[PATCH 0/5] Fix scan-build warnings

[PATCH 0/5] Fix scan-build warnings

[Dominique Martinet]

I ran scan-build very crudly on our source files, and there was at least
one real bug so we might as well run it once in a while, in which case
we probably ought to also fix the less important things hence this
series.
In here the first patch is a real fix and the rest is low priority, the
last one is arguably not an improvement and can be discussed (happy to
just move the 0-initializations around to variable declaration which
would also silence scan-build afaict)

Anyway, it can probably all wait until after this merge, sorry for the
timing.

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---
Dominique Martinet (5):
      9p: fix ignored return value in v9fs_dir_release
      9p: virtio: fix unlikely null pointer deref in handle_rerror
      9p: virtio: make sure 'offs' is initialized in zc_request
      9p: virtio: skip incrementing unused variable
      9p: remove dead stores (variable set again without being read)

 fs/9p/vfs_dir.c        |  5 +++--
 fs/9p/vfs_inode.c      |  6 ------
 fs/9p/vfs_inode_dotl.c |  1 -
 net/9p/client.c        | 46 ++++++++++++----------------------------------
 net/9p/trans_virtio.c  |  8 ++++----
 5 files changed, 19 insertions(+), 47 deletions(-)
---
base-commit: 4eb3117888a923f6b9b1ad2dd093641c49a63ae5
change-id: 20230427-scan-build-d894c16fc945

Best regards,
-- 
Dominique Martinet | Asmadeus

[PATCH 1/5] 9p: fix ignored return value in v9fs_dir_release

[Dominique Martinet]

retval from filemap_fdatawrite was immediately overwritten by the
following p9_fid_put: preserve any error in fdatawrite if there
was any first.

This fixes the following scan-build warning:
fs/9p/vfs_dir.c:220:4: warning: Value stored to 'retval' is never read [deadcode.DeadStores]
                        retval = filemap_fdatawrite(inode->i_mapping);
                        ^        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---
 fs/9p/vfs_dir.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c
index 289b58cb896e..54bb99f12390 100644
--- a/fs/9p/vfs_dir.c
+++ b/fs/9p/vfs_dir.c
@@ -209,7 +209,7 @@ int v9fs_dir_release(struct inode *inode, struct file *filp)
 	struct p9_fid *fid;
 	__le32 version;
 	loff_t i_size;
-	int retval = 0;
+	int retval = 0, put_err;
 
 	fid = filp->private_data;
 	p9_debug(P9_DEBUG_VFS, "inode: %p filp: %p fid: %d\n",
@@ -222,7 +222,8 @@ int v9fs_dir_release(struct inode *inode, struct file *filp)
 		spin_lock(&inode->i_lock);
 		hlist_del(&fid->ilist);
 		spin_unlock(&inode->i_lock);
-		retval = p9_fid_put(fid);
+		put_err = p9_fid_put(fid);
+		retval = retval < 0 ? retval : put_err;
 	}
 
 	if ((filp->f_mode & FMODE_WRITE)) {

-- 
2.39.2

[PATCH 2/5] 9p: virtio: fix unlikely null pointer deref in handle_rerror

[Dominique Martinet]

handle_rerror can dereference the pages pointer, but it is not
necessarily set for small payloads.
In practice these should be filtered out by the size check, but
might as well double-check explicitly.

