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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 <jbacik@fb.com> Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Josef Bacik
Chris Mason
parent
78a017a2c9
commit
dc046b10c8
@ -25,6 +25,9 @@
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#include "delayed-ref.h"
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#include "locking.h"
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/* Just an arbitrary number so we can be sure this happened */
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#define BACKREF_FOUND_SHARED 6
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struct extent_inode_elem {
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u64 inum;
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u64 offset;
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@ -377,7 +380,8 @@ out:
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static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
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struct btrfs_path *path, u64 time_seq,
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struct list_head *head,
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const u64 *extent_item_pos, u64 total_refs)
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const u64 *extent_item_pos, u64 total_refs,
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u64 root_objectid)
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{
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int err;
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int ret = 0;
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@ -402,6 +406,10 @@ static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
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continue;
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if (ref->count == 0)
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continue;
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if (root_objectid && ref->root_id != root_objectid) {
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ret = BACKREF_FOUND_SHARED;
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goto out;
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}
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err = __resolve_indirect_ref(fs_info, path, time_seq, ref,
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parents, extent_item_pos,
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total_refs);
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@ -561,7 +569,8 @@ static void __merge_refs(struct list_head *head, int mode)
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* smaller or equal that seq to the list
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*/
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static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
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struct list_head *prefs, u64 *total_refs)
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struct list_head *prefs, u64 *total_refs,
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u64 inum)
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{
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struct btrfs_delayed_extent_op *extent_op = head->extent_op;
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struct rb_node *n = &head->node.rb_node;
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@ -625,6 +634,16 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
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key.objectid = ref->objectid;
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key.type = BTRFS_EXTENT_DATA_KEY;
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key.offset = ref->offset;
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/*
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* Found a inum that doesn't match our known inum, we
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* know it's shared.
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*/
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if (inum && ref->objectid != inum) {
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ret = BACKREF_FOUND_SHARED;
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break;
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}
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ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
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node->bytenr,
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node->ref_mod * sgn, GFP_ATOMIC);
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@ -659,7 +678,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
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static int __add_inline_refs(struct btrfs_fs_info *fs_info,
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struct btrfs_path *path, u64 bytenr,
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int *info_level, struct list_head *prefs,
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u64 *total_refs)
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u64 *total_refs, u64 inum)
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{
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int ret = 0;
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int slot;
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@ -744,6 +763,12 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
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dref);
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key.type = BTRFS_EXTENT_DATA_KEY;
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key.offset = btrfs_extent_data_ref_offset(leaf, dref);
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if (inum && key.objectid != inum) {
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ret = BACKREF_FOUND_SHARED;
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break;
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}
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root = btrfs_extent_data_ref_root(leaf, dref);
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ret = __add_prelim_ref(prefs, root, &key, 0, 0,
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bytenr, count, GFP_NOFS);
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@ -765,7 +790,7 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
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*/
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static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
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struct btrfs_path *path, u64 bytenr,
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int info_level, struct list_head *prefs)
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int info_level, struct list_head *prefs, u64 inum)
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{
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struct btrfs_root *extent_root = fs_info->extent_root;
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int ret;
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@ -827,6 +852,12 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
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dref);
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key.type = BTRFS_EXTENT_DATA_KEY;
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key.offset = btrfs_extent_data_ref_offset(leaf, dref);
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if (inum && key.objectid != inum) {
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ret = BACKREF_FOUND_SHARED;
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break;
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}
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root = btrfs_extent_data_ref_root(leaf, dref);
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ret = __add_prelim_ref(prefs, root, &key, 0, 0,
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bytenr, count, GFP_NOFS);
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@ -854,7 +885,8 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
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static int find_parent_nodes(struct btrfs_trans_handle *trans,
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struct btrfs_fs_info *fs_info, u64 bytenr,
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u64 time_seq, struct ulist *refs,
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struct ulist *roots, const u64 *extent_item_pos)
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struct ulist *roots, const u64 *extent_item_pos,
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u64 root_objectid, u64 inum)
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{
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struct btrfs_key key;
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struct btrfs_path *path;
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@ -929,7 +961,8 @@ again:
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}
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spin_unlock(&delayed_refs->lock);
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ret = __add_delayed_refs(head, time_seq,
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&prefs_delayed, &total_refs);
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&prefs_delayed, &total_refs,
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inum);
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mutex_unlock(&head->mutex);
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if (ret)
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goto out;
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@ -951,11 +984,11 @@ again:
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key.type == BTRFS_METADATA_ITEM_KEY)) {
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ret = __add_inline_refs(fs_info, path, bytenr,
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&info_level, &prefs,
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&total_refs);
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&total_refs, inum);
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if (ret)
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goto out;
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ret = __add_keyed_refs(fs_info, path, bytenr,
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info_level, &prefs);
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info_level, &prefs, inum);
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if (ret)
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goto out;
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}
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@ -971,7 +1004,8 @@ again:
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__merge_refs(&prefs, 1);
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ret = __resolve_indirect_refs(fs_info, path, time_seq, &prefs,
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extent_item_pos, total_refs);
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extent_item_pos, total_refs,
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root_objectid);
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if (ret)
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goto out;
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@ -981,6 +1015,11 @@ again:
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ref = list_first_entry(&prefs, struct __prelim_ref, list);
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WARN_ON(ref->count < 0);
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if (roots && ref->count && ref->root_id && ref->parent == 0) {
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if (root_objectid && ref->root_id != root_objectid) {
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ret = BACKREF_FOUND_SHARED;
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goto out;
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}
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/* no parent == root of tree */
