Re: How best to bypass the page cache from within a kernel module?

On Wed, Sep 17, 2003 at 04:33:08PM -0400, Alan Stern wrote:

I really want this to work through the filesystem.  99% of what my driver 
does involves normal reads and writes.  And there are very good reasons 
for having it run as a kernel thread rather than a user process.  It's 
just that this one piece, which is a very minor part of the driver, needs 
to avoid the page cache.
So to reiterate my original questions:

Doesn't sound much most drivers after all that, but there's some weird
stuff out there.


On Wed, Sep 17, 2003 at 04:33:08PM -0400, Alan Stern wrote:

1. What's the proper way for a kernel thread running in a module to get
hold of an mm_struct or to keep the one it had before calling daemonize()?

Well, you can get one from the slab allocator, though I expect there will
be a followup question here...


On Wed, Sep 17, 2003 at 04:33:08PM -0400, Alan Stern wrote:

2. What's the proper way for a kernel thread to allocate a region of 
userspace memory?

Hmm. Sounds like you want to grab a user address space and do userspace
stuff inside there. Maybe avoid do_execve() etc. and call sys_*() for
everything else outright? The question itself probably wants sys_mmap()
or some such, or handle_mm_fault() depending on what you have in mind
for allocation.


On Wed, Sep 17, 2003 at 04:33:08PM -0400, Alan Stern wrote:

3. What's the proper way to invalidate all entries in the page cache
that refer to a particular file?

invalidate_inode_pages().


-- wli
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