On Wed, Jul 12, 2023 at 10:35:29 AM -0700, Darrick J. Wong wrote:
> 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.)
>
I agree with your review comment. I will make the required changes.
--
chandan
