From: Darrick J. Wong <djwong@xxxxxxxxxx>
When a writer thread executes a chain of log intent items for the
realtime volume, the ILOCKs taken during each step are for each rt
metadata file, not the entire rt volume itself. Although scrub takes
all rt metadata ILOCKs, this isn't sufficient to guard against scrub
checking the rt volume while that writer thread is in the middle of
finishing a chain because there's no higher level locking primitive
guarding the realtime volume.
When there's a collision, cross-referencing between data structures
(e.g. rtrmapbt and rtrefcountbt) yields false corruption events; if
repair is running, this results in incorrect repairs, which is
catastrophic.
Fix this by adding to the mount structure the same drain that we use to
protect scrub against concurrent AG updates, but this time for the
realtime volume.
[Contains a few cleanups from hch]
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
include/xfs_mount.h | 12 ++++++++++++
libxfs/defer_item.c | 31 +++++++++++++------------------
libxfs/xfs_rtgroup.c | 2 ++
libxfs/xfs_rtgroup.h | 9 +++++++++
4 files changed, 36 insertions(+), 18 deletions(-)
diff --git a/include/xfs_mount.h b/include/xfs_mount.h
index 4e4da5bc4fa..07f9e33b8b2 100644
--- a/include/xfs_mount.h
+++ b/include/xfs_mount.h
@@ -333,6 +333,18 @@ struct xfs_defer_drain { /* empty */ };
static inline void xfs_perag_intent_hold(struct xfs_perag *pag) {}
static inline void xfs_perag_intent_rele(struct xfs_perag *pag) {}
+struct xfs_rtgroup;
+
+#define xfs_rtgroup_intent_get(mp, rgno) \
+ xfs_rtgroup_get((mp), xfs_rtb_to_rgno((mp), (rgno)))
+#define xfs_rtgroup_intent_put(rtg) xfs_rtgroup_put(rtg)
+
+static inline void xfs_rtgroup_intent_hold(struct xfs_rtgroup *rtg) { }
+static inline void xfs_rtgroup_intent_rele(struct xfs_rtgroup *rtg) { }
+
+#define xfs_drain_free(dr) ((void)0)
+#define xfs_drain_init(dr) ((void)0)
+
static inline void libxfs_buftarg_drain(struct xfs_buftarg *btp)
{
cache_purge(btp->bcache);
diff --git a/libxfs/defer_item.c b/libxfs/defer_item.c
index a82d23c17cf..e7270d02c4b 100644
--- a/libxfs/defer_item.c
+++ b/libxfs/defer_item.c
@@ -88,11 +88,8 @@ xfs_extent_free_defer_add(
struct xfs_mount *mp = tp->t_mountp;
if (xfs_efi_is_realtime(xefi)) {
- xfs_rgnumber_t rgno;
-
- rgno = xfs_rtb_to_rgno(mp, xefi->xefi_startblock);
- xefi->xefi_rtg = xfs_rtgroup_get(mp, rgno);
-
+ xefi->xefi_rtg = xfs_rtgroup_intent_get(mp,
+ xefi->xefi_startblock);
*dfpp = xfs_defer_add(tp, &xefi->xefi_list,
&xfs_rtextent_free_defer_type);
return;
@@ -204,7 +201,7 @@ xfs_rtextent_free_cancel_item(
{
struct xfs_extent_free_item *xefi = xefi_entry(item);
- xfs_rtgroup_put(xefi->xefi_rtg);
+ xfs_rtgroup_intent_put(xefi->xefi_rtg);
kmem_cache_free(xfs_extfree_item_cache, xefi);
}
@@ -338,13 +335,12 @@ xfs_rmap_defer_add(
* section updates.
