scsi: tcmu: Simplify tcmu_update_uio_info() [Linux 5.3]

This Linux kernel change "scsi: tcmu: Simplify tcmu_update_uio_info()" is included in the Linux 5.3 release. This change is authored by Christophe JAILLET <christophe.jaillet [at] wanadoo.fr> on Sun Jun 16 09:02:20 2019 +0200. The commit for this change in Linux stable tree is 22c2f35 (patch).

scsi: tcmu: Simplify tcmu_update_uio_info()

Use 'kasprintf()' instead of:
   - snprintf(NULL, 0...
   - kmalloc(...
   - snprintf(...

This is less verbose and saves 7 bytes (i.e. the space for '/(null)') if
'udev->dev_config' is NULL.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

There are 16 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/target/target_core_user.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 40b29ca..9dbd0db 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -1836,20 +1836,18 @@ static int tcmu_update_uio_info(struct tcmu_dev *udev)
 {
    struct tcmu_hba *hba = udev->hba->hba_ptr;
    struct uio_info *info;
-   size_t size, used;
    char *str;

    info = &udev->uio_info;
-   size = snprintf(NULL, 0, "tcm-user/%u/%s/%s", hba->host_id, udev->name,
-           udev->dev_config);
-   size += 1; /* for \0 */
-   str = kmalloc(size, GFP_KERNEL);
-   if (!str)
-       return -ENOMEM;

-   used = snprintf(str, size, "tcm-user/%u/%s", hba->host_id, udev->name);
    if (udev->dev_config[0])
-       snprintf(str + used, size - used, "/%s", udev->dev_config);
+       str = kasprintf(GFP_KERNEL, "tcm-user/%u/%s/%s", hba->host_id,
+               udev->name, udev->dev_config);
+   else
+       str = kasprintf(GFP_KERNEL, "tcm-user/%u/%s", hba->host_id,
+               udev->name);
+   if (!str)
+       return -ENOMEM;

    /* If the old string exists, free it */
    kfree(info->name);

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