[dpdk-dev] [PATCH] eal/linux: allow hugetlbfs sub-directories

[John Levon <john.levon@nutanix.com>]

get_hugepage_dir() was implemented in such a way that a --huge-dir
option had to exactly match the mountpoint, but there's no reason for
this restriction: DPDK might not be the only user of hugepages, and
shouldn't assume it owns an entire mountpoint. For example, if I have
/dev/hugepages/myapp, and /dev/hugepages/dpdk, I should be able to
specify:

--huge-dir=/dev/hugepages/dpdk/

and have DPDK only use that sub-directory.

Fix the implementation to allow a sub-directory within a suitable
hugetlbfs mountpoint to be specified, preferring the closest match.

Signed-off-by: John Levon <john.levon@nutanix.com>
Acked-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
---
v2: prefer closer matches
v3: checkpatch fixes
v4: fix docs, added tests
v5: added release note

 app/test/test_eal_flags.c                     | 116 ++++++++++++------
 doc/guides/linux_gsg/linux_eal_parameters.rst |   3 +-
 doc/guides/rel_notes/release_21_11.rst        |   6 +-
 lib/eal/linux/eal_hugepage_info.c             |  83 +++++++++----
 4 files changed, 143 insertions(+), 65 deletions(-)

diff --git a/app/test/test_eal_flags.c b/app/test/test_eal_flags.c
index b4880ee802..1d18a0ba8f 100644
--- a/app/test/test_eal_flags.c
+++ b/app/test/test_eal_flags.c
@@ -14,8 +14,9 @@
 #include <errno.h>
 #include <unistd.h>
 #include <dirent.h>
-#include <sys/wait.h>
 #include <sys/file.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
 #include <limits.h>
 #include <fcntl.h>
 
@@ -800,6 +801,9 @@ static int
 test_misc_flags(void)
 {
 	char hugepath[PATH_MAX] = {0};
+	char hugepath_dir[PATH_MAX] = {0};
+	char hugepath_dir2[PATH_MAX] = {0};
+	char hugepath_dir3[PATH_MAX] = {0};
 #ifdef RTE_EXEC_ENV_FREEBSD
 	/* BSD target doesn't support prefixes at this point */
 	const char * prefix = "";
@@ -810,6 +814,7 @@ test_misc_flags(void)
 	FILE * hugedir_handle = NULL;
 	char line[PATH_MAX] = {0};
 	unsigned i, isempty = 1;
+
 	if (get_current_prefix(tmp, sizeof(tmp)) == NULL) {
 		printf("Error - unable to get current prefix!\n");
 		return -1;
@@ -849,6 +854,20 @@ test_misc_flags(void)
 	}
 #endif
 
+	snprintf(hugepath_dir, sizeof(hugepath_dir), "%s/dpdk.missing", hugepath);
+	snprintf(hugepath_dir2, sizeof(hugepath_dir2), "%s/dpdk.dir", hugepath);
+
+	if (mkdir(hugepath_dir2, 0700) != 0 && errno != EEXIST) {
+		printf("Error - failed to mkdir(%s)\n", hugepath_dir2);
+		return -1;
+	}
+
+	snprintf(hugepath_dir3, sizeof(hugepath_dir3), "%s/dpdk.dir/sub", hugepath);
+
+	if (mkdir(hugepath_dir3, 0700) != 0 && errno != EEXIST) {
+		printf("Error - failed to mkdir(%s)\n", hugepath_dir3);
+		goto fail;
+	}
 
 	/* check that some general flags don't prevent things from working.
 	 * All cases, apart from the first, app should run.
@@ -881,60 +900,66 @@ test_misc_flags(void)
 	/* With invalid --huge-dir */
 	const char *argv9[] = {prgname, "-m", DEFAULT_MEM_SIZE,
 			"--file-prefix=hugedir", "--huge-dir", "invalid"};
+	/* With invalid --huge-dir sub-directory */
+	const char *argv10[] = {prgname, "-m", DEFAULT_MEM_SIZE,
+			"--file-prefix=hugedir", "--huge-dir", hugepath_dir};
+	/* With valid --huge-dir sub-directory */
+	const char *argv11[] = {prgname, "-m", DEFAULT_MEM_SIZE,
+			"--file-prefix=hugedir", "--huge-dir", hugepath_dir2};
 	/* Secondary process with invalid --huge-dir (should run as flag has no
 	 * effect on secondary processes) */
-	const char *argv10[] = {prgname, prefix, mp_flag,
+	const char *argv12[] = {prgname, prefix, mp_flag,
 			"--huge-dir", "invalid"};
 
