[PATCH] virtiofs: Drop unnecessary initialization in send_forget_request and virtio_fs_get_tree

[PATCH] virtiofs: Drop unnecessary initialization in send_forget_request and virtio_fs_get_tree

[Deming Wang]

The variable is initialized but it is only used after its assignment.

Signed-off-by: Deming Wang <wangdeming@inspur.com>
---
 fs/fuse/virtio_fs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 4d8d4f16c..bffe74d44 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -414,7 +414,7 @@ static int send_forget_request(struct virtio_fs_vq *fsvq,
 {
 	struct scatterlist sg;
 	struct virtqueue *vq;
-	int ret = 0;
+	int ret;
 	bool notify;
 	struct virtio_fs_forget_req *req = &forget->req;
 
@@ -1414,10 +1414,10 @@ static int virtio_fs_get_tree(struct fs_context *fsc)
 {
 	struct virtio_fs *fs;
 	struct super_block *sb;
-	struct fuse_conn *fc = NULL;
+	struct fuse_conn *fc;
 	struct fuse_mount *fm;
 	unsigned int virtqueue_size;
-	int err = -EIO;
+	int err;
 
 	/* This gets a reference on virtio_fs object. This ptr gets installed
 	 * in fc->iq->priv. Once fuse_conn is going away, it calls ->put()
-- 
2.27.0

Re: [PATCH] virtiofs: Drop unnecessary initialization in send_forget_request and virtio_fs_get_tree

[kernel test robot]

Hi Deming,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on v6.0-rc4]
[also build test WARNING on linus/master next-20220901]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Deming-Wang/virtiofs-Drop-unnecessary-initialization-in-send_forget_request-and-virtio_fs_get_tree/20220906-135058
base:    7e18e42e4b280c85b76967a9106a13ca61c16179
config: hexagon-randconfig-r035-20220906 (https://download.01.org/0day-ci/archive/20220906/202209061738.Epufa2eF-lkp@intel.com/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project c55b41d5199d2394dd6cdb8f52180d8b81d809d4)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/a61f879fdb56490afddb6ddea4a9d57226f339f3
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Deming-Wang/virtiofs-Drop-unnecessary-initialization-in-send_forget_request-and-virtio_fs_get_tree/20220906-135058
        git checkout a61f879fdb56490afddb6ddea4a9d57226f339f3
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash fs/fuse/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> fs/fuse/virtio_fs.c:422:2: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
           if (!fsvq->connected) {
           ^~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:56:28: note: expanded from macro 'if'
   #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:58:30: note: expanded from macro '__trace_if_var'
   #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/fuse/virtio_fs.c:465:9: note: uninitialized use occurs here
           return ret;
                  ^~~
   fs/fuse/virtio_fs.c:422:2: note: remove the 'if' if its condition is always false
           if (!fsvq->connected) {
           ^~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:56:23: note: expanded from macro 'if'
   #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
                         ^
   fs/fuse/virtio_fs.c:417:9: note: initialize the variable 'ret' to silence this warning
           int ret;
                  ^
                   = 0
>> fs/fuse/virtio_fs.c:1433:2: warning: variable 'err' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
           if (WARN_ON(virtqueue_size <= FUSE_HEADER_OVERHEAD))
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:56:28: note: expanded from macro 'if'
   #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:58:30: note: expanded from macro '__trace_if_var'
   #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/fuse/virtio_fs.c:1481:9: note: uninitialized use occurs here
           return err;
                  ^~~
   fs/fuse/virtio_fs.c:1433:2: note: remove the 'if' if its condition is always false
           if (WARN_ON(virtqueue_size <= FUSE_HEADER_OVERHEAD))
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:56:23: note: expanded from macro 'if'
   #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
                         ^
   fs/fuse/virtio_fs.c:1420:9: note: initialize the variable 'err' to silence this warning
           int err;
                  ^
                   = 0
   2 warnings generated.


