On Tue, Jun 22, 2021 at 1:57 AM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> Commit aa60cfc3f7ee broke the error handling in these functions such
> that they don't handle non-ENOENT errors from ceph_mdsc_do_request
> properly.
>
> Move the checking of -ENOENT out of ceph_handle_snapdir and into the
> callers, and if we get a different error, return it immediately.
>
> Fixes: aa60cfc3f7ee ("ceph: don't use d_add in ceph_handle_snapdir")
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/ceph/dir.c | 22 ++++++++++++----------
> fs/ceph/file.c | 14 ++++++++------
> fs/ceph/super.h | 2 +-
> 3 files changed, 21 insertions(+), 17 deletions(-)
>
> This one fixes the bug that Ilya spotted in ceph_atomic_open. Also,
> there is no need to test IS_ERR(dentry) unless we called
> ceph_handle_snapdir. Finally, it's probably best not to pass
> ceph_finish_lookup an ERR_PTR as a dentry. Reinstate the res pointer and
> only reset the dentry pointer if it's valid.
>
> diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> index 5624fae7a603..e78da771ec96 100644
> --- a/fs/ceph/dir.c
> +++ b/fs/ceph/dir.c
> @@ -668,14 +668,13 @@ static loff_t ceph_dir_llseek(struct file *file, loff_t offset, int whence)
> * Handle lookups for the hidden .snap directory.
> */
> struct dentry *ceph_handle_snapdir(struct ceph_mds_request *req,
> - struct dentry *dentry, int err)
> + struct dentry *dentry)
> {
> struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
> struct inode *parent = d_inode(dentry->d_parent); /* we hold i_mutex */
>
> /* .snap dir? */
> - if (err == -ENOENT &&
> - ceph_snap(parent) == CEPH_NOSNAP &&
> + if (ceph_snap(parent) == CEPH_NOSNAP &&
> strcmp(dentry->d_name.name, fsc->mount_options->snapdir_name) == 0) {
> struct dentry *res;
> struct inode *inode = ceph_get_snapdir(parent);
> @@ -742,7 +741,6 @@ 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;
> @@ -793,12 +791,16 @@ 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);
> - res = ceph_handle_snapdir(req, dentry, err);
> - if (IS_ERR(res)) {
> - err = PTR_ERR(res);
> - } else {
> - dentry = res;
> - err = 0;
> + if (err == -ENOENT) {
> + struct dentry *res;
> +
> + res = ceph_handle_snapdir(req, dentry);
Stray space here, fixed in the branch.
> + 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) */
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 7aa20d50a231..7c08f864694f 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -739,14 +739,16 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
> err = ceph_mdsc_do_request(mdsc,
> (flags & (O_CREAT|O_TRUNC)) ? dir : NULL,
> req);
> - dentry = ceph_handle_snapdir(req, dentry, err);
> - if (IS_ERR(dentry)) {
> - err = PTR_ERR(dentry);
> - goto out_req;
> + if (err == -ENOENT) {
> + dentry = ceph_handle_snapdir(req, dentry);
> + if (IS_ERR(dentry)) {
> + err = PTR_ERR(dentry);
> + goto out_req;
> + }
> + err = 0;
> }
> - err = 0;
>
> - if ((flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
> + if (!err && (flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
> err = ceph_handle_notrace_create(dir, dentry);
>
> if (d_in_lookup(dentry)) {
I must admit that I don't understand the code that follows. For
example, if ceph_handle_notrace_create() returns ENOENT, is it supposed
to be resolved by ceph_finish_lookup()? Because if it gets resolved,
err is not reset and we still jump to out_req, possibly leaving some
dentry references behind. It appears to be an older bug though.
This fix for dealing with ceph_mdsc_do_request() errors seems correct,
but I really think this code needs massaging to disentangle handling of
special cases from actual errors.
Reviewed-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Thanks,
Ilya
