UBIFS: simplify locking
This patch simplifies lock_[23]_inodes functions. We do not have
to care about locking order, because UBIFS does this for @i_mutex
and this is enough. Thanks to Al Viro for suggesting this.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index d29b771..f55d523 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -482,30 +482,29 @@
}
/**
- * lock_2_inodes - lock two UBIFS inodes.
+ * lock_2_inodes - a wrapper for locking two UBIFS inodes.
* @inode1: first inode
* @inode2: second inode
+ *
+ * We do not implement any tricks to guarantee strict lock ordering, because
+ * VFS has already done it for us on the @i_mutex. So this is just a simple
+ * wrapper function.
*/
static void lock_2_inodes(struct inode *inode1, struct inode *inode2)
{
- if (inode1->i_ino < inode2->i_ino) {
- mutex_lock_nested(&ubifs_inode(inode1)->ui_mutex, WB_MUTEX_2);
- mutex_lock_nested(&ubifs_inode(inode2)->ui_mutex, WB_MUTEX_3);
- } else {
- mutex_lock_nested(&ubifs_inode(inode2)->ui_mutex, WB_MUTEX_2);
- mutex_lock_nested(&ubifs_inode(inode1)->ui_mutex, WB_MUTEX_3);
- }
+ mutex_lock_nested(&ubifs_inode(inode1)->ui_mutex, WB_MUTEX_1);
+ mutex_lock_nested(&ubifs_inode(inode2)->ui_mutex, WB_MUTEX_2);
}
/**
- * unlock_2_inodes - unlock two UBIFS inodes inodes.
+ * unlock_2_inodes - a wrapper for unlocking two UBIFS inodes.
* @inode1: first inode
* @inode2: second inode
*/
static void unlock_2_inodes(struct inode *inode1, struct inode *inode2)
{
- mutex_unlock(&ubifs_inode(inode1)->ui_mutex);
mutex_unlock(&ubifs_inode(inode2)->ui_mutex);
+ mutex_unlock(&ubifs_inode(inode1)->ui_mutex);
}
static int ubifs_link(struct dentry *old_dentry, struct inode *dir,
@@ -527,6 +526,8 @@
dbg_gen("dent '%.*s' to ino %lu (nlink %d) in dir ino %lu",
dentry->d_name.len, dentry->d_name.name, inode->i_ino,
inode->i_nlink, dir->i_ino);
+ ubifs_assert(mutex_is_locked(&dir->i_mutex));
+ ubifs_assert(mutex_is_locked(&inode->i_mutex));
err = dbg_check_synced_i_size(inode);
if (err)
return err;
@@ -580,6 +581,8 @@
dbg_gen("dent '%.*s' from ino %lu (nlink %d) in dir ino %lu",
dentry->d_name.len, dentry->d_name.name, inode->i_ino,
inode->i_nlink, dir->i_ino);
+ ubifs_assert(mutex_is_locked(&dir->i_mutex));
+ ubifs_assert(mutex_is_locked(&inode->i_mutex));
err = dbg_check_synced_i_size(inode);
if (err)
return err;
@@ -667,7 +670,8 @@
dbg_gen("directory '%.*s', ino %lu in dir ino %lu", dentry->d_name.len,
dentry->d_name.name, inode->i_ino, dir->i_ino);
-
+ ubifs_assert(mutex_is_locked(&dir->i_mutex));
+ ubifs_assert(mutex_is_locked(&inode->i_mutex));
err = check_dir_empty(c, dentry->d_inode);
if (err)
return err;
@@ -922,59 +926,30 @@
}
/**
- * lock_3_inodes - lock three UBIFS inodes for rename.
+ * lock_3_inodes - a wrapper for locking three UBIFS inodes.
* @inode1: first inode
* @inode2: second inode
* @inode3: third inode
*
- * For 'ubifs_rename()', @inode1 may be the same as @inode2 whereas @inode3 may
- * be null.
+ * This function is used for 'ubifs_rename()' and @inode1 may be the same as
+ * @inode2 whereas @inode3 may be %NULL.
+ *
+ * We do not implement any tricks to guarantee strict lock ordering, because
+ * VFS has already done it for us on the @i_mutex. So this is just a simple
+ * wrapper function.
*/
static void lock_3_inodes(struct inode *inode1, struct inode *inode2,
struct inode *inode3)
{
- struct inode *i1, *i2, *i3;
-
- if (!inode3) {
- if (inode1 != inode2) {
- lock_2_inodes(inode1, inode2);
- return;
- }
- mutex_lock_nested(&ubifs_inode(inode1)->ui_mutex, WB_MUTEX_1);
- return;
- }
-
- if (inode1 == inode2) {
- lock_2_inodes(inode1, inode3);
- return;
- }
-
- /* 3 different inodes */
- if (inode1 < inode2) {
- i3 = inode2;
- if (inode1 < inode3) {
- i1 = inode1;
- i2 = inode3;
- } else {
- i1 = inode3;
- i2 = inode1;
- }
- } else {
- i3 = inode1;
- if (inode2 < inode3) {
- i1 = inode2;
- i2 = inode3;
- } else {
- i1 = inode3;
- i2 = inode2;
- }
- }
- mutex_lock_nested(&ubifs_inode(i1)->ui_mutex, WB_MUTEX_1);
- lock_2_inodes(i2, i3);
+ mutex_lock_nested(&ubifs_inode(inode1)->ui_mutex, WB_MUTEX_1);
+ if (inode2 != inode1)
+ mutex_lock_nested(&ubifs_inode(inode2)->ui_mutex, WB_MUTEX_2);
+ if (inode3)
+ mutex_lock_nested(&ubifs_inode(inode3)->ui_mutex, WB_MUTEX_3);
}
/**
- * unlock_3_inodes - unlock three UBIFS inodes for rename.
+ * unlock_3_inodes - a wrapper for unlocking three UBIFS inodes for rename.
* @inode1: first inode
* @inode2: second inode
* @inode3: third inode
@@ -982,11 +957,11 @@
static void unlock_3_inodes(struct inode *inode1, struct inode *inode2,
struct inode *inode3)
{
- mutex_unlock(&ubifs_inode(inode1)->ui_mutex);
- if (inode1 != inode2)
- mutex_unlock(&ubifs_inode(inode2)->ui_mutex);
if (inode3)
mutex_unlock(&ubifs_inode(inode3)->ui_mutex);
+ if (inode1 != inode2)
+ mutex_unlock(&ubifs_inode(inode2)->ui_mutex);
+ mutex_unlock(&ubifs_inode(inode1)->ui_mutex);
}
static int ubifs_rename(struct inode *old_dir, struct dentry *old_dentry,
@@ -1020,6 +995,11 @@
"dir ino %lu", old_dentry->d_name.len, old_dentry->d_name.name,
old_inode->i_ino, old_dir->i_ino, new_dentry->d_name.len,
new_dentry->d_name.name, new_dir->i_ino);
+ ubifs_assert(mutex_is_locked(&old_dir->i_mutex));
+ ubifs_assert(mutex_is_locked(&new_dir->i_mutex));
+ if (unlink)
+ ubifs_assert(mutex_is_locked(&new_inode->i_mutex));
+
if (unlink && is_dir) {
err = check_dir_empty(c, new_inode);