*/
if (ri->ri_realtime) {
- xfs_rgnumber_t rgno;
-
- rgno = xfs_rtb_to_rgno(mp, ri->ri_bmap.br_startblock);
- ri->ri_rtg = xfs_rtgroup_get(mp, rgno);
+ ri->ri_rtg = xfs_rtgroup_intent_get(mp,
+ ri->ri_bmap.br_startblock);
xfs_defer_add(tp, &ri->ri_list, &xfs_rtrmap_update_defer_type);
} else {
- ri->ri_pag = xfs_perag_intent_get(mp, ri->ri_bmap.br_startblock);
+ ri->ri_pag = xfs_perag_intent_get(mp,
+ ri->ri_bmap.br_startblock);
xfs_defer_add(tp, &ri->ri_list, &xfs_rmap_update_defer_type);
}
}
@@ -445,7 +441,7 @@ xfs_rtrmap_update_cancel_item(
{
struct xfs_rmap_intent *ri = ri_entry(item);
- xfs_rtgroup_put(ri->ri_rtg);
+ xfs_rtgroup_intent_put(ri->ri_rtg);
kmem_cache_free(xfs_rmap_intent_cache, ri);
}
@@ -656,10 +652,8 @@ xfs_bmap_update_get_group(
{
if (xfs_ifork_is_realtime(bi->bi_owner, bi->bi_whichfork)) {
if (xfs_has_rtgroups(mp)) {
- xfs_rgnumber_t rgno;
-
- rgno = xfs_rtb_to_rgno(mp, bi->bi_bmap.br_startblock);
- bi->bi_rtg = xfs_rtgroup_get(mp, rgno);
+ bi->bi_rtg = xfs_rtgroup_intent_get(mp,
+ bi->bi_bmap.br_startblock);
} else {
bi->bi_rtg = NULL;
}
@@ -695,8 +689,9 @@ xfs_bmap_update_put_group(
struct xfs_bmap_intent *bi)
{
if (xfs_ifork_is_realtime(bi->bi_owner, bi->bi_whichfork)) {
- if (xfs_has_rtgroups(bi->bi_owner->i_mount))
- xfs_rtgroup_put(bi->bi_rtg);
+ if (xfs_has_rtgroups(bi->bi_owner->i_mount)) {
+ xfs_rtgroup_intent_put(bi->bi_rtg);
+ }
return;
}
diff --git a/libxfs/xfs_rtgroup.c b/libxfs/xfs_rtgroup.c
index 449cd57cf9e..1acf98f8c7e 100644
--- a/libxfs/xfs_rtgroup.c
+++ b/libxfs/xfs_rtgroup.c
@@ -159,6 +159,7 @@ xfs_initialize_rtgroups(
/* Place kernel structure only init below this point. */
spin_lock_init(&rtg->rtg_state_lock);
init_waitqueue_head(&rtg->rtg_active_wq);
+ xfs_defer_drain_init(&rtg->rtg_intents_drain);
#endif /* __KERNEL__ */
/* Active ref owned by mount indicates rtgroup is online. */
@@ -213,6 +214,7 @@ xfs_free_rtgroups(
spin_unlock(&mp->m_rtgroup_lock);
ASSERT(rtg);
XFS_IS_CORRUPT(mp, atomic_read(&rtg->rtg_ref) != 0);
+ xfs_defer_drain_free(&rtg->rtg_intents_drain);
/* drop the mount's active reference */
xfs_rtgroup_rele(rtg);
diff --git a/libxfs/xfs_rtgroup.h b/libxfs/xfs_rtgroup.h
index 559a5135820..9487c2e0047 100644
--- a/libxfs/xfs_rtgroup.h
+++ b/libxfs/xfs_rtgroup.h
@@ -39,6 +39,15 @@ struct xfs_rtgroup {
#ifdef __KERNEL__
/* -- kernel only structures below this line -- */
spinlock_t rtg_state_lock;
+
+ /*
+ * We use xfs_drain to track the number of deferred log intent items
+ * that have been queued (but not yet processed) so that waiters (e.g.
+ * scrub) will not lock resources when other threads are in the middle
+ * of processing a chain of intent items only to find momentary
+ * inconsistencies.
+ */
+ struct xfs_defer_drain rtg_intents_drain;
#endif /* __KERNEL__ */
};
