2.2.19(xx) file unmapping on abort

2.2.19(xx) file unmapping on abort

[Rakesh Tiwari]

Relevant code -

../src/linux/mm/filemap.c
static void filemap_unmap(struct vm_area_struct *vma, unsigned long
start, size_t len)
{
    filemap_sync(vma, start, len, MS_ASYNC);
}


Question -

Does this imply that every time a process terminates abonormally, all
the dirty pages related to that mapping are flushed to the disk, even if
that was not intended ?  Why can not it be simply  this ? -

static void filemap_unmap(struct vm_area_struct *vma, unsigned long
start, size_t len)
{
    filemap_sync(vma, start, len, MS_INVALIDATE);
}

I call msync() at various points in the program where data in the pages
is known to be in good condition. At the abnormal program termination, I
am not really sure if data in pages is valid or not.....

Thank you.
Rakesh :-)

Re: 2.2.19(xx) file unmapping on abort

[Alexander Viro]

On Fri, 22 Mar 2002, Rakesh Tiwari wrote:

> 
> I call msync() at various points in the program where data in the pages
> is known to be in good condition. At the abnormal program termination, I
> am not really sure if data in pages is valid or not.....

If you have a shared mapping it can be written to disk at any moment, so
you can't rely on that happening only at the moment of msync().