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Subject[PATCH 1/2] Use list.h instead of file_system_type next
Date
From: Tamir <carmeli.tamir@gmail.com>

Changed file_system_type next field to list_head and refactored
the code to use list.h functions.

Signed-off-by: Carmeli Tamir <carmeli.tamir@gmail.com>
---
fs/filesystems.c | 68 ++++++++++++++++++++++++----------------------
include/linux/fs.h | 2 +-
2 files changed, 36 insertions(+), 34 deletions(-)

diff --git a/fs/filesystems.c b/fs/filesystems.c
index 9135646e41ac..f12b98f2f079 100644
--- a/fs/filesystems.c
+++ b/fs/filesystems.c
@@ -31,7 +31,7 @@
* Once the reference is obtained we can drop the spinlock.
*/

-static struct file_system_type *file_systems;
+static LIST_HEAD(file_systems);
static DEFINE_RWLOCK(file_systems_lock);

/* WARNING: This can be used only if we _already_ own a reference */
@@ -46,14 +46,16 @@ void put_filesystem(struct file_system_type *fs)
module_put(fs->owner);
}

-static struct file_system_type **find_filesystem(const char *name, unsigned len)
+static struct file_system_type *find_filesystem(const char *name, unsigned len)
{
- struct file_system_type **p;
- for (p = &file_systems; *p; p = &(*p)->next)
- if (strncmp((*p)->name, name, len) == 0 &&
- !(*p)->name[len])
- break;
- return p;
+ struct file_system_type *p;
+
+ list_for_each_entry(p, &file_systems, fs_types) {
+ if (strncmp(p->name, name, len) == 0 &&
+ !p->name[len])
+ return p;
+ }
+ return NULL;
}

/**
@@ -72,20 +74,21 @@ static struct file_system_type **find_filesystem(const char *name, unsigned len)
int register_filesystem(struct file_system_type * fs)
{
int res = 0;
- struct file_system_type ** p;
+ struct file_system_type *p;

if (fs->parameters && !fs_validate_description(fs->parameters))
return -EINVAL;

BUG_ON(strchr(fs->name, '.'));
- if (fs->next)
- return -EBUSY;
+
+ INIT_LIST_HEAD(&fs->fs_types);
+
write_lock(&file_systems_lock);
p = find_filesystem(fs->name, strlen(fs->name));
- if (*p)
+ if (p)
res = -EBUSY;
else
- *p = fs;
+ list_add_tail(&fs->fs_types, &file_systems);
write_unlock(&file_systems_lock);
return res;
}
@@ -106,19 +109,16 @@ EXPORT_SYMBOL(register_filesystem);

int unregister_filesystem(struct file_system_type * fs)
{
- struct file_system_type ** tmp;
+ struct file_system_type *tmp;

write_lock(&file_systems_lock);
- tmp = &file_systems;
- while (*tmp) {
- if (fs == *tmp) {
- *tmp = fs->next;
- fs->next = NULL;
+ list_for_each_entry(tmp, &file_systems, fs_types) {
+ if (fs == tmp) {
+ list_del(&tmp->fs_types);
write_unlock(&file_systems_lock);
synchronize_rcu();
return 0;
}
- tmp = &(*tmp)->next;
}
write_unlock(&file_systems_lock);

@@ -141,7 +141,8 @@ static int fs_index(const char __user * __name)

err = -EINVAL;
read_lock(&file_systems_lock);
- for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
+ list_for_each_entry(tmp, &file_systems, fs_types) {
+ index++;
if (strcmp(tmp->name, name->name) == 0) {
err = index;
break;
@@ -158,9 +159,11 @@ static int fs_name(unsigned int index, char __user * buf)
int len, res;

read_lock(&file_systems_lock);
- for (tmp = file_systems; tmp; tmp = tmp->next, index--)
+ list_for_each_entry(tmp, &file_systems, fs_types) {
+ index--;
if (index <= 0 && try_module_get(tmp->owner))
break;
+ }
read_unlock(&file_systems_lock);
if (!tmp)
return -EINVAL;
@@ -174,12 +177,13 @@ static int fs_name(unsigned int index, char __user * buf)

static int fs_maxindex(void)
{
- struct file_system_type * tmp;
- int index;
+ struct list_head *pos;
+ int index = 0;

read_lock(&file_systems_lock);
- for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
- ;
+ list_for_each(pos, &file_systems) {
+ index++;
+ }
read_unlock(&file_systems_lock);
return index;
}
@@ -214,12 +218,12 @@ int __init get_filesystem_list(char *buf)
struct file_system_type * tmp;

read_lock(&file_systems_lock);
- tmp = file_systems;
- while (tmp && len < PAGE_SIZE - 80) {
+ list_for_each_entry(tmp, &file_systems, fs_types) {
+ if (len >= PAGE_SIZE - 80)
+ break;
len += sprintf(buf+len, "%s\t%s\n",
(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
tmp->name);
- tmp = tmp->next;
}
read_unlock(&file_systems_lock);
return len;
@@ -231,12 +235,10 @@ static int filesystems_proc_show(struct seq_file *m, void *v)
struct file_system_type * tmp;

read_lock(&file_systems_lock);
- tmp = file_systems;
- while (tmp) {
+ list_for_each_entry(tmp, &file_systems, fs_types) {
seq_printf(m, "%s\t%s\n",
(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
tmp->name);
- tmp = tmp->next;
}
read_unlock(&file_systems_lock);
return 0;
@@ -255,7 +257,7 @@ static struct file_system_type *__get_fs_type(const char *name, int len)
struct file_system_type *fs;

read_lock(&file_systems_lock);
- fs = *(find_filesystem(name, len));
+ fs = find_filesystem(name, len);
if (fs && !try_module_get(fs->owner))
fs = NULL;
read_unlock(&file_systems_lock);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index dd28e7679089..833ada15bc8a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2182,7 +2182,7 @@ struct file_system_type {
const char *, void *);
void (*kill_sb) (struct super_block *);
struct module *owner;
- struct file_system_type * next;
+ struct list_head fs_types; /* All registered file_system_type structs */
struct hlist_head fs_supers;

struct lock_class_key s_lock_key;
--
2.19.1
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