From: Thomas Betker <thomas.betker@rohde-schwarz.com>
Date: Tue, 10 Nov 2015 21:18:15 +0000 (+0100)
Subject: Revert "jffs2: Fix lock acquisition order bug in jffs2_write_begin"
X-Git-Tag: v3.2.79~26
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b7289da851178cdb10e4871547c36947eccd84af;p=pandora-kernel.git

Revert "jffs2: Fix lock acquisition order bug in jffs2_write_begin"

commit 157078f64b8a9cd7011b6b900b2f2498df850748 upstream.

This reverts commit 5ffd3412ae55
("jffs2: Fix lock acquisition order bug in jffs2_write_begin").

The commit modified jffs2_write_begin() to remove a deadlock with
jffs2_garbage_collect_live(), but this introduced new deadlocks found
by multiple users. page_lock() actually has to be called before
mutex_lock(&c->alloc_sem) or mutex_lock(&f->sem) because
jffs2_write_end() and jffs2_readpage() are called with the page locked,
and they acquire c->alloc_sem and f->sem, resp.

In other words, the lock order in jffs2_write_begin() was correct, and
it is the jffs2_garbage_collect_live() path that has to be changed.

Revert the commit to get rid of the new deadlocks, and to clear the way
for a better fix of the original deadlock.

Reported-by: Deng Chao <deng.chao1@zte.com.cn>
Reported-by: Ming Liu <liu.ming50@gmail.com>
Reported-by: wangzaiwei <wangzaiwei@top-vision.cn>
Signed-off-by: Thomas Betker <thomas.betker@rohde-schwarz.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
[bwh: Backported to 3.2: use D1(printk(KERN_DEBUG ...)) instead of
 jffs2_dbg(1, ...)]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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