This fixes the following scan-build warnings:
net/9p/trans_virtio.c:401:24: warning: Dereference of null pointer [core.NullDereference]
                memcpy_from_page(to, *pages++, offs, n);
                                     ^~~~~~~~
net/9p/trans_virtio.c:406:23: warning: Dereference of null pointer (loaded from variable 'pages') [core.NullDereference]
        memcpy_from_page(to, *pages, offs, size);
                             ^~~~~~

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---
 net/9p/trans_virtio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 3c27ffb781e3..2c9495ccda6b 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -384,7 +384,7 @@ static void handle_rerror(struct p9_req_t *req, int in_hdr_len,
 	void *to = req->rc.sdata + in_hdr_len;
 
 	// Fits entirely into the static data?  Nothing to do.
-	if (req->rc.size < in_hdr_len)
+	if (req->rc.size < in_hdr_len || !pages)
 		return;
 
 	// Really long error message?  Tough, truncate the reply.  Might get

-- 
2.39.2

[PATCH 3/5] 9p: virtio: make sure 'offs' is initialized in zc_request

[Dominique Martinet]

Similarly to the previous patch: offs can be used in handle_rerrors
without initializing on small payloads; in this case handle_rerrors will
not use it because of the size check, but it doesn't hurt to make sure
it is zero to please scan-build.

This fixes the following warning:
net/9p/trans_virtio.c:539:3: warning: 3rd function call argument is an uninitialized value [core.CallAndMessage]
                handle_rerror(req, in_hdr_len, offs, in_pages);
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---
 net/9p/trans_virtio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 2c9495ccda6b..f3f678289423 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -428,7 +428,7 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
 	struct page **in_pages = NULL, **out_pages = NULL;
 	struct virtio_chan *chan = client->trans;
 	struct scatterlist *sgs[4];
-	size_t offs;
+	size_t offs = 0;
 	int need_drop = 0;
 	int kicked = 0;
 

-- 
2.39.2

[PATCH 4/5] 9p: virtio: skip incrementing unused variable

[Dominique Martinet]

Fix the following scan-build warning:
net/9p/trans_virtio.c:504:3: warning: Value stored to 'in' is never read [deadcode.DeadStores]
                in += pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
                ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I'm honestly not 100% sure about this one; I'm tempted to think we
could (should?) just check the return value of pack_sg_list_p to skip
the in_sgs++ and setting sgs[] if it didn't process anything, but I'm
not sure it should ever happen so this is probably fine as is.

Just removing the assignment at least makes it clear the return value
isn't used, so it's an improvement in terms of readability.

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---
 net/9p/trans_virtio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index f3f678289423..e305071eb7b8 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -501,8 +501,8 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
 
 	if (in_pages) {
 		sgs[out_sgs + in_sgs++] = chan->sg + out + in;
-		in += pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
-				     in_pages, in_nr_pages, offs, inlen);
+		pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
+			       in_pages, in_nr_pages, offs, inlen);
 	}
 
 	BUG_ON(out_sgs + in_sgs > ARRAY_SIZE(sgs));

-- 
2.39.2

[PATCH 5/5] 9p: remove dead stores (variable set again without being read)

[Dominique Martinet]

The 9p code for some reason used to initialize variables outside of the
declaration, e.g. instead of just initializing the variable like this:

int retval = 0

We would be doing this:

int retval;
retval = 0;

This is perfectly fine and the compiler will just optimize dead stores
anyway, but scan-build seems to think this is a problem and there are
many of these warnings making the output of scan-build full of such
warnings:
fs/9p/vfs_inode.c:916:2: warning: Value stored to 'retval' is never read [deadcode.DeadStores]
        retval = 0;
        ^        ~

I have no strong opinion here, but if we want to regularily run
scan-build we should fix these just to silence the messages.

I've confirmed these all are indeed ok to remove.

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---
 fs/9p/vfs_inode.c      |  6 ------
 fs/9p/vfs_inode_dotl.c |  1 -
 net/9p/client.c        | 46 ++++++++++++----------------------------------
 3 files changed, 12 insertions(+), 41 deletions(-)

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 54dfe4f10f43..82589d1d9bbe 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -164,7 +164,6 @@ int v9fs_uflags2omode(int uflags, int extended)
 {
 	int ret;
 
-	ret = 0;
 	switch (uflags&3) {
 	default:
 	case O_RDONLY:
@@ -604,7 +603,6 @@ v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
 
 	p9_debug(P9_DEBUG_VFS, "name %pd\n", dentry);
 
