From dc046b10c8b7d4f40befe457acb82340bf8b0699 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Wed, 10 Sep 2014 16:20:45 -0400 Subject: Btrfs: make fiemap not blow when you have lots of snapshots We have been iterating all references for each extent we have in a file when we do fiemap to see if it is shared. This is fine when you have a few clones or a few snapshots, but when you have 5k snapshots suddenly fiemap just sits there and stares at you. So add btrfs_check_shared which will use the backref walking code but will short circuit as soon as it finds a root or inode that doesn't match the one we currently have. This makes fiemap on my testbox go from looking at me blankly for a day to spitting out actual output in a reasonable amount of time. Thanks, Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/backref.c | 109 +++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 98 insertions(+), 11 deletions(-) (limited to 'fs/btrfs/backref.c') diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c index 4de97926939e..6829dc5aa657 100644 --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -25,6 +25,9 @@ #include "delayed-ref.h" #include "locking.h" +/* Just an arbitrary number so we can be sure this happened */ +#define BACKREF_FOUND_SHARED 6 + struct extent_inode_elem { u64 inum; u64 offset; @@ -377,7 +380,8 @@ out: static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info, struct btrfs_path *path, u64 time_seq, struct list_head *head, - const u64 *extent_item_pos, u64 total_refs) + const u64 *extent_item_pos, u64 total_refs, + u64 root_objectid) { int err; int ret = 0; @@ -402,6 +406,10 @@ static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info, continue; if (ref->count == 0) continue; + if (root_objectid && ref->root_id != root_objectid) { + ret = BACKREF_FOUND_SHARED; + goto out; + } err = __resolve_indirect_ref(fs_info, path, time_seq, ref, parents, extent_item_pos, total_refs); @@ -561,7 +569,8 @@ static void __merge_refs(struct list_head *head, int mode) * smaller or equal that seq to the list */ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, - struct list_head *prefs, u64 *total_refs) + struct list_head *prefs, u64 *total_refs, + u64 inum) { struct btrfs_delayed_extent_op *extent_op = head->extent_op; struct rb_node *n = &head->node.rb_node; @@ -625,6 +634,16 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, key.objectid = ref->objectid; key.type = BTRFS_EXTENT_DATA_KEY; key.offset = ref->offset; + + /* + * Found a inum that doesn't match our known inum, we + * know it's shared. + */ + if (inum && ref->objectid != inum) { + ret = BACKREF_FOUND_SHARED; + break; + } + ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0, node->bytenr, node->ref_mod * sgn, GFP_ATOMIC); @@ -659,7 +678,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, static int __add_inline_refs(struct btrfs_fs_info *fs_info, struct btrfs_path *path, u64 bytenr, int *info_level, struct list_head *prefs, - u64 *total_refs) + u64 *total_refs, u64 inum) { int ret = 0; int slot; @@ -744,6 +763,12 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info, dref); key.type = BTRFS_EXTENT_DATA_KEY; key.offset = btrfs_extent_data_ref_offset(leaf, dref); + + if (inum && key.objectid != inum) { + ret = BACKREF_FOUND_SHARED; + break; + } + root = btrfs_extent_data_ref_root(leaf, dref); ret = __add_prelim_ref(prefs, root, &key, 0, 0, bytenr, count, GFP_NOFS); @@ -765,7 +790,7 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info, */ static int __add_keyed_refs(struct btrfs_fs_info *fs_info, struct btrfs_path *path, u64 bytenr, - int info_level, struct list_head *prefs) + int info_level, struct list_head *prefs, u64 inum) { struct btrfs_root *extent_root = fs_info->extent_root; int ret; @@ -827,6 +852,12 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info, dref); key.type = BTRFS_EXTENT_DATA_KEY; key.offset = btrfs_extent_data_ref_offset(leaf, dref); + + if (inum && key.objectid != inum) { + ret = BACKREF_FOUND_SHARED; + break; + } + root = btrfs_extent_data_ref_root(leaf, dref); ret = __add_prelim_ref(prefs, root, &key, 0, 0, bytenr, count, GFP_NOFS); @@ -854,7 +885,8 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info, 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) + struct ulist *roots, const u64 *extent_item_pos, + u64 root_objectid, u64 inum) { struct btrfs_key key; struct btrfs_path *path; @@ -929,7 +961,8 @@ again: } spin_unlock(&delayed_refs->lock); ret = __add_delayed_refs(head, time_seq, - &prefs_delayed, &total_refs); + &prefs_delayed, &total_refs, + inum); mutex_unlock(&head->mutex); if (ret) goto out; @@ -951,11 +984,11 @@ again: key.type == BTRFS_METADATA_ITEM_KEY)) { ret = __add_inline_refs(fs_info, path, bytenr, &info_level, &prefs, - &total_refs); + &total_refs, inum); if (ret) goto out; ret = __add_keyed_refs(fs_info, path, bytenr, - info_level, &prefs); + info_level, &prefs, inum); if (ret) goto out; } @@ -971,7 +1004,8 @@ again: __merge_refs(&prefs, 1); ret = __resolve_indirect_refs(fs_info, path, time_seq, &prefs, - extent_item_pos, total_refs); + extent_item_pos, total_refs, + root_objectid); if (ret) goto out; @@ -981,6 +1015,11 @@ again: ref = list_first_entry(&prefs, struct __prelim_ref, list); WARN_ON(ref->count < 0); if (roots && ref->count && ref->root_id && ref->parent == 0) { + if (root_objectid && ref->root_id != root_objectid) { + ret = BACKREF_FOUND_SHARED; + goto out; + } + /* no parent == root of tree */ ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS); if (ret < 0) @@ -1087,7 +1126,7 @@ 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); + time_seq, *leafs, NULL, extent_item_pos, 0, 0); if (ret < 0 && ret != -ENOENT) { free_leaf_list(*leafs); return ret; @@ -1130,7 +1169,7 @@ static int __btrfs_find_all_roots(struct btrfs_trans_handle *trans, ULIST_ITER_INIT(&uiter); while (1) { ret = find_parent_nodes(trans, fs_info, bytenr, - time_seq, tmp, *roots, NULL); + time_seq, tmp, *roots, NULL, 0, 0); if (ret < 0 && ret != -ENOENT) { ulist_free(tmp); ulist_free(*roots); @@ -1161,6 +1200,54 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans, return ret; } +int btrfs_check_shared(struct btrfs_trans_handle *trans, + struct btrfs_fs_info *fs_info, u64 root_objectid, + u64 inum, u64 bytenr) +{ + struct ulist *tmp = NULL; + struct ulist *roots = NULL; + struct ulist_iterator uiter; + struct ulist_node *node; + struct seq_list elem = {}; + int ret = 0; + + tmp = ulist_alloc(GFP_NOFS); + roots = ulist_alloc(GFP_NOFS); + if (!tmp || !roots) { + ulist_free(tmp); + ulist_free(roots); + return -ENOMEM; + } + + if (trans) + btrfs_get_tree_mod_seq(fs_info, &elem); + else + down_read(&fs_info->commit_root_sem); + ULIST_ITER_INIT(&uiter); + while (1) { + ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp, + roots, NULL, root_objectid, inum); + if (ret == BACKREF_FOUND_SHARED) { + ret = 1; + break; + } + if (ret < 0 && ret != -ENOENT) + break; + node = ulist_next(tmp, &uiter); + if (!node) + break; + bytenr = node->val; + cond_resched(); + } + if (trans) + btrfs_put_tree_mod_seq(fs_info, &elem); + else + up_read(&fs_info->commit_root_sem); + ulist_free(tmp); + ulist_free(roots); + return ret; +} + /* * this makes the path point to (inum INODE_ITEM ioff) */ -- cgit v1.2.3