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    SubjectRe: [patch 12/16] fix race between writeback and unlink


    On Tue, 4 Jun 2002, Andrew Morton wrote:
    >
    > But after the vma has been destroyed (the application did exit()),
    > the dirty pagecache data against the sparse mapped file still
    > hasn't been written, and still doesn't have a disk mapping.
    >
    > So in this case, we have an inode which still has pending block
    > allocations which has no struct file's pointing at it. Or
    > am I wrong?

    I think you're right..

    > The current preallocation will screw up is when there's a
    > large-and-sparse file which has blocks being allocated against it
    > at two or more offsets. And those allocations are for a large number
    > of blocks, and they are proceeding slowly.

    Sure. However, I don't think it should come as any surprise to anybody
    that trying to write to two different points in the same file is a bad
    idea. _regardless_ of whether you do pre-allocation or not, and whether
    the pre-allocation is on the inode or file level.

    I'd still love to see a "fast and slightly stupid" allocator for both
    blocks and inodes, and have some infrastructure to do run-time defragging
    in the background.

    Linus

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