-	err = 0;
 	name = dentry->d_name.name;
 	dfid = v9fs_parent_fid(dentry);
 	if (IS_ERR(dfid)) {
@@ -816,8 +814,6 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
 	if (!(flags & O_CREAT) || d_really_is_positive(dentry))
 		return finish_no_open(file, res);
 
-	err = 0;
-
 	v9ses = v9fs_inode2v9ses(dir);
 	perm = unixmode2p9mode(v9ses, mode);
 	p9_omode = v9fs_uflags2omode(flags, v9fs_proto_dotu(v9ses));
@@ -913,7 +909,6 @@ v9fs_vfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 		return -EINVAL;
 
 	p9_debug(P9_DEBUG_VFS, "\n");
-	retval = 0;
 	old_inode = d_inode(old_dentry);
 	new_inode = d_inode(new_dentry);
 	v9ses = v9fs_inode2v9ses(old_inode);
@@ -1067,7 +1062,6 @@ static int v9fs_vfs_setattr(struct mnt_idmap *idmap,
 	if (retval)
 		return retval;
 
-	retval = -EPERM;
 	v9ses = v9fs_dentry2v9ses(dentry);
 	if (iattr->ia_valid & ATTR_FILE) {
 		fid = iattr->ia_file->private_data;
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index f9371b5b70ea..df7023af17cf 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -367,7 +367,6 @@ static int v9fs_vfs_mkdir_dotl(struct mnt_idmap *idmap,
 	struct posix_acl *dacl = NULL, *pacl = NULL;
 
 	p9_debug(P9_DEBUG_VFS, "name %pd\n", dentry);
-	err = 0;
 	v9ses = v9fs_inode2v9ses(dir);
 
 	omode |= S_IFDIR;
diff --git a/net/9p/client.c b/net/9p/client.c
index a3340268ec8d..86bbc7147fc1 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -904,7 +904,7 @@ EXPORT_SYMBOL(do_trace_9p_fid_put);
 
 static int p9_client_version(struct p9_client *c)
 {
-	int err = 0;
+	int err;
 	struct p9_req_t *req;
 	char *version = NULL;
 	int msize;
@@ -975,7 +975,6 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 	struct p9_client *clnt;
 	char *client_id;
 
-	err = 0;
 	clnt = kmalloc(sizeof(*clnt), GFP_KERNEL);
 	if (!clnt)
 		return ERR_PTR(-ENOMEM);
@@ -1094,7 +1093,7 @@ struct p9_fid *p9_client_attach(struct p9_client *clnt, struct p9_fid *afid,
 				const char *uname, kuid_t n_uname,
 				const char *aname)
 {
-	int err = 0;
+	int err;
 	struct p9_req_t *req;
 	struct p9_fid *fid;
 	struct p9_qid qid;
@@ -1147,7 +1146,6 @@ struct p9_fid *p9_client_walk(struct p9_fid *oldfid, uint16_t nwname,
 	struct p9_req_t *req;
 	u16 nwqids, count;
 
-	err = 0;
 	wqids = NULL;
 	clnt = oldfid->clnt;
 	if (clone) {
@@ -1224,7 +1222,6 @@ int p9_client_open(struct p9_fid *fid, int mode)
 	clnt = fid->clnt;
 	p9_debug(P9_DEBUG_9P, ">>> %s fid %d mode %d\n",
 		 p9_is_proto_dotl(clnt) ? "TLOPEN" : "TOPEN", fid->fid, mode);
-	err = 0;
 
 	if (fid->mode != -1)
 		return -EINVAL;
@@ -1262,7 +1259,7 @@ EXPORT_SYMBOL(p9_client_open);
 int p9_client_create_dotl(struct p9_fid *ofid, const char *name, u32 flags,
 			  u32 mode, kgid_t gid, struct p9_qid *qid)
 {
-	int err = 0;
+	int err;
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 	int iounit;
@@ -1314,7 +1311,6 @@ int p9_client_fcreate(struct p9_fid *fid, const char *name, u32 perm, int mode,
 
