MDEV-28592 disks plugin - getmntinfo (BSD) & getmntent (AIX)

Thanks to references from Brad Smith, BSDs use getmntinfo as
a system call for mounted filesystems.

Most BSDs return statfs structures, (and we use OSX's statfs64),
but NetBSD uses a statvfs structure.

Simplify Linux getmntent_r to just use getmntent.

AIX uses getmntent.

An attempt at writing Solaris compatibility with
a small bit of HPUX compatibility was made based on man page
entries only. Fixes welcome.

statvfs structures now use f_bsize for consistency with statfs

Test case adjusted as PATH_MAX is OS defined (e.g. 1023 on AIX)

Fixes: 0ee5cf8

also fixes:

MDEV-27818: Disk plugin does not show zpool mounted devices

This is because zpool mounted point don't begin with /.

Due to the proliferation of multiple filesystem types since this
was written, we restrict the entries listed in the disks plugin
to excude:
* read only mount points (no point monitoring, and
  includes squash, snaps, sysfs, procfs, cgroups...)
* mount points that aren't directories (excludes /etc/hostname and
  similar mounts in containers). (getmntent (Linux/AIX) only)
* exclude systems where there is no capacity listed (excludes various
  virtual filesystem types).

Reviewer: Sergei Golubchik

Author: grooverdan

cmake/os/WindowsCache.cmake

@@ -64,6 +64,10 @@ SET(HAVE_GETHOSTBYADDR_R CACHE  INTERNAL "")
 SET(HAVE_GETHRTIME CACHE  INTERNAL "")
 SET(HAVE_GETPAGESIZE CACHE  INTERNAL "")
 SET(HAVE_GETPASS CACHE  INTERNAL "")
+SET(HAVE_GETMNTENT CACHE  INTERNAL "")
+SET(HAVE_GETMNTENT_IN_SYS_MNTAB CACHE  INTERNAL "")
+SET(HAVE_GETMNTINFO CACHE  INTERNAL "")
+SET(HAVE_GETMNTINFO64 CACHE  INTERNAL "")
 SET(HAVE_GETPASSPHRASE CACHE  INTERNAL "")
 SET(HAVE_GETPWNAM CACHE  INTERNAL "")
 SET(HAVE_GETPWUID CACHE  INTERNAL "")
@@ -146,6 +150,7 @@ SET(HAVE_SELECT 1 CACHE  INTERNAL "")
 SET(HAVE_SELECT_H CACHE  INTERNAL "")
 SET(HAVE_SETENV CACHE  INTERNAL "")
 SET(HAVE_SETLOCALE 1 CACHE  INTERNAL "")
+SET(HAVE_SETMNTENT CACHE  INTERNAL "")
 SET(HAVE_SIGACTION CACHE  INTERNAL "")
 SET(HAVE_SIGINT 1 CACHE  INTERNAL "")
 SET(HAVE_SIGPIPE CACHE  INTERNAL "")

config.h.cmake

@@ -35,6 +35,11 @@
 #cmakedefine HAVE_FLOAT_H 1
 #cmakedefine HAVE_FNMATCH_H 1
 #cmakedefine HAVE_FPU_CONTROL_H 1
+#cmakedefine HAVE_GETMNTENT 1
+#cmakedefine HAVE_GETMNTENT_IN_SYS_MNTAB 1
+#cmakedefine HAVE_GETMNTINFO 1
+#cmakedefine HAVE_GETMNTINFO64 1
+#cmakedefine HAVE_GETMNTINFO_TAKES_statvfs 1
 #cmakedefine HAVE_GRP_H 1
 #cmakedefine HAVE_IA64INTRIN_H 1
 #cmakedefine HAVE_IEEEFP_H 1
@@ -214,6 +219,7 @@
 #cmakedefine HAVE_SELECT 1
 #cmakedefine HAVE_SETENV 1
 #cmakedefine HAVE_SETLOCALE 1
+#cmakedefine HAVE_SETMNTENT 1
 #cmakedefine HAVE_SETUPTERM 1
 #cmakedefine HAVE_SIGSET 1
 #cmakedefine HAVE_SIGACTION 1

plugin/disks/CMakeLists.txt

@@ -1,7 +1,24 @@
 INCLUDE (CheckIncludeFiles)
-CHECK_INCLUDE_FILES ("sys/statvfs.h;mntent.h" INFO_HEADERS LANGUAGE CXX)
 
