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>
(cherry picked from commit 64c12921e11b3a0c10d088606e328c58e29274d8)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 7783b60fabf9156026b31f2844068ebb05f35b1e..34cb6864600eb532a61321a67183f95ee8e0c6ac 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1552,6 +1552,7 @@ 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;
        }
@@ -2783,8 +2784,10 @@ 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 f280a93b4e47f1fed43e6d34a8ac4a70e72b0899..c13d4702a3989173e20aa9ca823fce1e5461df06 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7963,7 +7963,7 @@ 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 236e2c322c1f1957a2e8f8230e8a1ee018fd71ec..86dc3d9ff3a7859b706862c3e64188945ac138cb 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -261,7 +261,7 @@ 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 72be51f7ca2fbf92507f2e2f36344a6b0a45f1a8..c0b501a5a3531ba8db95dd9e924df12f0aae6640 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