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

Babu Moger
2020-05-14T19:05:36Z

> -----Original Message-----
> From: Reinette Chatre <reinette.chatre@intel.com>
> Sent: Wednesday, May 6, 2020 6:50 PM
> To: tglx@linutronix.de; fenghua.yu@intel.com; bp@alien8.de;
> tony.luck@intel.com
> Cc: kuo-lang.tseng@intel.com; ravi.v.shankar@intel.com; mingo@redhat.com;
> Moger, Babu <Babu.Moger@amd.com>; hpa@zytor.com; x86@kernel.org;
> linux-kernel@vger.kernel.org; Reinette Chatre <reinette.chatre@intel.com>;
> Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Subject: [PATCH V3 4/4] x86/resctrl: Use appropriate API for strings terminated
> by newline
>
> 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.shevchenko@linux.intel.com>
> Signed-off-by: Reinette Chatre <reinette.chatre@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;

This is bit confusing here. Mode and user_m should have been of same type.
You can define user_m to user_mode to be very clear.

You can completely remove "mode" and directly use rdtgrp->mode instead. It
is left to you.

> > - /* 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