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

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

[Eric Sandeen]

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@redhat.com>
---

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]);

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

[Andreas Dilger]

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@redhat.com>

Makes sense:
Reviewed-by: Andreas Dilger <adilger@sun.com>

> ---
>
> 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.

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

[Theodore Tso]

On Tue, Nov 10, 2009 at 02:45:44PM -0600, 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@redhat.com>

Applied to the maint branch, thanks.

							- Ted