On 2024/4/14 5:57, Kent Overstreet wrote:
For those interested, this is a good tour of the facilities for rolling
out new on disk format features.

-- >8 --

This adds a small (64 bit) per-device bitmap that tracks ranges that
have btree nodes, for accelerating btree node scan if it is ever needed.

- New helpers, bch2_dev_btree_bitmap_marked() and
   bch2_dev_bitmap_mark(), for checking and updating the bitmap

- Interior btree update path updates the bitmaps when required

- The check_allocations pass has a new fsck_err check,
   btree_bitmap_not_marked

- New on disk format version, mi_btree_mitmap, which indicates the new
   bitmap is present

- Upgrade table lists the required recovery pass and expected fsck error

- Btree node scan uses the bitmap to skip ranges if we're on the new
   version

Signed-off-by: Kent Overstreet <[email protected]>
---
  fs/bcachefs/bcachefs_format.h       |  7 ++--
  fs/bcachefs/btree_gc.c              | 13 +++++++
  fs/bcachefs/btree_node_scan.c       |  9 +++--
  fs/bcachefs/btree_update_interior.c | 24 +++++++++++++
  fs/bcachefs/sb-downgrade.c          |  5 ++-
  fs/bcachefs/sb-errors_types.h       |  3 +-
  fs/bcachefs/sb-members.c            | 53 +++++++++++++++++++++++++++++
  fs/bcachefs/sb-members.h            | 21 ++++++++++++
  fs/bcachefs/sb-members_types.h      |  2 ++
  9 files changed, 131 insertions(+), 6 deletions(-)

diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index 9480f1b44f07..085987435a5e 100644
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -578,7 +578,8 @@ struct bch_member {
        __le64                  nbuckets;       /* device size */
        __le16                  first_bucket;   /* index of first bucket used */
        __le16                  bucket_size;    /* sectors */
-       __le32                  pad;
+       __u8                    btree_bitmap_shift;
+       __u8                    pad[3];
        __le64                  last_mount;     /* time_t */
__le64 flags;
@@ -587,6 +588,7 @@ struct bch_member {
        __le64                  errors_at_reset[BCH_MEMBER_ERROR_NR];
        __le64                  errors_reset_time;
        __le64                  seq;
+       __le64                  btree_allocated_bitmap;
  };
#define BCH_MEMBER_V1_BYTES 56
@@ -876,7 +878,8 @@ struct bch_sb_field_downgrade {
        x(rebalance_work,               BCH_VERSION(1,  3))             \
        x(member_seq,                   BCH_VERSION(1,  4))             \
        x(subvolume_fs_parent,          BCH_VERSION(1,  5))             \
-       x(btree_subvolume_children,     BCH_VERSION(1,  6))
+       x(btree_subvolume_children,     BCH_VERSION(1,  6))             \
+       x(mi_btree_bitmap,              BCH_VERSION(1,  7))
enum bcachefs_metadata_version {
        bcachefs_metadata_version_min = 9,
diff --git a/fs/bcachefs/btree_gc.c b/fs/bcachefs/btree_gc.c
index 10c41cf89212..a77c723a9cef 100644
--- a/fs/bcachefs/btree_gc.c
+++ b/fs/bcachefs/btree_gc.c
@@ -822,6 +822,7 @@ static int bch2_gc_mark_key(struct btree_trans *trans, enum 
btree_id btree_id,
        struct bch_fs *c = trans->c;
        struct bkey deleted = KEY(0, 0, 0);
        struct bkey_s_c old = (struct bkey_s_c) { &deleted, NULL };
+       struct printbuf buf = PRINTBUF;
        int ret = 0;
deleted.p = k->k->p;
@@ -842,11 +843,23 @@ static int bch2_gc_mark_key(struct btree_trans *trans, 
enum btree_id btree_id,
        if (ret)
                goto err;
+ if (mustfix_fsck_err_on(level && !bch2_dev_btree_bitmap_marked(c, *k),
+                               c, btree_bitmap_not_marked,
+                               "btree ptr not marked in member info btree allocated 
bitmap\n  %s",
+                               (bch2_bkey_val_to_text(&buf, c, *k),
+                                buf.buf))) {
+               mutex_lock(&c->sb_lock);
+               bch2_dev_btree_bitmap_mark(c, *k);
+               bch2_write_super(c);
+               mutex_unlock(&c->sb_lock);
+       }
+
        ret = commit_do(trans, NULL, NULL, 0,
                        bch2_key_trigger(trans, btree_id, level, old,
                                         unsafe_bkey_s_c_to_s(*k), 
BTREE_TRIGGER_gc));
  fsck_err:
  err:
+       printbuf_exit(&buf);
        bch_err_fn(c, ret);
        return ret;
  }
diff --git a/fs/bcachefs/btree_node_scan.c b/fs/bcachefs/btree_node_scan.c
index 20f2b37c4474..866bd278439f 100644
--- a/fs/bcachefs/btree_node_scan.c
+++ b/fs/bcachefs/btree_node_scan.c
@@ -205,8 +205,13 @@ static int read_btree_nodes_worker(void *p)
                                last_print = jiffies;
                        }
- try_read_btree_node(w->f, ca, bio, buf,
-                                           bucket * ca->mi.bucket_size + 
bucket_offset);
+                       u64 sector = bucket * ca->mi.bucket_size + 
bucket_offset;
+
+                       if (c->sb.version_upgrade_complete >= 
bcachefs_metadata_version_mi_btree_bitmap &&
+                           !bch2_dev_btree_bitmap_marked_sectors(ca, sector, 
btree_sectors(c)))
+                               continue;
+
+                       try_read_btree_node(w->f, ca, bio, buf, sector);
                }
  err:
        bio_put(bio);
diff --git a/fs/bcachefs/btree_update_interior.c 
b/fs/bcachefs/btree_update_interior.c
index 593241b15aa8..12ce6287416f 100644
--- a/fs/bcachefs/btree_update_interior.c
+++ b/fs/bcachefs/btree_update_interior.c
@@ -21,6 +21,7 @@
  #include "keylist.h"
  #include "recovery_passes.h"
  #include "replicas.h"
+#include "sb-members.h"
  #include "super-io.h"
  #include "trace.h"
@@ -644,6 +645,26 @@ static int btree_update_nodes_written_trans(struct btree_trans *trans,
        return 0;
  }
+static bool btree_update_new_nodes_marked_sb(struct btree_update *as)
+{
+       for_each_keylist_key(&as->new_keys, k)
+               if (!bch2_dev_btree_bitmap_marked(as->c, bkey_i_to_s_c(k)))
+                       return false;
+       return true;
+}
+
+static void btree_update_new_nodes_mark_sb(struct btree_update *as)
+{
+       struct bch_fs *c = as->c;
+
+       mutex_lock(&c->sb_lock);
+       for_each_keylist_key(&as->new_keys, k)
+               bch2_dev_btree_bitmap_mark(c, bkey_i_to_s_c(k));
+
+       bch2_write_super(c);
+       mutex_unlock(&c->sb_lock);
+}
+
  static void btree_update_nodes_written(struct btree_update *as)
  {
        struct bch_fs *c = as->c;
@@ -664,6 +685,9 @@ static void btree_update_nodes_written(struct btree_update 
*as)
        if (ret)
                goto err;
+ if (!btree_update_new_nodes_marked_sb(as))
+               btree_update_new_nodes_mark_sb(as);
+
        /*
         * Wait for any in flight writes to finish before we free the old nodes
         * on disk:
diff --git a/fs/bcachefs/sb-downgrade.c b/fs/bcachefs/sb-downgrade.c
index 56ac8f35cdc3..90b06f8aa1df 100644
--- a/fs/bcachefs/sb-downgrade.c
+++ b/fs/bcachefs/sb-downgrade.c
@@ -51,7 +51,10 @@
          BCH_FSCK_ERR_subvol_fs_path_parent_wrong)             \
        x(btree_subvolume_children,                             \
