[dm-devel] Re: Shared snapshots
Mike Snitzer
snitzer at redhat.com
Wed Dec 16 20:39:01 UTC 2009
On Wed, Dec 16 2009 at 3:05am -0500,
Mikulas Patocka <mpatocka at redhat.com> wrote:
> Hi
>
> I uploaded new shared snapshots here:
> http://people.redhat.com/mpatocka/patches/kernel/new-snapshots/devel/
Just a general observation:
You have an empty line separating your comment blocks above functions.
I think eliminating that empty line would help join the comment block to
the function a bit better (as is common in the rest of the kernel).
Also, a comment block of the form:
/* single line comment above function */
Is generally done as:
/*
* single line comment above function
*/
Hopefully I'm not triggering unhappy checkpatch.pl-type thoughts with
these recommendations :)
> changes:
>
> - Broken to separate patches, one patch per file. The last patch adds all
> the files to Makefile and makes it all compile. It allows you to ack
> patches individually. I didn't use stubs to compile intermediate patches,
> the problem is that if multiple patches modify the same file, general
> modifications to the code become harder. With one-patch-per-file I can
> edit it with normal text editor and quilt regenerates the patches.
>
> - Document on-disk format in dm-multisnap-mikulas-struct.h
>
> - More functions are commented
>
> - Removed /*printk ... */ statements. I left some #ifdefed debug routines,
> they are non-trivial to write again
I'm still seeing one in dm_bufio_client_create()
> - Fixed a bug on big-endian systems
>
> - Exposed interface for snapshots-of-snapshots, tested that they work
Where is that interface documented?
As an aside, I have some ideas for improving
Documentation/device-mapper/dm-multisnapshot.txt
I'll just send a patch and we can go from there.
> Mikulas
BTW, I'm getting the following warning when I build the code:
drivers/md/dm-bufio.c: In function ‘write_endio’:
drivers/md/dm-bufio.c:725: warning: value computed is not used
A cast fixes it:
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 1ab5304..be7b89b 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -722,7 +722,7 @@ static void write_endio(struct bio *bio, int error)
b->write_error = error;
if (unlikely(error)) {
struct dm_bufio_client *c = b->c;
- cmpxchg(&c->async_write_error, 0, error);
+ (void)cmpxchg(&c->async_write_error, 0, error);
}
BUG_ON(!test_bit(B_WRITING, &b->state));
smp_mb__before_clear_bit();
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