From 3ec4d3238ab1655ae3f696c412fb3244cd3b58de Mon Sep 17 00:00:00 2001 From: Edmund Nadolski Date: Wed, 12 Jul 2017 16:20:10 -0600 Subject: [PATCH] btrfs: allow backref search checks for shared extents When called with a struct share_check, find_parent_nodes() will detect a shared extent and immediately return with BACKREF_SHARED_FOUND. Signed-off-by: Edmund Nadolski Signed-off-by: Jeff Mahoney Reviewed-by: Liu Bo Signed-off-by: David Sterba --- fs/btrfs/backref.c | 164 +++++++++++++++++++++++++++++++-------------- 1 file changed, 115 insertions(+), 49 deletions(-) diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c index 9593102bdc2c..2a983a640069 100644 --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -134,6 +134,25 @@ struct preftrees { struct preftree indirect_missing_keys; }; +/* + * Checks for a shared extent during backref search. + * + * The share_count tracks prelim_refs (direct and indirect) having a + * ref->count >0: + * - incremented when a ref->count transitions to >0 + * - decremented when a ref->count transitions to <1 + */ +struct share_check { + u64 root_objectid; + u64 inum; + int share_count; +}; + +static inline int extent_is_shared(struct share_check *sc) +{ + return (sc && sc->share_count > 1) ? BACKREF_FOUND_SHARED : 0; +} + static struct kmem_cache *btrfs_prelim_ref_cache; int __init btrfs_prelim_ref_init(void) @@ -194,14 +213,26 @@ static int prelim_ref_compare(struct prelim_ref *ref1, return 0; } +void update_share_count(struct share_check *sc, int oldcount, int newcount) +{ + if ((!sc) || (oldcount == 0 && newcount < 1)) + return; + + if (oldcount > 0 && newcount < 1) + sc->share_count--; + else if (oldcount < 1 && newcount > 0) + sc->share_count++; +} + /* * Add @newref to the @root rbtree, merging identical refs. * - * Callers should assumed that newref has been freed after calling. + * Callers should assume that newref has been freed after calling. */ static void prelim_ref_insert(const struct btrfs_fs_info *fs_info, struct preftree *preftree, - struct prelim_ref *newref) + struct prelim_ref *newref, + struct share_check *sc) { struct rb_root *root; struct rb_node **p; @@ -233,12 +264,20 @@ static void prelim_ref_insert(const struct btrfs_fs_info *fs_info, eie->next = newref->inode_list; trace_btrfs_prelim_ref_merge(fs_info, ref, newref, preftree->count); + /* + * A delayed ref can have newref->count < 0. + * The ref->count is updated to follow any + * BTRFS_[ADD|DROP]_DELAYED_REF actions. + */ + update_share_count(sc, ref->count, + ref->count + newref->count); ref->count += newref->count; free_pref(newref); return; } } + update_share_count(sc, 0, newref->count); preftree->count++; trace_btrfs_prelim_ref_insert(fs_info, newref, NULL, preftree->count); rb_link_node(&newref->rbnode, parent, p); @@ -302,7 +341,8 @@ static void prelim_release(struct preftree *preftree) static int add_prelim_ref(const struct btrfs_fs_info *fs_info, struct preftree *preftree, u64 root_id, const struct btrfs_key *key, int level, u64 parent, - u64 wanted_disk_byte, int count, gfp_t gfp_mask) + u64 wanted_disk_byte, int count, + struct share_check *sc, gfp_t gfp_mask) { struct prelim_ref *ref; @@ -347,32 +387,33 @@ static int add_prelim_ref(const struct btrfs_fs_info *fs_info, ref->count = count; ref->parent = parent; ref->wanted_disk_byte = wanted_disk_byte; - prelim_ref_insert(fs_info, preftree, ref); - - return 0; + prelim_ref_insert(fs_info, preftree, ref, sc); + return extent_is_shared(sc); } /* direct refs use root == 0, key == NULL */ static int add_direct_ref(const struct btrfs_fs_info *fs_info, struct preftrees *preftrees, int level, u64 parent, - u64 wanted_disk_byte, int count, gfp_t gfp_mask) + u64 wanted_disk_byte, int count, + struct share_check *sc, gfp_t gfp_mask) { return