 	p9_debug(P9_DEBUG_9P, ">>> TCREATE fid %d name %s perm %d mode %d\n",
 		 fid->fid, name, perm, mode);
-	err = 0;
 	clnt = fid->clnt;
 
 	if (fid->mode != -1)
@@ -1350,7 +1346,7 @@ EXPORT_SYMBOL(p9_client_fcreate);
 int p9_client_symlink(struct p9_fid *dfid, const char *name,
 		      const char *symtgt, kgid_t gid, struct p9_qid *qid)
 {
-	int err = 0;
+	int err;
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 
@@ -1402,13 +1398,12 @@ EXPORT_SYMBOL(p9_client_link);
 
 int p9_client_fsync(struct p9_fid *fid, int datasync)
 {
-	int err;
+	int err = 0;
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 
 	p9_debug(P9_DEBUG_9P, ">>> TFSYNC fid %d datasync:%d\n",
 		 fid->fid, datasync);
-	err = 0;
 	clnt = fid->clnt;
 
 	req = p9_client_rpc(clnt, P9_TFSYNC, "dd", fid->fid, datasync);
@@ -1428,7 +1423,7 @@ EXPORT_SYMBOL(p9_client_fsync);
 
 int p9_client_clunk(struct p9_fid *fid)
 {
-	int err;
+	int err = 0;
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 	int retries = 0;
@@ -1436,7 +1431,6 @@ int p9_client_clunk(struct p9_fid *fid)
 again:
 	p9_debug(P9_DEBUG_9P, ">>> TCLUNK fid %d (try %d)\n",
 		 fid->fid, retries);
-	err = 0;
 	clnt = fid->clnt;
 
 	req = p9_client_rpc(clnt, P9_TCLUNK, "d", fid->fid);
@@ -1465,12 +1459,11 @@ EXPORT_SYMBOL(p9_client_clunk);
 
 int p9_client_remove(struct p9_fid *fid)
 {
-	int err;
+	int err = 0;
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 
 	p9_debug(P9_DEBUG_9P, ">>> TREMOVE fid %d\n", fid->fid);
-	err = 0;
 	clnt = fid->clnt;
 
 	req = p9_client_rpc(clnt, P9_TREMOVE, "d", fid->fid);
@@ -1680,7 +1673,6 @@ struct p9_wstat *p9_client_stat(struct p9_fid *fid)
 	if (!ret)
 		return ERR_PTR(-ENOMEM);
 
-	err = 0;
 	clnt = fid->clnt;
 
 	req = p9_client_rpc(clnt, P9_TSTAT, "d", fid->fid);
@@ -1733,7 +1725,6 @@ struct p9_stat_dotl *p9_client_getattr_dotl(struct p9_fid *fid,
 	if (!ret)
 		return ERR_PTR(-ENOMEM);
 
-	err = 0;
 	clnt = fid->clnt;
 
 	req = p9_client_rpc(clnt, P9_TGETATTR, "dq", fid->fid, request_mask);
@@ -1812,11 +1803,10 @@ static int p9_client_statsize(struct p9_wstat *wst, int proto_version)
 
 int p9_client_wstat(struct p9_fid *fid, struct p9_wstat *wst)
 {
-	int err;
+	int err = 0;
 	struct p9_req_t *req;
 	struct p9_client *clnt;
 
-	err = 0;
 	clnt = fid->clnt;
 	wst->size = p9_client_statsize(wst, clnt->proto_version);
 	p9_debug(P9_DEBUG_9P, ">>> TWSTAT fid %d\n",
@@ -1851,11 +1841,10 @@ EXPORT_SYMBOL(p9_client_wstat);
 
 int p9_client_setattr(struct p9_fid *fid, struct p9_iattr_dotl *p9attr)
 {
-	int err;
+	int err = 0;
 	struct p9_req_t *req;
 	struct p9_client *clnt;
 
