From: Stefan Hajnoczi Date: Mon, 27 Jan 2020 19:02:08 +0000 Subject: [PATCH] virtiofsd: rename inode->refcount to inode->nlookup MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This reference counter plays a specific role in the FUSE protocol. It's not a generic object reference counter and the FUSE kernel code calls it "nlookup". Signed-off-by: Stefan Hajnoczi Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Dr. David Alan Gilbert (cherry picked from commit 1222f015558fc34cea02aa3a5a92de608c82cec8) --- tools/virtiofsd/passthrough_ll.c | 37 +++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 12 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 2d703b57e5..c819b5f782 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -99,7 +99,20 @@ struct lo_inode { int fd; bool is_symlink; struct lo_key key; - uint64_t refcount; /* protected by lo->mutex */ + + /* + * This counter keeps the inode alive during the FUSE session. + * Incremented when the FUSE inode number is sent in a reply + * (FUSE_LOOKUP, FUSE_READDIRPLUS, etc). Decremented when an inode is + * released by requests like FUSE_FORGET, FUSE_RMDIR, FUSE_RENAME, etc. + * + * Note that this value is untrusted because the client can manipulate + * it arbitrarily using FUSE_FORGET requests. + * + * Protected by lo->mutex. + */ + uint64_t nlookup; + fuse_ino_t fuse_ino; pthread_mutex_t plock_mutex; GHashTable *posix_locks; /* protected by lo_inode->plock_mutex */ @@ -568,7 +581,7 @@ retry: if (last == path) { p = &lo->root; pthread_mutex_lock(&lo->mutex); - p->refcount++; + p->nlookup++; pthread_mutex_unlock(&lo->mutex); } else { *last = '\0'; @@ -786,8 +799,8 @@ static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st) pthread_mutex_lock(&lo->mutex); p = g_hash_table_lookup(lo->inodes, &key); if (p) { - assert(p->refcount > 0); - p->refcount++; + assert(p->nlookup > 0); + p->nlookup++; } pthread_mutex_unlock(&lo->mutex); @@ -855,7 +868,7 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name, } inode->is_symlink = S_ISLNK(e->attr.st_mode); - inode->refcount = 1; + inode->nlookup = 1; inode->fd = newfd; newfd = -1; inode->key.ino = e->attr.st_ino; @@ -1112,7 +1125,7 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent, } pthread_mutex_lock(&lo->mutex); - inode->refcount++; + inode->nlookup++; pthread_mutex_unlock(&lo->mutex); e.ino = inode->fuse_ino; @@ -1193,9 +1206,9 @@ static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode, } pthread_mutex_lock(&lo->mutex); - assert(inode->refcount >= n); - inode->refcount -= n; - if (!inode->refcount) { + assert(inode->nlookup >= n); + inode->nlookup -= n; + if (!inode->nlookup) { lo_map_remove(&lo->ino_map, inode->fuse_ino); g_hash_table_remove(lo->inodes, &inode->key); if (g_hash_table_size(inode->posix_locks)) { @@ -1216,7 +1229,7 @@ static int unref_all_inodes_cb(gpointer key, gpointer value, gpointer user_data) struct lo_inode *inode = value; struct lo_data *lo = user_data; - inode->refcount = 0; + inode->nlookup = 0; lo_map_remove(&lo->ino_map, inode->fuse_ino); close(inode->fd); @@ -1241,7 +1254,7 @@ static void lo_forget_one(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup) } fuse_log(FUSE_LOG_DEBUG, " forget %lli %lli -%lli\n", - (unsigned long long)ino, (unsigned long long)inode->refcount, + (unsigned long long)ino, (unsigned long long)inode->nlookup, (unsigned long long)nlookup); unref_inode_lolocked(lo, inode, nlookup); @@ -2609,7 +2622,7 @@ static void setup_root(struct lo_data *lo, struct lo_inode *root) root->fd = fd; root->key.ino = stat.st_ino; root->key.dev = stat.st_dev; - root->refcount = 2; + root->nlookup = 2; } static guint lo_key_hash(gconstpointer key)