From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Mon, 27 Jan 2020 19:02:08 +0000

Subject: [PATCH] virtiofsd: rename inode->refcount to inode->nlookup

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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 <stefanha@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(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)