Re: [RFC] Generic deferred file writing

[Alexander Viro]

On Mon, 1 Jan 2001, Roman Zippel wrote:

> The other reason for the question is that I'm currently overwork the block
> handling in affs, especially the extended block handling, where I'm
> implementing a new extended block cache, where I would pretty much prefer
> to use a semaphore to protect it. Although I could do it probably without
> the semaphore and use a spinlock+rechecking, but it would keep it so much
> simpler. (I can post more details about this part on fsdevel if needed /
> wanted.)

But... But with AFFS you _have_ exclusion between block-allocation and
truncate(). It has no sparse files, so pageout will never allocate
anything. I.e. all allocations come from write(2). And both write(2) and
truncate(2) hold i_sem.

Problem with AFFS is on the directory side of that business and there it's
really scary. Block allocation is trivial...