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Diffstat (limited to 'm4/o-direct.m4')
| -rw-r--r-- | m4/o-direct.m4 | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/m4/o-direct.m4 b/m4/o-direct.m4 new file mode 100644 index 0000000..7229d66 --- /dev/null +++ b/m4/o-direct.m4 @@ -0,0 +1,252 @@ +#serial 2 +# Find a directory in which a disk-simulating file is usable by parted. +# The problem is that on systems supporting O_DIRECT, open with O_DIRECT +# fails for some file system types (e.g., tmpfs on linux-2.6.21). + +# Copyright (C) 2007-2014, 2019-2023 Free Software Foundation, Inc. +# This file is free software; the Free Software Foundation +# gives unlimited permission to copy and/or distribute it, +# with or without modifications, as long as this notice is preserved. + +# From Jim Meyering. + +# Set PARTED_USABLE_TEST_DIR to the name of the first usable directory +# from the list below. If none is usable, set it to the empty string. +# Consider $TMPDIR only if it specifies an absolute name, and that +# name contains no shell meta-character. Likewise for $HOME. + +# This code is pretty picky. The chosen partition must support aligned reads +# and writes in blocks of size 512B and 4KB to a file descriptor opened with +# O_RDWR|O_DIRECT. Reiserfs doesn't support 512-byte reads. On tmpfs, +# the open fails. + +# The candidate directories: +# . $HOME $TMPDIR /tmp /var/tmp /dev/shm +AC_DEFUN([parted_FIND_USABLE_TEST_DIR], +[ + AC_CACHE_CHECK([for a usable (O_DIRECT-supporting) temporary dir], + [parted_cv_func_open_O_DIRECT_temp_dir], + [ + # First of all, if there is no O_DIRECT definition, use ".", + # and skip the run-test. + AC_EGREP_CPP([frobnozzle], [ +#include <fcntl.h> +#ifdef O_DIRECT +frobnozzle +#endif + ], pe_have_O_DIRECT=yes, pe_have_O_DIRECT=no) + if test $pe_have_O_DIRECT = no; then + # With no O_DIRECT definition, "." is fine. + pe_cand_dirs=. + else + pe_cand_dirs=. + for pe_dir in "$HOME" "$TMPDIR"; do + case $pe_dir in + /tmp) ;; + /var/tmp) ;; + /dev/shm) ;; + /*) case $pe_dir in + # Accept $HOME or $TMP only if the value is nice and boring. + *[^/a-zA-Z0-9_.-]*) ;; + *) pe_cand_dirs="$pe_cand_dirs $pe_dir";; + esac + esac + done + + case $PARTED_TMPDIR in + *[^/a-zA-Z0-9_.-]*) ;; + *) pe_cand_dirs="$PARTED_TMPDIR $pe_cand_dirs";; + esac + + # This is the list of candidate directories. + pe_cand_dirs="$pe_cand_dirs /tmp /var/tmp /dev/shm" + + PARTED_CANDIDATE_DIRS=$pe_cand_dirs + export PARTED_CANDIDATE_DIRS + + AC_RUN_IFELSE( + [AC_LANG_SOURCE( + [[ +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <unistd.h> +#include <stdlib.h> +#include <string.h> + +#define MAX_LOGICAL_BLOCK_SIZE 4096 +static char g_buf[2 * MAX_LOGICAL_BLOCK_SIZE]; + +static inline void * +ptr_align (void const *ptr, size_t alignment) +{ + char const *p0 = ptr; + char const *p1 = p0 + alignment - 1; + return (void *) (p1 - (size_t) p1 % alignment); +} + +static int +create_input_file (char const *file, char const *buf, size_t n_bytes) +{ + int fd = open (file, O_CREAT | O_WRONLY, 0600); + if (fd < 0) + return 1; + if (write (fd, buf, n_bytes) != n_bytes) + { + close (fd); + return 1; + } + return !! close (fd); +} + +static int +try_o_direct (char const *file, size_t block_size) +{ + char *p = ptr_align (g_buf, MAX_LOGICAL_BLOCK_SIZE); + int fd; + + if (!