diff options
Diffstat (limited to 'fs/xfs/linux-2.6/xfs_buf.h')
| -rw-r--r-- | fs/xfs/linux-2.6/xfs_buf.h | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/fs/xfs/linux-2.6/xfs_buf.h b/fs/xfs/linux-2.6/xfs_buf.h index 841d7883528d..f948ec7ba9a4 100644 --- a/fs/xfs/linux-2.6/xfs_buf.h +++ b/fs/xfs/linux-2.6/xfs_buf.h @@ -66,6 +66,25 @@ typedef enum { _XBF_PAGES = (1 << 18), /* backed by refcounted pages */ _XBF_RUN_QUEUES = (1 << 19),/* run block device task queue */ _XBF_DELWRI_Q = (1 << 21), /* buffer on delwri queue */ + + /* + * Special flag for supporting metadata blocks smaller than a FSB. + * + * In this case we can have multiple xfs_buf_t on a single page and + * need to lock out concurrent xfs_buf_t readers as they only + * serialise access to the buffer. + * + * If the FSB size >= PAGE_CACHE_SIZE case, we have no serialisation + * between reads of the page. Hence we can have one thread read the + * page and modify it, but then race with another thread that thinks + * the page is not up-to-date and hence reads it again. + * + * The result is that the first modifcation to the page is lost. + * This sort of AGF/AGI reading race can happen when unlinking inodes + * that require truncation and results in the AGI unlinked list + * modifications being lost. + */ + _XBF_PAGE_LOCKED = (1 << 22), } xfs_buf_flags_t; typedef enum { |