• Chris Mason's avatar
    Btrfs: Tree logging fixes · 4bef0848
    Chris Mason authored
    * Pin down data blocks to prevent them from being reallocated like so:
    
    trans 1: allocate file extent
    trans 2: free file extent
    trans 3: free file extent during old snapshot deletion
    trans 3: allocate file extent to new file
    trans 3: fsync new file
    
    Before the tree logging code, this was legal because the fsync
    would commit the transation that did the final data extent free
    and the transaction that allocated the extent to the new file
    at the same time.
    
    With the tree logging code, the tree log subtransaction can commit
    before the transaction that freed the extent.  If we crash,
    we're left with two different files using the extent.
    
    * Don't wait in start_transaction if log replay is going on.  This
    avoids deadlocks from iput while we're cleaning up link counts in the
    replay code.
    
    * Don't deadlock in replay_one_name by trying to read an inode off
    the disk while holding paths for the directory
    
    * Hold the buffer lock while we mark a buffer as written.  This
    closes a race where someone is changing a buffer while we write it.
    They are supposed to mark it dirty again after they change it, but
    this violates the cow rules.
    Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
    4bef0848
disk-io.c 53.2 KB