btrfs-progs: lowmem check: Fix inlined data extent ref lookup

When lowmem fsck tries to find backref of a specified file extent, it
searches inlined data ref first.

However, extent data ref contains both owner root objectid, inode number
and calculated offset (file offset - extent offset).

The code only checks owner root objectid, not checking inode number nor
calculated offset.

This makes lowmem mode fail to detect any backref mismatch if there is
a inlined data ref with the same owner objectid.

Fix it by also checking extent data ref's objectid and offset.

Fixes: b0d360b541f0 ("btrfs-progs: check: introduce function to check data backref in extent tree")
Reported-by: Chris Murphy <chris@colorremedies.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/cmds-check.c b/cmds-check.c
index 03ff89a..9f9eb50 100644 (file)
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -12005,11 +12005,11 @@ static int check_extent_data_item(struct btrfs_root *root,
        u64 disk_num_bytes;
        u64 extent_num_bytes;
        u64 extent_flags;
+       u64 offset;
        u32 item_size;
        unsigned long end;
        unsigned long ptr;
        int type;
-       u64 ref_root;
        int found_dbackref = 0;
        int slot = pathp->slots[0];
        int err = 0;
@@ -12027,6 +12027,7 @@ static int check_extent_data_item(struct btrfs_root *root,
        disk_bytenr = btrfs_file_extent_disk_bytenr(eb, fi);
        disk_num_bytes = btrfs_file_extent_disk_num_bytes(eb, fi);
        extent_num_bytes = btrfs_file_extent_num_bytes(eb, fi);
+       offset = btrfs_file_extent_offset(eb, fi);
 
        /* Check unaligned disk_num_bytes and num_bytes */
        if (!IS_ALIGNED(disk_num_bytes, root->fs_info->sectorsize)) {
@@ -12081,6 +12082,11 @@ static int check_extent_data_item(struct btrfs_root *root,
        strict = should_check_extent_strictly(root, nrefs, -1);
 
        while (ptr < end) {
+               u64 ref_root;
+               u64 ref_objectid;
+               u64 ref_offset;
+               bool match = false;
+
                iref = (struct btrfs_extent_inline_ref *)ptr;
                type = btrfs_extent_inline_ref_type(leaf, iref);
                dref = (struct btrfs_extent_data_ref *)(&iref->offset);
@@ -12092,9 +12098,15 @@ static int check_extent_data_item(struct btrfs_root *root,
                }
                if (type == BTRFS_EXTENT_DATA_REF_KEY) {
                        ref_root = btrfs_extent_data_ref_root(leaf, dref);
-                       if (ref_root == root->objectid)
+                       ref_objectid = btrfs_extent_data_ref_objectid(leaf, dref);
+                       ref_offset = btrfs_extent_data_ref_offset(leaf, dref);
+
+                       if (ref_objectid == fi_key.objectid &&
+                           ref_offset == fi_key.offset - offset)
+                               match = true;
+                       if (ref_root == root->objectid && match)
                                found_dbackref = 1;
-                       else if (!strict && owner == ref_root)
+                       else if (!strict && owner == ref_root && match)
                                found_dbackref = 1;
                } else if (type == BTRFS_SHARED_DATA_REF_KEY) {
                        found_dbackref = !check_tree_block_ref(root, NULL,