[systemd-devel] [PATCH] [PATCH v2] util: add rename_noreplace

Alban Crequy alban.crequy at gmail.com
Tue Mar 10 09:34:07 PDT 2015


From: Alban Crequy <alban at endocode.com>

renameat2() exists since Linux 3.15 but btrfs support for the flag
RENAME_NOREPLACE was added later.

This patch implements a fallback when renameat2() returns EINVAL.
EINVAL is the error returned when the filesystem does not support one of
the flags.
---
 src/import/import-raw.c    |  2 +-
 src/import/import-tar.c    |  2 +-
 src/import/pull-raw.c      |  2 +-
 src/import/pull-tar.c      |  2 +-
 src/shared/copy.c          |  7 ++++++-
 src/shared/machine-image.c |  2 +-
 src/shared/machine-pool.c  |  2 +-
 src/shared/util.c          | 32 ++++++++++++++++++++++++++++++++
 src/shared/util.h          |  2 ++
 9 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/src/import/import-raw.c b/src/import/import-raw.c
index 15e5eb2..e354023 100644
--- a/src/import/import-raw.c
+++ b/src/import/import-raw.c
@@ -245,7 +245,7 @@ static int raw_import_finish(RawImport *i) {
                 (void) rm_rf_dangerous(i->final_path, false, true, false);
         }
 
-        if (renameat2(AT_FDCWD, i->temp_path, AT_FDCWD, i->final_path, RENAME_NOREPLACE) < 0)
+        if (rename_noreplace(AT_FDCWD, i->temp_path, AT_FDCWD, i->final_path) < 0)
                 return log_error_errno(errno, "Failed to move image into place: %m");
 
         free(i->temp_path);
diff --git a/src/import/import-tar.c b/src/import/import-tar.c
index d5b6dad..dcbe721 100644
--- a/src/import/import-tar.c
+++ b/src/import/import-tar.c
@@ -201,7 +201,7 @@ static int tar_import_finish(TarImport *i) {
                 (void) rm_rf_dangerous(i->final_path, false, true, false);
         }
 
-        if (renameat2(AT_FDCWD, i->temp_path, AT_FDCWD, i->final_path, RENAME_NOREPLACE) < 0)
+        if (rename_noreplace(AT_FDCWD, i->temp_path, AT_FDCWD, i->final_path) < 0)
                 return log_error_errno(errno, "Failed to move image into place: %m");
 
         free(i->temp_path);
diff --git a/src/import/pull-raw.c b/src/import/pull-raw.c
index d1d77d5..d4b17e7 100644
--- a/src/import/pull-raw.c
+++ b/src/import/pull-raw.c
@@ -384,7 +384,7 @@ static void raw_pull_job_on_finished(PullJob *j) {
                 if (r < 0)
                         goto finish;
 
-                r = renameat2(AT_FDCWD, i->temp_path, AT_FDCWD, i->final_path, RENAME_NOREPLACE);
+                r = rename_noreplace(AT_FDCWD, i->temp_path, AT_FDCWD, i->final_path);
                 if (r < 0) {
                         r = log_error_errno(errno, "Failed to move RAW file into place: %m");
                         goto finish;
diff --git a/src/import/pull-tar.c b/src/import/pull-tar.c
index 504642f..69df7af 100644
--- a/src/import/pull-tar.c
+++ b/src/import/pull-tar.c
@@ -281,7 +281,7 @@ static void tar_pull_job_on_finished(PullJob *j) {
                 if (r < 0)
                         goto finish;
 
-                if (renameat2(AT_FDCWD, i->temp_path, AT_FDCWD, i->final_path, RENAME_NOREPLACE) < 0) {
+                if (rename_noreplace(AT_FDCWD, i->temp_path, AT_FDCWD, i->final_path) < 0) {
                         r = log_error_errno(errno, "Failed to rename to final image name: %m");
                         goto finish;
                 }
diff --git a/src/shared/copy.c b/src/shared/copy.c
index 0239a58..e578d03 100644
--- a/src/shared/copy.c
+++ b/src/shared/copy.c
@@ -404,7 +404,12 @@ int copy_file_atomic(const char *from, const char *to, mode_t mode, bool replace
         if (r < 0)
                 return r;
 
