On Tue, 2022-05-17 at 19:49 +0800, Xiubo Li wrote: > On 5/17/22 7:35 PM, Jeff Layton wrote: > > On Tue, 2022-05-17 at 09:03 +0800, Xiubo Li wrote: > > > In async unlink case the kclient won't wait for the first reply > > > from MDS and just drop all the links and unhash the dentry and then > > > succeeds immediately. > > > > > > For any new create/link/rename,etc requests followed by using the > > > same file names we must wait for the first reply of the inflight > > > unlink request, or the MDS possibly will fail these following > > > requests with -EEXIST if the inflight async unlink request was > > > delayed for some reasons. > > > > > > And the worst case is that for the none async openc request it will > > > successfully open the file if the CDentry hasn't been unlinked yet, > > > but later the previous delayed async unlink request will remove the > > > CDenty. That means the just created file is possiblly deleted later > > > by accident. > > > > > > We need to wait for the inflight async unlink requests to finish > > > when creating new files/directories by using the same file names. > > > > > > URL: https://tracker.ceph.com/issues/55332 > > > Reported-by: kernel test robot <lkp@xxxxxxxxx> > > > Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx> > > > --- > > > fs/ceph/dir.c | 70 +++++++++++++++++++++++++++++++++++++++---- > > > fs/ceph/file.c | 5 ++++ > > > fs/ceph/mds_client.c | 71 ++++++++++++++++++++++++++++++++++++++++++++ > > > fs/ceph/mds_client.h | 1 + > > > fs/ceph/super.c | 3 ++ > > > fs/ceph/super.h | 19 ++++++++---- > > > 6 files changed, 159 insertions(+), 10 deletions(-) > > > > > > diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c > > > index eae417d71136..88e0048d719e 100644 > > > --- a/fs/ceph/dir.c > > > +++ b/fs/ceph/dir.c > > > @@ -856,6 +856,10 @@ static int ceph_mknod(struct user_namespace *mnt_userns, struct inode *dir, > > > if (ceph_snap(dir) != CEPH_NOSNAP) > > > return -EROFS; > > > > > > + err = ceph_wait_on_conflict_unlink(dentry); > > > + if (err) > > > + return err; > > > + > > > if (ceph_quota_is_max_files_exceeded(dir)) { > > > err = -EDQUOT; > > > goto out; > > > @@ -918,6 +922,10 @@ static int ceph_symlink(struct user_namespace *mnt_userns, struct inode *dir, > > > if (ceph_snap(dir) != CEPH_NOSNAP) > > > return -EROFS; > > > > > > + err = ceph_wait_on_conflict_unlink(dentry); > > > + if (err) > > > + return err; > > > + > > > if (ceph_quota_is_max_files_exceeded(dir)) { > > > err = -EDQUOT; > > > goto out; > > > @@ -968,9 +976,13 @@ static int ceph_mkdir(struct user_namespace *mnt_userns, struct inode *dir, > > > struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb); > > > struct ceph_mds_request *req; > > > struct ceph_acl_sec_ctx as_ctx = {}; > > > - int err = -EROFS; > > > + int err; > > > int op; > > > > > > + err = ceph_wait_on_conflict_unlink(dentry); > > > + if (err) > > > + return err; > > > + > > > if (ceph_snap(dir) == CEPH_SNAPDIR) { > > > /* mkdir .snap/foo is a MKSNAP */ > > > op = CEPH_MDS_OP_MKSNAP; > > > @@ -980,6 +992,7 @@ static int ceph_mkdir(struct user_namespace *mnt_userns, struct inode *dir, > > > dout("mkdir dir %p dn %p mode 0%ho\n", dir, dentry, mode); > > > op = CEPH_MDS_OP_MKDIR; > > > } else { > > > + err = -EROFS; > > > goto out; > > > } > > > > > > @@ -1037,6 +1050,10 @@ static int ceph_link(struct dentry *old_dentry, struct inode *dir, > > > struct ceph_mds_request *req; > > > int err; > > > > > > + err = ceph_wait_on_conflict_unlink(dentry); > > > + if (err) > > > + return err; > > > + > > > if (ceph_snap(dir) != CEPH_NOSNAP) > > > return -EROFS; > > > > > > @@ -1071,9 +1088,27 @@ static int ceph_link(struct dentry *old_dentry, struct inode *dir, > > > static void ceph_async_unlink_cb(struct ceph_mds_client *mdsc, > > > struct ceph_mds_request *req) > > > { > > > + struct dentry *dentry = req->r_dentry; > > > + struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb); > > > + struct ceph_dentry_info *di = ceph_dentry(dentry); > > > int result = req->r_err ? req->r_err : > > > le32_to_cpu(req->r_reply_info.head->result); > > > > > > + if (test_bit(CEPH_DENTRY_ASYNC_UNLINK_BIT, &di->flags)) { > > Shouldn't this bit always be set in this case? Maybe this should be a > > WARN_ON ? > > Okay, maybe a pr_warn() as you mentioned below. > > > > > > > + BUG_ON(req->r_op != CEPH_MDS_OP_UNLINK); > > Note that this will crash the box in some environments (e.g. RHEL > > kernels). I really advise against adding new BUG_ON calls unless the > > situation is so dire that the machine can't (or shouldn't) continue on. > > > > In this case, we got a bogus reply from the MDS. I think throwing a > > pr_warn message and erroring out the unlink would be better. > > Makes sense. > > > > > + > > > + spin_lock(&fsc->async_unlink_conflict_lock); > > > + hash_del_rcu(&di->hnode); > > > + spin_unlock(&fsc->async_unlink_conflict_lock); > > > + > > > + spin_lock(&dentry->d_lock); > > > + di->flags &= ~CEPH_DENTRY_ASYNC_UNLINK; > > > + wake_up_bit(&di->flags, CEPH_DENTRY_ASYNC_UNLINK_BIT); > > > + spin_unlock(&dentry->d_lock); > > > + > > > + synchronize_rcu(); > > Why do you need to synchronize_rcu here? > > > > I guess the concern is that once we put the req, then it could put the > > dentry and free di while someone is still walking the hash? > > Yeah, right, we just need to make sure while iterating the hashtable the > di memory won't be released after this. > > > > + } > > > + > > > if (result == -EJUKEBOX) > > > goto out; > > > > > > @@ -1081,7 +1116,7 @@ static void ceph_async_unlink_cb(struct ceph_mds_client *mdsc, > > > if (result) { > > > int pathlen = 0; > > > u64 base = 0; > > > - char *path = ceph_mdsc_build_path(req->r_dentry, &pathlen, > > > + char *path = ceph_mdsc_build_path(dentry, &pathlen, > > > &base, 0); > > > > > > /* mark error on parent + clear complete */ > > > @@ -1089,13 +1124,13 @@ static void ceph_async_unlink_cb(struct ceph_mds_client *mdsc, > > > ceph_dir_clear_complete(req->r_parent); > > > > > > /* drop the dentry -- we don't know its status */ > > > - if (!d_unhashed(req->r_dentry)) > > > - d_drop(req->r_dentry); > > > + if (!d_unhashed(dentry)) > > > + d_drop(dentry); > > > > > > /* mark inode itself for an error (since metadata is bogus) */ > > > mapping_set_error(req->r_old_inode->i_mapping, result); > > > > > > - pr_warn("ceph: async unlink failure path=(%llx)%s result=%d!\n", > > > + pr_warn("async unlink failure path=(%llx)%s result=%d!