Hi,
On 31/05/16 07:05, Raghavendra Gowdappa wrote:
+gluster-devel, +Xavi
Hi all,
The context is [1], where bricks do pre-operation checks before doing a fop and proceed with fop only if pre-op check is successful.
@Xavi,
We need your inputs on behavior of EC subvolumes as well.
If I understand correctly, EC shouldn't have any problems here.
EC sends the mkdir request to all subvolumes that are currently
considered "good" and tries to combine the answers. Answers that match
in return code, errno (if necessary) and xdata contents (except for some
special xattrs that are ignored for combination purposes), are grouped.
Then it takes the group with more members/answers. If that group has a
minimum size of #bricks - redundancy, it is considered the good answer.
Otherwise EIO is returned because bricks are in an inconsistent state.
If there's any answer in another group, it's considered bad and gets
marked so that self-heal will repair it using the good information from
the majority of bricks.
xdata is combined and returned even if return code is -1.
Is that enough to cover the needed behavior ?
Xavi
[1] http://review.gluster.org/13885
regards,
Raghavendra
----- Original Message -----
From: "Pranith Kumar Karampuri" <pkarampu@xxxxxxxxxx>
To: "Raghavendra Gowdappa" <rgowdapp@xxxxxxxxxx>
Cc: "team-quine-afr" <team-quine-afr@xxxxxxxxxx>, "rhs-zteam" <rhs-zteam@xxxxxxxxxx>
Sent: Tuesday, May 31, 2016 10:22:49 AM
Subject: Re: dht mkdir preop check, afr and (non-)readable afr subvols
I think you should start a discussion on gluster-devel so that Xavi gets a
chance to respond on the mails as well.
On Tue, May 31, 2016 at 10:21 AM, Raghavendra Gowdappa <rgowdapp@xxxxxxxxxx>
wrote:
Also note that we've plans to extend this pre-op check to all dentry
operations which also depend parent layout. So, the discussion need to
cover all dentry operations like:
1. create
2. mkdir
3. rmdir
4. mknod
5. symlink
6. unlink
7. rename
We also plan to have similar checks in lock codepath for directories too
(planning to use hashed-subvolume as lock-subvolume for directories). So,
more fops :)
8. lk (posix locks)
9. inodelk
10. entrylk
regards,
Raghavendra
----- Original Message -----
From: "Raghavendra Gowdappa" <rgowdapp@xxxxxxxxxx>
To: "team-quine-afr" <team-quine-afr@xxxxxxxxxx>
Cc: "rhs-zteam" <rhs-zteam@xxxxxxxxxx>
Sent: Tuesday, May 31, 2016 10:15:04 AM
Subject: dht mkdir preop check, afr and (non-)readable afr subvols
Hi all,
I have some queries related to the behavior of afr_mkdir with respect to
readable subvols.
1. While winding mkdir to subvols does afr check whether the subvolume is
good/readable? Or does it wind to all subvols irrespective of whether a
subvol is good/bad? In the latter case, what if
a. mkdir succeeds on non-readable subvolume
b. fails on readable subvolume
What is the result reported to higher layers in the above scenario? If
mkdir is failed, is it cleaned up on non-readable subvolume where it
failed?
I am interested in this case as dht-preop check relies on layout xattrs
and I
assume layout xattrs in particular (and all xattrs in general) are
guaranteed to be correct only on a readable subvolume of afr. So, in
essence
we shouldn't be winding down mkdir on non-readable subvols as whatever
the
decision brick makes as part of pre-op check is inherently flawed.
regards,
Raghavendra
--
Pranith
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