From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Eric W. Biederman" Subject: [PATCH 06/26] sysfs: Don't hold addrm_start/addrm_finish over multiple removals. Date: Fri, 29 May 2009 13:19:16 -0700 Message-ID: <1243628376-22905-6-git-send-email-ebiederm@xmission.com> References: Cc: , Tejun Heo , Cornelia Huck , , Kay Sievers , Greg KH , "Eric W. Biederman" , "Eric W. Biederman" To: Andrew Morton , Greg Kroah-Hartman Return-path: Received: from out02.mta.xmission.com ([166.70.13.232]:45195 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763280AbZE2UTx (ORCPT ); Fri, 29 May 2009 16:19:53 -0400 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: From: Eric W. Biederman With respect to the basic integrity of the sysfs data structures holding the locks across the deletion of multiple sysfs_dirents is unnecessary. Upper layers are required to coordinate their activity so that they do not add or delete entries in sysfs directories as they are being removed, and I have seen nothing to indicate the don't. The upper layers can not rely on sysfs doing anything for them as it is a compile option and may not be there. So the previous atomic delete of the directory entries and the directory serves no useful purpose. By removing the only case where addrm_start/addrm_finish are held over multiple dirent removals I simplify the requirements and pave the way removing sysfs_addrm_start and sysfs_addrm_finish completely. Additionally add some comments explaining some of the thinking behind sysfs_dirent removal in __sysfs_remove_dir. Signed-off-by: Eric W. Biederman --- fs/sysfs/dir.c | 36 +++++++++++++++++++++++++----------- 1 files changed, 25 insertions(+), 11 deletions(-) diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index 60482be..3e3a87f 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -762,23 +762,37 @@ void sysfs_remove_subdir(struct sysfs_dirent *sd) remove_dir(sd); } +static struct sysfs_dirent *get_dirent_to_remove(struct sysfs_dirent *dir_sd) +{ + struct sysfs_dirent *sd; + + mutex_lock(&sysfs_mutex); + for (sd = dir_sd->s_dir.children; sd; sd = sd->s_sibling) { + /* Directories might be owned by someone else + * making recursive directory removal unsafe. + */ + if (sysfs_type(sd) == SYSFS_DIR) + continue; + break; + } + sysfs_get(sd); + mutex_unlock(&sysfs_mutex); + + return sd; +} static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd) { struct sysfs_addrm_cxt acxt; - struct sysfs_dirent **pos; - - sysfs_addrm_start(&acxt, dir_sd); - pos = &dir_sd->s_dir.children; - while (*pos) { - struct sysfs_dirent *sd = *pos; + struct sysfs_dirent *sd; - if (sysfs_type(sd) != SYSFS_DIR) - sysfs_remove_one(&acxt, sd); - else - pos = &(*pos)->s_sibling; + /* Remove children that we think are safe */ + while ((sd = get_dirent_to_remove(dir_sd))) { + sysfs_addrm_start(&acxt, sd->s_parent); + sysfs_remove_one(&acxt, sd); + sysfs_addrm_finish(&acxt); + sysfs_put(sd); } - sysfs_addrm_finish(&acxt); remove_dir(dir_sd); } -- 1.6.3.1.54.g99dd.dirty