The dedup reference is a special kind of delayed refs, and the delayed refs
are batched to be processed later.
If we find a matched dedup extent, then we queue an ADD delayed ref on it within
endio work, but there is already a DROP delayed ref queued,
t1 t2 t3
->writepage commit transaction
->run_delalloc_dedup
find_dedup
------------------------------------------------------------------------------
process_delayed refs
(it deletes the dedup
extent)
add ordered extent |
submit pages |
finish ordered io |
insert file extents |
queue delayed refs |
queue dedup ref |
"process delayed refs"
continues
(insert a ref on an extent
deleted by the above)
This senario ends up with a crash because we're going to insert a ref on
a deleted extent.
To avoid the race, we need to check if there is a ADD delayed ref on deleting
the extent and protect this job with lock.
Signed-off-by: Liu Bo <bo.li....@oracle.com>
---
fs/btrfs/ctree.h | 3 ++-
fs/btrfs/extent-tree.c | 35 +++++++++++++++++++----------------
fs/btrfs/file-item.c | 36 +++++++++++++++++++++++++++++++++++-
fs/btrfs/inode.c | 10 ++--------
4 files changed, 58 insertions(+), 26 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 65adf07..48f587e 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3764,7 +3764,8 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64
start, u64 end,
struct list_head *list, int search_commit);
int noinline_for_stack
-btrfs_find_dedup_extent(struct btrfs_root *root, struct btrfs_dedup_hash
*hash);
+btrfs_find_dedup_extent(struct btrfs_root *root, struct btrfs_dedup_hash *hash,
+ struct inode *inode, u64 file_pos);
int noinline_for_stack
btrfs_insert_dedup_extent(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 191f0a7..a8da7aa 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5937,9 +5937,23 @@ again:
goto again;
}
} else {
- if (!dedup_hash && is_data &&
- root_objectid == BTRFS_DEDUP_TREE_OBJECTID)
- dedup_hash = extent_data_ref_offset(root, path, iref);
+ if (is_data && root_objectid == BTRFS_DEDUP_TREE_OBJECTID) {
+ if (!dedup_hash)
+ dedup_hash = extent_data_ref_offset(root,
+ path, iref);
+
+ ret = btrfs_free_dedup_extent(trans, root,
+ dedup_hash, bytenr);
+ if (ret) {
+ if (ret == -EAGAIN)
+ ret = 0;
+ else
+ btrfs_abort_transaction(trans,
+ extent_root,
+ ret);
+ goto out;
+ }
+ }
if (found_extent) {
BUG_ON(is_data && refs_to_drop !=
@@ -5964,21 +5978,10 @@ again:
if (is_data) {
ret = btrfs_del_csums(trans, root, bytenr, num_bytes);
if (ret) {
- btrfs_abort_transaction(trans, extent_root,
ret);
+ btrfs_abort_transaction(trans,
+ extent_root, ret);
goto out;
}
-
- if (root_objectid == BTRFS_DEDUP_TREE_OBJECTID) {
- ret = btrfs_free_dedup_extent(trans, root,
- dedup_hash,
- bytenr);
- if (ret) {
- btrfs_abort_transaction(trans,
- extent_root,
- ret);
- goto out;
- }
- }
}
ret = update_block_group(root, bytenr, num_bytes, 0);
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 068112c..d842cf8 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -887,13 +887,15 @@ fail_unlock:
/* 1 means we find one, 0 means we dont. */
int noinline_for_stack
-btrfs_find_dedup_extent(struct btrfs_root *root, struct btrfs_dedup_hash *hash)
+btrfs_find_dedup_extent(struct btrfs_root *root, struct btrfs_dedup_hash *hash,
+ struct inode *inode, u64 file_pos)
{
struct btrfs_key key;
struct btrfs_path *path;
struct extent_buffer *leaf;
struct btrfs_root *dedup_root;
struct btrfs_dedup_item *item;
+ struct btrfs_trans_handle *trans;
u64 hash_value;
u64 length;
u64 dedup_size;
@@ -916,6 +918,12 @@ btrfs_find_dedup_extent(struct btrfs_root *root, struct
btrfs_dedup_hash *hash)
if (!path)
return 0;
+ trans = btrfs_join_transaction(root);
+ if (IS_ERR(trans)) {
+ trans = NULL;
+ goto out;
+ }
+
/*
* For SHA256 dedup algorithm, we store the last 64bit as the
* key.objectid, and the rest in the tree item.
@@ -972,8 +980,16 @@ prev_slot:
hash->num_bytes = length;
hash->compression = compression;
found = 1;
+
+ ret = btrfs_inc_extent_ref(trans, root, key.offset, length, 0,
+ BTRFS_I(inode)->root->root_key.objectid,
+ btrfs_ino(inode),
+ file_pos, /* file_pos - 0 */
+ 0);
out:
btrfs_free_path(path);
+ if (trans)
+ btrfs_end_transaction(trans, root);
return found;
}
@@ -1055,6 +1071,8 @@ btrfs_free_dedup_extent(struct btrfs_trans_handle *trans,
struct btrfs_path *path;
struct extent_buffer *leaf;
struct btrfs_root *dedup_root;
+ struct btrfs_delayed_ref_root *delayed_refs;
+ struct btrfs_delayed_ref_head *head;
int ret = 0;
if (!root->fs_info->dedup_root)
@@ -1088,6 +1106,22 @@ btrfs_free_dedup_extent(struct btrfs_trans_handle *trans,
if (key.objectid != hash || key.offset != bytenr)
goto out;
+ ret = 0;
+
+ /* check if ADD_DELAYED delayed refs exist */
+ delayed_refs = &trans->transaction->delayed_refs;
+
+ spin_lock(&delayed_refs->lock);
+ head = btrfs_find_delayed_ref_head(trans, bytenr);
+
+ /* the mutex has been acquired by the caller */
+ if (head && head->add_cnt) {
+ spin_unlock(&delayed_refs->lock);
+ ret = -EAGAIN;
+ goto out;
+ }
+ spin_unlock(&delayed_refs->lock);
+
ret = btrfs_del_item(trans, dedup_root, path);
WARN_ON(ret);
out:
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d32b066..9c8bea9 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -988,7 +988,8 @@ run_delalloc_dedup(struct inode *inode, struct page
*locked_page, u64 start,
found = 0;
compr = BTRFS_COMPRESS_NONE;
} else {
- found = btrfs_find_dedup_extent(root, hash);
+ found = btrfs_find_dedup_extent(root, hash,
+ inode, start);
compr = hash->compression;
}
@@ -2388,13 +2389,6 @@ static int __insert_reserved_file_extent(struct
btrfs_trans_handle *trans,
btrfs_ino(inode),
hash->hash[index], 0);
}
- } else {
- ret = btrfs_inc_extent_ref(trans, root, ins.objectid,
- ins.offset, 0,
- root->root_key.objectid,
- btrfs_ino(inode),
- file_pos, /* file_pos - 0 */
- 0);
}
out:
btrfs_free_path(path);
--
1.8.2.1
--
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