On Thu, May 17, 2018 at 08:51:55PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Add some helpers to assemble a list of fs block extents. Generally,
> repair functions will iterate the rmapbt to make a list (1) of all
> extents owned by the nominal owner of the metadata structure; then they
> will iterate all other structures with the same rmap owner to make a
> list (2) of active blocks; and finally we have a subtraction function to
> subtract all the blocks in (2) from (1), with the result that (1) is now
> a list of blocks that were owned by the old btree and must be disposed.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> v2: document the design of how repair functions are supposed to work,
> implement review comments
> ---
Much easier to understand now. Thanks!
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
One thing for a followup patch, though.
> +/* Collect a dead btree extent for later disposal. */
> +int
> +xfs_repair_collect_btree_extent(
> + struct xfs_scrub_context *sc,
> + struct xfs_repair_extent_list *exlist,
> + xfs_fsblock_t fsbno,
> + xfs_extlen_t len)
> +{
> + struct xfs_repair_extent *rex;
> +
> + trace_xfs_repair_collect_btree_extent(sc->mp,
> + XFS_FSB_TO_AGNO(sc->mp, fsbno),
> + XFS_FSB_TO_AGBNO(sc->mp, fsbno), len);
> +
> + rex = kmem_alloc(sizeof(struct xfs_repair_extent), KM_MAYFAIL);
> + if (!rex)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(&rex->list);
> + rex->fsbno = fsbno;
> + rex->len = len;
This allocation is repeated a couple of times. Single function to do
it would be nice to encapsulate alloc+setup - something like rex =
alloc_rex(fsbno, len) which returns NULL if it fails.
> + case LEFT_ALIGNED | RIGHT_ALIGNED:
> + /* Total overlap, just delete ex. */
> + lp = lp->next;
> + list_del(&ex->list);
> + kmem_free(ex);
> + break;
> + case 0:
> + /*
> + * Deleting from the middle: add the new right extent
> + * and then shrink the left extent.
> + */
> + newex = kmem_alloc(sizeof(struct xfs_repair_extent),
> + KM_MAYFAIL);
> + if (!newex) {
> + error = -ENOMEM;
> + goto out;
> + }
> + INIT_LIST_HEAD(&newex->list);
> + newex->fsbno = sub_fsb + sub_len;
> + newex->len = ex->fsbno + ex->len - newex->fsbno;
This is the other place it is called...
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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