btrfs-progs: send: check for output file existence before creating

In some cases the root might not be able to create the output file (and
streaming to stdout is not an option). Make the output file creation two
step and let it work if the file is already created.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2016-11-07 16:51:20 +01:00
parent 7d405df0da
commit 84d1f29d47

View File

@ -571,7 +571,20 @@ int cmd_send(int argc, char **argv)
usage(cmd_send_usage);
if (outname[0]) {
send.dump_fd = creat(outname, 0600);
int tmpfd;
/*
* Try to use an existing file first. Even if send runs as
* root, it might not have permissions to create file (eg. on a
* NFS) but it should still be able to use a pre-created file.
*/
tmpfd = open(outname, O_WRONLY | O_TRUNC);
if (tmpfd < 0) {
if (errno == ENOENT)
tmpfd = open(outname,
O_CREAT | O_WRONLY | O_TRUNC, 0600);
}
send.dump_fd = tmpfd;
if (send.dump_fd == -1) {
ret = -errno;
error("cannot create '%s': %s", outname, strerror(-ret));