From 8d0d254b15cc5b7d46d85fb7ab8ecede9575e672 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Fri, 30 Sep 2022 16:56:02 -0400 Subject: nfsd: fix nfsd_file_unhash_and_dispose nfsd_file_unhash_and_dispose() is called for two reasons: We're either shutting down and purging the filecache, or we've gotten a notification about a file delete, so we want to go ahead and unhash it so that it'll get cleaned up when we close. We're either walking the hashtable or doing a lookup in it and we don't take a reference in either case. What we want to do in both cases is to try and unhash the object and put it on the dispose list if that was successful. If it's no longer hashed, then we don't want to touch it, with the assumption being that something else is already cleaning up the sentinel reference. Instead of trying to selectively decrement the refcount in this function, just unhash it, and if that was successful, move it to the dispose list. Then, the disposal routine will just clean that up as usual. Also, just make this a void function, drop the WARN_ON_ONCE, and the comments about deadlocking since the nature of the purported deadlock is no longer clear. Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever --- fs/nfsd/filecache.c | 36 +++++++----------------------------- 1 file changed, 7 insertions(+), 29 deletions(-) (limited to 'fs') diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index d5c57360b418..640a3c52c056 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -405,22 +405,15 @@ nfsd_file_unhash(struct nfsd_file *nf) return false; } -/* - * Return true if the file was unhashed. - */ -static bool +static void nfsd_file_unhash_and_dispose(struct nfsd_file *nf, struct list_head *dispose) { trace_nfsd_file_unhash_and_dispose(nf); - if (!nfsd_file_unhash(nf)) - return false; - /* keep final reference for nfsd_file_lru_dispose */ - if (refcount_dec_not_one(&nf->nf_ref)) - return true; - - nfsd_file_lru_remove(nf); - list_add(&nf->nf_lru, dispose); - return true; + if (nfsd_file_unhash(nf)) { + /* caller must call nfsd_file_dispose_list() later */ + nfsd_file_lru_remove(nf); + list_add(&nf->nf_lru, dispose); + } } static void @@ -562,8 +555,6 @@ nfsd_file_dispose_list_delayed(struct list_head *dispose) * @lock: LRU list lock (unused) * @arg: dispose list * - * Note this can deadlock with nfsd_file_cache_purge. - * * Return values: * %LRU_REMOVED: @item was removed from the LRU * %LRU_ROTATE: @item is to be moved to the LRU tail @@ -748,8 +739,6 @@ nfsd_file_close_inode(struct inode *inode) * * Walk the LRU list and close any entries that have not been used since * the last scan. - * - * Note this can deadlock with nfsd_file_cache_purge. */ static void nfsd_file_delayed_close(struct work_struct *work) @@ -891,16 +880,12 @@ out_err: goto out; } -/* - * Note this can deadlock with nfsd_file_lru_cb. - */ static void __nfsd_file_cache_purge(struct net *net) { struct rhashtable_iter iter; struct nfsd_file *nf; LIST_HEAD(dispose); - bool del; rhashtable_walk_enter(&nfsd_file_rhash_tbl, &iter); do { @@ -910,14 +895,7 @@ __nfsd_file_cache_purge(struct net *net) while (!IS_ERR_OR_NULL(nf)) { if (net && nf->nf_net != net) continue; - del = nfsd_file_unhash_and_dispose(nf, &dispose); - - /* - * Deadlock detected! Something marked this entry as - * unhased, but hasn't removed it from the hash list. - */ - WARN_ON_ONCE(!del); - + nfsd_file_unhash_and_dispose(nf, &dispose); nf = rhashtable_walk_next(&iter); } -- cgit From 243a5263014a30436c93ed3f1f864c1da845455e Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Tue, 4 Oct 2022 15:41:10 -0400 Subject: nfsd: rework hashtable handling in nfsd_do_file_acquire nfsd_file is RCU-freed, so we need to hold the rcu_read_lock long enough to get a reference after finding it in the hash. Take the rcu_read_lock() and call rhashtable_lookup directly. Switch to using rhashtable_lookup_insert_key as well, and use the usual retry mechanism if we hit an -EEXIST. Rename the "retry" bool to open_retry, and eliminiate the insert_err goto target. Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever --- fs/nfsd/filecache.c | 52 ++++++++++++++++++++++------------------------------ 1 file changed, 22 insertions(+), 30 deletions(-) (limited to 'fs') diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 640a3c52c056..29a62db155fb 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -1042,9 +1042,10 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, .need = may_flags & NFSD_FILE_MAY_MASK, .net = SVC_NET(rqstp), }; - struct nfsd_file *nf, *new; - bool retry = true; + bool open_retry = true; + struct nfsd_file *nf; __be32 status; + int ret; status = fh_verify(rqstp, fhp, S_IFREG, may_flags|NFSD_MAY_OWNER_OVERRIDE); @@ -1054,35 +1055,33 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, key.cred = get_current_cred(); retry: - /* Avoid allocation if the item is already in cache */ - nf = rhashtable_lookup_fast(&nfsd_file_rhash_tbl, &key, - nfsd_file_rhash_params); + rcu_read_lock(); + nf = rhashtable_lookup(&nfsd_file_rhash_tbl, &key, + nfsd_file_rhash_params); if (nf) nf = nfsd_file_get(nf); + rcu_read_unlock(); if (nf) goto wait_for_construction; - new = nfsd_file_alloc(&key, may_flags); - if (!new) { + nf = nfsd_file_alloc(&key, may_flags); + if (!nf) { status = nfserr_jukebox; goto out_status; } - nf = rhashtable_lookup_get_insert_key(&nfsd_file_rhash_tbl, - &key, &new->nf_rhash, - nfsd_file_rhash_params); - if (!nf) { - nf = new; - goto open_file; - } - if (IS_ERR(nf)) - goto insert_err; - nf = nfsd_file_get(nf); - if (nf == NULL) { - nf = new; + ret = rhashtable_lookup_insert_key(&nfsd_file_rhash_tbl, + &key, &nf->nf_rhash, + nfsd_file_rhash_params); + if (likely(ret == 0)) goto open_file; - } - nfsd_file_slab_free(&new->nf_rcu); + + nfsd_file_slab_free(&nf->nf_rcu); + if (ret == -EEXIST) + goto retry; + trace_nfsd_file_insert_err(rqstp, key.inode, may_flags, ret); + status = nfserr_jukebox; + goto out_status; wait_for_construction: wait_on_bit(&nf->nf_flags, NFSD_FILE_PENDING, TASK_UNINTERRUPTIBLE); @@ -1090,11 +1089,11 @@ wait_for_construction: /* Did construction of this file fail? */ if (!test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) { trace_nfsd_file_cons_err(rqstp, key.inode, may_flags, nf); - if (!retry) { + if (!open_retry) { status = nfserr_jukebox; goto out; } - retry = false; + open_retry = false; nfsd_file_put_noref(nf); goto retry; } @@ -1142,13 +1141,6 @@ open_file: smp_mb__after_atomic(); wake_up_bit(&nf->nf_flags, NFSD_FILE_PENDING); goto out; - -insert_err: - nfsd_file_slab_free(&new->nf_rcu); - trace_nfsd_file_insert_err(rqstp, key.inode, may_flags, PTR_ERR(nf)); - nf = NULL; - status = nfserr_jukebox; - goto out_status; } /** -- cgit