From: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Date: Tue, 28 Apr 2009 12:04:59 +0000 (+0900)
Subject: nilfs2: fix circular locking dependency of writer mutex
X-Git-Tag: linux-omap-v2.6.30-rc6~19^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=201913ed746c7724a40d33ee5a0b6a1fd2ef3193;p=pandora-kernel.git

nilfs2: fix circular locking dependency of writer mutex

This fixes the following circular locking dependency problem:

 =======================================================
 [ INFO: possible circular locking dependency detected ]
 2.6.30-rc3 #5
 -------------------------------------------------------
 segctord/3895 is trying to acquire lock:
  (&nilfs->ns_writer_mutex){+.+...}, at: [<d0d02172>]
   nilfs_mdt_get_block+0x89/0x20f [nilfs2]

 but task is already holding lock:
  (&bmap->b_sem){++++..}, at: [<d0d02d99>]
   nilfs_bmap_propagate+0x14/0x2e [nilfs2]

 which lock already depends on the new lock.

The bugfix is done by replacing call sites of nilfs_get_writer() which
are never called from read-only context with direct dereferencing of
pointer to a writable FS-instance.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
---

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