 	/* try running with base-virtaddr param */
-	const char *argv11[] = {prgname, "--file-prefix=virtaddr",
+	const char *argv13[] = {prgname, "--file-prefix=virtaddr",
 			"--base-virtaddr=0x12345678"};
 
 	/* try running with --vfio-intr INTx flag */
-	const char *argv12[] = {prgname, "--file-prefix=intr",
+	const char *argv14[] = {prgname, "--file-prefix=intr",
 			"--vfio-intr=legacy"};
 
 	/* try running with --vfio-intr MSI flag */
-	const char *argv13[] = {prgname, "--file-prefix=intr",
+	const char *argv15[] = {prgname, "--file-prefix=intr",
 			"--vfio-intr=msi"};
 
 	/* try running with --vfio-intr MSI-X flag */
-	const char *argv14[] = {prgname, "--file-prefix=intr",
+	const char *argv16[] = {prgname, "--file-prefix=intr",
 			"--vfio-intr=msix"};
 
 	/* try running with --vfio-intr invalid flag */
-	const char *argv15[] = {prgname, "--file-prefix=intr",
+	const char *argv17[] = {prgname, "--file-prefix=intr",
 			"--vfio-intr=invalid"};
 
 	/* With process type as auto-detect */
-	const char * const argv16[] = {prgname, "--file-prefix=auto",
+	const char * const argv18[] = {prgname, "--file-prefix=auto",
 			"--proc-type=auto"};
 
 	/* With process type as auto-detect with no-shconf */
-	const char * const argv17[] = {prgname, "--proc-type=auto",
+	const char * const argv19[] = {prgname, "--proc-type=auto",
 			no_shconf, nosh_prefix, no_huge};
 
 	/* With process type as --create-uio-dev flag */
-	const char * const argv18[] = {prgname, "--file-prefix=uiodev",
+	const char * const argv20[] = {prgname, "--file-prefix=uiodev",
 			"--create-uio-dev"};
 
 	/* run all tests also applicable to FreeBSD first */
 
 	if (launch_proc(argv0) == 0) {
 		printf("Error - process ran ok with invalid flag\n");
-		return -1;
+		goto fail;
 	}
 	if (launch_proc(argv1) != 0) {
 		printf("Error - process did not run ok with --no-pci flag\n");
-		return -1;
+		goto fail;
 	}
 	if (launch_proc(argv2) != 0) {
 		printf("Error - process did not run ok with -v flag\n");
-		return -1;
+		goto fail;
 	}
 	if (launch_proc(argv6) != 0) {
 		printf("Error - process did not run ok with --no-shconf flag\n");
-		return -1;
+		goto fail;
 	}
 
 #ifdef RTE_EXEC_ENV_FREEBSD
@@ -944,73 +969,88 @@ test_misc_flags(void)
 
