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SubjectRe: [replace-alexv-buffer.c-patch] Re: [PATCH] Several bad bugs in fs/*


On Thu, 22 Apr 1999, Andrea Arcangeli wrote:

> >> @@ -653,10 +629,13 @@
> >> * around on the free list, and we can get in a loop if we are not careful.
> >> */
> >> for(nlist = 0; nlist < NR_LIST; nlist++) {
> >> + refiled:
> >> bh = lru_list[nlist];
> >> for (i = nr_buffers_type[nlist]*2 ; --i > 0 ; bh = bhnext) {
> >> if(!bh)
> >> break;
> >> + if (bh->b_list != nlist)
> >> + goto refiled;
> >
> > Ahem... Busy-waiting is fun, ain't it? What did you really mean
> >in the chunk above?
>
> Starting from the second run of the loop bh is == bhnext. But bhnext is
> been moved from the dirty list to the clean list while we was sleeping in
> wait_on_buffer(). So without my patch we could continue browsing the clean
> list instead of continue to browse the dirty list.

Andrea, look what will happen if lru_list[nlist]->b_list!=nlist. You will
not get to the end of the inner loop - it will just spin. I'll try to look
at buffer.c situation tonight - sorry, right now I'm way too low on
caffeine.


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