[PATCH 4/4] xfs: hook live rmap operations during a repair operation

Darrick J. Wong
2023-12-31T22:18:12Z

Hook the regular rmap code when an rmapbt repair operation is running so
that we can unlock the AGF buffer to scan the filesystem and keep the
in-memory btree up to date during the scan.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
include/xfs_mount.h | 6 ++
libxfs/xfs_ag.c | 1
libxfs/xfs_ag.h | 3 +
libxfs/xfs_rmap.c | 145 +++++++++++++++++++++++++++++++++++++++------------
libxfs/xfs_rmap.h | 28 ++++++++++
5 files changed, 150 insertions(+), 33 deletions(-)

diff --git a/include/xfs_mount.h b/include/xfs_mount.h
index 80e40e7c60e..8a2ffa4e7cc 100644
--- a/include/xfs_mount.h
+++ b/include/xfs_mount.h
@@ -24,6 +24,12 @@ enum {
XFS_LOWSP_MAX,
};

+/* Stubbed-out functionality from the kernel. */
+struct xfs_hook_chain {
+};
+#define xfs_hook_init(chain) ((void)0)
+#define xfs_hook_call(chain, val, priv) (0)
+
/*
* Define a user-level mount structure with all we need
* in order to make use of the numerous XFS_* macros.
diff --git a/libxfs/xfs_ag.c b/libxfs/xfs_ag.c
index 8e40026436a..1ba23ab533b 100644
--- a/libxfs/xfs_ag.c
+++ b/libxfs/xfs_ag.c
@@ -390,6 +390,7 @@ xfs_initialize_perag(
init_waitqueue_head(&pag->pag_active_wq);
pag->pagb_count = 0;
pag->pagb_tree = RB_ROOT;
+ xfs_hooks_init(&pag->pag_rmap_update_hooks);
#endif /* __KERNEL__ */

error = xfs_buf_cache_init(&pag->pag_bcache);
diff --git a/libxfs/xfs_ag.h b/libxfs/xfs_ag.h
index fe5852873b8..06506e09a82 100644
--- a/libxfs/xfs_ag.h
+++ b/libxfs/xfs_ag.h
@@ -117,6 +117,9 @@ struct xfs_perag {
* inconsistencies.
*/
struct xfs_defer_drain pag_intents_drain;
+
+ /* Hook to feed rmapbt updates to an active online repair. */
+ struct xfs_hooks pag_rmap_update_hooks;
#endif /* __KERNEL__ */
};

diff --git a/libxfs/xfs_rmap.c b/libxfs/xfs_rmap.c
index b4a1f7e5189..8df591840dc 100644
--- a/libxfs/xfs_rmap.c
+++ b/libxfs/xfs_rmap.c
@@ -820,6 +820,77 @@ xfs_rmap_unmap(
return error;
}

