btrfs: account for non-CoW'd blocks in btrfs_abort_transaction

The test for !trans->blocks_used in btrfs_abort_transaction is
insufficient to determine whether it's safe to drop the transaction
handle on the floor.  btrfs_cow_block, informed by should_cow_block,
can return blocks that have already been CoW'd in the current
transaction.  trans->blocks_used is only incremented for new block
allocations. If an operation overlaps the blocks in the current
transaction entirely and must abort the transaction, we'll happily
let it clean up the trans handle even though it may have modified
the blocks and will commit an incomplete operation.

In the long-term, I'd like to do closer tracking of when the fs
is actually modified so we can still recover as gracefully as possible,
but that approach will need some discussion.  In the short term,
since this is the only code using trans->blocks_used, let's just
switch it to a bool indicating whether any blocks were used and set
it when should_cow_block returns false.

Cc: stable@vger.kernel.org # 3.4+
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 827c949fa4bc2a32bce473cf49f76e6d794b8e8b..6276add8538a43b2832fcaf5067cf3c081504192 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1554,6 +1554,7 @@ noinline int btrfs_cow_block(struct btrfs_trans_handle *trans,
                       trans->transid, root->fs_info->generation);
 
        if (!should_cow_block(trans, root, buf)) {
+               trans->dirty = true;
                *cow_ret = buf;
                return 0;
        }
@@ -2777,8 +2778,10 @@ again:
                         * then we don't want to set the path blocking,
                         * so we test it here
                         */
-                       if (!should_cow_block(trans, root, b))
+                       if (!should_cow_block(trans, root, b)) {
+                               trans->dirty = true;
                                goto cow_done;
+                       }
 
                        /*
                         * must have write locks on this node and the

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5439e85c4813fa7440b0c2a9be11aaabac8361c8..29e5d000bbeec3bb3ce053e8ccaae6e521ab977d 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8045,7 +8045,7 @@ btrfs_init_new_buffer(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                set_extent_dirty(&trans->transaction->dirty_pages, buf->start,
                         buf->start + buf->len - 1, GFP_NOFS);
        }
-       trans->blocks_used++;
+       trans->dirty = true;
        /* this returns a buffer locked for blocking */
        return buf;
 }

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4339b6613f190da6feaf83b2e2c2e07ea0aca062..bf70d33b57910f3bc821c1c7fce755103f5d8bba 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -235,7 +235,7 @@ void __btrfs_abort_transaction(struct btrfs_trans_handle *trans,
        trans->aborted = errno;
        /* Nothing used. The other threads that have joined this
         * transaction may be able to continue. */
-       if (!trans->blocks_used && list_empty(&trans->new_bgs)) {
+       if (!trans->dirty && list_empty(&trans->new_bgs)) {
                const char *errstr;
 
                errstr = btrfs_decode_error(errno);

diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 9fe0ec2bf0fe7fefda878bb9e885071f0d8e3f7e..c5abee4f01add54f811c78fac76170f8b5c02bb3 100644 (file)
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -110,7 +110,6 @@ struct btrfs_trans_handle {
        u64 chunk_bytes_reserved;
        unsigned long use_count;
        unsigned long blocks_reserved;
-       unsigned long blocks_used;
        unsigned long delayed_ref_updates;
        struct btrfs_transaction *transaction;
        struct btrfs_block_rsv *block_rsv;
@@ -121,6 +120,7 @@ struct btrfs_trans_handle {
        bool can_flush_pending_bgs;
        bool reloc_reserved;
        bool sync;
+       bool dirty;
        unsigned int type;
        /*
         * this root is only needed to validate that the root passed to