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    xfs: Make fiemap work with sparse files · 9af25465
    Tao Ma 提交于
    In xfs_vn_fiemap, we set bvm_count to fi_extent_max + 1 and want
    to return fi_extent_max extents, but actually it won't work for
    a sparse file. The reason is that in xfs_getbmap we will
    calculate holes and set it in 'out', while out is malloced by
    bmv_count(fi_extent_max+1) which didn't consider holes. So in the
    worst case, if 'out' vector looks like
    [hole, extent, hole, extent, hole, ... hole, extent, hole],
    we will only return half of fi_extent_max extents.
    
    This patch add a new parameter BMV_IF_NO_HOLES for bvm_iflags.
    So with this flags, we don't use our 'out' in xfs_getbmap for
    a hole. The solution is a bit ugly by just don't increasing
    index of 'out' vector. I felt that it is not easy to skip it
    at the very beginning since we have the complicated check and
    some function like xfs_getbmapx_fix_eof_hole to adjust 'out'.
    
    Cc: Dave Chinner <david@fromorbit.com>
    Signed-off-by: NTao Ma <tao.ma@oracle.com>
    Signed-off-by: NAlex Elder <aelder@sgi.com>
    9af25465
xfs_fs.h 18.7 KB