Commit 12c6510e authored by Darrick J. Wong's avatar Darrick J. Wong

xfs: add helpers to dispose of old btree blocks after a repair

Now that we've plumbed in the ability to construct a list of dead btree
blocks following a repair, add more helpers to dispose of them.  This is
done by examining the rmapbt -- if the btree was the only owner we can
free the block, otherwise it's crosslinked and we can only remove the
rmapbt record.
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
parent 64a39d87
......@@ -585,3 +585,254 @@ xfs_repair_subtract_extents(
}
#undef LEFT_ALIGNED
#undef RIGHT_ALIGNED
/*
* Disposal of Blocks from Old per-AG Btrees
*
* Now that we've constructed a new btree to replace the damaged one, we want
* to dispose of the blocks that (we think) the old btree was using.
* Previously, we used the rmapbt to collect the extents (exlist) with the
* rmap owner corresponding to the tree we rebuilt, collected extents for any
* blocks with the same rmap owner that are owned by another data structure
* (sublist), and subtracted sublist from exlist. In theory the extents
* remaining in exlist are the old btree's blocks.
*
* Unfortunately, it's possible that the btree was crosslinked with other
* blocks on disk. The rmap data can tell us if there are multiple owners, so
* if the rmapbt says there is an owner of this block other than @oinfo, then
* the block is crosslinked. Remove the reverse mapping and continue.
*
* If there is one rmap record, we can free the block, which removes the
* reverse mapping but doesn't add the block to the free space. Our repair
* strategy is to hope the other metadata objects crosslinked on this block
* will be rebuilt (atop different blocks), thereby removing all the cross
* links.
*
* If there are no rmap records at all, we also free the block. If the btree
* being rebuilt lives in the free space (bnobt/cntbt/rmapbt) then there isn't
* supposed to be a rmap record and everything is ok. For other btrees there
* had to have been an rmap entry for the block to have ended up on @exlist,
* so if it's gone now there's something wrong and the fs will shut down.
*
* Note: If there are multiple rmap records with only the same rmap owner as
* the btree we're trying to rebuild and the block is indeed owned by another
* data structure with the same rmap owner, then the block will be in sublist
* and therefore doesn't need disposal. If there are multiple rmap records
* with only the same rmap owner but the block is not owned by something with
* the same rmap owner, the block will be freed.
*
* The caller is responsible for locking the AG headers for the entire rebuild
* operation so that nothing else can sneak in and change the AG state while
* we're not looking. We also assume that the caller already invalidated any
* buffers associated with @exlist.
*/
/*
* Invalidate buffers for per-AG btree blocks we're dumping. This function
* is not intended for use with file data repairs; we have bunmapi for that.
*/
int
xfs_repair_invalidate_blocks(
struct xfs_scrub_context *sc,
struct xfs_repair_extent_list *exlist)
{
struct xfs_repair_extent *rex;
struct xfs_repair_extent *n;
struct xfs_buf *bp;
xfs_fsblock_t fsbno;
xfs_agblock_t i;
/*
* For each block in each extent, see if there's an incore buffer for
* exactly that block; if so, invalidate it. The buffer cache only
* lets us look for one buffer at a time, so we have to look one block
* at a time. Avoid invalidating AG headers and post-EOFS blocks
* because we never own those; and if we can't TRYLOCK the buffer we
* assume it's owned by someone else.
*/
for_each_xfs_repair_extent_safe(rex, n, exlist) {
for (fsbno = rex->fsbno, i = rex->len; i > 0; fsbno++, i--) {
/* Skip AG headers and post-EOFS blocks */
if (!xfs_verify_fsbno(sc->mp, fsbno))
continue;
bp = xfs_buf_incore(sc->mp->m_ddev_targp,
XFS_FSB_TO_DADDR(sc->mp, fsbno),
XFS_FSB_TO_BB(sc->mp, 1), XBF_TRYLOCK);
if (bp) {
xfs_trans_bjoin(sc->tp, bp);
xfs_trans_binval(sc->tp, bp);
}
}
}
return 0;
}
/* Ensure the freelist is the correct size. */
int
xfs_repair_fix_freelist(
struct xfs_scrub_context *sc,
bool can_shrink)
{
struct xfs_alloc_arg args = {0};
args.mp = sc->mp;
args.tp = sc->tp;
args.agno = sc->sa.agno;
args.alignment = 1;
args.pag = sc->sa.pag;
return xfs_alloc_fix_freelist(&args,
can_shrink ? 0 : XFS_ALLOC_FLAG_NOSHRINK);
}
/*
* Put a block back on the AGFL.
*/
STATIC int
xfs_repair_put_freelist(
struct xfs_scrub_context *sc,
xfs_agblock_t agbno)
{
struct xfs_owner_info oinfo;
int error;
/* Make sure there's space on the freelist. */
error = xfs_repair_fix_freelist(sc, true);
if (error)
return error;
/*
* Since we're "freeing" a lost block onto the AGFL, we have to
* create an rmap for the block prior to merging it or else other
* parts will break.
