New workaround renamexdev to enable moving files across remote filesystems

sshfs.rst: update the documentation.

Author: g-raud

sshfs.c

@@ -214,6 +214,7 @@ struct sshfs {
 	struct fuse_args ssh_args;
 	char *workarounds;
 	int rename_workaround;
+	int renamexdev_workaround;
 	int truncate_workaround;
 	int buflimit_workaround;
 	int unrel_append;
@@ -446,6 +447,8 @@ static struct fuse_opt workaround_opts[] = {
 	SSHFS_OPT("none",       fstat_workaround, 0),
 	SSHFS_OPT("rename",     rename_workaround, 1),
 	SSHFS_OPT("norename",   rename_workaround, 0),
+	SSHFS_OPT("renamexdev",   renamexdev_workaround, 1),
+	SSHFS_OPT("norenamexdev", renamexdev_workaround, 0),
 	SSHFS_OPT("truncate",   truncate_workaround, 1),
 	SSHFS_OPT("notruncate", truncate_workaround, 0),
 	SSHFS_OPT("buflimit",   buflimit_workaround, 1),
@@ -2333,6 +2336,8 @@ static int sshfs_rename(const char *from, const char *to, unsigned int flags)
 			}
 		}
 	}
+	if (err == -EPERM && sshfs.renamexdev_workaround)
+		err = -EXDEV;
 	return err;
 }
 
@@ -3365,6 +3370,7 @@ static void usage(const char *progname)
 "    -o workaround=LIST     colon separated list of workarounds\n"
 "             none             no workarounds enabled\n"
 "             [no]rename       fix renaming to existing file (default: off)\n"
+"             [no]renamexdev   fix moving across filesystems (default: off)\n"
 "             [no]truncate     fix truncate for old servers (default: off)\n"
 "             [no]buflimit     fix buffer fillup bug in server (default: on)\n"
 "             [no]fstat        always use stat() instead of fstat() (default: off)\n"
@@ -3851,6 +3857,7 @@ int main(int argc, char *argv[])
 #else
 	sshfs.rename_workaround = 0;
 #endif
+	sshfs.renamexdev_workaround = 0;
 	sshfs.truncate_workaround = 0;
 	sshfs.buflimit_workaround = 1;
 	sshfs.ssh_ver = 2;

sshfs.rst

@@ -107,6 +107,8 @@ Options
 
    :rename: Emulate overwriting an existing file by deleting and
         renaming.
+   :renamexdev: Make rename fail with EXDEV instead of the default EPERM
+        to allow moving files across remote filesystems.
    :truncate: Work around servers that don't support truncate by
         coping the whole file, truncating it locally, and sending it
         back.
@@ -228,6 +230,17 @@ removed it, but before SSHFS had the time to rename the old file. In
 this case, the rename will still fail.
 
 
+Permission denied when moving files across remote filesystems
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Most SFTP servers return only a generic "failure" when failing to rename
+across filesystem boundaries (EXDEV).  sshfs normally converts this generic
+failure to a permission denied error (EPERM).  If the option ``-o
+workaround=renamexdev`` is given, generic failures will be considered EXDEV
+errors which will make programs like `mv(1)` attempt to actually move the
+file after the failed rename.
+
+
 SSHFS hangs
 ~~~~~~~~~~~