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Thu, 12 Dec 2019 16:41:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576168913; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Xe0Smz7KCQ1tatJhdpkcqF38kefQFyt1PnKLRIic9VM=; b=Ox678Zcm3W30XTIULXzipEAXhRYIFkmj0PUuM4I4BDnriFFlx3G5xLkKn9fnSQsOhH1io5 5IovWGvGFmiUzQOGSjRoDKAAcDAGiPU9sKKC/ADWKKsWrpN6nIuJIDsDYFFIqJf1loBCvw +G84g7lkACFA8xEoyFC2W6JFxJSKYS4= From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com Subject: [PATCH 104/104] virtiofsd: Convert lo_destroy to take the lo->mutex lock itself Date: Thu, 12 Dec 2019 16:39:04 +0000 Message-Id: <20191212163904.159893-105-dgilbert@redhat.com> In-Reply-To: <20191212163904.159893-1-dgilbert@redhat.com> References: <20191212163904.159893-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: 39LhyZhmOcKAqfm8G6Cq2Q-1 X-Mimecast-Spam-Score: 0 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: 205.139.110.61 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+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" From: "Dr. David Alan Gilbert" lo_destroy was relying on some implicit knowledge of the locking; we can avoid this if we create an unref_inode that doesn't take the lock and then grab it for the whole of the lo_destroy. Suggested-by: Vivek Goyal Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/passthrough_ll.c | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough= _ll.c index 38f4948e61..c37f57157e 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -1328,14 +1328,13 @@ static void lo_unlink(fuse_req_t req, fuse_ino_t pa= rent, const char *name) lo_inode_put(lo, &inode); } =20 -static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inod= e, - uint64_t n) +/* To be called with lo->mutex held */ +static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64= _t n) { if (!inode) { return; } =20 - pthread_mutex_lock(&lo->mutex); assert(inode->nlookup >=3D n); inode->nlookup -=3D n; if (!inode->nlookup) { @@ -1346,15 +1345,24 @@ static void unref_inode_lolocked(struct lo_data *lo= , struct lo_inode *inode, } g_hash_table_destroy(inode->posix_locks); pthread_mutex_destroy(&inode->plock_mutex); - pthread_mutex_unlock(&lo->mutex); =20 /* Drop our refcount from lo_do_lookup() */ lo_inode_put(lo, &inode); - } else { - pthread_mutex_unlock(&lo->mutex); } } =20 +static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inod= e, + uint64_t n) +{ + if (!inode) { + return; + } + + pthread_mutex_lock(&lo->mutex); + unref_inode(lo, inode, n); + pthread_mutex_unlock(&lo->mutex); +} + static void lo_forget_one(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup) { struct lo_data *lo =3D lo_data(req); @@ -2441,13 +2449,7 @@ static void lo_destroy(void *userdata) { struct lo_data *lo =3D (struct lo_data *)userdata; =20 - /* - * Normally lo->mutex must be taken when traversing lo->inodes but - * lo_destroy() is a serialized request so no races are possible here. - * - * In addition, we cannot acquire lo->mutex since unref_inode() takes = it - * too and this would result in a recursive lock. - */ + pthread_mutex_lock(&lo->mutex); while (true) { GHashTableIter iter; gpointer key, value; @@ -2458,8 +2460,9 @@ static void lo_destroy(void *userdata) } =20 struct lo_inode *inode =3D value; - unref_inode_lolocked(lo, inode, inode->nlookup); + unref_inode(lo, inode, inode->nlookup); } + pthread_mutex_unlock(&lo->mutex); } =20 static struct fuse_lowlevel_ops lo_oper =3D { --=20 2.23.0