Author: cem
Date: Fri Aug 25 16:38:21 2017
New Revision: 322895
URL: https://svnweb.freebsd.org/changeset/base/322895
Log:
getmntinfo(3): Scale faster, and return sooner
getmntinfo(3) is designed around a relatively static or slow growing set of
current mounts. It tried to detect a race with somewhat concurrent mount
and re-call getfsstat(2) in that case, looping indefinitely. It also
allocated space for a single extra mount as slop.
In the case where the user has a large number of mounts and is adding them
at a rapid pace, it fell over.
This patch makes two functional changes:
1. Allocate even more slop. Double whatever the last getfsstat(2) returned.
2. Abort and return some known results after looping a few times
(arbitrarily, 3). If the list is constantly changing, we can't guarantee
we return a full result to the user at any point anyways.
While here, add very basic functional tests for getmntinfo(3) to the libc
suite.
PR: 221743
Submitted by: Peter Eriksson <peter AT ifm.liu.se> (earlier version)
Sponsored by: Dell EMC Isilon
Added:
head/lib/libc/tests/gen/getmntinfo_test.c (contents, props changed)
Modified:
head/lib/libc/gen/getmntinfo.c
head/lib/libc/tests/gen/Makefile
Modified: head/lib/libc/gen/getmntinfo.c
==============================================================================
--- head/lib/libc/gen/getmntinfo.c Fri Aug 25 16:10:16 2017
(r322894)
+++ head/lib/libc/gen/getmntinfo.c Fri Aug 25 16:38:21 2017
(r322895)
@@ -38,6 +38,9 @@ __FBSDID("$FreeBSD$");
#include <sys/mount.h>
#include <stdlib.h>
+#define MAX_TRIES 3
+#define SCALING_FACTOR 2
+
/*
* Return information about mounted filesystems.
*/
@@ -47,20 +50,21 @@ getmntinfo(struct statfs **mntbufp, int mode)
static struct statfs *mntbuf;
static int mntsize;
static long bufsize;
+ unsigned tries = 0;
if (mntsize <= 0 && (mntsize = getfsstat(0, 0, MNT_NOWAIT)) < 0)
return (0);
if (bufsize > 0 && (mntsize = getfsstat(mntbuf, bufsize, mode)) < 0)
return (0);
- while (bufsize <= mntsize * sizeof(struct statfs)) {
- if (mntbuf)
- free(mntbuf);
- bufsize = (mntsize + 1) * sizeof(struct statfs);
- if ((mntbuf = malloc(bufsize)) == NULL)
+ while (tries++ < MAX_TRIES && bufsize <= mntsize * sizeof(*mntbuf)) {
+ bufsize = (mntsize * SCALING_FACTOR) * sizeof(*mntbuf);
+ if ((mntbuf = reallocf(mntbuf, bufsize)) == NULL)
return (0);
if ((mntsize = getfsstat(mntbuf, bufsize, mode)) < 0)
return (0);
}
*mntbufp = mntbuf;
+ if (mntsize > (bufsize / sizeof(*mntbuf)))
+ return (bufsize / sizeof(*mntbuf));
return (mntsize);
}
Modified: head/lib/libc/tests/gen/Makefile
==============================================================================
--- head/lib/libc/tests/gen/Makefile Fri Aug 25 16:10:16 2017
(r322894)
+++ head/lib/libc/tests/gen/Makefile Fri Aug 25 16:38:21 2017
(r322895)
@@ -8,6 +8,7 @@ ATF_TESTS_C+= fmtmsg_test
ATF_TESTS_C+= fnmatch2_test
ATF_TESTS_C+= fpclassify2_test
ATF_TESTS_C+= ftw_test
+ATF_TESTS_C+= getmntinfo_test
ATF_TESTS_C+= glob2_test
ATF_TESTS_C+= popen_test
ATF_TESTS_C+= posix_spawn_test
Added: head/lib/libc/tests/gen/getmntinfo_test.c
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/lib/libc/tests/gen/getmntinfo_test.c Fri Aug 25 16:38:21 2017
(r322895)
@@ -0,0 +1,86 @@
+/*-
+ * Copyright (c) 2017 Conrad Meyer <c...@freebsd.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Limited test program for getmntinfo(3), a non-standard BSDism.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/mount.h>
+#include <sys/ucred.h>
+
+#include <errno.h>
+
+#include <atf-c.h>
+
+static void
+check_mntinfo(struct statfs *mntinfo, int n)
+{
+ int i;
+
+ for (i = 0; i < n; i++) {
+ ATF_REQUIRE_MSG(mntinfo[i].f_version == STATFS_VERSION, "%ju",
+ (uintmax_t)mntinfo[i].f_version);
+ ATF_REQUIRE(mntinfo[i].f_namemax <=
sizeof(mntinfo[0].f_mntonname));
+ }
+}
+
+ATF_TC_WITHOUT_HEAD(getmntinfo_test);
+ATF_TC_BODY(getmntinfo_test, tc)
+{
+ int nmnts;
+ struct statfs *mntinfo;
+
+ /* Test bogus mode */
+ nmnts = getmntinfo(&mntinfo, 199);
+ ATF_REQUIRE_MSG(nmnts == 0 && errno == EINVAL,
+ "getmntinfo() succeeded; errno=%d", errno);
+
+ /* Valid modes */
+ nmnts = getmntinfo(&mntinfo, MNT_NOWAIT);
+ ATF_REQUIRE_MSG(nmnts != 0, "getmntinfo(MNT_NOWAIT) failed; errno=%d",
+ errno);
+
+ check_mntinfo(mntinfo, nmnts);
+ memset(mntinfo, 0xdf, sizeof(*mntinfo) * nmnts);
+
+ nmnts = getmntinfo(&mntinfo, MNT_WAIT);
+ ATF_REQUIRE_MSG(nmnts != 0, "getmntinfo(MNT_WAIT) failed; errno=%d",
+ errno);
+
+ check_mntinfo(mntinfo, nmnts);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+ ATF_TP_ADD_TC(tp, getmntinfo_test);
+
+ return (atf_no_error());
+}
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