X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=src%2Fshared%2Fpath-util.c;h=537705446a026eddd55750103747a9882ed5037c;hp=8c43d060fb2ed93f1eb008f4c56cb63cfe3352a9;hb=91fe8b8a5cb47b44dcaf72c9760f1bda001c011b;hpb=6feeeab0bc40b5a7f208adf79909fb85e2208e8e
diff --git a/src/shared/path-util.c b/src/shared/path-util.c
index 8c43d060f..537705446 100644
--- a/src/shared/path-util.c
+++ b/src/shared/path-util.c
@@ -19,15 +19,12 @@
along with systemd; If not, see .
***/
-#include
#include
#include
#include
#include
-#include
#include
#include
-#include
#include
#include "macro.h"
@@ -36,6 +33,7 @@
#include "strv.h"
#include "path-util.h"
#include "missing.h"
+#include "fileio.h"
bool path_is_absolute(const char *p) {
return p[0] == '/';
@@ -403,12 +401,18 @@ char* path_startswith(const char *path, const char *prefix) {
}
}
-bool path_equal(const char *a, const char *b) {
+int path_compare(const char *a, const char *b) {
+ int d;
+
assert(a);
assert(b);
- if ((a[0] == '/') != (b[0] == '/'))
- return false;
+ /* A relative path and an abolute path must not compare as equal.
+ * Which one is sorted before the other does not really matter.
+ * Here a relative path is ordered before an absolute path. */
+ d = (a[0] == '/') - (b[0] == '/');
+ if (d)
+ return d;
for (;;) {
size_t j, k;
@@ -417,25 +421,40 @@ bool path_equal(const char *a, const char *b) {
b += strspn(b, "/");
if (*a == 0 && *b == 0)
- return true;
+ return 0;
- if (*a == 0 || *b == 0)
- return false;
+ /* Order prefixes first: "/foo" before "/foo/bar" */
+ if (*a == 0)
+ return -1;
+ if (*b == 0)
+ return 1;
j = strcspn(a, "/");
k = strcspn(b, "/");
- if (j != k)
- return false;
+ /* Alphabetical sort: "/foo/aaa" before "/foo/b" */
+ d = memcmp(a, b, MIN(j, k));
+ if (d)
+ return (d > 0) - (d < 0); /* sign of d */
- if (memcmp(a, b, j) != 0)
- return false;
+ /* Sort "/foo/a" before "/foo/aaa" */
+ d = (j > k) - (j < k); /* sign of (j - k) */
+ if (d)
+ return d;
a += j;
b += k;
}
}
+bool path_equal(const char *a, const char *b) {
+ return path_compare(a, b) == 0;
+}
+
+bool path_equal_or_files_same(const char *a, const char *b) {
+ return path_equal(a, b) || files_same(a, b) > 0;
+}
+
char* path_join(const char *root, const char *path, const char *rest) {
assert(path);
@@ -452,83 +471,202 @@ char* path_join(const char *root, const char *path, const char *rest) {
NULL);
}
-int path_is_mount_point(const char *t, bool allow_symlink) {
+static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *mnt_id) {
+ char path[strlen("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
+ _cleanup_free_ char *fdinfo = NULL;
+ _cleanup_close_ int subfd = -1;
+ char *p;
+ int r;
+
+ if ((flags & AT_EMPTY_PATH) && isempty(filename))
+ xsprintf(path, "/proc/self/fdinfo/%i", fd);
+ else {
+ subfd = openat(fd, filename, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_PATH);
+ if (subfd < 0)
+ return -errno;
+
+ xsprintf(path, "/proc/self/fdinfo/%i", subfd);
+ }
+
+ r = read_full_file(path, &fdinfo, NULL);
+ if (r == -ENOENT) /* The fdinfo directory is a relatively new addition */
+ return -EOPNOTSUPP;
+ if (r < 0)
+ return -errno;
+
+ p = startswith(fdinfo, "mnt_id:");
+ if (!p) {
+ p = strstr(fdinfo, "\nmnt_id:");
+ if (!p) /* The mnt_id field is a relatively new addition */
+ return -EOPNOTSUPP;
+
+ p += 8;
+ }
+
+ p += strspn(p, WHITESPACE);
+ p[strcspn(p, WHITESPACE)] = 0;
- union file_handle_union h = {
- .handle.handle_bytes = MAX_HANDLE_SZ
- };
+ return safe_atoi(p, mnt_id);
+}
- int mount_id, mount_id_parent;
- _cleanup_free_ char *parent = NULL;
+int fd_is_mount_point(int fd, const char *filename, int flags) {
+ union file_handle_union h = FILE_HANDLE_INIT, h_parent = FILE_HANDLE_INIT;
+ int mount_id = -1, mount_id_parent = -1;
+ bool nosupp = false, check_st_dev = true;
struct stat a, b;
int r;
- bool nosupp = false;
- /* We are not actually interested in the file handles, but
- * name_to_handle_at() also passes us the mount ID, hence use
- * it but throw the handle away */
-
- if (path_equal(t, "/"))
- return 1;
+ assert(fd >= 0);
+ assert(filename);
- r = name_to_handle_at(AT_FDCWD, t, &h.handle, &mount_id, allow_symlink ? AT_SYMLINK_FOLLOW : 0);
+ /* First we will try the name_to_handle_at() syscall, which
+ * tells us the mount id and an opaque file "handle". It is
+ * not supported everywhere though (kernel compile-time
+ * option, not all file systems are hooked up). If it works
+ * the mount id is usually good enough to tell us whether
+ * something is a mount point.
