In some cases we need to take both source (old) and target(new) dentry
ovl_inode->lock. This patch adds support for that. Locks are taken in
order of increasing inode address to avoid deadlock. This code has been
taken from lock_two_nondirectories().
As of now, metacopy needs this lock if we are planning to update redirect
information on source/target ovl_inode. nlink related accounting takes this
lock on target for the case of overwrite.
One change w.r.t existing code is mutex_lock() vs mutex_lock_interruptible().
Now ovl_rename() code path has switched to mutex_lock() variant for
ovl_inode->lock. There is no particular reason, I just found it easier
to reuse lock_two_nondirectories(), that's why. Hoping its not a concern.
Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
fs/overlayfs/dir.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 82 insertions(+), 5 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 1f003be4a19e..3ea052b6bac7 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -896,12 +896,84 @@ static int ovl_set_redirect(struct dentry *dentry, bool samedir)
return err;
}
+static void ovl_lock_two_nondirectories(struct ovl_inode *oi1,
+ struct ovl_inode *oi2)
+{
+ if (oi1 > oi2)
+ swap(oi1, oi2);
+
+ if (oi1)
+ mutex_lock(&oi1->lock);
+ if (oi2 && oi2 != oi1)
+ mutex_lock_nested(&oi2->lock, I_MUTEX_NONDIR2);
+}
+
+static void ovl_rename_lock_ovl_inodes(struct dentry *old, struct dentry *new,
+ bool overwrite, bool *old_locked,
+ bool *new_locked)
+{
+ bool lock_old = false, lock_new = false;
+ struct ovl_inode * oi1 = NULL, *oi2 = NULL;
+
+ /*
+ * First determine which inodes need to be locked.
+ *
+ * If "old" is metacopy, oi->redirect will be set. So we need lock
+ * on old ovl_inode. If "new" is metacopy, and it is not being
+ * overwritten, then oi->redirect will be set and we will need
+ * lock on new ovl_inode.
+ */
+
+ if (ovl_is_metacopy_dentry(old))
+ lock_old = true;
+
+ if (!overwrite && ovl_is_metacopy_dentry(new))
+ lock_new = true;
+ /*
+ * For nlink, if we are overwriting and new->inode is not empty,
+ * then we need to take lock on new ovl_inode.
+ */
+ if (overwrite && d_inode(new))
+ lock_new = true;
+
+ oi1 = OVL_I(d_inode(old));
+ if (lock_new)
+ oi2 = OVL_I(d_inode(new));
+
+ if (lock_old && lock_new) {
+ ovl_lock_two_nondirectories(oi1, oi2);
+ *old_locked = *new_locked = true;
+ return;
+ }
+
+ if (lock_old) {
+ mutex_lock(&oi1->lock);
+ *old_locked = true;
+ return;
+ }
+
+ if (lock_new) {
+ mutex_lock(&oi2->lock);
+ *new_locked = true;
+ }
+}
+
+static void ovl_rename_unlock_ovl_inodes(struct dentry *old, struct dentry *new,
+ bool old_locked, bool new_locked)
+{
+ if (old_locked)
+ mutex_unlock(&OVL_I(d_inode(old))->lock);
+
+ if (new_locked && d_inode(old) != d_inode(new))
+ mutex_unlock(&OVL_I(d_inode(new))->lock);
+}
+
static int ovl_rename(struct inode *olddir, struct dentry *old,
struct inode *newdir, struct dentry *new,
unsigned int flags)
{
int err;
- bool new_locked = false;
+ bool old_locked = false, new_locked = false;
struct dentry *old_upperdir;
struct dentry *new_upperdir;
struct dentry *olddentry;
@@ -973,10 +1045,12 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
goto out_drop_write;
}
- if (overwrite) {
- err = ovl_nlink_start(new, &new_locked);
+ ovl_rename_lock_ovl_inodes(old, new, overwrite, &old_locked,
+ &new_locked);
+ if (overwrite && new_locked) {
+ err = ovl_nlink_start_locked(new);
if (err)
- goto out_drop_write;
+ goto out_unlock_inodes;
}
old_cred = ovl_override_creds(old->d_sb);
@@ -1102,7 +1176,10 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
unlock_rename(new_upperdir, old_upperdir);
out_revert_creds:
revert_creds(old_cred);
- ovl_nlink_end(new, new_locked);
+ if (new_locked)
+ ovl_nlink_end_locked(new);
+out_unlock_inodes:
+ ovl_rename_unlock_ovl_inodes(old, new, old_locked, new_locked);
out_drop_write:
ovl_drop_write(old);
out:
--
2.13.6
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