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Date:   Tue, 24 Oct 2023 15:23:20 -0700
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Subject: [PATCH v3 17/50] tools api fs: Avoid reading whole file for a 1 byte bool
From:   Ian Rogers <irogers@google.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Nick Terrell <terrelln@fb.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>, Leo Yan <leo.yan@linaro.org>,
        Song Liu <song@kernel.org>,
        Sandipan Das <sandipan.das@amd.com>,
        James Clark <james.clark@arm.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Liam Howlett <liam.howlett@oracle.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Athira Rajeev <atrajeev@linux.vnet.ibm.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        Sean Christopherson <seanjc@google.com>,
        Yanteng Si <siyanteng@loongson.cn>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        German Gomez <german.gomez@arm.com>,
        Changbin Du <changbin.du@huawei.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        liuwenyu <liuwenyu7@huawei.com>, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

sysfs__read_bool used the first byte from a fully read file into a
string. It then looked at the first byte's value. Avoid doing this and
just read the first byte.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/lib/api/fs/fs.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index 496812b5f1d2..4c35a689d1fc 100644
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -447,15 +447,16 @@ int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
 
 int sysfs__read_bool(const char *entry, bool *value)
 {
-	char *buf;
-	size_t size;
-	int ret;
+	struct io io;
+	char bf[16];
+	int ret = 0;
 
-	ret = sysfs__read_str(entry, &buf, &size);
-	if (ret < 0)
-		return ret;
+	io.fd = open(entry, O_RDONLY);
+	if (io.fd < 0)
+		return -errno;
 
-	switch (buf[0]) {
+	io__init(&io, io.fd, bf, sizeof(bf));
+	switch (io__get_char(&io)) {
 	case '1':
 	case 'y':
 	case 'Y':
@@ -469,8 +470,7 @@ int sysfs__read_bool(const char *entry, bool *value)
 	default:
 		ret = -1;
 	}
-
-	free(buf);
+	close(io.fd);
 
 	return ret;
 }
-- 
2.42.0.758.gaed0368e0e-goog