*/
xfs_rmap_ag_owner(&oinfo, XFS_RMAP_OWN_AG);
error = xfs_rmap_alloc(sc->tp, sc->sa.agf_bp, sc->sa.agno, agbno, 1,
&oinfo);
if (error)
return error;
/* Put the block on the AGFL. */
error = xfs_alloc_put_freelist(sc->tp, sc->sa.agf_bp, sc->sa.agfl_bp,
agbno, 0);
if (error)
return error;
xfs_extent_busy_insert(sc->tp, sc->sa.agno, agbno, 1,
XFS_EXTENT_BUSY_SKIP_DISCARD);
return 0;
}
/* Dispose of a single metadata block. */
STATIC int
xfs_repair_dispose_btree_block(
struct xfs_scrub_context *sc,
xfs_fsblock_t fsbno,
struct xfs_owner_info *oinfo,
enum xfs_ag_resv_type resv)
{
struct xfs_btree_cur *cur;
struct xfs_buf *agf_bp = NULL;
xfs_agnumber_t agno;
xfs_agblock_t agbno;
bool has_other_rmap;
int error;
agno = XFS_FSB_TO_AGNO(sc->mp, fsbno);
agbno = XFS_FSB_TO_AGBNO(sc->mp, fsbno);
/*
* If we are repairing per-inode metadata, we need to read in the AGF
* buffer. Otherwise, we're repairing a per-AG structure, so reuse
* the AGF buffer that the setup functions already grabbed.
*/
if (sc->ip) {
error = xfs_alloc_read_agf(sc->mp, sc->tp, agno, 0, &agf_bp);
if (error)
return error;
if (!agf_bp)
return -ENOMEM;
} else {
agf_bp = sc->sa.agf_bp;
}
cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, agf_bp, agno);
/* Can we find any other rmappings? */
error = xfs_rmap_has_other_keys(cur, agbno, 1, oinfo, &has_other_rmap);
if (error)
goto out_cur;
xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
/*
* If there are other rmappings, this block is cross linked and must
* not be freed. Remove the reverse mapping and move on. Otherwise,
* we were the only owner of the block, so free the extent, which will
* also remove the rmap.
*
* XXX: XFS doesn't support detecting the case where a single block
* metadata structure is crosslinked with a multi-block structure
* because the buffer cache doesn't detect aliasing problems, so we
* can't fix 100% of crosslinking problems (yet). The verifiers will
* blow on writeout, the filesystem will shut down, and the admin gets
* to run xfs_repair.
*/
if (has_other_rmap)
error = xfs_rmap_free(sc->tp, agf_bp, agno, agbno, 1, oinfo);
else if (resv == XFS_AG_RESV_AGFL)
error = xfs_repair_put_freelist(sc, agbno);
else
error = xfs_free_extent(sc->tp, fsbno, 1, oinfo, resv);
if (agf_bp != sc->sa.agf_bp)
xfs_trans_brelse(sc->tp, agf_bp);
if (error)
return error;
if (sc->ip)
return xfs_trans_roll_inode(&sc->tp, sc->ip);
return xfs_repair_roll_ag_trans(sc);
out_cur:
xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
if (agf_bp != sc->sa.agf_bp)
xfs_trans_brelse(sc->tp, agf_bp);
return error;
}
/* Dispose of btree blocks from an old per-AG btree. */
int
xfs_repair_reap_btree_extents(
struct xfs_scrub_context *sc,
struct xfs_repair_extent_list *exlist,
struct xfs_owner_info *oinfo,
enum xfs_ag_resv_type type)
{
struct xfs_repair_extent *rex;
struct xfs_repair_extent *n;
int error = 0;
ASSERT(xfs_sb_version_hasrmapbt(&sc->mp->m_sb));
/* Dispose of every block from the old btree. */
for_each_xfs_repair_extent_safe(rex, n, exlist) {
ASSERT(sc->ip != NULL ||
XFS_FSB_TO_AGNO(sc->mp, rex->fsbno) == sc->sa.agno);
trace_xfs_repair_dispose_btree_extent(sc->mp,
XFS_FSB_TO_AGNO(sc->mp, rex->fsbno),
XFS_FSB_TO_AGBNO(sc->mp, rex->fsbno), rex->len);
for (; rex->len > 0; rex->len--, rex->fsbno++) {
error = xfs_repair_dispose_btree_block(sc, rex->fsbno,
oinfo, type);
if (error)
goto out;
}
list_del(&rex->list);
kmem_free(rex);
}
out:
xfs_repair_cancel_btree_extents(sc, exlist);
return error;
}
......@@ -70,6 +70,12 @@ void xfs_repair_cancel_btree_extents(struct xfs_scrub_context *sc,
int xfs_repair_subtract_extents(struct xfs_scrub_context *sc,
struct xfs_repair_extent_list *exlist,
struct xfs_repair_extent_list *sublist);
int xfs_repair_fix_freelist(struct xfs_scrub_context *sc, bool can_shrink);
int xfs_repair_invalidate_blocks(struct xfs_scrub_context *sc,
struct xfs_repair_extent_list *btlist);
int xfs_repair_reap_btree_extents(struct xfs_scrub_context *sc,
struct xfs_repair_extent_list *exlist,
struct xfs_owner_info *oinfo, enum xfs_ag_resv_type type);
/* Metadata repairers */
......
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