linux-ext4 - write/write/fallocate quota leakage

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Message-ID: <87typk1q8i.fsf@openvz.org>
Date:	Thu, 03 Jun 2010 12:21:01 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	"Aneesh Kumar K. V." <aneesh.kumar@...ux.vnet.ibm.com>
CC:	linux-ext4@...r.kernel.org
Subject: write/write/fallocate quota leakage

Recently one "write vs fallocate" quota leakage was fixed, but
not completely. It is still possible if uninitialized extent which
covers several delay allocated regions converted to initialized one.

Take a look at test-case attached.
The issue is clear enough, but I don't have a good solution for now.
Off course we can add one more restriction to zeroout logic, but this is
unproductive way because we have to keep zeroout logic simple as possible.

Aneesh, do you have any sound ideas?

View attachment "falloc_opt.c" of type "text/plain" (1172 bytes)