Linux Virtualization - May 2017 - [PATCH 1/2] vhost/scsi: Improve a size determination in four functions

From: Markus Elfring <elfring at users.sourceforge.net>
Date: Sat, 20 May 2017 16:25:04 +0200

A few update suggestions were taken into account
from static source code analysis.

Markus Elfring (2):
  Improve a size determination in four functions
  Delete error messages for failed memory allocations in five functions

 drivers/vhost/scsi.c | 33 +++++++++++----------------------
 1 file changed, 11 insertions(+), 22 deletions(-)

-- 
2.13.0

From: Markus Elfring <elfring at users.sourceforge.net>
Date: Sat, 20 May 2017 13:48:44 +0200

Replace the specification of four data structures by pointer dereferences
as the parameter for the operator "sizeof" to make the corresponding
size
determination a bit safer according to the Linux coding style convention.

Signed-off-by: Markus Elfring <elfring at users.sourceforge.net>
---
 drivers/vhost/scsi.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index fd6c8b66f06f..650533916c19 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -597,8 +597,7 @@ vhost_scsi_get_tag(struct vhost_virtqueue *vq, struct
vhost_scsi_tpg *tpg,
 	sg = cmd->tvc_sgl;
 	prot_sg = cmd->tvc_prot_sgl;
 	pages = cmd->tvc_upages;
-	memset(cmd, 0, sizeof(struct vhost_scsi_cmd));
-
+	memset(cmd, 0, sizeof(*cmd));
 	cmd->tvc_sgl = sg;
 	cmd->tvc_prot_sgl = prot_sg;
 	cmd->tvc_upages = pages;
@@ -1757,5 +1756,5 @@ static int vhost_scsi_make_nexus(struct vhost_scsi_tpg
*tpg,
 		return -EEXIST;
 	}
 
-	tv_nexus = kzalloc(sizeof(struct vhost_scsi_nexus), GFP_KERNEL);
+	tv_nexus = kzalloc(sizeof(*tv_nexus), GFP_KERNEL);
 	if (!tv_nexus) {
@@ -1958,5 +1957,5 @@ vhost_scsi_make_tpg(struct se_wwn *wwn,
 	if (kstrtou16(name + 5, 10, &tpgt) || tpgt >= VHOST_SCSI_MAX_TARGET)
 		return ERR_PTR(-EINVAL);
 
-	tpg = kzalloc(sizeof(struct vhost_scsi_tpg), GFP_KERNEL);
+	tpg = kzalloc(sizeof(*tpg), GFP_KERNEL);
 	if (!tpg) {
@@ -2012,5 +2011,5 @@ vhost_scsi_make_tport(struct target_fabric_configfs *tf,
 	/* if (vhost_scsi_parse_wwn(name, &wwpn, 1) < 0)
 		return ERR_PTR(-EINVAL); */
 
-	tport = kzalloc(sizeof(struct vhost_scsi_tport), GFP_KERNEL);
+	tport = kzalloc(sizeof(*tport), GFP_KERNEL);
 	if (!tport) {
-- 
2.13.0

From: Markus Elfring <elfring at users.sourceforge.net>
Date: Sat, 20 May 2017 15:50:30 +0200

Omit seven extra messages for memory allocation failures in these functions.

This issue was detected by using the Coccinelle software.

Link:
http://events.linuxfoundation.org/sites/events/files/slides/LCJ16-Refactor_Strings-WSang_0.pdf
Signed-off-by: Markus Elfring <elfring at users.sourceforge.net>
---
 drivers/vhost/scsi.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 650533916c19..49d07950e2e5 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -417,5 +417,4 @@ vhost_scsi_allocate_evt(struct vhost_scsi *vs,
 	if (!evt) {
-		vq_err(vq, "Failed to allocate vhost_scsi_evt\n");
 		vs->vs_events_missed = true;
 		return NULL;
 	}
@@ -1722,21 +1721,15 @@ static int vhost_scsi_nexus_cb(struct se_portal_group
*se_tpg,
-		if (!tv_cmd->tvc_sgl) {
-			pr_err("Unable to allocate tv_cmd->tvc_sgl\n");
+		if (!tv_cmd->tvc_sgl)
 			goto out;
-		}
 