-IF (INFO_HEADERS)
+CHECK_SYMBOL_EXISTS (getmntent "mntent.h" HAVE_GETMNTENT)
+CHECK_SYMBOL_EXISTS (getmntent "sys/mnttab.h" HAVE_GETMNTENT_IN_SYS_MNTAB)
+CHECK_SYMBOL_EXISTS (setmntent "mntent.h" HAVE_SETMNTENT)
+CHECK_SYMBOL_EXISTS (getmntinfo "sys/types.h;sys/mount.h" HAVE_GETMNTINFO)
+CHECK_SYMBOL_EXISTS (getmntinfo64 "sys/types.h;sys/mount.h" HAVE_GETMNTINFO64)
+
+IF (HAVE_GETMNTINFO)
+CHECK_CXX_SOURCE_COMPILES("
+#include <sys/types.h>
+#include <sys/statvfs.h>
+int main()
+{
+  struct statvfs *s;
+  return getmntinfo(&s, ST_WAIT);
+}
+  " HAVE_GETMNTINFO_TAKES_statvfs)
+ENDIF()
+IF (HAVE_GETMNTENT OR HAVE_GETMNTENT_IN_SYS_MNTAB OR
+    HAVE_GETMNTINFO OR HAVE_GETMNTINFO64)
   INCLUDE_DIRECTORIES(${CMAKE_SOURCE_DIR}/sql)
   MYSQL_ADD_PLUGIN(DISKS information_schema_disks.cc MODULE_ONLY RECOMPILE_FOR_EMBEDDED)
 ENDIF()

plugin/disks/information_schema_disks.cc

@@ -17,11 +17,45 @@
 #include <my_global.h>
 #include <sys/statvfs.h>
 #include <sys/types.h>
+#if defined(HAVE_GETMNTENT)
 #include <mntent.h>
+#elif !defined(HAVE_GETMNTINFO_TAKES_statvfs)
+/* getmntinfo (the not NetBSD variants) */
+#include <sys/param.h>
+#include <sys/ucred.h>
+#include <sys/mount.h>
+#endif
+#if defined(HAVE_GETMNTENT_IN_SYS_MNTAB)
+#include <sys/mnttab.h>
+#define HAVE_GETMNTENT
+#endif
 #include <sql_class.h>
 #include <table.h>
 #include <sql_acl.h>                            /* check_global_access() */
 
+/*
+  This intends to support *BSD's, macOS, Solaris, AIX, HP-UX, and Linux.
+
+  specificly:
+  FreeBSD/OpenBSD/DragonFly (statfs) NetBSD (statvfs) uses getmntinfo().
+  macOS uses getmntinfo64().
+  Linux can use getmntent_r(), but we've just used getmntent for simplification.
+  Linux/Solaris/AIX/HP-UX uses setmntent()/getmntent().
+  Solaris uses getmntent() with a diffent prototype, return structure, and
+    no setmntent(fopen instead)
+*/
+#if defined(HAVE_GETMNTINFO_TAKES_statvfs) || defined(HAVE_GETMNTENT)
+typedef struct statvfs st_info;
+#elif defined(HAVE_GETMNTINFO64)
+typedef struct statfs64 st_info;
+#else // GETMNTINFO
+typedef struct statfs st_info;
+#endif
+#ifndef MOUNTED
+/* HPUX - https://docstore.mik.ua/manuals/hp-ux/en/B2355-60130/getmntent.3X.html */
+#define MOUNTED MNT_MNTTAB
+#endif
+
 bool schema_table_store_record(THD *thd, TABLE *table);
 
 namespace
@@ -39,23 +73,40 @@ ST_FIELD_INFO disks_table_fields[]=
     { 0, 0, MYSQL_TYPE_NULL, 0, 0, 0, 0 }
 };
 
-int disks_table_add_row(THD* pThd,
-                        TABLE* pTable,
-                        const char* zDisk,
-                        const char* zPath,
-                        const struct statvfs& info)
+static int disks_table_add_row_stat(
+                                    THD* pThd,
+                                    TABLE* pTable,
+                                    const char* zDisk,
+                                    const char* zPath,
+                                    const st_info &info)
 {
     // From: http://pubs.opengroup.org/onlinepubs/009695399/basedefs/sys/statvfs.h.html
+    // and same for statfs:
+    // From: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/statfs.2.html#//apple_ref/doc/man/2/statfs
+    // and: https://www.freebsd.org/cgi/man.cgi?query=statfs&sektion=2&apropos=0&manpath=FreeBSD+13.1-RELEASE+and+Ports
     //
-    // f_frsize   Fundamental file system block size.
+    // f_bsize    Fundamental file system block size.
     // f_blocks   Total number of blocks on file system in units of f_frsize.
     // f_bfree    Total number of free blocks.
     // f_bavail   Number of free blocks available to non-privileged process.
+    ulong block_size= (ulong) info.f_bsize;
 
