lkml.org 
[lkml]   [2000]   [Dec]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] Generic deferred file writing
Hi,

On Sun, 31 Dec 2000, Linus Torvalds wrote:

> cached_allocation = NULL;
>
> repeat:
> spin_lock();
> result = try_to_find_existing();
> if (!result) {
> if (!cached_allocation) {
> spin_unlock();
> cached_allocation = allocate_block();
> goto repeat;
> }
> result = cached_allocation;
> add_to_datastructures(result);
> }
> spin_unlock();
> return result;
>
> This is quite standard, and Linux does it in many places. It doesn't have
> to be complex or ugly.

No problem with that.

> Also, I don't see why you claim the current get_block() is recursive and
> hard to use: it obviously isn't. If you look at the current ext2
> get_block(), the way it protects most of its data structures is by the
> super-block-global lock. That wouldn't work if your claims of recursive
> invocation were true.

I just rechecked that, but I don't see no superblock lock here, it uses
the kernel_lock instead. Although Al could give the definitive answer for
this, he wrote it. :)

> The way the Linux MM works, if the lower levels need to do buffer
> allocations, they will use GFP_BUFFER (which "bread()" does internally),
> which will mean that the VM layer will _not_ call down recursively to
> write stuff out while it's already trying to write something else. This is
> exactly so that filesystems don't have to release and re-try if they don't
> want to.
>
> In short, I don't see any of your arguments.

Then I must have misunderstood Al. Al?
If you were right here, I would see absolutely no reason for the current
complexity. (Me is a bit confused here.)

bye, Roman

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:52    [W:0.046 / U:2.640 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site