(p + block_size < g_buf + sizeof g_buf)) + return 4; + + fd = open (file, O_RDWR | O_DIRECT); + if (fd < 0) + return 1; + + if (write (fd, p, block_size) != block_size) + return 1; + + if (lseek (fd, 0, SEEK_SET) != 0) + return 1; + + if (read (fd, p, block_size) != block_size) + return 1; + + return !! close (fd); +} + +#undef stpcpy +#define stpcpy(a, b) my_stpcpy (a, b) +static char * +my_stpcpy (char *dest, const char *src) +{ + char *d = dest; + const char *s = src; + do *d++ = *s; while (*s++ != '\0'); + return d - 1; +} + +/* The base name of the file we'll create in the mkdtemp-returned + temporary directory. */ +#define BASENAME "x" + +/* Return 0 upon failure, else the 1-based index of the first + useful directory name from PARTED_CANDIDATE_DIRS. */ +int +main () +{ + char const *env_dirs; + char *dirs; + char *dir; + unsigned int n; + int found = 0; + size_t dirs_len; + + if ((env_dirs = getenv ("PARTED_CANDIDATE_DIRS")) == NULL) + return 0; + + dirs_len = strlen (env_dirs); + if ((dirs = strndup (env_dirs, dirs_len)) == NULL) + return 0; + dir = dirs; + + for (n = 1; ; n++) + { + size_t dirname_len; + char *space; + + /* Skip any leading spaces. */ + while (*dir == ' ') + ++dir; + + space = strchr (dir, ' '); + if (space) + { + *space = '\0'; + dirname_len = space - dir; + } + else + { + dirname_len = strlen (dir); + } + + if (dirname_len != 0) + { + /* Create an mkdtemp template starting with dir. */ + char *tmp; + char *endp; + char const *base = "partedOD.XXXXXX"; + /* Allocate enough space not just for the dir name, but + also for the name of the file to create within it. */ + char *template = malloc (dirname_len + 1 + strlen (base) + + 1 + strlen (BASENAME) + 1); + if (template != NULL + && (endp = stpcpy (stpcpy (stpcpy (template, dir), "/"), base)) + && (tmp = mkdtemp (template)) != NULL) + { + /* Append "/BASENAME" to create the file name. */ + stpcpy (stpcpy (endp, "/"), BASENAME); + + if (create_input_file (tmp, g_buf, sizeof g_buf) == 0 + && try_o_direct (tmp, 512) == 0 + && try_o_direct (tmp, MAX_LOGICAL_BLOCK_SIZE) == 0) + found = 1; + + unlink (tmp); /* ignore failure */ + *endp = '\0'; + rmdir (tmp); /* ignore failure */ + } + free (template); + } + + if (found) + break; + + dir += dirname_len + 1; + if (dirs + dirs_len < dir) + { + n = 0; + break; + } + } + free (dirs); + + return n; +} + ]])], + # If the above program exits with status 0, then + # there it found no useful directory. Use ".". + [parted_cv_func_open_O_DIRECT_temp_dir=.], + + # It found one. The exit status is an index into the list. + # We also run this code when the program fails to compile or + # to link, as will happen on systems without a mkdtemp function. + [pe_err=$?; set _ $pe_cand_dirs; shift + eval parted_cv_func_open_O_DIRECT_temp_dir='$'$pe_err], + + # When cross-compiling, use ".". + [parted_cv_func_open_O_DIRECT_temp_dir=.] + ) + fi + ]) + PARTED_USABLE_TEST_DIR=$parted_cv_func_open_O_DIRECT_temp_dir + AC_SUBST([PARTED_USABLE_TEST_DIR]) + + # If the result is ".", don't cache it. The next user of + # the cache may well be running from a different file system. + dnl Here, I'm using "$as_unset", which is a non-published (i.e., internal) + dnl part of autoconf, but we don't expect its name to change any time soon. + dnl and by then, it'll probably be ok to use "unset" all by itself. + if test "$parted_cv_func_open_O_DIRECT_temp_dir" = .; then + $as_unset parted_cv_func_open_O_DIRECT_temp_dir + fi +]) |