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xfs: compute realtime device CoW staging extent reap limits dynamically

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Calculate the maximum number of CoW staging extents that can be reaped
in a single transaction chain.  The rough calculation here is:

nr_extents = (logres - reservation used by any one step) /
		(space used by intents per extent)

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong 2025-04-08 16:14:34 -07:00
parent 442bc127d4
commit 74fc66ee17
2 changed files with 68 additions and 4 deletions
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71
fs/xfs/scrub/reap.c
View File

@ -984,7 +984,7 @@ xreap_rgextent_iter(
rtbno = xfs_rgbno_to_rtb(sc->sr.rtg, rgbno);
/*
* If there are other rmappings, this block is cross linked and must
* t1: There are other rmappings; this block is cross linked and must
* not be freed. Remove the forward and reverse mapping and move on.
*/
if (crosslinked) {
@ -999,7 +999,7 @@ xreap_rgextent_iter(
trace_xreap_dispose_free_extent(rtg_group(sc->sr.rtg), rgbno, *rglenp);
/*
* The CoW staging extent is not crosslinked. Use deferred work items
* t2: The CoW staging extent is not crosslinked. Use deferred work
* to remove the refcountbt records (which removes the rmap records)
* and free the extent. We're not worried about the system going down
* here because log recovery walks the refcount btree to clean out the
@ -1017,6 +1017,69 @@ xreap_rgextent_iter(
return 0;
}
/*
* Compute the maximum number of intent items that reaping can attach to the
* scrub transaction given the worst case log overhead of the intent items
* needed to reap a single CoW staging extent. This is not for freeing
* metadata blocks.
*/
STATIC void
xreap_configure_rgcow_limits(
struct xreap_state *rs)
{
struct xfs_scrub *sc = rs->sc;
struct xfs_mount *mp = sc->mp;
/*
* In the worst case, relogging an intent item causes both an intent
* item and a done item to be attached to a transaction for each extent
* that we'd like to process.
*/
const unsigned int efi = xfs_efi_log_space(1) +
xfs_efd_log_space(1);
const unsigned int rui = xfs_rui_log_space(1) +
xfs_rud_log_space();
const unsigned int cui = xfs_cui_log_space(1) +
xfs_cud_log_space();
/*
* Various things can happen when reaping non-CoW metadata blocks:
*
* t1: Unmapping crosslinked CoW blocks: deferred removal of refcount
* record, which defers removal of rmap record
*
* t2: Freeing CoW blocks: deferred removal of refcount record, which
* defers removal of rmap record; and deferred removal of the space
*
* For simplicity, we'll use the worst-case intents size to determine
* the maximum number of deferred extents before we have to finish the
* whole chain. If we're trying to reap a btree larger than this size,
* a crash midway through reaping can result in leaked blocks.
*/
const unsigned int t1 = cui + rui;
const unsigned int t2 = cui + rui + efi;
const unsigned int per_intent = max(t1, t2);
/*
* For each transaction in a reap chain, we must be able to take one
* step in the defer item chain, which should only consist of CUI, EFI,
* or RUI items.
*/
const unsigned int f1 = xfs_calc_finish_rt_efi_reservation(mp, 1);
const unsigned int f2 = xfs_calc_finish_rt_rui_reservation(mp, 1);
const unsigned int f3 = xfs_calc_finish_rt_cui_reservation(mp, 1);
const unsigned int step_size = max3(f1, f2, f3);
/*
* The only buffer for the rt device is the rtgroup super, so we don't
* need to save space for buffer invalidations.
*/
xreap_configure_limits(rs, step_size, per_intent, per_intent, 0);
trace_xreap_rgcow_limits(sc->tp, 0, 0, step_size, per_intent,
rs->max_deferred);
}
#define XREAP_RTGLOCK_ALL (XFS_RTGLOCK_BITMAP | \
XFS_RTGLOCK_RMAP | \
XFS_RTGLOCK_REFCOUNT)
@ -1100,14 +1163,14 @@ xrep_reap_rtblocks(
.sc = sc,
.oinfo = oinfo,
.resv = XFS_AG_RESV_NONE,
.max_binval = XREAP_MAX_BINVAL,
.max_deferred = XREAP_MAX_DEFER_CHAIN,
};
int error;
ASSERT(xfs_has_rmapbt(sc->mp));
ASSERT(sc->ip != NULL);
ASSERT(oinfo == &XFS_RMAP_OINFO_COW);
xreap_configure_rgcow_limits(&rs);
error = xrtb_bitmap_walk(bitmap, xreap_rtmeta_extent, &rs);
if (error)
return error;

1
fs/xfs/scrub/trace.h
View File

@ -2042,6 +2042,7 @@ DEFINE_EVENT(xrep_reap_limits_class, name, \
TP_ARGS(tp, per_binval, max_binval, step_size, per_intent, max_deferred))
DEFINE_REPAIR_REAP_LIMITS_EVENT(xreap_agextent_limits);
DEFINE_REPAIR_REAP_LIMITS_EVENT(xreap_agcow_limits);
DEFINE_REPAIR_REAP_LIMITS_EVENT(xreap_rgcow_limits);
DECLARE_EVENT_CLASS(xrep_reap_find_class,
TP_PROTO(const struct xfs_group *xg, xfs_agblock_t agbno,