• David Howells's avatar
    afs: Fix directory handling · f3ddee8d
    David Howells authored
    AFS directories are structured blobs that are downloaded just like files
    and then parsed by the lookup and readdir code and, as such, are currently
    handled in the pagecache like any other file, with the entire directory
    content being thrown away each time the directory changes.
    
    However, since the blob is a known structure and since the data version
    counter on a directory increases by exactly one for each change committed
    to that directory, we can actually edit the directory locally rather than
    fetching it from the server after each locally-induced change.
    
    What we can't do, though, is mix data from the server and data from the
    client since the server is technically at liberty to rearrange or compress
    a directory if it sees fit, provided it updates the data version number
    when it does so and breaks the callback (ie. sends a notification).
    
    Further, lookup with lookup-ahead, readdir and, when it arrives, local
    editing are likely want to scan the whole of a directory.
    
    So directory handling needs to be improved to maintain the coherency of the
    directory blob prior to permitting local directory editing.
    
    To this end:
    
     (1) If any directory page gets discarded, invalidate and reread the entire
         directory.
    
     (2) If readpage notes that if when it fetches a single page that the
         version number has changed, the entire directory is flagged for
         invalidation.
    
     (3) Read as much of the directory in one go as we can.
    
    Note that this removes local caching of directories in fscache for the
    moment as we can't pass the pages to fscache_read_or_alloc_pages() since
    page->lru is in use by the LRU.
    Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
    f3ddee8d
internal.h 39.2 KB