hostfs: support rename flags

Support RENAME_NOREPLACE and RENAME_EXCHANGE flags on hostfs if the
underlying filesystem supports it.

Since renameat2(2) is not yet in any libc, use syscall(2) to invoke the
renameat2 syscall.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Richard Weinberger <richard@nod.at>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 49 insertions, 10 deletions

diff --git a/fs/hostfs/hostfs.h b/fs/hostfs/hostfs.h
index 9c88da0e855a..4fcd40d6f308 100644
--- a/fs/hostfs/hostfs.h
+++ b/fs/hostfs/hostfs.h
@@ -89,6 +89,7 @@ extern int do_mknod(const char *file, int mode, unsigned int major,
 extern int link_file(const char *from, const char *to);
 extern int hostfs_do_readlink(char *file, char *buf, int size);
 extern int rename_file(char *from, char *to);
+extern int rename2_file(char *from, char *to, unsigned int flags);
 extern int do_statfs(char *root, long *bsize_out, long long *blocks_out,
                      long long *bfree_out, long long *bavail_out,
                      long long *files_out, long long *ffree_out,
diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index bb529f3b7f2b..fd62cae0fdcb 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -741,21 +741,31 @@ static int hostfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
         return err;
 }
 
-static int hostfs_rename(struct inode *from_ino, struct dentry *from,
-                         struct inode *to_ino, struct dentry *to)
+static int hostfs_rename2(struct inode *old_dir, struct dentry *old_dentry,
+                          struct inode *new_dir, struct dentry *new_dentry,
+                          unsigned int flags)
 {
-        char *from_name, *to_name;
+        char *old_name, *new_name;
         int err;
 
-        if ((from_name = dentry_name(from)) == NULL)
+        if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
+                return -EINVAL;
+
+        old_name = dentry_name(old_dentry);
+        if (old_name == NULL)
                 return -ENOMEM;
-        if ((to_name = dentry_name(to)) == NULL) {
-                __putname(from_name);
+        new_name = dentry_name(new_dentry);
+        if (new_name == NULL) {
+                __putname(old_name);
                 return -ENOMEM;
         }
-        err = rename_file(from_name, to_name);
-        __putname(from_name);
-        __putname(to_name);
+        if (!flags)
+                err = rename_file(old_name, new_name);
+        else
+                err = rename2_file(old_name, new_name, flags);
+
+        __putname(old_name);
+        __putname(new_name);
         return err;
 }
 
@@ -867,7 +877,7 @@ static const struct inode_operations hostfs_dir_iops = {
         .mkdir          = hostfs_mkdir,
         .rmdir          = hostfs_rmdir,
         .mknod          = hostfs_mknod,
-        .rename         = hostfs_rename,
+        .rename2        = hostfs_rename2,
         .permission     = hostfs_permission,
         .setattr        = hostfs_setattr,
 };
diff --git a/fs/hostfs/hostfs_user.c b/fs/hostfs/hostfs_user.c
index 67838f3aa20a..9765dab95cbd 100644
--- a/fs/hostfs/hostfs_user.c
+++ b/fs/hostfs/hostfs_user.c
@@ -14,6 +14,7 @@
 #include <sys/time.h>
 #include <sys/types.h>
 #include <sys/vfs.h>
+#include <sys/syscall.h>
 #include "hostfs.h"
 #include <utime.h>
 
@@ -360,6 +361,33 @@ int rename_file(char *from, char *to)
         return 0;
 }
 
+int rename2_file(char *from, char *to, unsigned int flags)
+{
+        int err;
+
+#ifndef SYS_renameat2
+#  ifdef __x86_64__
+#    define SYS_renameat2 316
+#  endif
+#  ifdef __i386__
+#    define SYS_renameat2 353
+#  endif
+#endif
+
+#ifdef SYS_renameat2
+        err = syscall(SYS_renameat2, AT_FDCWD, from, AT_FDCWD, to, flags);
+        if (err < 0) {
+                if (errno != ENOSYS)
+                        return -errno;
+                else
+                        return -EINVAL;
+        }
+        return 0;
+#else
+        return -EINVAL;
+#endif
+}
+
 int do_statfs(char *root, long *bsize_out, long long *blocks_out,
               long long *bfree_out, long long *bavail_out,
               long long *files_out, long long *ffree_out,