+ *
+ * If that didn't work we will try to read the mount id from
+ * /proc/self/fdinfo/. This is almost as good as
+ * name_to_handle_at(), however, does not return the the
+ * opaque file handle. The opaque file handle is pretty useful
+ * to detect the root directory, which we should always
+ * consider a mount point. Hence we use this only as
+ * fallback. Exporting the mnt_id in fdinfo is a pretty recent
+ * kernel addition.
+ *
+ * As last fallback we do traditional fstat() based st_dev
+ * comparisons. This is how things were traditionally done,
+ * but unionfs breaks breaks this since it exposes file
+ * systems with a variety of st_dev reported. Also, btrfs
+ * subvolumes have different st_dev, even though they aren't
+ * real mounts of their own. */
+
+ r = name_to_handle_at(fd, filename, &h.handle, &mount_id, flags);
if (r < 0) {
- if (IN_SET(errno, ENOSYS, EOPNOTSUPP))
+ if (errno == ENOSYS)
+ /* This kernel does not support name_to_handle_at()
+ * fall back to simpler logic. */
+ goto fallback_fdinfo;
+ else if (errno == EOPNOTSUPP)
/* This kernel or file system does not support
- * name_to_handle_at(), hence fallback to the
+ * name_to_handle_at(), hence let's see if the
+ * upper fs supports it (in which case it is a
+ * mount point), otherwise fallback to the
* traditional stat() logic */
nosupp = true;
- else if (errno == ENOENT)
- return 0;
else
return -errno;
}
- r = path_get_parent(t, &parent);
- if (r < 0)
- return r;
-
- h.handle.handle_bytes = MAX_HANDLE_SZ;
- r = name_to_handle_at(AT_FDCWD, parent, &h.handle, &mount_id_parent, AT_SYMLINK_FOLLOW);
- if (r < 0)
- if (errno == EOPNOTSUPP)
+ r = name_to_handle_at(fd, "", &h_parent.handle, &mount_id_parent, AT_EMPTY_PATH);
+ if (r < 0) {
+ if (errno == EOPNOTSUPP) {
if (nosupp)
/* Neither parent nor child do name_to_handle_at()?
We have no choice but to fall back. */
- goto fallback;
+ goto fallback_fdinfo;
else
- /* The parent can't do name_to_handle_at() but
- * the directory we are interested in can?
- * Or the other way around?
+ /* The parent can't do name_to_handle_at() but the
+ * directory we are interested in can?
