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backend/sftp: Support atomic rename

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... if the server has posix-rename@openssh.com.
OpenSSH introduced this extension in 2008:
7c29661471
This commit is contained in:
greatroar 2022-06-06 13:17:07 +02:00
parent b7c990871f
commit fa8f02292e
1 changed files with 11 additions and 4 deletions
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15
internal/backend/sftp/sftp.go
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@ -31,6 +31,8 @@ type SFTP struct {
cmd *exec.Cmd cmd *exec.Cmd
result <-chan error result <-chan error
posixRename bool
sem *backend.Semaphore sem *backend.Semaphore
backend.Layout backend.Layout
Config Config
@ -96,7 +98,8 @@ func startClient(program string, args ...string) (*SFTP, error) {
return nil, errors.Wrap(err, "bg") return nil, errors.Wrap(err, "bg")
} }
return &SFTP{c: client, cmd: cmd, result: ch}, nil _, posixRename := client.HasExtension("posix-rename@openssh.com")
return &SFTP{c: client, cmd: cmd, result: ch, posixRename: posixRename}, nil
} }
// clientError returns an error if the client has exited. Otherwise, nil is // clientError returns an error if the client has exited. Otherwise, nil is
@ -269,8 +272,7 @@ func (r *SFTP) Hasher() hash.Hash {
// HasAtomicReplace returns whether Save() can atomically replace files // HasAtomicReplace returns whether Save() can atomically replace files
func (r *SFTP) HasAtomicReplace() bool { func (r *SFTP) HasAtomicReplace() bool {
// we use sftp's 'Rename()' in 'Save()' which does not allow overwriting return r.posixRename
return false
} }
// Join joins the given paths and cleans them afterwards. This always uses // Join joins the given paths and cleans them afterwards. This always uses
@ -364,7 +366,12 @@ func (r *SFTP) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader
return errors.Wrap(err, "Close") return errors.Wrap(err, "Close")
} }
err = r.c.Rename(tmpFilename, filename) // Prefer POSIX atomic rename if available.
if r.posixRename {
err = r.c.PosixRename(tmpFilename, filename)
} else {
err = r.c.Rename(tmpFilename, filename)
}
return errors.Wrap(err, "Rename") return errors.Wrap(err, "Rename")
} }