		sb->s_hash_seed[i] = ext2fs_swab32(sb->s_hash_seed[i]);
+
+	/* if journal backup is for a valid extent-based journal... */
+	if (!ext2fs_extent_header_verify(sb->s_jnl_blocks,
+					 sizeof(sb->s_jnl_blocks))) {
+		/* ... swap only the journal i_size */
+		sb->s_jnl_blocks[16] = ext2fs_swab32(sb->s_jnl_blocks[16]);
+		/* and the extent data is not swapped on read */
+		return;
+	}
+
+	/* direct/indirect journal: swap it all */
	for (i=0; i < 17; i++)
		sb->s_jnl_blocks[i] = ext2fs_swab32(sb->s_jnl_blocks[i]);

I wouldn't object to fixing the formatting above to "for (i = 0; ...)"

}

void ext2fs_swap_group_desc(struct ext2_group_desc *gdp)


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Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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