+#ifdef CONFIG_XFS_LIVE_HOOKS
+/*
+ * Use a static key here to reduce the overhead of rmapbt live updates. If
+ * the compiler supports jump labels, the static branch will be replaced by a
+ * nop sled when there are no hook users. Online fsck is currently the only
+ * caller, so this is a reasonable tradeoff.
+ *
+ * Note: Patching the kernel code requires taking the cpu hotplug lock. Other
+ * parts of the kernel allocate memory with that lock held, which means that
+ * XFS callers cannot hold any locks that might be used by memory reclaim or
+ * writeback when calling the static_branch_{inc,dec} functions.
+ */
+DEFINE_STATIC_XFS_HOOK_SWITCH(xfs_rmap_hooks_switch);
+
+void
+xfs_rmap_hook_disable(void)
+{
+ xfs_hooks_switch_off(&xfs_rmap_hooks_switch);
+}
+
+void
+xfs_rmap_hook_enable(void)
+{
+ xfs_hooks_switch_on(&xfs_rmap_hooks_switch);
+}
+
+/* Call downstream hooks for a reverse mapping update. */
+static inline void
+xfs_rmap_update_hook(
+ struct xfs_trans *tp,
+ struct xfs_perag *pag,
+ enum xfs_rmap_intent_type op,
+ xfs_agblock_t startblock,
+ xfs_extlen_t blockcount,
+ bool unwritten,
+ const struct xfs_owner_info *oinfo)
+{
+ if (xfs_hooks_switched_on(&xfs_rmap_hooks_switch)) {
+ struct xfs_rmap_update_params p = {
+ .startblock = startblock,
+ .blockcount = blockcount,
+ .unwritten = unwritten,
+ .oinfo = *oinfo, /* struct copy */
+ };
+
+ if (pag)
+ xfs_hooks_call(&pag->pag_rmap_update_hooks, op, &p);
+ }
+}
+
+/* Call the specified function during a reverse mapping update. */
+int
+xfs_rmap_hook_add(
+ struct xfs_perag *pag,
+ struct xfs_rmap_hook *hook)
+{
+ return xfs_hooks_add(&pag->pag_rmap_update_hooks, &hook->update_hook);
+}
+
+/* Stop calling the specified function during a reverse mapping update. */
+void
+xfs_rmap_hook_del(
+ struct xfs_perag *pag,
+ struct xfs_rmap_hook *hook)
+{
+ xfs_hooks_del(&pag->pag_rmap_update_hooks, &hook->update_hook);
+}
+#else
+# define xfs_rmap_update_hook(t, p, o, s, b, u, oi) do { } while (0)
+#endif /* CONFIG_XFS_LIVE_HOOKS */
+
/*
* Remove a reference to an extent in the rmap btree.
*/
@@ -840,7 +911,7 @@ xfs_rmap_free(
return 0;

cur = xfs_rmapbt_init_cursor(mp, tp, agbp, pag);
-
+ xfs_rmap_update_hook(tp, pag, XFS_RMAP_UNMAP, bno, len, false, oinfo);
error = xfs_rmap_unmap(cur, bno, len, false, oinfo);

xfs_btree_del_cursor(cur, error);
@@ -1092,6 +1163,7 @@ xfs_rmap_alloc(
return 0;

cur = xfs_rmapbt_init_cursor(mp, tp, agbp, pag);
+ xfs_rmap_update_hook(tp, pag, XFS_RMAP_MAP, bno, len, false, oinfo);
error = xfs_rmap_map(cur, bno, len, false, oinfo);

xfs_btree_del_cursor(cur, error);
@@ -2507,6 +2579,38 @@ xfs_rmap_finish_one_cleanup(
xfs_trans_brelse(tp, agbp);
}

+/* Commit an rmap operation into the ondisk tree. */
+int
+__xfs_rmap_finish_intent(
+ struct xfs_btree_cur *rcur,
+ enum xfs_rmap_intent_type op,
+ xfs_agblock_t bno,
+ xfs_extlen_t len,
+ const struct xfs_owner_info *oinfo,
+ bool unwritten)
+{
+ switch (op) {
+ case XFS_RMAP_ALLOC:
+ case XFS_RMAP_MAP:
+ return xfs_rmap_map(rcur, bno, len, unwritten, oinfo);
+ case XFS_RMAP_MAP_SHARED:
+ return xfs_rmap_map_shared(rcur, bno, len, unwritten, oinfo);
+ case XFS_RMAP_FREE:
+ case XFS_RMAP_UNMAP:
+ return xfs_rmap_unmap(rcur, bno, len, unwritten, oinfo);
+ case XFS_RMAP_UNMAP_SHARED:
+ return xfs_rmap_unmap_shared(rcur, bno, len, unwritten, oinfo);
+ case XFS_RMAP_CONVERT:
+ return xfs_rmap_convert(rcur, bno, len, !unwritten, oinfo);
+ case XFS_RMAP_CONVERT_SHARED:
+ return xfs_rmap_convert_shared(rcur, bno, len, !unwritten,
+ oinfo);
+ default:
+ ASSERT(0);
+ return -EFSCORRUPTED;
+ }
+}
+
/*
* Process one of the deferred rmap operations. We pass back the
* btree cursor to maintain our lock on the rmapbt between calls.
@@ -2573,39 +2677,14 @@ xfs_rmap_finish_one(
unwritten = ri->ri_bmap.br_state == XFS_EXT_UNWRITTEN;
bno = XFS_FSB_TO_AGBNO(rcur->bc_mp, ri->ri_bmap.br_startblock);