vim +422 fs/fuse/virtio_fs.c

a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  406  
58ada94f95f71d Vivek Goyal     2019-10-30  407  /*
58ada94f95f71d Vivek Goyal     2019-10-30  408   * Returns 1 if queue is full and sender should wait a bit before sending
58ada94f95f71d Vivek Goyal     2019-10-30  409   * next request, 0 otherwise.
58ada94f95f71d Vivek Goyal     2019-10-30  410   */
58ada94f95f71d Vivek Goyal     2019-10-30  411  static int send_forget_request(struct virtio_fs_vq *fsvq,
58ada94f95f71d Vivek Goyal     2019-10-30  412  			       struct virtio_fs_forget *forget,
58ada94f95f71d Vivek Goyal     2019-10-30  413  			       bool in_flight)
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  414  {
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  415  	struct scatterlist sg;
58ada94f95f71d Vivek Goyal     2019-10-30  416  	struct virtqueue *vq;
a61f879fdb5649 Deming Wang     2022-09-06  417  	int ret;
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  418  	bool notify;
1efcf39eb62757 Vivek Goyal     2019-10-30  419  	struct virtio_fs_forget_req *req = &forget->req;
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  420  
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  421  	spin_lock(&fsvq->lock);
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12 @422  	if (!fsvq->connected) {
58ada94f95f71d Vivek Goyal     2019-10-30  423  		if (in_flight)
c17ea009610366 Vivek Goyal     2019-10-15  424  			dec_in_flight_req(fsvq);
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  425  		kfree(forget);
58ada94f95f71d Vivek Goyal     2019-10-30  426  		goto out;
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  427  	}
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  428  
1efcf39eb62757 Vivek Goyal     2019-10-30  429  	sg_init_one(&sg, req, sizeof(*req));
58ada94f95f71d Vivek Goyal     2019-10-30  430  	vq = fsvq->vq;
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  431  	dev_dbg(&vq->vdev->dev, "%s\n", __func__);
58ada94f95f71d Vivek Goyal     2019-10-30  432  
58ada94f95f71d Vivek Goyal     2019-10-30  433  	ret = virtqueue_add_outbuf(vq, &sg, 1, forget, GFP_ATOMIC);
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  434  	if (ret < 0) {
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  435  		if (ret == -ENOMEM || ret == -ENOSPC) {
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  436  			pr_debug("virtio-fs: Could not queue FORGET: err=%d. Will try later\n",
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  437  				 ret);
58ada94f95f71d Vivek Goyal     2019-10-30  438  			list_add_tail(&forget->list, &fsvq->queued_reqs);
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  439  			schedule_delayed_work(&fsvq->dispatch_work,
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  440  					      msecs_to_jiffies(1));
58ada94f95f71d Vivek Goyal     2019-10-30  441  			if (!in_flight)
58ada94f95f71d Vivek Goyal     2019-10-30  442  				inc_in_flight_req(fsvq);
58ada94f95f71d Vivek Goyal     2019-10-30  443  			/* Queue is full */
58ada94f95f71d Vivek Goyal     2019-10-30  444  			ret = 1;
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  445  		} else {
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  446  			pr_debug("virtio-fs: Could not queue FORGET: err=%d. Dropping it.\n",
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  447  				 ret);
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  448  			kfree(forget);
58ada94f95f71d Vivek Goyal     2019-10-30  449  			if (in_flight)
58ada94f95f71d Vivek Goyal     2019-10-30  450  				dec_in_flight_req(fsvq);
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  451  		}
58ada94f95f71d Vivek Goyal     2019-10-30  452  		goto out;
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  453  	}
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  454  
58ada94f95f71d Vivek Goyal     2019-10-30  455  	if (!in_flight)
58ada94f95f71d Vivek Goyal     2019-10-30  456  		inc_in_flight_req(fsvq);
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  457  	notify = virtqueue_kick_prepare(vq);
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  458  	spin_unlock(&fsvq->lock);
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  459  
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  460  	if (notify)
a62a8ef9d97da2 Stefan Hajnoczi 2018-06-12  461  		virtqueue_notify(vq);
58ada94f95f71d Vivek Goyal     2019-10-30  462  	return ret;
58ada94f95f71d Vivek Goyal     2019-10-30  463  out:
58ada94f95f71d Vivek Goyal     2019-10-30  464  	spin_unlock(&fsvq->lock);
58ada94f95f71d Vivek Goyal     2019-10-30  465  	return ret;
58ada94f95f71d Vivek Goyal     2019-10-30  466  }
58ada94f95f71d Vivek Goyal     2019-10-30  467  

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

Re: [PATCH] virtiofs: Drop unnecessary initialization in send_forget_request and virtio_fs_get_tree

[Stefan Hajnoczi]

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On Tue, Sep 06, 2022 at 01:38:48AM -0400, Deming Wang wrote:
> The variable is initialized but it is only used after its assignment.
> 
> Signed-off-by: Deming Wang <wangdeming@inspur.com>
> ---
>  fs/fuse/virtio_fs.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> index 4d8d4f16c..bffe74d44 100644
> --- a/fs/fuse/virtio_fs.c
> +++ b/fs/fuse/virtio_fs.c
> @@ -414,7 +414,7 @@ static int send_forget_request(struct virtio_fs_vq *fsvq,
>  {
>  	struct scatterlist sg;
>  	struct virtqueue *vq;
> -	int ret = 0;
> +	int ret;
>  	bool notify;
>  	struct virtio_fs_forget_req *req = &forget->req;
>  

That causes an uninitialized access in the source tree I'm looking at
(c5e4d5e99162ba8025d58a3af7ad103f155d2df7):

  static int send_forget_request(struct virtio_fs_vq *fsvq,
                     struct virtio_fs_forget *forget,
                     bool in_flight)
  {
      struct scatterlist sg;
      struct virtqueue *vq;
      int ret = 0;
      ^^^^^^^
      bool notify;
      struct virtio_fs_forget_req *req = &forget->req;
  
      spin_lock(&fsvq->lock);
      if (!fsvq->connected) {
          if (in_flight)
              dec_in_flight_req(fsvq);
          kfree(forget);
          goto out;
      ...
      out:
      spin_unlock(&fsvq->lock);
      return ret;
             ^^^
  }

What is the purpose of this patch? Is there a compiler warning (if so,
which compiler and version)? Do you have a static analysis tool that
reported this (if yes, then maybe it's broken)?

Stefan

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