* If so, it must be a mount point. */
return 1;
- else
+ } else
return -errno;
- else
- return mount_id != mount_id_parent;
+ }
-fallback:
- if (allow_symlink)
- r = stat(t, &a);
- else
- r = lstat(t, &a);
+ /* The parent can do name_to_handle_at() but the
+ * directory we are interested in can't? If so, it
+ * must be a mount point. */
+ if (nosupp)
+ return 1;
- if (r < 0) {
- if (errno == ENOENT)
- return 0;
+ /* If the file handle for the directory we are
+ * interested in and its parent are identical, we
+ * assume this is the root directory, which is a mount
+ * point. */
+
+ if (h.handle.handle_bytes == h_parent.handle.handle_bytes &&
+ h.handle.handle_type == h_parent.handle.handle_type &&
+ memcmp(h.handle.f_handle, h_parent.handle.f_handle, h.handle.handle_bytes) == 0)
+ return 1;
+ return mount_id != mount_id_parent;
+
+fallback_fdinfo:
+ r = fd_fdinfo_mnt_id(fd, filename, flags, &mount_id);
+ if (r == -EOPNOTSUPP)
+ goto fallback_fstat;
+ if (r < 0)
+ return r;
+
+ r = fd_fdinfo_mnt_id(fd, "", AT_EMPTY_PATH, &mount_id_parent);
+ if (r < 0)
+ return r;
+
+ if (mount_id != mount_id_parent)
+ return 1;
+
+ /* Hmm, so, the mount ids are the same. This leaves one
+ * special case though for the root file system. For that,
+ * let's see if the parent directory has the same inode as we
+ * are interested in. Hence, let's also do fstat() checks now,
+ * too, but avoid the st_dev comparisons, since they aren't
+ * that useful on unionfs mounts. */
+ check_st_dev = false;
+
+fallback_fstat:
+ /* yay for fstatat() taking a different set of flags than the other
+ * _at() above */
+ if (flags & AT_SYMLINK_FOLLOW)
+ flags &= ~AT_SYMLINK_FOLLOW;
+ else
+ flags |= AT_SYMLINK_NOFOLLOW;
+ if (fstatat(fd, filename, &a, flags) < 0)
return -errno;
+
+ if (fstatat(fd, "", &b, AT_EMPTY_PATH) < 0)
+ return -errno;
+
+ /* A directory with same device and inode as its parent? Must
+ * be the root directory */
+ if (a.st_dev == b.st_dev &&
+ a.st_ino == b.st_ino)
+ return 1;
+
+ return check_st_dev && (a.st_dev != b.st_dev);
+}
+
+/* flags can be AT_SYMLINK_FOLLOW or 0 */
+int path_is_mount_point(const char *t, int flags) {
+ _cleanup_close_ int fd = -1;
+ _cleanup_free_ char *canonical = NULL, *parent = NULL;
+ int r;
+
+ assert(t);
+
+ if (path_equal(t, "/"))
+ return 1;
+
+ /* we need to resolve symlinks manually, we can't just rely on
+ * fd_is_mount_point() to do that for us; if we have a structure like
+ * /bin -> /usr/bin/ and /usr is a mount point, then the parent that we
+ * look at needs to be /usr, not /. */
+ if (flags & AT_SYMLINK_FOLLOW) {
+ canonical = canonicalize_file_name(t);
+ if (!canonical)
+ return -errno;
}
- r = path_get_parent(t, &parent);
+ r = path_get_parent(canonical ?: t, &parent);
if (r < 0)
return r;
- r = stat(parent, &b);
- if (r < 0)
+ fd = openat(AT_FDCWD, parent, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_PATH);
+ if (fd < 0)
return -errno;
- return a.st_dev != b.st_dev;
+ return fd_is_mount_point(fd, basename(canonical ?: t), flags);
}
int path_is_read_only_fs(const char *path) {
@@ -556,14 +694,14 @@ int path_is_os_tree(const char *path) {
int r;
/* We use /usr/lib/os-release as flag file if something is an OS */
- p = strappenda(path, "/usr/lib/os-release");
+ p = strjoina(path, "/usr/lib/os-release");
r = access(p, F_OK);
if (r >= 0)
return 1;
/* Also check for the old location in /etc, just in case. */
- p = strappenda(path, "/etc/os-release");
+ p = strjoina(path, "/etc/os-release");
r = access(p, F_OK);
return r >= 0;
@@ -661,7 +799,7 @@ int fsck_exists(const char *fstype) {
const char *checker;
int r;
- checker = strappenda("fsck.", fstype);
+ checker = strjoina("fsck.", fstype);
r = find_binary(checker, true, &p);
if (r < 0)
@@ -679,3 +817,37 @@ int fsck_exists(const char *fstype) {
return 0;
}
+
+char *prefix_root(const char *root, const char *path) {
+ char *n, *p;
+ size_t l;
+
+ /* If root is passed, prefixes path with it. Otherwise returns
+ * it as is. */
+
+ assert(path);
+
+ /* First, drop duplicate prefixing slashes from the path */
+ while (path[0] == '/' && path[1] == '/')
+ path++;
+
+ if (isempty(root) || path_equal(root, "/"))
+ return strdup(path);
+
+ l = strlen(root) + 1 + strlen(path) + 1;
+
+ n = new(char, l);
+ if (!n)
+ return NULL;
+
+ p = stpcpy(n, root);
+
+ while (p > n && p[-1] == '/')
+ p--;
+
+ if (path[0] != '/')
+ *(p++) = '/';
+
+ strcpy(p, path);
+ return n;
+}