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SubjectRe: 2.4.21pre5aa1
Andrea Arcangeli <andrea@suse.de> wrote:
>
> Only in 2.4.21pre5aa1: 00_clean-inode-fix-1
>
> Reset r_dev.

oops. What problem was this observed to cause btw?

> Only in 2.4.21pre5aa1: 00_smp-timers-not-deadlocking-1
>
> Corrected varsion of the smp timers that can deadlock in 2.5
> and in all kernels that were used to incorporate this patch,
> including jam.

OK, I'll take a look at that thanks.

> This is fixed so that a timer reinserting
> itself to run immediate, won't loop forever deadlocking
> a CPU spinning in a tight loop. This bug was present in
> ancient 2.4 kernels too and this is been fixed after bugreports
> in both 2.2 and again in 2.4 because we forgotten to forward
> port it to 2.4, these fixes must be forward ported today
> to 2.5 too. Fixed also run_all_timers to correctly convert
> the logical to physical cpu id (doesn't matter on x86, but
> run_all_timers doesn't matter either on x86, other archs
> may need this fix to avoid crashing too). This patch
> was originally written from Ingo Molnar, David Miller with the help of
> Alexey Kuznetsov, for more details see the timer.c added credit lines.

This code is buggy. See

http://linux.bkbits.net:8080/linux-2.5/user=akpm/cset@1.786.202.5?nav=!-|index.html|stats|!+|index.html|ChangeSet@-6M


> Only in 2.4.21pre5aa1: 9999_fsync-msync-async-errors-1
>
> Allow userspace to always be notified about async write failures
> when calling msync and fsync even if they happened long before
> the systemcall run.

The code in shrink_cache() has a couple of problems.

a) If someone else is truncating the file at the same time,
block_write_full_page() will see the page is outside i_size and will
return -EIO. That will be propagated into the address_space and
userspace will see a bogus I/O error.

Fix: just return zero from writepage-outside-i_size. There are several
instances.

b) Can't touch `mapping' after calling writepage(). The page can now be
unlocked, truncated off the inode and the inode could be freed up.

No, I don't have a testcase ;)

The fix is to lock the page again, see if it still has a ->mapping,
then set mapping->error.


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