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    SubjectRe: [PATCH] vfs: calculate block-size correctly
    On Wed, 8 Sep 2010 18:07:10 +0800
    Cong Meng <mcpacino@gmail.com> wrote:

    > I sent this patch half mount ago, but no response at all. If anything is
    > wrong, please tell me. Thanks a lots. This is my first time to send patch
    > to linux kernel.
    >
    > The invocation of __getblk(bdev, block, size) will cause kernel stall if
    > the @size parameter is not equal to the blockr-size of @bdev, which is saved
    > in bdev->bd_inode->i_blkbits.
    >
    > submit_bh() has the similar problem.
    >
    > This patch calculates the block-size using i_blkbits.
    > So that, for example, __getblk() can get a 4K buffer head while the
    > block-size of @bdev is 1K.
    >

    This comes up every couple of years and iirc we always decided that
    it's a bug in the calling code somewhere. How did you hit it?


    > --- a/fs/buffer.c
    > +++ b/fs/buffer.c
    > @@ -1051,10 +1051,7 @@ grow_buffers(struct block_device *bdev, sector_t block, int size)
    > pgoff_t index;
    > int sizebits;
    >
    > - sizebits = -1;
    > - do {
    > - sizebits++;
    > - } while ((size << sizebits) < PAGE_SIZE);

    I'm sure the existing code could use __roundup_pow_of_two() here.



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