- switch (ri->ri_type) {
- case XFS_RMAP_ALLOC:
- case XFS_RMAP_MAP:
- error = xfs_rmap_map(rcur, bno, ri->ri_bmap.br_blockcount,
- unwritten, &oinfo);
- break;
- case XFS_RMAP_MAP_SHARED:
- error = xfs_rmap_map_shared(rcur, bno,
- ri->ri_bmap.br_blockcount, unwritten, &oinfo);
- break;
- case XFS_RMAP_FREE:
- case XFS_RMAP_UNMAP:
- error = xfs_rmap_unmap(rcur, bno, ri->ri_bmap.br_blockcount,
- unwritten, &oinfo);
- break;
- case XFS_RMAP_UNMAP_SHARED:
- error = xfs_rmap_unmap_shared(rcur, bno,
- ri->ri_bmap.br_blockcount, unwritten, &oinfo);
- break;
- case XFS_RMAP_CONVERT:
- error = xfs_rmap_convert(rcur, bno, ri->ri_bmap.br_blockcount,
- !unwritten, &oinfo);
- break;
- case XFS_RMAP_CONVERT_SHARED:
- error = xfs_rmap_convert_shared(rcur, bno,
- ri->ri_bmap.br_blockcount, !unwritten, &oinfo);
- break;
- default:
- ASSERT(0);
- error = -EFSCORRUPTED;
- }
+ error = __xfs_rmap_finish_intent(rcur, ri->ri_type, bno,
+ ri->ri_bmap.br_blockcount, &oinfo, unwritten);
+ if (error)
+ return error;

- return error;
+ xfs_rmap_update_hook(tp, ri->ri_pag, ri->ri_type, bno,
+ ri->ri_bmap.br_blockcount, unwritten, &oinfo);
+ return 0;
}

/*
diff --git a/libxfs/xfs_rmap.h b/libxfs/xfs_rmap.h
index 58c67896d12..3a153b4801b 100644
--- a/libxfs/xfs_rmap.h
+++ b/libxfs/xfs_rmap.h
@@ -186,6 +186,10 @@ void xfs_rmap_finish_one_cleanup(struct xfs_trans *tp,
struct xfs_btree_cur *rcur, int error);
int xfs_rmap_finish_one(struct xfs_trans *tp, struct xfs_rmap_intent *ri,
struct xfs_btree_cur **pcur);
+int __xfs_rmap_finish_intent(struct xfs_btree_cur *rcur,
+ enum xfs_rmap_intent_type op, xfs_agblock_t bno,
+ xfs_extlen_t len, const struct xfs_owner_info *oinfo,
+ bool unwritten);

int xfs_rmap_lookup_le_range(struct xfs_btree_cur *cur, xfs_agblock_t bno,
uint64_t owner, uint64_t offset, unsigned int flags,
@@ -235,4 +239,28 @@ extern struct kmem_cache *xfs_rmap_intent_cache;
int __init xfs_rmap_intent_init_cache(void);
void xfs_rmap_intent_destroy_cache(void);

+/*
+ * Parameters for tracking reverse mapping changes. The hook function arg
+ * parameter is enum xfs_rmap_intent_type, and the rest is below.
+ */
+struct xfs_rmap_update_params {
+ xfs_agblock_t startblock;
+ xfs_extlen_t blockcount;
+ struct xfs_owner_info oinfo;
+ bool unwritten;
+};
+
+#ifdef CONFIG_XFS_LIVE_HOOKS
+
+struct xfs_rmap_hook {
+ struct xfs_hook update_hook;
+};
+
+void xfs_rmap_hook_disable(void);
+void xfs_rmap_hook_enable(void);
+
+int xfs_rmap_hook_add(struct xfs_perag *pag, struct xfs_rmap_hook *hook);
+void xfs_rmap_hook_del(struct xfs_perag *pag, struct xfs_rmap_hook *hook);
+#endif
+
#endif /* __XFS_RMAP_H__ */