From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
To rely on the i_mutex for exclusion between setlease and rename, we
need rename to take the i_mutex on the source as well as on any possible
target.
Also fix up lockdep and the Documentation/filesystems/directory-locking
documentation.
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
---
Documentation/filesystems/directory-locking | 11 ++++++-----
fs/namei.c | 12 ++++++++++++
include/linux/fs.h | 9 ++++++---
3 files changed, 24 insertions(+), 8 deletions(-)
diff --git a/Documentation/filesystems/directory-locking b/Documentation/filesystems/directory-locking
index ff7b611..9edbcd2 100644
--- a/Documentation/filesystems/directory-locking
+++ b/Documentation/filesystems/directory-locking
@@ -12,8 +12,8 @@ kinds of locks - per-inode (->i_mutex) and per-filesystem
locks victim and calls the method.
4) rename() that is _not_ cross-directory. Locking rules: caller locks
-the parent, finds source and target, if target already exists - locks it
-and then calls the method.
+the parent, finds source and target, locks source, also locks target if
+it already exists, and then calls the method.
5) link creation. Locking rules:
* lock parent
@@ -30,6 +30,7 @@ rules:
fail with -ENOTEMPTY
* if new parent is equal to or is a descendent of source
fail with -ELOOP
+ * lock source if it is not a directory.
* if target exists - lock it.
* call the method.
@@ -56,9 +57,9 @@ objects - A < B iff A is an ancestor of B.
renames will be blocked on filesystem lock and we don't start changing
the order until we had acquired all locks).
-(3) any operation holds at most one lock on non-directory object and
- that lock is acquired after all other locks. (Proof: see descriptions
- of operations).
+(3) locks on non-directory objects are acquired only after taking locks
+ on their parents (which remain their parents until all locks are
+ acquired, by (1) and (2)). (Proof: see descriptions of operations).
Now consider the minimal deadlock. Each process is blocked on
attempt to acquire some lock and already holds at least one lock. Let's
diff --git a/fs/namei.c b/fs/namei.c
index 4516958..1e0c383 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3076,6 +3076,7 @@ static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
struct inode *target = new_dentry->d_inode;
+ struct inode *source = old_dentry->d_inode;
int error;
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
@@ -3083,6 +3084,7 @@ static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
return error;
dget(new_dentry);
+ mutex_lock_nested(&source->i_mutex, I_MUTEX_RENAME_SOURCE);
if (target)
mutex_lock(&target->i_mutex);
@@ -3090,6 +3092,14 @@ static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
goto out;
+ error = break_lease(source, BREAK_ONLY_DELEGS|BREAK_R_AND_W_LEASES);
+ if (error)
+ goto out;
+ if (target) {
+ error = break_lease(target, BREAK_ONLY_DELEGS|BREAK_R_AND_W_LEASES);
+ if (error)
+ goto out;
+ }
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
goto out;
@@ -3101,6 +3111,8 @@ static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
out:
if (target)
mutex_unlock(&target->i_mutex);
+out_unlock_source:
+ mutex_unlock(&source->i_mutex);
dput(new_dentry);
return error;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 89c8481..f6a09b4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -855,10 +855,12 @@ static inline int inode_unhashed(struct inode *inode)
* 0: the object of the current VFS operation
* 1: parent
* 2: child/target
- * 3: quota file
+ * 3: xattr
+ * 4: quota file
+ * 5: the file being renamed (used only in rename of a non-directory)
*
* The locking order between these classes is
- * parent -> child -> normal -> xattr -> quota
+ * parent -> child -> rename_source -> normal -> xattr -> quota
*/
enum inode_i_mutex_lock_class
{
@@ -866,7 +868,8 @@ enum inode_i_mutex_lock_class
I_MUTEX_PARENT,
I_MUTEX_CHILD,
I_MUTEX_XATTR,
- I_MUTEX_QUOTA
+ I_MUTEX_QUOTA,
+ I_MUTEX_RENAME_SOURCE
};
/*
--
1.7.5.4
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