linux-kernel - [PATCH 04/24] sysfs: Normalize removing sysfs directories.

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Date:	Thu, 28 May 2009 16:00:45 -0700
From:	"Eric W. Biederman" <ebiederm@...ssion.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Cc:	<linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	<linux-fsdevel@...r.kernel.org>,
	Kay Sievers <kay.sievers@...y.org>, Greg KH <greg@...ah.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: [PATCH 04/24] sysfs: Normalize removing sysfs directories.

From: Eric W. Biederman <ebiederm@...ssion.com>

Individually wrap each call to sysfs_remove_one with sysfs_addrm_start
and sysfs_addrm_finish this prepares for these functions to be removed.

I don't change the logic of which dirents we remove.  I do document
what we are doing and why what we are doing it.

A warning is added if we attempt to remove an non-empty directories
so that users that would prevsiosly have had leaks and other problems
like the scsi layer get a clear warning that there is a problem.

I don't hold sysfs_mutex across the entire operation as that is unneeded
for coherence at the sysfs level and some level of coordination is expected
at the upper layers.

Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
---
 fs/sysfs/dir.c |   62 +++++++++++++++++++++++++++++++++++++++----------------
 1 files changed, 44 insertions(+), 18 deletions(-)

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index b95cc07..3e3a87f 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -732,12 +732,28 @@ const struct inode_operations sysfs_dir_inode_operations = {
 	.setattr	= sysfs_setattr,
 };
 
-static void remove_dir(struct sysfs_dirent *sd)
+static void remove_dir(struct sysfs_dirent *dir_sd)
 {
 	struct sysfs_addrm_cxt acxt;
 
-	sysfs_addrm_start(&acxt, sd->s_parent);
-	sysfs_remove_one(&acxt, sd);
+	pr_debug("sysfs %s: removing dir\n", dir_sd->s_name);
+
+	/* Removing non-empty directories is not valid complain! */
+	if (unlikely(dir_sd->s_dir.children)) {
+		struct sysfs_dirent *sd;
+
+		WARN(1, KERN_WARNING "sysfs: removing non-empty dir: %s\n",
+			dir_sd->s_name);
+
+		mutex_lock(&sysfs_mutex);
+		for (sd = dir_sd->s_dir.children; sd; sd  = sd->s_sibling)
+			printk(KERN_WARNING "%s/%s\n",
+				dir_sd->s_name, sd->s_name);
+		mutex_unlock(&sysfs_mutex);
+	}
+
+	sysfs_addrm_start(&acxt, dir_sd->s_parent);
+	sysfs_remove_one(&acxt, dir_sd);
 	sysfs_addrm_finish(&acxt);
 }
 
@@ -746,27 +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;
-
-	if (!dir_sd)
-		return;
-
-	pr_debug("sysfs %s: removing dir\n", dir_sd->s_name);
-	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

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