Re: 2.4.11pre4 swapping out all over the place

[Alexander Viro]

On Sun, 7 Oct 2001, Linus Torvalds wrote:

> > I just noticed that when reading from an umounted block device, the pages
> > are not cached between runs, i.e. the cache is dropped on close().  If the
> > block device contains a mounted filesystem, the pages are not dropped.
> > Is this intentional?

Actually, they are dropped as soon as there's no openers left.  mounted
fs counts as opener, so does opened file.

> It's intentional, although something that can probably be discussed. The
> reasons for it are:
>  - devices with broken or unreliable disk change mechanisms
>  - the current dynamic [de-]allocation of block device data structures.
>  - historical coherency reasons.
 
   - current logics for driver use count.  Block ones do MOD_INC_US_COUNT
on->open() and MOD_DEC_USE_COUNT on ->release().