On Thu, Jun 22, 2017 at 02:33:52PM -0500, Bill O'Donnell wrote:
> xfs_db doesn't take sector size into account when setting type.
> This can result in an errant crc. For example, with a sector size
> of 4096:
>
> xfs_db> agi 0
> xfs_db> p crc
> crc = 0xab85043e (correct)
> xfs_db> daddr
> current daddr is 16
> xfs_db> daddr 42
> xfs_db> daddr 16
> xfs_db> type agi
> Metadata CRC error detected at xfs_agi block 0x10/0x200
> xfs_db> p crc
> crc = 0xab85043e (bad)
>
> When xfs_db sets the new daddr in daddr_f, it does so with one
> BBSIZE sector (512). Changing the type doesn't change the size
> of the current buffer in iocur_top, so the checksum is calculated
> on the wrong length for the type (when the actual sector size > BBSIZE (512).
>
> For types with fields, reread the buffer to pick up the correct size for
> the new type when it gets set. Facilitate the reread by setting the cursor
> with set_cur().
>
> Signed-off-by: Bill O'Donnell <billodo@xxxxxxxxxx>
> ---
> db/io.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/db/io.c b/db/io.c
> index 9918a51..7e6d330 100644
> --- a/db/io.c
> +++ b/db/io.c
> @@ -616,6 +616,12 @@ set_iocur_type(
> {
> struct xfs_buf *bp = iocur_top->bp;
>
> + if (t->fields)
> + set_cur(t,
> + iocur_top->bb,
> + fsize(t->fields, iocur_top->data,
> + 0, 0) / mp->m_sb.sb_blocksize,
I thought the third parameter to set_cur (which is fed as the third
parameter to libxfs_readbuf) was expressed in units of basic blocks
(i.e. 512 bytes)? fsize returns the size of the field in bytes (I
think?), so dividing by sb_blocksize renders units of fs blocks, not
basic blocks.
<shrug> the naming isn't helpful at all:
void
set_cur(
const typ_t *t,
int64_t d,
int c,
...
iocur_top->len = BBTOB(c);
<codeconfused>
--D
> + DB_RING_IGN, NULL);
> iocur_top->typ = t;
>
> /* verify the buffer if the type has one. */
> --
> 2.9.4
>
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