On 15 Oct 1999, Christoph Rohland wrote:
> Actually I am working on extending SYSV shared memory to be able to
> implement posix shared memory. What I need is the ability to resize
> shared memory segments. These are now implemented by vmalloc'ing a
> contiguous array of size (pages*sizeof(long)). This array has to be
> resized in ftruncate.
Ahh. Well, this is definately one of those cases where you don't want to
use vmalloc. In fact, don't even use the sysv code as a starting point
since it's a mess. We've discussed a few different ways of doing this on
linux-mm a while back (archieves on ftp.kvack.org/pub/archives/linux-mm/),
but I think the best way to handle it is along the lines of what Eric did
for his shmfs: provide a set of inode operations to back the vma. That
way, all the duplication of (sometimes trick) mm code is eliminated. Eric
had a rather complete filesystem, but it was broken when the page cache
code was changed. Nevertheless, it's a good starting point.
-ben
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