On Tue, Mar 06, 2012 at 12:49:41PM -0800, Darrick J. Wong wrote:
> @@ -177,11 +189,17 @@ typedef struct journal_block_tag_s
> __be32 t_blocknr; /* The on-disk block number */
> __be32 t_flags; /* See below */
> __be32 t_blocknr_high; /* most-significant high 32bits. */
> + __be32 t_checksum; /* crc32c(uuid+seq+block) */
> } journal_block_tag_t;
>
> #define JBD2_TAG_SIZE32 (offsetof(journal_block_tag_t, t_blocknr_high))
> #define JBD2_TAG_SIZE64 (sizeof(journal_block_tag_t))
There's a problem with this patch here --- we are changing the size of
journal_block_tag_t, which is an on-disk data structure. So for
64-bit journals, this represents a format change. This means that if
you have a 64-bit file system that needs to have its journal
recovered, if the journal was written with an older kernel, and then
we try to recover it with a new kernel, things won't be good.
Similarly, for e2fsck's recovery code, it's not going to be able to
recover 64-bit file systems using current coding, since this patch
series changes the size of JBD2_TAG_SIZE64.
What we need to do is something like this:
#define JBD2_TAG_SIZE64 (offsetof(journal_block_tag_t, t_checksum))
#define JBD2_TAG_SIZE_CSUM (sizeof(journal_block_tag_t))
And then change the code appropriately in e2fsprogs and in the kernel
to use the correct tag size depending on the journal options.
- Ted
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