Josef Bacik
2013-May-09 14:09 UTC
[PATCH] Btrfs-progs: add the ability to find mismmatching backrefs
An unfortunate side effect to my fsync bug means that anybody who
didn''t hit the
BUG_ON() during tree log replay would have ended up with a corrupted file
system. Currently our fsck does not catch this because it just looks for
bytenrs for backrefs, it doesn''t look at the num_bytes at all. So this
patch
makes us keep track of how big the backrefs are, since their disk_num_bytes
_have_ to match the number of bytes for the actual extent item. With this patch
fsck now finds problems with a file system it previously thought was ok.
Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
---
cmds-check.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++----------
1 files changed, 53 insertions(+), 12 deletions(-)
diff --git a/cmds-check.c b/cmds-check.c
index 71f5959..1e5e005 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -66,6 +66,7 @@ struct data_backref {
};
u64 owner;
u64 offset;
+ u64 bytes;
u32 num_refs;
u32 found_ref;
};
@@ -1922,6 +1923,17 @@ static int all_backpointers_checked(struct extent_record
*rec, int print_errs)
(unsigned long long)dback->offset,
dback->found_ref, dback->num_refs, back);
}
+ if (dback->bytes != rec->nr) {
+ err = 1;
+ if (!print_errs)
+ goto out;
+ fprintf(stderr, "Backref bytes do not match "
+ "extent backref, bytenr=%llu, ref "
+ "bytes=%llu, backref bytes=%llu\n",
+ (unsigned long long)rec->start,
+ (unsigned long long)rec->nr,
+ (unsigned long long)dback->bytes);
+ }
}
if (!back->is_data) {
found += 1;
@@ -2167,7 +2179,8 @@ static struct tree_backref *alloc_tree_backref(struct
extent_record *rec,
static struct data_backref *find_data_backref(struct extent_record *rec,
u64 parent, u64 root,
- u64 owner, u64 offset)
+ u64 owner, u64 offset,
+ int found_ref, u64 bytes)
{
struct list_head *cur = rec->backrefs.next;
struct extent_backref *node;
@@ -2188,8 +2201,12 @@ static struct data_backref *find_data_backref(struct
extent_record *rec,
if (node->full_backref)
continue;
if (back->root == root && back->owner == owner &&
- back->offset == offset)
+ back->offset == offset) {
+ if (found_ref && node->found_ref &&
+ back->bytes != bytes)
+ continue;
return back;
+ }
}
}
return NULL;
@@ -2215,6 +2232,7 @@ static struct data_backref *alloc_data_backref(struct
extent_record *rec,
ref->offset = offset;
ref->node.full_backref = 0;
}
+ ref->bytes = max_size;
ref->found_ref = 0;
ref->num_refs = 0;
list_add_tail(&ref->node.list, &rec->backrefs);
@@ -2227,7 +2245,7 @@ static int add_extent_rec(struct cache_tree *extent_cache,
struct btrfs_key *parent_key,
u64 start, u64 nr, u64 extent_item_refs,
int is_root, int inc_ref, int set_checked,
- int metadata, u64 max_size)
+ int metadata, int extent_rec, u64 max_size)
{
struct extent_record *rec;
struct cache_extent *cache;
@@ -2241,6 +2259,14 @@ static int add_extent_rec(struct cache_tree
*extent_cache,
if (rec->nr == 1)
rec->nr = max(nr, max_size);
+ /*
+ * We need to make sure to reset nr to whatever the extent
+ * record says was the real size, this way we can compare it to
+ * the backrefs.
