It's possible ceph_get_snapdir could end up finding a (disconnected)
inode that already exists in the cache. Change the prototype for
ceph_handle_snapdir to return a dentry pointer and have it use
d_splice_alias so we don't end up with an aliased dentry in the cache.
URL: https://tracker.ceph.com/issues/49843
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/ceph/dir.c | 32 ++++++++++++++++++++------------
fs/ceph/file.c | 7 +++++--
fs/ceph/super.h | 2 +-
3 files changed, 26 insertions(+), 15 deletions(-)
v2:
zero out err var when ceph_handle_snapdir returns success
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index 113f669d71dd..570662dec3fe 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -667,8 +667,8 @@ static loff_t ceph_dir_llseek(struct file *file, loff_t offset, int whence)
/*
* Handle lookups for the hidden .snap directory.
*/
-int ceph_handle_snapdir(struct ceph_mds_request *req,
- struct dentry *dentry, int err)
+struct dentry *ceph_handle_snapdir(struct ceph_mds_request *req,
+ struct dentry *dentry, int err)
{
struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
struct inode *parent = d_inode(dentry->d_parent); /* we hold i_mutex */
@@ -676,18 +676,19 @@ int ceph_handle_snapdir(struct ceph_mds_request *req,
/* .snap dir? */
if (err == -ENOENT &&
ceph_snap(parent) == CEPH_NOSNAP &&
- strcmp(dentry->d_name.name,
- fsc->mount_options->snapdir_name) == 0) {
+ strcmp(dentry->d_name.name, fsc->mount_options->snapdir_name) == 0) {
+ struct dentry *res;
struct inode *inode = ceph_get_snapdir(parent);
+
if (IS_ERR(inode))
- return PTR_ERR(inode);
- dout("ENOENT on snapdir %p '%pd', linking to snapdir %p\n",
- dentry, dentry, inode);
- BUG_ON(!d_unhashed(dentry));
- d_add(dentry, inode);
- err = 0;
+ return ERR_CAST(inode);
+ res = d_splice_alias(inode, dentry);
+ dout("ENOENT on snapdir %p '%pd', linking to snapdir %p. Spliced dentry %p\n",
+ dentry, dentry, inode, res);
+ if (res)
+ dentry = res;
}
- return err;
+ return dentry;
}
/*
@@ -743,6 +744,7 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb);
struct ceph_mds_request *req;
+ struct dentry *res;
int op;
int mask;
int err;
@@ -793,7 +795,13 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
req->r_parent = dir;
set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
err = ceph_mdsc_do_request(mdsc, NULL, req);
- err = ceph_handle_snapdir(req, dentry, err);
+ res = ceph_handle_snapdir(req, dentry, err);
+ if (IS_ERR(res)) {
+ err = PTR_ERR(res);
+ } else {
+ dentry = res;
+ err = 0;
+ }
dentry = ceph_finish_lookup(req, dentry, err);
ceph_mdsc_put_request(req); /* will dput(dentry) */
dout("lookup result=%p\n", dentry);
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 209535d5b8d3..a6ef1d143308 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -739,9 +739,12 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
err = ceph_mdsc_do_request(mdsc,
(flags & (O_CREAT|O_TRUNC)) ? dir : NULL,
req);
- err = ceph_handle_snapdir(req, dentry, err);
- if (err)
+ dentry = ceph_handle_snapdir(req, dentry, err);
+ if (IS_ERR(dentry)) {
+ err = PTR_ERR(dentry);
goto out_req;
+ }
+ err = 0;
if ((flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
err = ceph_handle_notrace_create(dir, dentry);
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 188565d806b2..07a3fb52ae30 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -1193,7 +1193,7 @@ extern const struct dentry_operations ceph_dentry_ops;
extern loff_t ceph_make_fpos(unsigned high, unsigned off, bool hash_order);
extern int ceph_handle_notrace_create(struct inode *dir, struct dentry *dentry);
-extern int ceph_handle_snapdir(struct ceph_mds_request *req,
+extern struct dentry *ceph_handle_snapdir(struct ceph_mds_request *req,
struct dentry *dentry, int err);
extern struct dentry *ceph_finish_lookup(struct ceph_mds_request *req,
struct dentry *dentry, int err);