          BIT_ULL(BCH_RECOVERY_PASS_check_subvols),             \
-         BCH_FSCK_ERR_subvol_children_not_set)
+         BCH_FSCK_ERR_subvol_children_not_set)                 \
+       x(mi_btree_bitmap,                                      \
+         BIT_ULL(BCH_RECOVERY_PASS_check_allocations),         \
+         BCH_FSCK_ERR_btree_bitmap_not_marked)
#define DOWNGRADE_TABLE() diff --git a/fs/bcachefs/sb-errors_types.h b/fs/bcachefs/sb-errors_types.h
index d7d609131030..5b600c6d7aca 100644
--- a/fs/bcachefs/sb-errors_types.h
+++ b/fs/bcachefs/sb-errors_types.h
@@ -270,7 +270,8 @@
        x(btree_ptr_v2_min_key_bad,                             262)    \
        x(btree_root_unreadable_and_scan_found_nothing,         263)    \
        x(snapshot_node_missing,                                264)    \
-       x(dup_backpointer_to_bad_csum_extent,                   265)
+       x(dup_backpointer_to_bad_csum_extent,                   265)    \
+       x(btree_bitmap_not_marked,                              266)
enum bch_sb_error_id {
  #define x(t, n) BCH_FSCK_ERR_##t = n,
diff --git a/fs/bcachefs/sb-members.c b/fs/bcachefs/sb-members.c
index 9b7a2f300182..d5937aba0910 100644
--- a/fs/bcachefs/sb-members.c
+++ b/fs/bcachefs/sb-members.c
@@ -1,6 +1,7 @@
  // SPDX-License-Identifier: GPL-2.0
#include "bcachefs.h"
+#include "btree_cache.h"
  #include "disk_groups.h"
  #include "opts.h"
  #include "replicas.h"
@@ -378,3 +379,55 @@ void bch2_dev_errors_reset(struct bch_dev *ca)
        bch2_write_super(c);
        mutex_unlock(&c->sb_lock);
  }
+
+/*
+ * Per member "range has btree nodes" bitmap:
+ *
+ * This is so that if we ever have to run the btree node scan to repair we 
don't
+ * have to scan full devices:
+ */
+
+bool bch2_dev_btree_bitmap_marked(struct bch_fs *c, struct bkey_s_c k)
+{
+       bkey_for_each_ptr(bch2_bkey_ptrs_c(k), ptr)
+               if (!bch2_dev_btree_bitmap_marked_sectors(bch2_dev_bkey_exists(c, 
ptr->dev),
+                                                         ptr->offset, 
btree_sectors(c)))
+                       return false;
+       return true;
+}
+
+static void __bch2_dev_btree_bitmap_mark(struct bch_sb_field_members_v2 *mi, 
unsigned dev,
+                               u64 start, unsigned sectors)
+{
+       struct bch_member *m = __bch2_members_v2_get_mut(mi, dev);
+       u64 bitmap = le64_to_cpu(m->btree_allocated_bitmap);
+
+       u64 end = start + sectors;
+
+       int resize = ilog2(roundup_pow_of_two(end)) - (m->btree_bitmap_shift + 
6);
+       if (resize > 0) {
+               u64 new_bitmap = 0;
+
+               for (unsigned i = 0; i < 64; i++)
+                       if (bitmap & BIT_ULL(i))
+                               new_bitmap |= BIT_ULL(i >> resize);
+               bitmap = new_bitmap;
+               m->btree_bitmap_shift += resize;
+       }
+
+       for (unsigned bit = sectors >> m->btree_bitmap_shift;
+            bit << m->btree_bitmap_shift < end;
+            bit++)
+               bitmap |= BIT_ULL(bit);
+
+       m->btree_allocated_bitmap = cpu_to_le64(bitmap);
+}
+
+void bch2_dev_btree_bitmap_mark(struct bch_fs *c, struct bkey_s_c k)
+{
+       lockdep_assert_held(&c->sb_lock);
+
+       struct bch_sb_field_members_v2 *mi = bch2_sb_field_get(c->disk_sb.sb, 
members_v2);
+       bkey_for_each_ptr(bch2_bkey_ptrs_c(k), ptr)
+               __bch2_dev_btree_bitmap_mark(mi, ptr->dev, ptr->offset, 
btree_sectors(c));
+}
diff --git a/fs/bcachefs/sb-members.h b/fs/bcachefs/sb-members.h
index bc3bcfef7b3a..8bbad30a4370 100644
--- a/fs/bcachefs/sb-members.h
+++ b/fs/bcachefs/sb-members.h
@@ -3,6 +3,7 @@
  #define _BCACHEFS_SB_MEMBERS_H
#include "darray.h"
+#include "bkey_types.h"
extern char * const bch2_member_error_strs[]; @@ -234,6 +235,8 @@ static inline struct bch_member_cpu bch2_mi_to_cpu(struct bch_member *mi)
                        : 1,
                .freespace_initialized = BCH_MEMBER_FREESPACE_INITIALIZED(mi),
                .valid          = bch2_member_alive(mi),
+               .btree_bitmap_shift     = mi->btree_bitmap_shift,
+               .btree_allocated_bitmap = 
le64_to_cpu(mi->btree_allocated_bitmap),
        };
  }
@@ -242,4 +245,22 @@ void bch2_sb_members_from_cpu(struct bch_fs *);
  void bch2_dev_io_errors_to_text(struct printbuf *, struct bch_dev *);
  void bch2_dev_errors_reset(struct bch_dev *);
+static inline bool bch2_dev_btree_bitmap_marked_sectors(struct bch_dev *ca, u64 start, unsigned sectors)
+{
+       u64 end = start + sectors;
+
+       if (end > 64 << ca->mi.btree_bitmap_shift)
+               return false;
+
+       for (unsigned bit = sectors >> ca->mi.btree_bitmap_shift;
+            bit << ca->mi.btree_bitmap_shift < end;
+            bit++)
+               if (!(ca->mi.btree_allocated_bitmap & BIT_ULL(bit)))
Should it be transferred by le64_to_cpu?
+                       return false;
+       return true;
+}
+
+bool bch2_dev_btree_bitmap_marked(struct bch_fs *, struct bkey_s_c);
+void bch2_dev_btree_bitmap_mark(struct bch_fs *, struct bkey_s_c);
+
  #endif /* _BCACHEFS_SB_MEMBERS_H */
diff --git a/fs/bcachefs/sb-members_types.h b/fs/bcachefs/sb-members_types.h
index 3f915536d554..c0eda888fe39 100644
--- a/fs/bcachefs/sb-members_types.h
+++ b/fs/bcachefs/sb-members_types.h
@@ -14,6 +14,8 @@ struct bch_member_cpu {
        u8                      durability;
        u8                      freespace_initialized;
        u8                      valid;
+       u8                      btree_bitmap_shift;
+       u64                     btree_allocated_bitmap;
  };
#endif /* _BCACHEFS_SB_MEMBERS_H */

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