-	err = 0;
 	clnt = fid->clnt;
 	p9_debug(P9_DEBUG_9P, ">>> TSETATTR fid %d\n", fid->fid);
 	p9_debug(P9_DEBUG_9P, "    valid=%x mode=%x uid=%d gid=%d size=%lld\n",
@@ -1887,7 +1876,6 @@ int p9_client_statfs(struct p9_fid *fid, struct p9_rstatfs *sb)
 	struct p9_req_t *req;
 	struct p9_client *clnt;
 
-	err = 0;
 	clnt = fid->clnt;
 
 	p9_debug(P9_DEBUG_9P, ">>> TSTATFS fid %d\n", fid->fid);
@@ -1921,11 +1909,10 @@ EXPORT_SYMBOL(p9_client_statfs);
 int p9_client_rename(struct p9_fid *fid,
 		     struct p9_fid *newdirfid, const char *name)
 {
-	int err;
+	int err = 0;
 	struct p9_req_t *req;
 	struct p9_client *clnt;
 
-	err = 0;
 	clnt = fid->clnt;
 
 	p9_debug(P9_DEBUG_9P, ">>> TRENAME fid %d newdirfid %d name %s\n",
@@ -1949,11 +1936,10 @@ EXPORT_SYMBOL(p9_client_rename);
 int p9_client_renameat(struct p9_fid *olddirfid, const char *old_name,
 		       struct p9_fid *newdirfid, const char *new_name)
 {
-	int err;
+	int err = 0;
 	struct p9_req_t *req;
 	struct p9_client *clnt;
 
-	err = 0;
 	clnt = olddirfid->clnt;
 
 	p9_debug(P9_DEBUG_9P,
@@ -1986,7 +1972,6 @@ struct p9_fid *p9_client_xattrwalk(struct p9_fid *file_fid,
 	struct p9_client *clnt;
 	struct p9_fid *attr_fid;
 
-	err = 0;
 	clnt = file_fid->clnt;
 	attr_fid = p9_fid_create(clnt);
 	if (!attr_fid) {
@@ -2027,14 +2012,13 @@ EXPORT_SYMBOL_GPL(p9_client_xattrwalk);
 int p9_client_xattrcreate(struct p9_fid *fid, const char *name,
 			  u64 attr_size, int flags)
 {
-	int err;
+	int err = 0;
 	struct p9_req_t *req;
 	struct p9_client *clnt;
 
 	p9_debug(P9_DEBUG_9P,
 		 ">>> TXATTRCREATE fid %d name  %s size %llu flag %d\n",
 		 fid->fid, name, attr_size, flags);
-	err = 0;
 	clnt = fid->clnt;
 	req = p9_client_rpc(clnt, P9_TXATTRCREATE, "dsqd",
 			    fid->fid, name, attr_size, flags);
@@ -2063,7 +2047,6 @@ int p9_client_readdir(struct p9_fid *fid, char *data, u32 count, u64 offset)
 	p9_debug(P9_DEBUG_9P, ">>> TREADDIR fid %d offset %llu count %d\n",
 		 fid->fid, offset, count);
 
-	err = 0;
 	clnt = fid->clnt;
 
