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
