From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Date: Sun, 16 Jan 2011 17:22:02 +0000 (+0200)
Subject: UBIFS: do not start the commit if there is nothing to commit
X-Git-Tag: v2.6.39-rc1~421^2~22
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=944fdef52ca9fc0fe077578f51201ef397e30abe;p=pandora-kernel.git

UBIFS: do not start the commit if there is nothing to commit

This patch fixes suboptimal UBIFS 'sync_fs()' implementation which causes
flash I/O even if the file-system is synchronized. E.g., a 'printk()'
in the MTD erasure function (e.g., 'nand_erase_nand()') can show that
for every 'sync' shell command UBIFS erases at least one eraseblock.

So '$ while true; do sync; done' will cause huge amount of flash I/O.

The reason for this is that UBIFS commits in 'sync_fs()', and starts the
commit even if there is nothing to commit, e.g., it anyway changes the
log. This patch adds a check in the 'do_commit()' UBIFS functions which
prevents the commit if there is nothing to commit.

Reported-by: Hans J. Koch <hjk@linutronix.de>
Tested-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
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