 	if (launch_proc(argv3) != 0) {
 		printf("Error - process did not run ok with --syslog flag\n");
-		return -1;
+		goto fail;
 	}
 	if (launch_proc(argv4) == 0) {
 		printf("Error - process run ok with empty --syslog flag\n");
-		return -1;
+		goto fail;
 	}
 	if (launch_proc(argv5) == 0) {
 		printf("Error - process run ok with invalid --syslog flag\n");
-		return -1;
+		goto fail;
 	}
 	if (launch_proc(argv7) != 0) {
 		printf("Error - process did not run ok with --huge-dir flag\n");
-		return -1;
+		goto fail;
 	}
 	if (launch_proc(argv8) == 0) {
 		printf("Error - process run ok with empty --huge-dir flag\n");
-		return -1;
+		goto fail;
 	}
 	if (launch_proc(argv9) == 0) {
 		printf("Error - process run ok with invalid --huge-dir flag\n");
-		return -1;
+		goto fail;
 	}
-	if (launch_proc(argv10) != 0) {
-		printf("Error - secondary process did not run ok with invalid --huge-dir flag\n");
-		return -1;
+	if (launch_proc(argv10) == 0) {
+		printf("Error - process run ok with invalid --huge-dir sub-dir flag\n");
+		goto fail;
 	}
 	if (launch_proc(argv11) != 0) {
-		printf("Error - process did not run ok with --base-virtaddr parameter\n");
-		return -1;
+		printf("Error - process did not run ok with --huge-dir subdir flag\n");
+		goto fail;
 	}
 	if (launch_proc(argv12) != 0) {
+		printf("Error - secondary process did not run ok with invalid --huge-dir flag\n");
+		goto fail;
+	}
+	if (launch_proc(argv13) != 0) {
+		printf("Error - process did not run ok with --base-virtaddr parameter\n");
+		goto fail;
+	}
+	if (launch_proc(argv14) != 0) {
 		printf("Error - process did not run ok with "
 				"--vfio-intr INTx parameter\n");
-		return -1;
+		goto fail;
 	}
-	if (launch_proc(argv13) != 0) {
+	if (launch_proc(argv15) != 0) {
 		printf("Error - process did not run ok with "
 				"--vfio-intr MSI parameter\n");
-		return -1;
+		goto fail;
 	}
-	if (launch_proc(argv14) != 0) {
+	if (launch_proc(argv16) != 0) {
 		printf("Error - process did not run ok with "
 				"--vfio-intr MSI-X parameter\n");
-		return -1;
+		goto fail;
 	}
-	if (launch_proc(argv15) == 0) {
+	if (launch_proc(argv17) == 0) {
 		printf("Error - process run ok with "
 				"--vfio-intr invalid parameter\n");
-		return -1;
+		goto fail;
 	}
-	if (launch_proc(argv16) != 0) {
+	if (launch_proc(argv18) != 0) {
 		printf("Error - process did not run ok with "
 				"--proc-type as auto parameter\n");
-		return -1;
+		goto fail;
 	}
-	if (launch_proc(argv17) != 0) {
+	if (launch_proc(argv19) != 0) {
 		printf("Error - process did not run ok with "
 				"--proc-type and --no-shconf parameter\n");
-		return -1;
+		goto fail;
 	}
-	if (launch_proc(argv18) != 0) {
+	if (launch_proc(argv20) != 0) {
 		printf("Error - process did not run ok with "
 				"--create-uio-dev parameter\n");
-		return -1;
+		goto fail;
 	}
 
+	rmdir(hugepath_dir3);
+	rmdir(hugepath_dir2);
 	return 0;
+
+fail:
+	rmdir(hugepath_dir3);
+	rmdir(hugepath_dir2);
+	return -1;
 }
 
 static int
diff --git a/doc/guides/linux_gsg/linux_eal_parameters.rst b/doc/guides/linux_gsg/linux_eal_parameters.rst
index bd3977cb3d..74df2611b5 100644
--- a/doc/guides/linux_gsg/linux_eal_parameters.rst
+++ b/doc/guides/linux_gsg/linux_eal_parameters.rst
@@ -81,7 +81,8 @@ Memory-related options
 
 *   ``--huge-dir <path to hugetlbfs directory>``
 
-    Use specified hugetlbfs directory instead of autodetected ones.
+    Use specified hugetlbfs directory instead of autodetected ones. This can be
+    a sub-directory within a hugetlbfs mountpoint.
 
 *   ``--huge-unlink``
 
diff --git a/doc/guides/rel_notes/release_21_11.rst b/doc/guides/rel_notes/release_21_11.rst
index 54718ff367..9fe689356b 100644
--- a/doc/guides/rel_notes/release_21_11.rst
+++ b/doc/guides/rel_notes/release_21_11.rst
@@ -62,6 +62,11 @@ New Features
   * Added bus-level parsing of the devargs syntax.
   * Kept compatibility with the legacy syntax as parsing fallback.
 
+* **Updated EAL hugetlbfs mount handling.**
+
+  * Modified to allow ``--huge-dir`` option to specify a sub-directory
+    within a hugetlbfs mountpoint.
+
 * **Added new RSS offload types for IPv4/L4 checksum in RSS flow.**
 
   Added macros ETH_RSS_IPV4_CHKSUM and ETH_RSS_L4_CHKSUM, now IPv4 and
@@ -154,7 +159,6 @@ New Features
   * Added tests to verify tunnel header verification in IPsec inbound.
   * Added tests to verify inner checksum.
 