\n", > > > base, IS_ERR(path) ? "<<bad>>" : path, result); > > > ceph_mdsc_free_path(path, pathlen); > > > } > > > @@ -1180,6 +1215,8 @@ static int ceph_unlink(struct inode *dir, struct dentry *dentry) > > > > > > if (try_async && op == CEPH_MDS_OP_UNLINK && > > > (req->r_dir_caps = get_caps_for_async_unlink(dir, dentry))) { > > > + struct ceph_dentry_info *di = ceph_dentry(dentry); > > > + > > > dout("async unlink on %llu/%.*s caps=%s", ceph_ino(dir), > > > dentry->d_name.len, dentry->d_name.name, > > > ceph_cap_string(req->r_dir_caps)); > > > @@ -1187,6 +1224,16 @@ static int ceph_unlink(struct inode *dir, struct dentry *dentry) > > > req->r_callback = ceph_async_unlink_cb; > > > req->r_old_inode = d_inode(dentry); > > > ihold(req->r_old_inode); > > > + > > > + spin_lock(&dentry->d_lock); > > > + di->flags |= CEPH_DENTRY_ASYNC_UNLINK; > > > + spin_unlock(&dentry->d_lock); > > > + > > > + spin_lock(&fsc->async_unlink_conflict_lock); > > > + hash_add_rcu(fsc->async_unlink_conflict, &di->hnode, > > > + dentry->d_name.hash); > > > + spin_unlock(&fsc->async_unlink_conflict_lock); > > > + > > > err = ceph_mdsc_submit_request(mdsc, dir, req); > > > if (!err) { > > > /* > > > @@ -1198,6 +1245,15 @@ static int ceph_unlink(struct inode *dir, struct dentry *dentry) > > > } else if (err == -EJUKEBOX) { > > > try_async = false; > > > ceph_mdsc_put_request(req); > > > + > > > + spin_lock(&dentry->d_lock); > > > + di->flags &= ~CEPH_DENTRY_ASYNC_UNLINK; > > > + spin_unlock(&dentry->d_lock); > > > + > > > + spin_lock(&fsc->async_unlink_conflict_lock); > > > + hash_del_rcu(&di->hnode); > > > + spin_unlock(&fsc->async_unlink_conflict_lock); > > > + > > > goto retry; > > > } > > > } else { > > > @@ -1237,6 +1293,10 @@ static int ceph_rename(struct user_namespace *mnt_userns, struct inode *old_dir, > > > (!ceph_quota_is_same_realm(old_dir, new_dir))) > > > return -EXDEV; > > > > > > + err = ceph_wait_on_conflict_unlink(new_dentry); > > > + if (err) > > > + return err; > > > + > > > dout("rename dir %p dentry %p to dir %p dentry %p\n", > > > old_dir, old_dentry, new_dir, new_dentry); > > > req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS); > > > diff --git a/fs/ceph/file.c b/fs/ceph/file.c > > > index 8c8226c0feac..47d068e6436a 100644 > > > --- a/fs/ceph/file.c > > > +++ b/fs/ceph/file.c > > > @@ -740,6 +740,10 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry, > > > if (dentry->d_name.len > NAME_MAX) > > > return -ENAMETOOLONG; > > > > > > + err = ceph_wait_on_conflict_unlink(dentry); > > > + if (err) > > > + return err; > > > + > > > if (flags & O_CREAT) { > > > if (ceph_quota_is_max_files_exceeded(dir)) > > > return -EDQUOT; > > > @@ -757,6 +761,7 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry, > > > /* If it's not being looked up, it's negative */ > > > return -ENOENT; > > > } > > > + > > > retry: > > > /* do the open */ > > > req = prepare_open_request(dir->i_sb, flags, mode); > > > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c > > > index e8c87dea0551..bb67f3d5a337 100644 > > > --- a/fs/ceph/mds_client.c > > > +++ b/fs/ceph/mds_client.c > > > @@ -655,6 +655,77 @@ static void destroy_reply_info(struct ceph_mds_reply_info_parsed *info) > > > free_pages((unsigned