Messages in this thread | | | Subject | Re: [PATCH 2/2] ceph: wait the first reply of inflight unlink/rmdir | From | Xiubo Li <> | Date | Tue, 17 May 2022 08:48:14 +0800 |
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On 5/17/22 12:58 AM, Jeff Layton wrote: > On Mon, 2022-05-16 at 22:56 +0800, Xiubo Li wrote: >> On 5/16/22 9:23 PM, Jeff Layton wrote: >>> On Mon, 2022-05-16 at 20:20 +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 >>>> Signed-off-by: Xiubo Li <xiubli@redhat.com> >>>> --- >>>> fs/ceph/dir.c | 55 +++++++++++++++++++++++++++++++---- >>>> fs/ceph/file.c | 5 ++++ >>>> fs/ceph/mds_client.c | 69 ++++++++++++++++++++++++++++++++++++++++++++ >>>> fs/ceph/mds_client.h | 1 + >>>> fs/ceph/super.c | 2 ++ >>>> fs/ceph/super.h | 18 ++++++++---- >>>> 6 files changed, 140 insertions(+), 10 deletions(-) >>>> >>>> diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c >>>> index eae417d71136..20c648406528 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 +1088,24 @@ 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_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)) { >>>> + BUG_ON(req->r_op != CEPH_MDS_OP_UNLINK); >>>> + >>>> + hash_del_rcu(&di->hnode); >>>> + >>>> + 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(); >>>> + } >>>> + >>>> if (result == -EJUKEBOX) >>>> goto out; >>>> >>>> @@ -1081,7 +1113,7 @@ 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 +1121,13 @@ 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); >>>> } >>>> @@ -1189,12 +1221,21 @@ static int ceph_unlink(struct inode *dir, struct dentry *dentry) >>>> ihold(req->r_old_inode); >>>> err = ceph_mdsc_submit_request(mdsc, dir, req); >>>> if (!err) { >>>> + struct ceph_dentry_info *di; >>>> + >>>> /* >>>> * We have enough caps, so we assume that the unlink >>>> * will succeed. Fix up the target inode and dcache. >>>> */ >>>> drop_nlink(inode); >>>> d_delete(dentry); >>>> + >>>> + spin_lock(&dentry->d_lock); >>>> + di = ceph_dentry(dentry); >>>> + di->flags |= CEPH_DENTRY_ASYNC_UNLINK; >>>> + hash_add_rcu(fsc->async_unlink_conflict, &di->hnode, >>>> + dentry->d_name.hash); >>>> + spin_unlock(&dentry->d_lock); >>> This looks racy. It's possible that the reply comes in before we get to >>> the point of setting this flag. You probably want to do this before >>> calling ceph_mdsc_submit_request, and just unwind it if the submission >>> fails. >> Ah, right. Will fix it. >> >> >>> Also, you do still need some sort of lock to protect the >>> hash_add/del/_rcu calls. >> Sure, will fix it too. >> >>> Those don't do any locking on their own. The >>> d_lock is insufficient here since it can't protect the whole list. You >>> may be able to use the i_ceph_lock of the parent though? >> The hashtable is a global one, so we couldn't use the i_ceph_lock here. >> I will add one dedicated spin lock for each sb. >> >>>> } else if (err == -EJUKEBOX) { >>>> try_async = false; >>>> ceph_mdsc_put_request(req); >>>> @@ -1237,6 +1278,10 @@ 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; >>>> + >>> What might be nice here eventually is to not block an async create here, >>> but instead queue the request so that it gets transmitted after the >>> async unlink reply comes in. >>> >>> That'll be hard to get right though, so this is fine for now. >> Sure. >> >>>> 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..0ae0e0110eb4 100644 >>>> --- a/fs/ceph/mds_client.c >>>> +++ b/fs/ceph/mds_client.c >>>> @@ -468,6 +468,75 @@ static int ceph_parse_deleg_inos(void **p, void *end, >>>> return -EIO; >>>> } >>>> >>>> +/* >>>> + * 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; >>>> + >>>> + if (!test_bit(CEPH_DENTRY_ASYNC_UNLINK_BIT, &di->flags)) >>>> + goto next; >>>> + >>> Maybe this should be a warning? Will we ever have entries in this >>> hashtable that don't have this bit set? >> Just before we take "spin_lock(&udentry->d_lock)" the udentry could be >> already removed from hashtable and the bit was cleared ? >> >> > > The point is that you're removing the dentry from the hash before you > clear the flag, so there should never be a dentry in the hash that has > the flag cleared. > Yeah, makes sense. Will make it a warning here.
-- XIubo
>>>> + 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; >>>> + >>>> + err = wait_on_bit(&di->flags, CEPH_DENTRY_ASYNC_UNLINK_BIT, >>>> + TASK_INTERRUPTIBLE); >>>> + dput(found); >>>> + return err; >>>> +} >>>> + >>>> u64 ceph_get_deleg_ino(struct ceph_mds_session *s) >>>> { >>>> unsigned long ino; >>>> 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..7ae65001f04c 100644 >>>> --- a/fs/ceph/super.c >>>> +++ b/fs/ceph/super.c >>>> @@ -816,6 +816,8 @@ 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(&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..58bbb5df42da 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 >>>> + >>>> struct ceph_fs_client { >>>> struct super_block *sb; >>>> >>>> @@ -124,6 +127,8 @@ struct ceph_fs_client { >>>> struct workqueue_struct *inode_wq; >>>> struct workqueue_struct *cap_wq; >>>> >>>> + DECLARE_HASHTABLE(async_unlink_conflict, CEPH_ASYNC_CREATE_CONFLICT_BITS); >>>> + >>>> #ifdef CONFIG_DEBUG_FS >>>> struct dentry *debugfs_dentry_lru, *debugfs_caps; >>>> struct dentry *debugfs_congestion_kb; >>>> @@ -281,7 +286,8 @@ 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 +296,12 @@ 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 { >>>> /*
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