-
 Removed Items
 -------------
 
diff --git a/lib/eal/linux/eal_hugepage_info.c b/lib/eal/linux/eal_hugepage_info.c
index d97792cade..9fb0e968db 100644
--- a/lib/eal/linux/eal_hugepage_info.c
+++ b/lib/eal/linux/eal_hugepage_info.c
@@ -213,10 +213,19 @@ get_hugepage_dir(uint64_t hugepage_sz, char *hugedir, int len)
 	const size_t pagesize_opt_len = sizeof(pagesize_opt) - 1;
 	const char split_tok = ' ';
 	char *splitstr[_FIELDNAME_MAX];
+	char found[PATH_MAX] = "";
 	char buf[BUFSIZ];
-	int retval = -1;
 	const struct internal_config *internal_conf =
 		eal_get_internal_configuration();
+	struct stat st;
+
+	/*
+	 * If the specified dir doesn't exist, we can't match it.
+	 */
+	if (internal_conf->hugepage_dir != NULL &&
+		stat(internal_conf->hugepage_dir, &st) != 0) {
+		return -1;
+	}
 
 	FILE *fd = fopen(proc_mounts, "r");
 	if (fd == NULL)
@@ -226,42 +235,66 @@ get_hugepage_dir(uint64_t hugepage_sz, char *hugedir, int len)
 		default_size = get_default_hp_size();
 
 	while (fgets(buf, sizeof(buf), fd)){
+		const char *pagesz_str;
+
 		if (rte_strsplit(buf, sizeof(buf), splitstr, _FIELDNAME_MAX,
 				split_tok) != _FIELDNAME_MAX) {
 			RTE_LOG(ERR, EAL, "Error parsing %s\n", proc_mounts);
 			break; /* return NULL */
 		}
 
-		/* we have a specified --huge-dir option, only examine that dir */
-		if (internal_conf->hugepage_dir != NULL &&
-				strcmp(splitstr[MOUNTPT], internal_conf->hugepage_dir) != 0)
+		if (strncmp(splitstr[FSTYPE], hugetlbfs_str, htlbfs_str_len) != 0)
 			continue;
 
-		if (strncmp(splitstr[FSTYPE], hugetlbfs_str, htlbfs_str_len) == 0){
-			const char *pagesz_str = strstr(splitstr[OPTIONS], pagesize_opt);
+		pagesz_str = strstr(splitstr[OPTIONS], pagesize_opt);
 
-			/* if no explicit page size, the default page size is compared */
-			if (pagesz_str == NULL){
-				if (hugepage_sz == default_size){
-					strlcpy(hugedir, splitstr[MOUNTPT], len);
-					retval = 0;
-					break;
-				}
-			}
-			/* there is an explicit page size, so check it */
-			else {
-				uint64_t pagesz = rte_str_to_size(&pagesz_str[pagesize_opt_len]);
-				if (pagesz == hugepage_sz) {
-					strlcpy(hugedir, splitstr[MOUNTPT], len);
-					retval = 0;
-					break;
-				}
-			}
-		} /* end if strncmp hugetlbfs */
+		/* if no explicit page size, the default page size is compared */
+		if (pagesz_str == NULL) {
+			if (hugepage_sz != default_size)
+				continue;
+		}
+		/* there is an explicit page size, so check it */
+		else {
+			uint64_t pagesz = rte_str_to_size(&pagesz_str[pagesize_opt_len]);
+			if (pagesz != hugepage_sz)
+				continue;
+		}
+
+		/*
+		 * If no --huge-dir option has been given, we're done.
+		 */
+		if (internal_conf->hugepage_dir == NULL) {
+			strlcpy(found, splitstr[MOUNTPT], len);
+			break;
+		}
+
+		/*
+		 * Ignore any mount that doesn't contain the --huge-dir
+		 * directory.
+		 */
+		if (strncmp(internal_conf->hugepage_dir, splitstr[MOUNTPT],
+			strlen(splitstr[MOUNTPT])) != 0) {
+			continue;
+		}
+
+		/*
+		 * We found a match, but only prefer it if it's a longer match
+		 * (so /mnt/1 is preferred over /mnt for matching /mnt/1/2)).
+		 */
+		if (strlen(splitstr[MOUNTPT]) > strlen(found))
+			strlcpy(found, splitstr[MOUNTPT], len);
 	} /* end while fgets */
 
 	fclose(fd);
-	return retval;
+
+	if (found[0] != '\0') {
+		/* If needed, return the requested dir, not the mount point. */
+		strlcpy(hugedir, internal_conf->hugepage_dir != NULL ?
+			internal_conf->hugepage_dir : found, len);
+		return 0;
+	}
+
+	return -1;
 }
 
 /*
-- 
2.30.2