-    ulonglong total = ((ulonglong)info.f_frsize * info.f_blocks) / 1024;
-    ulonglong used  = ((ulonglong)info.f_frsize *
+    ulonglong total = ((ulonglong) block_size * info.f_blocks) / 1024;
+    ulonglong used  = ((ulonglong) block_size *
                             (info.f_blocks - info.f_bfree)) / 1024;
-    ulonglong avail = ((ulonglong)info.f_frsize * info.f_bavail) / 1024;
+    ulonglong avail = ((ulonglong) block_size * info.f_bavail) / 1024;
+
+    /* skip filesystems that don't have any space */
+    if (!info.f_blocks)
+        return 0;
+
+    /* skip RO mounted filesystems */
+#if defined(HAVE_GETMNTINFO_TAKES_statvfs) || defined(HAVE_GETMNTENT)
+    if (info.f_flag & ST_RDONLY)
+#else
+    if (info.f_flags & MNT_RDONLY)
+#endif
+	return 0;
 
     pTable->field[0]->store(zDisk, strlen(zDisk), system_charset_info);
     pTable->field[1]->store(zPath, strlen(zPath), system_charset_info);
@@ -67,71 +118,147 @@ int disks_table_add_row(THD* pThd,
     return (schema_table_store_record(pThd, pTable) != 0) ? 1 : 0;
 }
 
-int disks_table_add_row(THD* pThd, TABLE* pTable, const char* zDisk, const char* zPath)
+
+#ifdef HAVE_GETMNTENT
+static int disks_table_add_row(THD* pThd, TABLE* pTable, const char* zDisk, const char* zPath)
 {
     int rv = 0;
 
-    struct statvfs info;
+    st_info info;
 
     if (statvfs(zPath, &info) == 0) // We ignore failures.
     {
-        rv = disks_table_add_row(pThd, pTable, zDisk, zPath, info);
+        rv = disks_table_add_row_stat(pThd, pTable, zDisk, zPath, info);
     }
 
     return rv;
 }
+#endif
 
-int disks_fill_table(THD* pThd, TABLE_LIST* pTables, Item* pCond)
+
+#ifdef HAVE_GETMNTINFO
+static int disks_fill_table(THD* pThd, TABLE_LIST* pTables, Item* pCond)
 {
-    int rv = 1;
-    TABLE* pTable = pTables->table;
+    st_info *s;
+    int count, rv= 0;
+    TABLE* pTable= pTables->table;
 
     if (check_global_access(pThd, FILE_ACL, true))
-      return 0;
+        return 0;
+
+#if defined(HAVE_GETMNTINFO_TAKES_statvfs)
+    count= getmntinfo(&s, ST_WAIT);
+#elif defined(HAVE_GETMNTINFO64)
+    count= getmntinfo64(&s, MNT_WAIT);
+#else
+    count= getmntinfo(&s, MNT_WAIT);
+#endif
+    if (count == 0)
+        return 1;
+
+    while (count && rv == 0)
+    {
+        rv= disks_table_add_row_stat(pThd, pTable, s->f_mntfromname, s->f_mntonname, *s);
+        count--;
+        s++;
+    }
+    return rv;
+}
+#else /* HAVE_GETMNTINFO */
+
+static mysql_mutex_t m_getmntent;
 
-    FILE* pFile = setmntent("/etc/mtab", "r");
+/* HAVE_GETMNTENT */
+static int disks_fill_table(THD* pThd, TABLE_LIST* pTables, Item* pCond)
+{
+    int rv= 1;
+#ifdef HAVE_SETMNTENT
+    struct mntent* pEnt;
+#else
+    struct mnttab mnttabent, *pEnt= &mnttabent;
+#endif
+    FILE* pFile;
+    TABLE* pTable= pTables->table;
 