add_prelim_ref(fs_info, &preftrees->direct, 0, NULL, level, - parent, wanted_disk_byte, count, gfp_mask); + parent, wanted_disk_byte, count, sc, gfp_mask); } /* indirect refs use parent == 0 */ static int add_indirect_ref(const struct btrfs_fs_info *fs_info, struct preftrees *preftrees, u64 root_id, const struct btrfs_key *key, int level, - u64 wanted_disk_byte, int count, gfp_t gfp_mask) + u64 wanted_disk_byte, int count, + struct share_check *sc, gfp_t gfp_mask) { struct preftree *tree = &preftrees->indirect; if (!key) tree = &preftrees->indirect_missing_keys; return add_prelim_ref(fs_info, tree, root_id, key, level, 0, - wanted_disk_byte, count, gfp_mask); + wanted_disk_byte, count, sc, gfp_mask); } static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path, @@ -575,7 +616,7 @@ static int resolve_indirect_refs(struct btrfs_fs_info *fs_info, struct btrfs_path *path, u64 time_seq, struct preftrees *preftrees, const u64 *extent_item_pos, u64 total_refs, - u64 root_objectid) + struct share_check *sc) { int err; int ret = 0; @@ -612,7 +653,8 @@ static int resolve_indirect_refs(struct btrfs_fs_info *fs_info, continue; } - if (root_objectid && ref->root_id != root_objectid) { + if (sc && sc->root_objectid && + ref->root_id != sc->root_objectid) { free_pref(ref); ret = BACKREF_FOUND_SHARED; goto out; @@ -625,7 +667,8 @@ static int resolve_indirect_refs(struct btrfs_fs_info *fs_info, * and return directly. */ if (err == -ENOENT) { - prelim_ref_insert(fs_info, &preftrees->direct, ref); + prelim_ref_insert(fs_info, &preftrees->direct, ref, + NULL); continue; } else if (err) { free_pref(ref); @@ -653,11 +696,15 @@ static int resolve_indirect_refs(struct btrfs_fs_info *fs_info, memcpy(new_ref, ref, sizeof(*ref)); new_ref->parent = node->val; new_ref->inode_list = unode_aux_to_inode_list(node); - prelim_ref_insert(fs_info, &preftrees->direct, new_ref); + prelim_ref_insert(fs_info, &preftrees->direct, + new_ref, NULL); } - /* Now it's a direct ref, put it in the the direct tree */ - prelim_ref_insert(fs_info, &preftrees->direct, ref); + /* + * Now it's a direct ref, put it in the the direct tree. We must + * do this last because the ref could be merged/freed here. + */ + prelim_ref_insert(fs_info, &preftrees->direct, ref, NULL); ulist_reinit(parents); cond_resched(); @@ -702,7 +749,7 @@ static int add_missing_keys(struct btrfs_fs_info *fs_info, btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0); btrfs_tree_read_unlock(eb); free_extent_buffer(eb); - prelim_ref_insert(fs_info, &preftrees->indirect, ref); + prelim_ref_insert(fs_info, &preftrees->indirect, ref, NULL); cond_resched(); } return 0; @@ -715,7 +762,7 @@ static int add_missing_keys(struct btrfs_fs_info *fs_info, static int add_delayed_refs(const struct btrfs_fs_info *fs_info, struct btrfs_delayed_ref_head *head, u64 seq, struct preftrees *preftrees, u64 *total_refs, - u64 inum) + struct share_check *sc) { struct btrfs_delayed_ref_node *node; struct btrfs_delayed_extent_op *extent_op = head->extent_op; @@ -760,7 +807,7 @@ static int add_delayed_refs(const struct btrfs_fs_info *fs_info, &tmp_op_key, ref->level + 1, node->bytenr, node->ref_mod * sgn, - GFP_ATOMIC); + sc, GFP_ATOMIC); break; } case BTRFS_SHARED_BLOCK_REF_KEY: { @@ -772,7 +819,7 @@ static int add_delayed_refs(const struct btrfs_fs_info *fs_info, ret = add_direct_ref(fs_info, preftrees, ref->level + 1, ref->parent, node->bytenr, node->ref_mod * sgn, - GFP_ATOMIC); + sc, GFP_ATOMIC); break; } case BTRFS_EXTENT_DATA_REF_KEY: { @@ -788,15 +835,15 @@ static int add_delayed_refs(const struct btrfs_fs_info *fs_info, * Found a inum that doesn't match our known inum, we * know it's shared. */ - if (inum && ref->objectid != inum) { + if (sc && sc->inum && ref->objectid != sc->inum) { ret = BACKREF_FOUND_SHARED; - break; + goto