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[83.57.172.113]) by smtp.gmail.com with ESMTPSA id x11sm12474wmg.46.2020.01.17.05.54.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Jan 2020 05:54:02 -0800 (PST) Subject: Re: [PATCH 090/104] virtiofsd: rename inode->refcount to inode->nlookup To: "Dr. David Alan Gilbert (git)" , qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com References: <20191212163904.159893-1-dgilbert@redhat.com> <20191212163904.159893-91-dgilbert@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: Date: Fri, 17 Jan 2020 14:54:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20191212163904.159893-91-dgilbert@redhat.com> Content-Language: en-US X-MC-Unique: bXCNJOWHN5OxYcJYFIJxIg-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/12/19 5:38 PM, Dr. David Alan Gilbert (git) wrote: > From: Stefan Hajnoczi >=20 > 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". >=20 > Signed-off-by: Stefan Hajnoczi > --- > tools/virtiofsd/passthrough_ll.c | 37 +++++++++++++++++++++----------- > 1 file changed, 25 insertions(+), 12 deletions(-) >=20 > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrou= gh_ll.c > index 7663e574d8..b19c9ee328 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -101,7 +101,20 @@ 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, e= tc. > + * > + * Note that this value is untrusted because the client can manipula= te > + * 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 */ > @@ -570,7 +583,7 @@ retry: > if (last =3D=3D path) { > p =3D &lo->root; > pthread_mutex_lock(&lo->mutex); > - p->refcount++; > + p->nlookup++; > pthread_mutex_unlock(&lo->mutex); > } else { > *last =3D '\0'; > @@ -788,8 +801,8 @@ static struct lo_inode *lo_find(struct lo_data *lo, s= truct stat *st) > pthread_mutex_lock(&lo->mutex); > p =3D 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); > =20 > @@ -857,7 +870,7 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t pa= rent, const char *name, > } > =20 > inode->is_symlink =3D S_ISLNK(e->attr.st_mode); > - inode->refcount =3D 1; > + inode->nlookup =3D 1; > inode->fd =3D newfd; > newfd =3D -1; > inode->key.ino =3D e->attr.st_ino; > @@ -1097,7 +1110,7 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino,= fuse_ino_t parent, > } > =20 > pthread_mutex_lock(&lo->mutex); > - inode->refcount++; > + inode->nlookup++; > pthread_mutex_unlock(&lo->mutex); > e.ino =3D inode->fuse_ino; > =20 > @@ -1226,9 +1239,9 @@ static void unref_inode_lolocked(struct lo_data *lo= , struct lo_inode *inode, > } > =20 > pthread_mutex_lock(&lo->mutex); > - assert(inode->refcount >=3D n); > - inode->refcount -=3D n; > - if (!inode->refcount) { > + assert(inode->nlookup >=3D n); > + inode->nlookup -=3D 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)) { > @@ -1249,7 +1262,7 @@ static int unref_all_inodes_cb(gpointer key, gpoint= er value, gpointer user_data) > struct lo_inode *inode =3D value; > struct lo_data *lo =3D user_data; > =20 > - inode->refcount =3D 0; > + inode->nlookup =3D 0; > lo_map_remove(&lo->ino_map, inode->fuse_ino); > close(inode->fd); > =20 > @@ -1274,7 +1287,7 @@ static void lo_forget_one(fuse_req_t req, fuse_ino_= t ino, uint64_t nlookup) > } > =20 > fuse_log(FUSE_LOG_DEBUG, " forget %lli %lli -%lli\n", > - (unsigned long long)ino, (unsigned long long)inode->refcoun= t, > + (unsigned long long)ino, (unsigned long long)inode->nlookup= , > (unsigned long long)nlookup); > =20 > unref_inode_lolocked(lo, inode, nlookup); > @@ -2642,7 +2655,7 @@ static void setup_root(struct lo_data *lo, struct l= o_inode *root) > root->fd =3D fd; > root->key.ino =3D stat.st_ino; > root->key.dev =3D stat.st_dev; > - root->refcount =3D 2; > + root->nlookup =3D 2; > } > =20 > static guint lo_key_hash(gconstpointer key) >=20 Reviewed-by: Philippe Mathieu-Daud=C3=A9