 	rsize = fid->iounit;
@@ -2122,7 +2105,6 @@ int p9_client_mknod_dotl(struct p9_fid *fid, const char *name, int mode,
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 
-	err = 0;
 	clnt = fid->clnt;
 	p9_debug(P9_DEBUG_9P,
 		 ">>> TMKNOD fid %d name %s mode %d major %d minor %d\n",
@@ -2153,7 +2135,6 @@ int p9_client_mkdir_dotl(struct p9_fid *fid, const char *name, int mode,
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 
-	err = 0;
 	clnt = fid->clnt;
 	p9_debug(P9_DEBUG_9P, ">>> TMKDIR fid %d name %s mode %d gid %d\n",
 		 fid->fid, name, mode, from_kgid(&init_user_ns, gid));
@@ -2182,7 +2163,6 @@ int p9_client_lock_dotl(struct p9_fid *fid, struct p9_flock *flock, u8 *status)
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 
-	err = 0;
 	clnt = fid->clnt;
 	p9_debug(P9_DEBUG_9P,
 		 ">>> TLOCK fid %d type %i flags %d start %lld length %lld proc_id %d client_id %s\n",
@@ -2214,7 +2194,6 @@ int p9_client_getlock_dotl(struct p9_fid *fid, struct p9_getlock *glock)
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 
-	err = 0;
 	clnt = fid->clnt;
 	p9_debug(P9_DEBUG_9P,
 		 ">>> TGETLOCK fid %d, type %i start %lld length %lld proc_id %d client_id %s\n",
@@ -2251,7 +2230,6 @@ int p9_client_readlink(struct p9_fid *fid, char **target)
 	struct p9_client *clnt;
 	struct p9_req_t *req;
 
-	err = 0;
 	clnt = fid->clnt;
 	p9_debug(P9_DEBUG_9P, ">>> TREADLINK fid %d\n", fid->fid);
 

-- 
2.39.2

Re: [PATCH 1/5] 9p: fix ignored return value in v9fs_dir_release

[Simon Horman]

On Thu, Apr 27, 2023 at 08:23:34PM +0900, Dominique Martinet wrote:
> retval from filemap_fdatawrite was immediately overwritten by the
> following p9_fid_put: preserve any error in fdatawrite if there
> was any first.
> 
> This fixes the following scan-build warning:
> fs/9p/vfs_dir.c:220:4: warning: Value stored to 'retval' is never read [deadcode.DeadStores]
>                         retval = filemap_fdatawrite(inode->i_mapping);
>                         ^        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Perhaps:

Fixes: 89c58cb395ec ("fs/9p: fix error reporting in v9fs_dir_release")

> Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

Re: [PATCH 5/5] 9p: remove dead stores (variable set again without being read)

[Simon Horman]

On Thu, Apr 27, 2023 at 08:23:38PM +0900, Dominique Martinet wrote:
> The 9p code for some reason used to initialize variables outside of the
> declaration, e.g. instead of just initializing the variable like this:
> 
> int retval = 0
> 
> We would be doing this:
> 
> int retval;
> retval = 0;
> 
> This is perfectly fine and the compiler will just optimize dead stores
> anyway, but scan-build seems to think this is a problem and there are
> many of these warnings making the output of scan-build full of such
> warnings:
> fs/9p/vfs_inode.c:916:2: warning: Value stored to 'retval' is never read [deadcode.DeadStores]
>         retval = 0;
>         ^        ~
> 
> I have no strong opinion here, but if we want to regularily run

s/regularily/regularly/

> scan-build we should fix these just to silence the messages.
> 
> I've confirmed these all are indeed ok to remove.

Likewise, these look good to me.

> Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

Re: [PATCH 4/5] 9p: virtio: skip incrementing unused variable

[Simon Horman]

On Thu, Apr 27, 2023 at 08:23:37PM +0900, Dominique Martinet wrote:
> Fix the following scan-build warning:
> net/9p/trans_virtio.c:504:3: warning: Value stored to 'in' is never read [deadcode.DeadStores]
>                 in += pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
>                 ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> I'm honestly not 100% sure about this one; I'm tempted to think we
> could (should?) just check the return value of pack_sg_list_p to skip
> the in_sgs++ and setting sgs[] if it didn't process anything, but I'm
> not sure it should ever happen so this is probably fine as is.
> 
> Just removing the assignment at least makes it clear the return value
> isn't used, so it's an improvement in terms of readability.
> 
> Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