long)info->dir_entries, get_order(info->dir_buf_size)); > > > } > > > > > > +/* > > > + * In async unlink case the kclient won't wait for the first reply > > > + * from MDS and just drop all the links and unhash the dentry and then > > > + * succeeds immediately. > > > + * > > > + * For any new create/link/rename,etc requests followed by using the > > > + * same file names we must wait for the first reply of the inflight > > > + * unlink request, or the MDS possibly will fail these following > > > + * requests with -EEXIST if the inflight async unlink request was > > > + * delayed for some reasons. > > > + * > > > + * And the worst case is that for the none async openc request it will > > > + * successfully open the file if the CDentry hasn't been unlinked yet, > > > + * but later the previous delayed async unlink request will remove the > > > + * CDenty. That means the just created file is possiblly deleted later > > > + * by accident. > > > + * > > > + * We need to wait for the inflight async unlink requests to finish > > > + * when creating new files/directories by using the same file names. > > > + */ > > > +int ceph_wait_on_conflict_unlink(struct dentry *dentry) > > > +{ > > > + struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb); > > > + struct dentry *pdentry = dentry->d_parent; > > > + struct dentry *udentry, *found = NULL; > > > + struct ceph_dentry_info *di; > > > + struct qstr dname; > > > + u32 hash = dentry->d_name.hash; > > > + int err; > > > + > > > + dname.name = dentry->d_name.name; > > > + dname.len = dentry->d_name.len; > > > + > > > + rcu_read_lock(); > > > + hash_for_each_possible_rcu(fsc->async_unlink_conflict, di, > > > + hnode, hash) { > > > + udentry = di->dentry; > > > + > > > + spin_lock(&udentry->d_lock); > > > + if (udentry->d_name.hash != hash) > > > + goto next; > > > + if (unlikely(udentry->d_parent != pdentry)) > > > + goto next; > > > + if (!hash_hashed(&di->hnode)) > > > + goto next; > > > + > > > + WARN_ON_ONCE(!test_bit(CEPH_DENTRY_ASYNC_UNLINK_BIT, &di->flags)); > > A stack trace is not likely to be useful here. This means that we have > > an entry in the hash that looks invalid. The stack trace of the waiter > > probably won't tell us anything useful. > > > > What might be better is to pr_warn some info about the dentry in this > > case. Maybe the name, parent inode, etc... > Sure. > > > > > + > > > + if (d_compare(pdentry, udentry, &dname)) > > > + goto next; > > > + > > > + spin_unlock(&udentry->d_lock); > > > + found = dget(udentry); > > > + break; > > > +next: > > > + spin_unlock(&udentry->d_lock); > > > + } > > > + rcu_read_unlock(); > > > + > > > + if (likely(!found)) > > > + return 0; > > > + > > > + dout("%s dentry %p:%pd conflict with old %p:%pd\n", __func__, > > > + dentry, dentry, found, found); > > > + > > > + err = wait_on_bit(&di->flags, CEPH_DENTRY_ASYNC_UNLINK_BIT, > > > + TASK_INTERRUPTIBLE); > > > + dput(found); > > > + return err; > > > +} > > > + > > > > > > /* > > > * sessions > > > diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h > > > index 33497846e47e..d1ae679c52c3 100644 > > > --- a/fs/ceph/mds_client.h > > > +++ b/fs/ceph/mds_client.h > > > @@ -582,6 +582,7 @@ static inline int ceph_wait_on_async_create(struct inode *inode) > > > TASK_INTERRUPTIBLE); > > > } > > > > > > +extern