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From: NeilBrown <neilb@suse.com>
To: "Dilger\, Andreas" <andreas.dilger@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: James Simmons <jsimmons@infradead.org>,
	"devel\@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
	"Drokin\, Oleg" <oleg.drokin@intel.com>, "Hammond\,
	John" <john.hammond@intel.com>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	Lustre Development List <lustre-devel@lists.lustre.org>
Subject: Re: [PATCH v2 6/6] staging: lustre: mdc: use large xattr buffers for old servers
Date: Fri, 01 Jun 2018 15:38:15 +1000	[thread overview]
Message-ID: <87po1brrqw.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <AE3B1D00-46A8-42FA-9025-2E680C185294@intel.com>

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On Thu, May 31 2018, Dilger, Andreas wrote:

> On May 31, 2018, at 18:54, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
>> 
>> On Tue, May 29, 2018 at 10:21:45AM -0400, James Simmons wrote:
>>> From: "John L. Hammond" <john.hammond@intel.com>
>>> 
>>> Pre 2.10.1 MDTs will crash when they receive a listxattr (MDS_GETXATTR
>>> with OBD_MD_FLXATTRLS) RPC for an orphan or dead object. So for
>>> clients connected to these older MDTs, try to avoid sending listxattr
>>> RPCs by making the bulk getxattr (MDS_GETXATTR with OBD_MD_FLXATTRALL)
>>> more likely to succeed and thereby reducing the chances of falling
>>> back to listxattr.
>>> 
>>> +#if LUSTRE_VERSION_CODE < OBD_OCD_VERSION(3, 0, 53, 0)
>> 
>> Why are you adding pointless version checks to mainline?  Please don't
>> add new ones of these, you need to be working on removing the existing
>> ones.
>
> These are not Linux kernel version checks, but rather Lustre release version
> checks.  This allows us to remove workarounds like this in the future when
> they are no longer needed, rather than accumulating cruft forever.  It's like
> the separation of NFSv2 vs NFSv3 vs NFSv4.

It looks very different to the separation of NFSv{2,3,4}.  Those are
conditionally compiled on a whole-file basis.
If we ever want to remove this code it should be hard to search for
occurances of OBD_OCD_VERSION() in the code, we don't need the C
preprocessor to be able to remove them for us.
In this particular example:

+	if (exp->exp_connect_data.ocd_version < OBD_OCD_VERSION(2, 10, 1, 0))
+		min_buf_size = exp->exp_connect_data.ocd_max_easize;

if you want to be able to compile without that one test, you could arrange
that OBD_OSC_VERSION(2, 10, 1, 0) evaluates to 0.
As ocd_version is unsigned, the comparison will always be false, and
the compiler will optimize the code away.

As a general rule, you need a very good reason to have #if or #ifdef in
.c files.  They are usually OK in .h files.

Thanks,
NeilBrown


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  reply	other threads:[~2018-06-01  5:38 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-29 14:21 [PATCH v2 0/6] staging: lustre: llite: remaining xattr patches James Simmons
2018-05-29 14:21 ` [PATCH v2 1/6] staging: lustre: llite: create acl.c file James Simmons
2018-05-29 14:21 ` [PATCH v2 2/6] staging: lustre: llite: add support set_acl method in inode operations James Simmons
2018-05-29 14:21 ` [PATCH v2 3/6] staging: lustre: llite: remove unused parameters from md_{get,set}xattr() James Simmons
2018-05-29 14:21 ` [PATCH v2 4/6] staging: lustre: acl: increase ACL entries limitation James Simmons
2018-05-29 14:21 ` [PATCH v2 5/6] staging: lustre: mdc: excessive memory consumption by the xattr cache James Simmons
2018-05-29 14:21 ` [PATCH v2 6/6] staging: lustre: mdc: use large xattr buffers for old servers James Simmons
2018-05-31 16:54   ` Greg Kroah-Hartman
2018-05-31 17:30     ` Dilger, Andreas
2018-06-01  5:38       ` NeilBrown [this message]
2018-06-01  8:12       ` Greg Kroah-Hartman

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