out; } ret = add_indirect_ref(fs_info, preftrees, ref->root, &key, 0, node->bytenr, node->ref_mod * sgn, - GFP_ATOMIC); + sc, GFP_ATOMIC); break; } case BTRFS_SHARED_DATA_REF_KEY: { @@ -808,26 +855,35 @@ static int add_delayed_refs(const struct btrfs_fs_info *fs_info, ret = add_direct_ref(fs_info, preftrees, 0, ref->parent, node->bytenr, node->ref_mod * sgn, - GFP_ATOMIC); + sc, GFP_ATOMIC); break; } default: WARN_ON(1); } - if (ret) + /* + * We must ignore BACKREF_FOUND_SHARED until all delayed + * refs have been checked. + */ + if (ret && (ret != BACKREF_FOUND_SHARED)) break; } + if (!ret) + ret = extent_is_shared(sc); +out: spin_unlock(&head->lock); return ret; } /* * add all inline backrefs for bytenr to the list + * + * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED. */ static int add_inline_refs(const struct btrfs_fs_info *fs_info, struct btrfs_path *path, u64 bytenr, int *info_level, struct preftrees *preftrees, - u64 *total_refs, u64 inum) + u64 *total_refs, struct share_check *sc) { int ret = 0; int slot; @@ -884,7 +940,7 @@ static int add_inline_refs(const struct btrfs_fs_info *fs_info, case BTRFS_SHARED_BLOCK_REF_KEY: ret = add_direct_ref(fs_info, preftrees, *info_level + 1, offset, - bytenr, 1, GFP_NOFS); + bytenr, 1, NULL, GFP_NOFS); break; case BTRFS_SHARED_DATA_REF_KEY: { struct btrfs_shared_data_ref *sdref; @@ -894,13 +950,13 @@ static int add_inline_refs(const struct btrfs_fs_info *fs_info, count = btrfs_shared_data_ref_count(leaf, sdref); ret = add_direct_ref(fs_info, preftrees, 0, offset, - bytenr, count, GFP_NOFS); + bytenr, count, sc, GFP_NOFS); break; } case BTRFS_TREE_BLOCK_REF_KEY: ret = add_indirect_ref(fs_info, preftrees, offset, NULL, *info_level + 1, - bytenr, 1, GFP_NOFS); + bytenr, 1, NULL, GFP_NOFS); break; case BTRFS_EXTENT_DATA_REF_KEY: { struct btrfs_extent_data_ref *dref; @@ -914,7 +970,7 @@ static int add_inline_refs(const struct btrfs_fs_info *fs_info, key.type = BTRFS_EXTENT_DATA_KEY; key.offset = btrfs_extent_data_ref_offset(leaf, dref); - if (inum && key.objectid != inum) { + if (sc && sc->inum && key.objectid != sc->inum) { ret = BACKREF_FOUND_SHARED; break; } @@ -923,7 +979,7 @@ static int add_inline_refs(const struct btrfs_fs_info *fs_info, ret = add_indirect_ref(fs_info, preftrees, root, &key, 0, bytenr, count, - GFP_NOFS); + sc, GFP_NOFS); break; } default: @@ -939,11 +995,13 @@ static int add_inline_refs(const struct btrfs_fs_info *fs_info, /* * add all non-inline backrefs for bytenr to the list + * + * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED. */ static int add_keyed_refs(struct btrfs_fs_info *fs_info, struct btrfs_path *path, u64 bytenr, int info_level, struct preftrees *preftrees, - u64 inum) + struct share_check *sc) { struct btrfs_root *extent_root = fs_info->extent_root; int ret; @@ -976,7 +1034,7 @@ static int add_keyed_refs(struct btrfs_fs_info *fs_info, /* SHARED DIRECT METADATA backref */ ret = add_direct_ref(fs_info, preftrees, info_level + 1, key.offset, - bytenr, 1, GFP_NOFS); + bytenr, 1, NULL, GFP_NOFS); break; case BTRFS_SHARED_DATA_REF_KEY: { /* SHARED DIRECT FULL backref */ @@ -988,14 +1046,14 @@ static int add_keyed_refs(struct btrfs_fs_info *fs_info, count = btrfs_shared_data_ref_count(leaf, sdref); ret = add_direct_ref(fs_info, preftrees, 0, key.offset, bytenr, count, - GFP_NOFS); + sc, GFP_NOFS); break; } case BTRFS_TREE_BLOCK_REF_KEY: /* NORMAL INDIRECT METADATA backref */ ret = add_indirect_ref(fs_info, preftrees, key.offset, NULL, info_level + 1, bytenr, - 1, GFP_NOFS); + 1, NULL, GFP_NOFS); break; case BTRFS_EXTENT_DATA_REF_KEY: { /* NORMAL INDIRECT DATA backref */ @@ -1011,7 +1069,7 @@ static int add_keyed_refs(struct btrfs_fs_info *fs_info, key.type = BTRFS_EXTENT_DATA_KEY; key.offset = btrfs_extent_data_ref_offset(leaf, dref); - if (inum && key.objectid != inum) { + if (sc && sc->inum && key.objectid != sc->inum) { ret = BACKREF_FOUND_SHARED; break; } @@ -1019,7 +1077,7 @@ static int add_keyed_refs(struct btrfs_fs_info *fs_info, root = btrfs_extent_data_ref_root(leaf, dref); ret = add_indirect_ref(fs_info, preftrees, root, &key, 0, bytenr, count, - GFP_NOFS); + sc, GFP_NOFS); break; } default: @@ -1039,20 +1097,23 @@ static int add_keyed_refs(struct btrfs_fs_info *fs_info, * indirect refs to their parent bytenr. * When roots are found, they're added to the roots list * - * NOTE: This can return values > 0 - * * If time_seq is set to SEQ_LAST, it will not search delayed_refs, and behave * much like trans == NULL case, the difference only lies in it will not * commit root. * The special case is for qgroup to search roots in commit_transaction(). * + * @sc - if !NULL, then immediately return BACKREF_FOUND_SHARED when a + * shared extent is detected. + * + * Otherwise this returns 0 for success and <0 for an error. + * * FIXME some caching might speed things up */ static int find_parent_nodes(struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info, u64 bytenr, u64 time_seq, struct ulist *refs, struct ulist *roots, const u64 *extent_item_pos, - u64 root_objectid, u64 inum) + struct share_check *sc) { struct btrfs_key key; struct btrfs_path *path; @@ -1133,7 +1194,7 @@ again: } spin_unlock(&delayed_refs->lock); ret = add_delayed_refs(fs_info, head, time_seq, - &preftrees, &total_refs, inum); + &preftrees, &total_refs, sc); mutex_unlock(&head->mutex); if (ret) goto out; @@ -1155,11 +1216,11 @@ again: key.type == BTRFS_METADATA_ITEM_KEY)) { ret = add_inline_refs(fs_info, path, bytenr, &info_level, &preftrees, - &total_refs, inum); + &total_refs, sc); if (ret) goto out; ret = add_keyed_refs(fs_info, path, bytenr, info_level, - &preftrees, inum); + &preftrees, sc); if (ret) goto out; } @@ -1174,8 +1235,7 @@ again: WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root)); ret = resolve_indirect_refs(fs_info, path, time_seq, &preftrees, - extent_item_pos, total_refs, - root_objectid); + extent_item_pos, total_refs, sc); if (ret) goto out; @@ -1194,7 +1254,8 @@ again: node = rb_next(&ref->rbnode); WARN_ON(ref->count < 0); if (roots && ref->count && ref->root_id && ref->parent == 0) { - if (root_objectid && ref->root_id != root_objectid) { + if (sc && sc->root_objectid && + ref->root_id != sc->root_objectid) { ret = BACKREF_FOUND_SHARED; goto out; } @@ -1298,7 +1359,7 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans, return -ENOMEM; ret = find_parent_nodes(trans, fs_info, bytenr, time_seq, - *leafs, NULL, extent_item_pos, 0, 0); + *leafs, NULL, extent_item_pos, NULL); if (ret < 0 && ret != -ENOENT) { free_leaf_list(*leafs); return ret; @@ -1341,7 +1402,7 @@ static int btrfs_find_all_roots_safe(struct btrfs_trans_handle *trans, ULIST_ITER_INIT(&uiter); while (1) { ret = find_parent_nodes(trans, fs_info, bytenr, time_seq, - tmp, *roots, NULL, 0, 0); + tmp, *roots, NULL, NULL); if (ret < 0 && ret != -ENOENT) { ulist_free(tmp); ulist_free(*roots); @@ -1397,6 +1458,11 @@ int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr) struct ulist_node *node; struct seq_list elem = SEQ_LIST_INIT(elem); int ret = 0; + struct share_check shared = { + .root_objectid = root->objectid, + .inum = inum, + .share_count = 0, + }; tmp = ulist_alloc(GFP_NOFS); roots = ulist_alloc(GFP_NOFS); @@ -1417,7 +1483,7 @@ int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr) ULIST_ITER_INIT(&uiter); while (1) { ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp, - roots, NULL, root->objectid, inum); + roots, NULL, &shared); if (ret == BACKREF_FOUND_SHARED) { /* this is the only condition under which we return 1 */ ret = 1; -- 2.20.1