From 0ad4f36bf387e3513b0401eed7abeda7bbffe4e1 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Wed, 22 Nov 2017 17:03:22 +0800 Subject: [PATCH] btrfs-progs: lowmem check: Fix false alerts for image with shared block ref only backref [BUG] For image with shared block ref only metadata item like: ------ item 66 key (21573632 METADATA_ITEM 0) itemoff 3971 itemsize 24 refs 66 gen 9 flags TREE_BLOCK|FULL_BACKREF tree block skinny level 0 item 0 key (21573632 SHARED_BLOCK_REF 21676032) itemoff 3995 itemsize 0 shared block backref item 1 key (21573632 SHARED_BLOCK_REF 21921792) itemoff 3995 itemsize 0 shared block backref item 2 key (21573632 SHARED_BLOCK_REF 21995520) itemoff 3995 itemsize 0 shared block backref item 3 key (21573632 SHARED_BLOCK_REF 22077440) itemoff 3995 itemsize 0 shared block backref ... ------ Lowmem mode check will report false alerts like: ------ ERROR: extent[21573632 4096] backref lost (owner: 256, level: 0) ------ [CAUSE] In fact, the false alerts are not even from extent tree verfication, but a fs tree helper which is designed to make sure there is some tree block referring to the fs tree block. The idea is to find inlined tree backref then keyed TREE_BLOCK_REF_KEY. However it missed SHARED_BLOCK_REF_KEY, and caused such false alert. [FIX] Add SHARED_BLOCK_REF_KEY to make the warning shut up. Signed-off-by: Qu Wenruo Signed-off-by: David Sterba --- cmds-check.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/cmds-check.c b/cmds-check.c index 7eb08b6..791fab6 100644 --- a/cmds-check.c +++ b/cmds-check.c @@ -11850,6 +11850,30 @@ static int check_tree_block_ref(struct btrfs_root *root, if (!ret) found_ref = 1; } + /* + * Finally check SHARED BLOCK REF, any found will be good + * Here we're not doing comprehensive extent backref checking, + * only need to ensure there is some extent referring to this + * tree block. + */ + if (!found_ref) { + btrfs_release_path(&path); + key.objectid = bytenr; + key.type = BTRFS_SHARED_BLOCK_REF_KEY; + key.offset = (u64)-1; + + ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0); + if (ret < 0) { + err |= BACKREF_MISSING; + goto out; + } + ret = btrfs_previous_extent_item(extent_root, &path, bytenr); + if (ret) { + err |= BACKREF_MISSING; + goto out; + } + found_ref = 1; + } if (!found_ref) err |= BACKREF_MISSING; out: -- 2.7.4