[PATCH 04/20] sysfs: Handle the general case of removing of directories with subdirectories

[Eric W. Biederman]

From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>

Modify sysfs to properly remove directories containing attributes and
subdirectories.  The code is relatively simple and means we don't have
to worry about what might use this logic.

In a quick survey I have only found /sys/dev/char and /sys/dev/block that are
removing non-enmpty directories today (and they are exclusively filled with symlinks).
So only removing empty directories does not appear to be an option.

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@xxxxxxxxxxxxxxxxxx>
---
 fs/sysfs/dir.c |   54 ++++++++++++++++++++++++++----------------------------
 1 files changed, 26 insertions(+), 28 deletions(-)

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index b95cc07..50702b3 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -732,43 +732,41 @@ const struct inode_operations sysfs_dir_inode_operations = {
 	.setattr	= sysfs_setattr,
 };
 
-static void remove_dir(struct sysfs_dirent *sd)
+static struct sysfs_dirent *sysfs_get_one(struct sysfs_dirent *dir_sd)
 {
-	struct sysfs_addrm_cxt acxt;
-
-	sysfs_addrm_start(&acxt, sd->s_parent);
-	sysfs_remove_one(&acxt, sd);
-	sysfs_addrm_finish(&acxt);
-}
-
-void sysfs_remove_subdir(struct sysfs_dirent *sd)
-{
-	remove_dir(sd);
+	struct sysfs_dirent *sd = dir_sd;
+	mutex_lock(&sysfs_mutex);
+	while ((sysfs_type(sd) == SYSFS_DIR) && sd->s_dir.children)
+		sd = sd->s_dir.children;
+	if (sd != dir_sd)
+		sysfs_get(sd);
+	else
+		sd = NULL;
+	mutex_unlock(&sysfs_mutex);
+	return sd;
 }
 
-
-static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)
+static void remove_dir(struct sysfs_dirent *dir_sd)
 {
 	struct sysfs_addrm_cxt acxt;
-	struct sysfs_dirent **pos;
-
-	if (!dir_sd)
-		return;
+	struct sysfs_dirent *sd;
 
 	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;
 
-		if (sysfs_type(sd) != SYSFS_DIR)
-			sysfs_remove_one(&acxt, sd);
-		else
-			pos = &(*pos)->s_sibling;
+	while ((sd = sysfs_get_one(dir_sd))) {
+		sysfs_addrm_start(&acxt, sd->s_parent);
+		sysfs_remove_one(&acxt, sd);
+		sysfs_addrm_finish(&acxt);
+		sysfs_put(sd);
 	}
+	sysfs_addrm_start(&acxt, dir_sd->s_parent);
+	sysfs_remove_one(&acxt, dir_sd);
 	sysfs_addrm_finish(&acxt);
+}
 
-	remove_dir(dir_sd);
+void sysfs_remove_subdir(struct sysfs_dirent *sd)
+{
+	remove_dir(sd);
 }
 
 /**
@@ -788,7 +786,7 @@ void sysfs_remove_dir(struct kobject * kobj)
 	kobj->sd = NULL;
 	spin_unlock(&sysfs_assoc_lock);
 
-	__sysfs_remove_dir(sd);
+	remove_dir(sd);
 }
 
 int sysfs_rename_dir(struct kobject * kobj, const char *new_name)
-- 
1.6.1.2.350.g88cc

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