-    if (pFile)
+    if (check_global_access(pThd, FILE_ACL, true))
+        return 0;
+
+#ifdef HAVE_SETMNTENT
+    pFile= setmntent(MOUNTED, "r");
+#else
+    /* Solaris */
+    pFile= fopen("/etc/mnttab", "r");
+#endif
+
+    if (!pFile)
+        return 1;
+
+    rv= 0;
+
+    /*
+      We lock the outer loop rather than between getmntent so the multiple
+      infomation_schema.disks reads don't all start blocking each other and
+      no-one gets any answers.
+    */
+    mysql_mutex_lock(&m_getmntent);
+
+    while ((rv == 0) &&
+#if defined(HAVE_SETMNTENT)
+        (pEnt = getmntent(pFile))
+
+#else
+        getmntent(pFile, pEnt) != 0
+#endif
+        )
     {
-        const size_t BUFFER_SIZE = 4096; // 4K should be sufficient.
-
-        char* pBuffer = new (std::nothrow) char [BUFFER_SIZE];
-
-        if (pBuffer)
-        {
-            rv = 0;
-
-            struct mntent ent;
-            struct mntent* pEnt;
-
-            while ((rv == 0) && (pEnt = getmntent_r(pFile, &ent, pBuffer, BUFFER_SIZE)))
-            {
-                // We only report the ones that refer to physical disks.
-                if (pEnt->mnt_fsname[0] == '/')
-                {
-                    rv = disks_table_add_row(pThd, pTable, pEnt->mnt_fsname, pEnt->mnt_dir);
-                }
-            }
-
-            delete [] pBuffer;
-        }
-        else
-        {
-            rv = 1;
-        }
-
-        endmntent(pFile);
+        struct stat f;
+	const char *path, *point;
+#ifdef HAVE_SETMNTENT
+	path= pEnt->mnt_dir;
+	point= pEnt->mnt_fsname;
+#else
+	path= pEnt->mnt_mountp;
+	point= pEnt->mnt_special;
+#endif
+	// Try to keep to real storage by excluding
+        // read only mounts, and mount points that aren't directories
+        if (hasmntopt(pEnt, MNTOPT_RO) != NULL)
+            continue;
+        if (stat(path, &f))
+            continue;
+        if (!S_ISDIR(f.st_mode))
+            continue;
+        rv= disks_table_add_row(pThd, pTable, point, path);
     }
+    mysql_mutex_unlock(&m_getmntent);
+
+#ifdef HAVE_SETMNTENT
+    endmntent(pFile);
+#else
+    fclose(pFile);
+#endif
 
     return rv;
 }
+#endif /* HAVE_GETMNTINFO */
 
-int disks_table_init(void *ptr)
+static int disks_table_init(void *ptr)
 {
     ST_SCHEMA_TABLE* pSchema_table = (ST_SCHEMA_TABLE*)ptr;
 
     pSchema_table->fields_info = disks_table_fields;
     pSchema_table->fill_table = disks_fill_table;
+#ifndef HAVE_GETMNTINFO
+    mysql_mutex_init(0, &m_getmntent, MY_MUTEX_INIT_SLOW);
+#endif
+    return 0;
+}
+
+static int disks_table_deinit(void *ptr __attribute__((unused)))
+{
+#ifndef HAVE_GETMNTINFO
+    mysql_mutex_destroy(&m_getmntent);
+#endif
     return 0;
 }
 
@@ -145,15 +272,15 @@ maria_declare_plugin(disks)
     MYSQL_INFORMATION_SCHEMA_PLUGIN,
     &disks_table_info,                 /* type-specific descriptor */
     "DISKS",                           /* table name */
-    "Johan Wikman",                    /* author */
+    "Johan Wikman, Daniel Black",      /* author */
     "Disk space information",          /* description */
     PLUGIN_LICENSE_GPL,                /* license type */
     disks_table_init,                  /* init function */
-    NULL,                              /* deinit function */
-    0x0101,                            /* version = 1.1 */
+    disks_table_deinit,                /* deinit function */
+    0x0102,                            /* version = 1.2 */
     NULL,                              /* no status variables */
     NULL,                              /* no system variables */
-    "1.1",                             /* String version representation */
+    "1.2",                             /* String version representation */
     MariaDB_PLUGIN_MATURITY_STABLE     /* Maturity (see include/mysql/plugin.h)*/
 }
 mysql_declare_plugin_end;

plugin/disks/mysql-test/disks/disks.result

@@ -1,8 +1,8 @@
 show create table information_schema.disks;
 Table	Create Table
 DISKS	CREATE TEMPORARY TABLE `DISKS` (
-  `Disk` varchar(4096) NOT NULL,
-  `Path` varchar(4096) NOT NULL,
+  `Disk` varchar(pathlen) NOT NULL,
+  `Path` varchar(pathlen) NOT NULL,
   `Total` bigint(32) NOT NULL,
   `Used` bigint(32) NOT NULL,
   `Available` bigint(32) NOT NULL

plugin/disks/mysql-test/disks/disks.test

@@ -1,2 +1,3 @@
+--replace_regex /varchar\([0-9]+\)/varchar(pathlen)/
 show create table information_schema.disks;
 select sum(Total) > sum(Available), sum(Total)>sum(Used) from information_schema.disks;