Re: [PATCH 3/5] 9p: virtio: make sure 'offs' is initialized in zc_request

[Simon Horman]

On Thu, Apr 27, 2023 at 08:23:36PM +0900, Dominique Martinet wrote:
> Similarly to the previous patch: offs can be used in handle_rerrors
> without initializing on small payloads; in this case handle_rerrors will
> not use it because of the size check, but it doesn't hurt to make sure
> it is zero to please scan-build.
> 
> This fixes the following warning:
> net/9p/trans_virtio.c:539:3: warning: 3rd function call argument is an uninitialized value [core.CallAndMessage]
>                 handle_rerror(req, in_hdr_len, offs, in_pages);
>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

Re: [PATCH 2/5] 9p: virtio: fix unlikely null pointer deref in handle_rerror

[Simon Horman]

On Thu, Apr 27, 2023 at 08:23:35PM +0900, Dominique Martinet wrote:
> handle_rerror can dereference the pages pointer, but it is not
> necessarily set for small payloads.
> In practice these should be filtered out by the size check, but
> might as well double-check explicitly.
> 
> This fixes the following scan-build warnings:
> net/9p/trans_virtio.c:401:24: warning: Dereference of null pointer [core.NullDereference]
>                 memcpy_from_page(to, *pages++, offs, n);
>                                      ^~~~~~~~
> net/9p/trans_virtio.c:406:23: warning: Dereference of null pointer (loaded from variable 'pages') [core.NullDereference]
>         memcpy_from_page(to, *pages, offs, size);
>                              ^~~~~~
> 
> Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

Re: [PATCH 1/5] 9p: fix ignored return value in v9fs_dir_release

[Dominique Martinet]

Thanks for all the reviews!

Simon Horman wrote on Tue, May 02, 2023 at 04:46:17PM +0200:
> On Thu, Apr 27, 2023 at 08:23:34PM +0900, Dominique Martinet wrote:
> > retval from filemap_fdatawrite was immediately overwritten by the
> > following p9_fid_put: preserve any error in fdatawrite if there
> > was any first.
> > 
> > This fixes the following scan-build warning:
> > fs/9p/vfs_dir.c:220:4: warning: Value stored to 'retval' is never read [deadcode.DeadStores]
> >                         retval = filemap_fdatawrite(inode->i_mapping);
> >                         ^        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Perhaps:
> 
> Fixes: 89c58cb395ec ("fs/9p: fix error reporting in v9fs_dir_release")

Right, this one warrants a fix tag as it's the only real bug in this
series.
I'll add the Fixes and fix the typo in patch 5 and send a v2 later
today.

-- 
Dominique Martinet | Asmadeus

Re: [PATCH 1/5] 9p: fix ignored return value in v9fs_dir_release

[Simon Horman]

On Wed, May 03, 2023 at 08:32:49AM +0900, Dominique Martinet wrote:
> Thanks for all the reviews!
> 
> Simon Horman wrote on Tue, May 02, 2023 at 04:46:17PM +0200:
> > On Thu, Apr 27, 2023 at 08:23:34PM +0900, Dominique Martinet wrote:
> > > retval from filemap_fdatawrite was immediately overwritten by the
> > > following p9_fid_put: preserve any error in fdatawrite if there
> > > was any first.
> > > 
> > > This fixes the following scan-build warning:
> > > fs/9p/vfs_dir.c:220:4: warning: Value stored to 'retval' is never read [deadcode.DeadStores]
> > >                         retval = filemap_fdatawrite(inode->i_mapping);
> > >                         ^        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > 
> > Perhaps:
> > 
> > Fixes: 89c58cb395ec ("fs/9p: fix error reporting in v9fs_dir_release")
> 
> Right, this one warrants a fix tag as it's the only real bug in this
> series.

Hi Dominique,

Yes, I agree that this seems to be the only patch in this series
that warrants a fixes tag.