linux-kernel - Reiserfs and MMAP (was: How many people are using 2.6.16?)

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Date:	Wed, 31 Jan 2007 21:42:48 +1100
From:	Bron Gondwana <brong@...tmail.fm>
To:	Adrian Bunk <bunk@...sta.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mark Lord <lkml@....ca>, Bron Gondwana <brong@...tmail.fm>,
	Mike Houston <mikeserv@...s.com>,
	Chuck Ebbert <cebbert@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Steve French <smfltc@...ibm.com>,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>,
	Daniel Drake <dsd@...too.org>, samba-technical@...ts.samba.org,
	Vladimir Saveliev <vs@...esys.com>, reiserfs-dev@...esys.com,
	David Chinner <dgc@....com>, xfs-masters@....sgi.com
Subject: Reiserfs and MMAP (was: How many people are using 2.6.16?)

On Wed, Jan 31, 2007 at 08:02:37AM +0100, Adrian Bunk wrote:
> reiserfs:
> commit de14569f94513279e3d44d9571a421e9da1759ae
>   [PATCH] resierfs: avoid tail packing if an inode was ever mmapped
> backport to 2.6.16 required

Which would explain the "notail" I've been careful to cargo-cult
into every mount string since I started at this job, even though
we're storing mainly very small files.

Referring back to: <43BE1EDF.3010305@...esys.com> (which went
to reiserfs-dev and a couple of the ever-growing CC list above)
we're still not 100% sure if it's safe to remove the patch that
I attached there:

>>>>--- file.c~ 2004-10-02 12:29:33.223660850 +0400
>>>>+++ file.c 2004-10-08 10:03:03.001561661 +0400
>>>>@@ -1137,6 +1137,8 @@
>>>>return result;
>>>>  }
>>>>
>>>>+    return generic_file_write(file, buf, count, ppos);
>>>>+
>>>>  if ( unlikely((ssize_t) count < 0 ))
>>>>      return -EINVAL;

which Hans asserted was about 5% slower than the resierfs custom
write implementation, but we countered at least meant that we
didn't crash in a steaming pile of processes stuck in D state
with no way out every few days.

It doesn't apply against 2.6.19 any more, which may be a good
sign.  I haven't seen anything in the changelogs that jumped
out at me as the fix though.

Regards,

Bron.
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