On Tue, Jun 06, 2023 at 02:57:55PM +0530, Chandan Babu R wrote:
> This commit introduces a new function set_log_cur() allowing xfs_db to read
> from an external log device. This is required by a future commit which will
> add the ability to dump metadata from external log devices.
>
> Signed-off-by: Chandan Babu R <chandan.babu@xxxxxxxxxx>
> ---
> db/io.c | 57 ++++++++++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 44 insertions(+), 13 deletions(-)
>
> diff --git a/db/io.c b/db/io.c
> index 3d257236..a6feaba3 100644
> --- a/db/io.c
> +++ b/db/io.c
> @@ -508,18 +508,19 @@ write_cur(void)
>
> }
>
> -void
> -set_cur(
> - const typ_t *type,
> - xfs_daddr_t blknum,
> - int len,
> - int ring_flag,
> - bbmap_t *bbmap)
> +static void
> +__set_cur(
> + struct xfs_buftarg *btargp,
> + const typ_t *type,
> + xfs_daddr_t blknum,
> + int len,
> + int ring_flag,
> + bbmap_t *bbmap)
> {
> - struct xfs_buf *bp;
> - xfs_ino_t dirino;
> - xfs_ino_t ino;
> - uint16_t mode;
> + struct xfs_buf *bp;
> + xfs_ino_t dirino;
> + xfs_ino_t ino;
> + uint16_t mode;
> const struct xfs_buf_ops *ops = type ? type->bops : NULL;
> int error;
>
> @@ -548,11 +549,11 @@ set_cur(
> if (!iocur_top->bbmap)
> return;
> memcpy(iocur_top->bbmap, bbmap, sizeof(struct bbmap));
> - error = -libxfs_buf_read_map(mp->m_ddev_targp, bbmap->b,
> + error = -libxfs_buf_read_map(btargp, bbmap->b,
> bbmap->nmaps, LIBXFS_READBUF_SALVAGE, &bp,
> ops);
> } else {
> - error = -libxfs_buf_read(mp->m_ddev_targp, blknum, len,
> + error = -libxfs_buf_read(btargp, blknum, len,
> LIBXFS_READBUF_SALVAGE, &bp, ops);
> iocur_top->bbmap = NULL;
> }
> @@ -589,6 +590,36 @@ set_cur(
> ring_add();
> }
>
> +void
> +set_cur(
> + const typ_t *type,
> + xfs_daddr_t blknum,
> + int len,
> + int ring_flag,
> + bbmap_t *bbmap)
> +{
> + __set_cur(mp->m_ddev_targp, type, blknum, len, ring_flag, bbmap);
> +}
> +
> +void
> +set_log_cur(
> + const typ_t *type,
> + xfs_daddr_t blknum,
> + int len,
> + int ring_flag,
> + bbmap_t *bbmap)
> +{
> + struct xfs_buftarg *btargp = mp->m_ddev_targp;
> +
> + if (mp->m_logdev_targp->bt_bdev != mp->m_ddev_targp->bt_bdev) {
> + ASSERT(mp->m_sb.sb_logstart == 0);
> + btargp = mp->m_logdev_targp;
> + }
I think this should print an error message if there isn't an external
log device and then leave iocur_top unchanged:
if (mp->m_logdev_targp->bt_bdev == mp->m_ddev_targp->bt_bdev) {
fprintf(stderr, "no external log specified\n");
exitcode = 1;
return;
}
__set_cur(mp->m_logdev_targp, type, blknum, len, ring_flag, bbmap);
because metadump shouldn't crash if there's an external log device but
sb_logstart is zero. The superblock fields /could/ be corrupt, or other
weird shenanigans are going on.
(Also it's a layering violation for the io cursors to know anything at
all about the filesystem stored above them.)
--D
> +
> + __set_cur(btargp, type, blknum, len, ring_flag, bbmap);
> +}
> +
> +
> void
> set_iocur_type(
> const typ_t *type)
> --
> 2.39.1
>