-        if (renameat2(AT_FDCWD, t, AT_FDCWD, to, replace ? 0 : RENAME_NOREPLACE) < 0) {
+        if (replace) {
+                r = renameat(AT_FDCWD, t, AT_FDCWD, to);
+        } else {
+                r = rename_noreplace(AT_FDCWD, t, AT_FDCWD, to);
+        }
+        if (r < 0) {
                 unlink_noerrno(t);
                 return -errno;
         }
diff --git a/src/shared/machine-image.c b/src/shared/machine-image.c
index c6d2850..ad5bff4 100644
--- a/src/shared/machine-image.c
+++ b/src/shared/machine-image.c
@@ -440,7 +440,7 @@ int image_rename(Image *i, const char *new_name) {
         if (!nn)
                 return -ENOMEM;
 
-        if (renameat2(AT_FDCWD, i->path, AT_FDCWD, new_path, RENAME_NOREPLACE) < 0)
+        if (rename_noreplace(AT_FDCWD, i->path, AT_FDCWD, new_path) < 0)
                 return -errno;
 
         /* Restore the immutable bit, if it was set before */
diff --git a/src/shared/machine-pool.c b/src/shared/machine-pool.c
index e7671a3..7e902a3 100644
--- a/src/shared/machine-pool.c
+++ b/src/shared/machine-pool.c
@@ -140,7 +140,7 @@ static int setup_machine_raw(uint64_t size, sd_bus_error *error) {
                 goto fail;
         }
 
-        if (renameat2(AT_FDCWD, tmp, AT_FDCWD, "/var/lib/machines.raw", RENAME_NOREPLACE) < 0) {
+        if (rename_noreplace(AT_FDCWD, tmp, AT_FDCWD, "/var/lib/machines.raw") < 0) {
                 r = sd_bus_error_set_errnof(error, errno, "Failed to move /var/lib/machines.raw into place: %m");
                 goto fail;
         }
diff --git a/src/shared/util.c b/src/shared/util.c
index 74f2994..2ab7270 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -8118,3 +8118,35 @@ void cmsg_close_all(struct msghdr *mh) {
                 if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS)
                         close_many((int*) CMSG_DATA(cmsg), (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int));
 }
+
+int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) {
+        struct stat buf;
+        int ret;
+
+        ret = renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE);
+
+        /* Even though renameat2() exists since Linux 3.15, btrfs added
+         * support for it later. If it is not implemented, fallback to another
+         * method. */
+        if (ret == 0 || errno != EINVAL)
+                return ret;
+
+        /* The link()/unlink() fallback does not work on directories. But
+         * renameat() without RENAME_NOREPLACE gives the same semantics on
+         * directories, except when newpath is an *empty* directory. This is
+         * good enough. */
+        ret = fstatat(olddirfd, oldpath, &buf, AT_SYMLINK_NOFOLLOW);
+        if (ret == 0 && S_ISDIR(buf.st_mode))
+                return renameat(olddirfd, oldpath, newdirfd, newpath);
+
+        /* If it is not a directory, use the link()/unlink() fallback. */
+        ret = linkat(olddirfd, oldpath, newdirfd, newpath, 0);
+        if (ret < 0)
+                return ret;
+
+        ret = unlinkat(olddirfd, oldpath, 0);
+        if (ret < 0)
+                unlinkat(newdirfd, newpath, 0);
+
+        return ret;
+}
diff --git a/src/shared/util.h b/src/shared/util.h
index 2de654f..45a8d37 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -1080,3 +1080,5 @@ void sigkill_wait(pid_t *pid);
 int syslog_parse_priority(const char **p, int *priority, bool with_facility);
 
 void cmsg_close_all(struct msghdr *mh);
+
+int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath);
-- 
2.1.4



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