int ceph_wait_on_conflict_unlink(struct dentry *dentry); > > > extern u64 ceph_get_deleg_ino(struct ceph_mds_session *session); > > > extern int ceph_restore_deleg_ino(struct ceph_mds_session *session, u64 ino); > > > #endif > > > diff --git a/fs/ceph/super.c b/fs/ceph/super.c > > > index b73b4f75462c..6542b71f8627 100644 > > > --- a/fs/ceph/super.c > > > +++ b/fs/ceph/super.c > > > @@ -816,6 +816,9 @@ static struct ceph_fs_client *create_fs_client(struct ceph_mount_options *fsopt, > > > if (!fsc->cap_wq) > > > goto fail_inode_wq; > > > > > > + hash_init(fsc->async_unlink_conflict); > > > + spin_lock_init(&fsc->async_unlink_conflict_lock); > > > + > > > spin_lock(&ceph_fsc_lock); > > > list_add_tail(&fsc->metric_wakeup, &ceph_fsc_list); > > > spin_unlock(&ceph_fsc_lock); > > > diff --git a/fs/ceph/super.h b/fs/ceph/super.h > > > index 506d52633627..c10adb7c1cde 100644 > > > --- a/fs/ceph/super.h > > > +++ b/fs/ceph/super.h > > > @@ -19,6 +19,7 @@ > > > #include <linux/security.h> > > > #include <linux/netfs.h> > > > #include <linux/fscache.h> > > > +#include <linux/hashtable.h> > > > > > > #include <linux/ceph/libceph.h> > > > > > > @@ -99,6 +100,8 @@ struct ceph_mount_options { > > > char *mon_addr; > > > }; > > > > > > +#define CEPH_ASYNC_CREATE_CONFLICT_BITS 12 > > > + > > Wow, that's 4k buckets. The hashtable alone will take 32k of memory on > > 64 bit arch. > > Okay, I miss reading the DECLARE_HASHTABLE macro, I thought this will be > the item number of the hash table arrary. > > > > I doubt you need this large a hashtable, particularly given that this is > > per-superblock. In most cases, we'll just have a few of these in flight > > at a time. > > A global hashtable ? And set the order to 8 ? Per-sb is fine, IMO. 6-8 bits sounds reasonable. > > > > struct ceph_fs_client { > > > struct super_block *sb; > > > > > > @@ -124,6 +127,9 @@ struct ceph_fs_client { > > > struct workqueue_struct *inode_wq; > > > struct workqueue_struct *cap_wq; > > > > > > + DECLARE_HASHTABLE(async_unlink_conflict, CEPH_ASYNC_CREATE_CONFLICT_BITS); > > > + spinlock_t async_unlink_conflict_lock; > > > + > > > #ifdef CONFIG_DEBUG_FS > > > struct dentry *debugfs_dentry_lru, *debugfs_caps; > > > struct dentry *debugfs_congestion_kb; > > > @@ -281,7 +287,8 @@ struct ceph_dentry_info { > > > struct dentry *dentry; > > > struct ceph_mds_session *lease_session; > > > struct list_head lease_list; > > > - unsigned flags; > > > + struct hlist_node hnode; > > > + unsigned long flags; > > > int lease_shared_gen; > > > u32 lease_gen; > > > u32 lease_seq; > > > @@ -290,10 +297,12 @@ struct ceph_dentry_info { > > > u64 offset; > > > }; > > > > > > -#define CEPH_DENTRY_REFERENCED 1 > > > -#define CEPH_DENTRY_LEASE_LIST 2 > > > -#define CEPH_DENTRY_SHRINK_LIST 4 > > > -#define CEPH_DENTRY_PRIMARY_LINK 8 > > > +#define CEPH_DENTRY_REFERENCED (1 << 0) > > > +#define CEPH_DENTRY_LEASE_LIST (1 << 1) > > > +#define CEPH_DENTRY_SHRINK_LIST (1 << 2) > > > +#define CEPH_DENTRY_PRIMARY_LINK (1 << 3) > > > +#define CEPH_DENTRY_ASYNC_UNLINK_BIT (4) > > > +#define CEPH_DENTRY_ASYNC_UNLINK (1 << CEPH_DENTRY_ASYNC_UNLINK_BIT) > > > > > > struct ceph_inode_xattrs_info { > > > /* > -- Jeff Layton <jlayton@xxxxxxxxxx>