 		tv_cmd->tvc_upages = kzalloc(sizeof(struct page *) *
 				VHOST_SCSI_PREALLOC_UPAGES, GFP_KERNEL);
-		if (!tv_cmd->tvc_upages) {
-			pr_err("Unable to allocate tv_cmd->tvc_upages\n");
+		if (!tv_cmd->tvc_upages)
 			goto out;
-		}
 
 		tv_cmd->tvc_prot_sgl = kzalloc(sizeof(struct scatterlist) *
 				VHOST_SCSI_PREALLOC_PROT_SGLS, GFP_KERNEL);
-		if (!tv_cmd->tvc_prot_sgl) {
-			pr_err("Unable to allocate tv_cmd->tvc_prot_sgl\n");
+		if (!tv_cmd->tvc_prot_sgl)
 			goto out;
-		}
 	}
 	return 0;
 out:
@@ -1760,6 +1753,5 @@ static int vhost_scsi_make_nexus(struct vhost_scsi_tpg
*tpg,
 	if (!tv_nexus) {
 		mutex_unlock(&tpg->tv_tpg_mutex);
-		pr_err("Unable to allocate struct vhost_scsi_nexus\n");
 		return -ENOMEM;
 	}
 	/*
@@ -1961,7 +1953,6 @@ vhost_scsi_make_tpg(struct se_wwn *wwn,
-	if (!tpg) {
-		pr_err("Unable to allocate struct vhost_scsi_tpg");
+	if (!tpg)
 		return ERR_PTR(-ENOMEM);
-	}
+
 	mutex_init(&tpg->tv_tpg_mutex);
 	INIT_LIST_HEAD(&tpg->tv_tpg_list);
 	tpg->tport = tport;
@@ -2015,7 +2006,6 @@ vhost_scsi_make_tport(struct target_fabric_configfs *tf,
-	if (!tport) {
-		pr_err("Unable to allocate struct vhost_scsi_tport");
+	if (!tport)
 		return ERR_PTR(-ENOMEM);
-	}
+
 	tport->tport_wwpn = wwpn;
 	/*
 	 * Determine the emulated Protocol Identifier and Target Port Name
-- 
2.13.0

On Sat, May 20, 2017 at 04:31:13PM +0200, SF Markus Elfring
wrote:
> From: Markus Elfring <elfring at users.sourceforge.net>
> Date: Sat, 20 May 2017 13:48:44 +0200
> 
> Replace the specification of four data structures by pointer dereferences
> as the parameter for the operator "sizeof" to make the
corresponding size
> determination a bit safer according to the Linux coding style convention.
> 
> Signed-off-by: Markus Elfring <elfring at users.sourceforge.net>
> ---
>  drivers/vhost/scsi.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
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On Sat, May 20, 2017 at 04:32:17PM +0200, SF Markus Elfring
wrote:
> From: Markus Elfring <elfring at users.sourceforge.net>
> Date: Sat, 20 May 2017 15:50:30 +0200
> 
> Omit seven extra messages for memory allocation failures in these
functions.
> 
> This issue was detected by using the Coccinelle software.
> 
> Link:
http://events.linuxfoundation.org/sites/events/files/slides/LCJ16-Refactor_Strings-WSang_0.pdf
Please include an actual explanation for this change instead of linking
to slides.  Why are you trying to get rid of memory allocation failure
messages?
> Signed-off-by: Markus Elfring <elfring at users.sourceforge.net>
> ---
>  drivers/vhost/scsi.c | 24 +++++++-----------------
>  1 file changed, 7 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index 650533916c19..49d07950e2e5 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -417,5 +417,4 @@ vhost_scsi_allocate_evt(struct vhost_scsi *vs,
>  	if (!evt) {
> -		vq_err(vq, "Failed to allocate vhost_scsi_evt\n");
#define vq_err(vq, fmt, ...) do {                                  \
                pr_debug(pr_fmt(fmt), ##__VA_ARGS__);       \
                if ((vq)->error_ctx)                               \
                                eventfd_signal((vq)->error_ctx, 1);\
        } while (0)

You silently dropped the eventfd_signal() call.  Please explain.
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