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    SubjectRe: [CFT][PATCH] block_write_*_buffer rewrite

    On Tue, 30 Nov 1999, Alexander Viro wrote:

    > Patch merges most of block_write_{partial,cont}_page and fixes a
    > couple of bad bugs in the latter. It should fix the problems with
    > write-beyond-EOF on FAT and HPFS and it cleans the code up. [...]

    looks good, but i think you have removed an important optimization:
    overlapping the issuing/finishing of read requests with copying memory, on
    1k filesystems. This should not matter much on bigger boxes, but on
    smaller ones i've seen a definite advantage. So it's fine (and wanted) to
    issue read requests first (the old version didnt do this), but you are
    waiting for them to finish synchronously - this should be interleaved with
    memory copies. Also there is a deadlock situation which David Miller
    noticed some time ago (i think this is still present): just try read()-ing
    a file into a freshly mmap()-ed memory area. (where the mmap-ed page is
    the same as the read() page.) Legal combination, instant stuck process.

    -- mingo


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