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ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
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if (ret < 0)
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@ -1087,7 +1126,7 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
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return -ENOMEM;
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ret = find_parent_nodes(trans, fs_info, bytenr,
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time_seq, *leafs, NULL, extent_item_pos);
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time_seq, *leafs, NULL, extent_item_pos, 0, 0);
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if (ret < 0 && ret != -ENOENT) {
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free_leaf_list(*leafs);
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return ret;
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@ -1130,7 +1169,7 @@ static int __btrfs_find_all_roots(struct btrfs_trans_handle *trans,
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ULIST_ITER_INIT(&uiter);
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while (1) {
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ret = find_parent_nodes(trans, fs_info, bytenr,
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time_seq, tmp, *roots, NULL);
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time_seq, tmp, *roots, NULL, 0, 0);
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if (ret < 0 && ret != -ENOENT) {
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ulist_free(tmp);
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ulist_free(*roots);
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@ -1161,6 +1200,54 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
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return ret;
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}
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int btrfs_check_shared(struct btrfs_trans_handle *trans,
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struct btrfs_fs_info *fs_info, u64 root_objectid,
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u64 inum, u64 bytenr)
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{
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struct ulist *tmp = NULL;
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struct ulist *roots = NULL;
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struct ulist_iterator uiter;
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struct ulist_node *node;
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struct seq_list elem = {};
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int ret = 0;
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tmp = ulist_alloc(GFP_NOFS);
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roots = ulist_alloc(GFP_NOFS);
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if (!tmp || !roots) {
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ulist_free(tmp);
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ulist_free(roots);
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return -ENOMEM;
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}
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if (trans)
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btrfs_get_tree_mod_seq(fs_info, &elem);
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else
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down_read(&fs_info->commit_root_sem);
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ULIST_ITER_INIT(&uiter);
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while (1) {
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ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
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roots, NULL, root_objectid, inum);
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if (ret == BACKREF_FOUND_SHARED) {
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ret = 1;
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break;
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}
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if (ret < 0 && ret != -ENOENT)
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break;
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node = ulist_next(tmp, &uiter);
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if (!node)
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break;
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bytenr = node->val;
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cond_resched();
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}
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if (trans)
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btrfs_put_tree_mod_seq(fs_info, &elem);
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else
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up_read(&fs_info->commit_root_sem);
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ulist_free(tmp);
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ulist_free(roots);
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return ret;
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}
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/*
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* this makes the path point to (inum INODE_ITEM ioff)
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*/
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@ -71,6 +71,9 @@ int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
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u64 start_off, struct btrfs_path *path,
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struct btrfs_inode_extref **ret_extref,
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u64 *found_off);
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int btrfs_check_shared(struct btrfs_trans_handle *trans,
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struct btrfs_fs_info *fs_info, u64 root_objectid,
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u64 inum, u64 bytenr);
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int __init btrfs_prelim_ref_init(void);
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void btrfs_prelim_ref_exit(void);
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@ -4169,19 +4169,6 @@ static struct extent_map *get_extent_skip_holes(struct inode *inode,
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return NULL;
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}
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static noinline int count_ext_ref(u64 inum, u64 offset, u64 root_id, void *ctx)
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{
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unsigned long cnt = *((unsigned long *)ctx);
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cnt++;
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*((unsigned long *)ctx) = cnt;
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/* Now we're sure that the extent is shared. */
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if (cnt > 1)
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return 1;
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return 0;
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}
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int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
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__u64 start, __u64 len, get_extent_t *get_extent)
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{
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@ -4198,6 +4185,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
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struct extent_map *em = NULL;
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struct extent_state *cached_state = NULL;
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struct btrfs_path *path;
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struct btrfs_root *root = BTRFS_I(inode)->root;
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int end = 0;
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u64 em_start = 0;
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u64 em_len = 0;
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@ -4218,8 +4206,8 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
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* lookup the last file extent. We're not using i_size here
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* because there might be preallocation past i_size
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*/
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ret = btrfs_lookup_file_extent(NULL, BTRFS_I(inode)->root,
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path, btrfs_ino(inode), -1, 0);
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ret = btrfs_lookup_file_extent(NULL, root, path, btrfs_ino(inode), -1,
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0);
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if (ret < 0) {
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btrfs_free_path(path);
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return ret;
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@ -4312,25 +4300,27 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
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} else if (em->block_start == EXTENT_MAP_DELALLOC) {
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flags |= (FIEMAP_EXTENT_DELALLOC |
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FIEMAP_EXTENT_UNKNOWN);
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} else {
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unsigned long ref_cnt = 0;
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} else if (fieinfo->fi_extents_max) {
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u64 bytenr = em->block_start -
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(em->start - em->orig_start);
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disko = em->block_start + offset_in_extent;
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/*
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* As btrfs supports shared space, this information
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* can be exported to userspace tools via
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* flag FIEMAP_EXTENT_SHARED.
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* flag FIEMAP_EXTENT_SHARED. If fi_extents_max == 0
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* then we're just getting a count and we can skip the
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* lookup stuff.
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*/
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ret = iterate_inodes_from_logical(
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em->block_start,
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BTRFS_I(inode)->root->fs_info,
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path, count_ext_ref, &ref_cnt);
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if (ret < 0 && ret != -ENOENT)
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ret = btrfs_check_shared(NULL, root->fs_info,
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root->objectid,
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btrfs_ino(inode), bytenr);
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if (ret < 0)
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goto out_free;
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if (ref_cnt > 1)
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if (ret)
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flags |= FIEMAP_EXTENT_SHARED;
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ret = 0;
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}
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if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
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flags |= FIEMAP_EXTENT_ENCODED;
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