From: Tejun Heo <htejun@gmail.com>
Date: Mon, 11 Jun 2007 05:04:01 +0000 (+0900)
Subject: sysfs: fix race condition around sd->s_dentry, take#2
X-Git-Tag: v2.6.22-rc5~45
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dd14cbc994709a1c5a64ed3621f583c49a27e521;p=pandora-kernel.git

sysfs: fix race condition around sd->s_dentry, take#2

Allowing attribute and symlink dentries to be reclaimed means
sd->s_dentry can change dynamically.  However, updates to the field
are unsynchronized leading to race conditions.  This patch adds
sysfs_lock and use it to synchronize updates to sd->s_dentry.

Due to the locking around ->d_iput, the check in sysfs_drop_dentry()
is complex.  sysfs_lock only protect sd->s_dentry pointer itself.  The
validity of the dentry is protected by dcache_lock, so whether dentry
is alive or not can only be tested while holding both locks.

This is minimal backport of sysfs_drop_dentry() rewrite in devel
branch.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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