[PATCH V3 4/4] x86/resctrl: Use appropriate API for strings terminated by newline

[Reinette Chatre]

The user input to files in the resctrl filesystem are expected to be
terminated with a newline. Testing the user input includes a test for
the presence of a newline and then replacing the newline with NUL
byte followed by comparison using strcmp().

sysfs_streq() exists to test if strings are equal, treating both NUL and
newline-then-NUL as equivalent string terminations. Even more,
sysfs_match_string() exists to match a given string in an array using
sysfs_streq().

Replace existing strcmp() comparisons of strings that are terminated
with a newline with more appropriate sysfs_streq() via the
sysfs_match_string() API that can perform the match across the different
mode strings that are already maintained in an array.

Suggested-by: Andy Shevchenko <andriy.shevche...@linux.intel.com>
Signed-off-by: Reinette Chatre <reinette.cha...@intel.com>
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 32 ++++++++++++++------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c 
b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index c60a3b307f7d..e70694892c02 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1408,12 +1408,11 @@ static ssize_t rdtgroup_mode_write(struct 
kernfs_open_file *of,
 {
        struct rdtgroup *rdtgrp;
        enum rdtgrp_mode mode;
-       int ret = 0;
+       int user_m;
+       int ret;
 
-       /* Valid input requires a trailing newline */
-       if (nbytes == 0 || buf[nbytes - 1] != '\n')
+       if (nbytes == 0)
                return -EINVAL;
-       buf[nbytes - 1] = '\0';
 
        rdtgrp = rdtgroup_kn_lock_live(of->kn);
        if (!rdtgrp) {
@@ -1425,11 +1424,17 @@ static ssize_t rdtgroup_mode_write(struct 
kernfs_open_file *of,
 
        mode = rdtgrp->mode;
 
-       if ((!strcmp(buf, "shareable") && mode == RDT_MODE_SHAREABLE) ||
-           (!strcmp(buf, "exclusive") && mode == RDT_MODE_EXCLUSIVE) ||
-           (!strcmp(buf, "pseudo-locksetup") &&
-            mode == RDT_MODE_PSEUDO_LOCKSETUP) ||
-           (!strcmp(buf, "pseudo-locked") && mode == RDT_MODE_PSEUDO_LOCKED))
+       ret = sysfs_match_string(rdt_mode_str, buf);
+       if (ret < 0) {
+               rdt_last_cmd_puts("Unknown or unsupported mode\n");
+               goto out;
+       }
+
+       user_m = ret;
+       ret = 0;
+
+       /* Do nothing and return success if user asks for current mode */
+       if (user_m == mode)
                goto out;
 
        if (mode == RDT_MODE_PSEUDO_LOCKED) {
@@ -1438,14 +1443,14 @@ static ssize_t rdtgroup_mode_write(struct 
kernfs_open_file *of,
                goto out;
        }
 
-       if (!strcmp(buf, "shareable")) {
+       if (user_m == RDT_MODE_SHAREABLE) {
                if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
                        ret = rdtgroup_locksetup_exit(rdtgrp);
                        if (ret)
                                goto out;
                }
                rdtgrp->mode = RDT_MODE_SHAREABLE;
-       } else if (!strcmp(buf, "exclusive")) {
+       } else if (user_m == RDT_MODE_EXCLUSIVE) {
                if (!rdtgroup_mode_test_exclusive(rdtgrp)) {
                        ret = -EINVAL;
                        goto out;
@@ -1456,14 +1461,11 @@ static ssize_t rdtgroup_mode_write(struct 
kernfs_open_file *of,
                                goto out;
                }
                rdtgrp->mode = RDT_MODE_EXCLUSIVE;
-       } else if (!strcmp(buf, "pseudo-locksetup")) {
+       } else if (user_m == RDT_MODE_PSEUDO_LOCKSETUP) {
                ret = rdtgroup_locksetup_enter(rdtgrp);
                if (ret)
                        goto out;
                rdtgrp->mode = RDT_MODE_PSEUDO_LOCKSETUP;
-       } else {
-               rdt_last_cmd_puts("Unknown or unsupported mode\n");
-               ret = -EINVAL;
        }
 
 out:
-- 
2.21.0