+ */
+ if (extent_rec)
+ rec->nr = nr;
+
if (start != rec->start) {
fprintf(stderr, "warning, start mismatch %llu %llu\n",
(unsigned long long)rec->start,
@@ -2325,7 +2351,7 @@ static int add_tree_backref(struct cache_tree
*extent_cache, u64 bytenr,
cache = find_cache_extent(extent_cache, bytenr, 1);
if (!cache) {
add_extent_rec(extent_cache, NULL, bytenr,
- 1, 0, 0, 0, 0, 1, 0);
+ 1, 0, 0, 0, 0, 1, 0, 0);
cache = find_cache_extent(extent_cache, bytenr, 1);
if (!cache)
abort();
@@ -2373,7 +2399,7 @@ static int add_data_backref(struct cache_tree
*extent_cache, u64 bytenr,
cache = find_cache_extent(extent_cache, bytenr, 1);
if (!cache) {
add_extent_rec(extent_cache, NULL, bytenr, 1, 0, 0, 0, 0,
- 0, max_size);
+ 0, 0, max_size);
cache = find_cache_extent(extent_cache, bytenr, 1);
if (!cache)
abort();
@@ -2386,15 +2412,29 @@ static int add_data_backref(struct cache_tree
*extent_cache, u64 bytenr,
if (rec->max_size < max_size)
rec->max_size = max_size;
- back = find_data_backref(rec, parent, root, owner, offset);
+ /*
+ * If found_ref is set then max_size is the real size and must match the
+ * existing refs. So if we have already found a ref then we need to
+ * make sure that this ref matches the existing one, otherwise we need
+ * to add a new backref so we can notice that the backrefs don''t
match
+ * and we need to figure out who is telling the truth. This is to
+ * account for that awful fsync bug I introduced where we''d end up
with
+ * a btrfs_file_extent_item that would have its length include multiple
+ * prealloc extents or point inside of a prealloc extent.
+ */
+ back = find_data_backref(rec, parent, root, owner, offset, found_ref,
+ max_size);
if (!back)
back = alloc_data_backref(rec, parent, root, owner, offset,
max_size);
if (found_ref) {
BUG_ON(num_refs != 1);
+ if (back->node.found_ref)
+ BUG_ON(back->bytes != max_size);
back->node.found_ref = 1;
back->found_ref += 1;
+ back->bytes = max_size;
} else {
if (back->node.found_extent_tree) {
fprintf(stderr, "Extent back ref already exists "
@@ -2548,7 +2588,7 @@ static int process_extent_item(struct btrfs_root *root,
BUG();
#endif
return add_extent_rec(extent_cache, NULL, key.objectid,
- num_bytes, refs, 0, 0, 0, metadata,
+ num_bytes, refs, 0, 0, 0, metadata, 1,
num_bytes);
}
@@ -2556,7 +2596,7 @@ static int process_extent_item(struct btrfs_root *root,
refs = btrfs_extent_refs(eb, ei);
add_extent_rec(extent_cache, NULL, key.objectid, num_bytes,
- refs, 0, 0, 0, metadata, num_bytes);
+ refs, 0, 0, 0, metadata, 1, num_bytes);
ptr = (unsigned long)(ei + 1);
if (btrfs_extent_flags(eb, ei) & BTRFS_EXTENT_FLAG_TREE_BLOCK &&
@@ -3203,7 +3243,7 @@ static int run_next_block(struct btrfs_root *root,
ret = add_extent_rec(extent_cache, NULL,
btrfs_file_extent_disk_bytenr(buf, fi),
btrfs_file_extent_disk_num_bytes(buf, fi),
- 0, 0, 1, 1, 0,
+ 0, 0, 1, 1, 0, 0,
btrfs_file_extent_disk_num_bytes(buf, fi));
add_data_backref(extent_cache,
btrfs_file_extent_disk_bytenr(buf, fi),
@@ -3226,7 +3266,8 @@ static int run_next_block(struct btrfs_root *root,
u32 size = btrfs_level_size(root, level - 1);
btrfs_node_key_to_cpu(buf, &key, i);
ret = add_extent_rec(extent_cache, &key,
- ptr, size, 0, 0, 1, 0, 1, size);
+ ptr, size, 0, 0, 1, 0, 1, 0,
+ size);
BUG_ON(ret);
add_tree_backref(extent_cache, ptr, parent, owner, 1);
@@ -3267,7 +3308,7 @@ static int add_root_to_pending(struct extent_buffer *buf,
else
add_pending(pending, seen, buf->start, buf->len);
add_extent_rec(extent_cache, NULL, buf->start, buf->len,
- 0, 1, 1, 0, 1, buf->len);
+ 0, 1, 1, 0, 1, 0, buf->len);
if (root_key->objectid == BTRFS_TREE_RELOC_OBJECTID ||
btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
@@ -3303,7 +3344,7 @@ static int free_extent_hook(struct btrfs_trans_handle
*trans,
if (is_data) {
struct data_backref *back;
back = find_data_backref(rec, parent, root_objectid, owner,
- offset);
+ offset, 1, num_bytes);
if (!back)
goto out;
if (back->node.found_ref) {
--
1.7.7.6
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