Merge pull request #6301 from ThomasWaldmann/safe-unlink-master

safe_unlink (was: truncate_and_unlink)

src/borg/cache.py

@@ -26,7 +26,7 @@ from .helpers import yes
 from .helpers import remove_surrogates
 from .helpers import ProgressIndicatorPercent, ProgressIndicatorMessage
 from .helpers import set_ec, EXIT_WARNING
-from .helpers import truncate_and_unlink
+from .helpers import safe_unlink
 from .helpers import msgpack
 from .item import ArchiveItem, ChunkListEntry
 from .crypto.key import PlaintextKey
@@ -774,7 +774,7 @@ class LocalCache(CacheStatsMixin):
                                                   filename=bin_to_hex(archive_id) + '.compact') as fd:
                     chunk_idx.write(fd)
             except Exception:
-                truncate_and_unlink(fn_tmp)
+                safe_unlink(fn_tmp)
             else:
                 os.rename(fn_tmp, fn)
 

src/borg/helpers/fs.py

@@ -205,12 +205,12 @@ def secure_erase(path):
     os.unlink(path)
 
 
-def truncate_and_unlink(path):
+def safe_unlink(path):
     """
-    Truncate and then unlink *path*.
+    Safely unlink (delete) *path*.
 
-    Do not create *path* if it does not exist.
-    Open *path* for truncation in r+b mode (=O_RDWR|O_BINARY).
+    If we run out of space while deleting the file, we try truncating it first.
+    BUT we truncate only if path is the only hardlink referring to this content.
 
     Use this when deleting potentially large files when recovering
     from a VFS error such as ENOSPC. It can help a full file system
@@ -218,13 +218,27 @@ def truncate_and_unlink(path):
     in repository.py for further explanations.
     """
     try:
-        with open(path, 'r+b') as fd:
-            fd.truncate()
-    except OSError as err:
-        if err.errno != errno.ENOTSUP:
+        os.unlink(path)
+    except OSError as unlink_err:
+        if unlink_err.errno != errno.ENOSPC:
+            # not free space related, give up here.
             raise
-        # don't crash if the above ops are not supported.
-    os.unlink(path)
+        # we ran out of space while trying to delete the file.
+        st = os.stat(path)
+        if st.st_nlink > 1:
+            # rather give up here than cause collateral damage to the other hardlink.
+            raise
+        # no other hardlink! try to recover free space by truncating this file.
+        try:
+            # Do not create *path* if it does not exist, open for truncation in r+b mode (=O_RDWR|O_BINARY).
+            with open(path, 'r+b') as fd:
+                fd.truncate()
+        except OSError:
+            # truncate didn't work, so we still have the original unlink issue - give up:
+            raise unlink_err
+        else:
+            # successfully truncated the file, try again deleting it:
+            os.unlink(path)
 
 
 def dash_open(path, mode):

src/borg/platform/base.py

@@ -3,7 +3,7 @@ import os
 import socket
 import uuid
 
-from borg.helpers import truncate_and_unlink
+from borg.helpers import safe_unlink
 from borg.platformflags import is_win32
 
 """
@@ -212,7 +212,7 @@ class SaveFile:
     def __enter__(self):
         from .. import platform
         try:
-            truncate_and_unlink(self.tmppath)
+            safe_unlink(self.tmppath)
         except FileNotFoundError:
             pass
         self.fd = platform.SyncFile(self.tmppath, self.binary)
@@ -222,7 +222,7 @@ class SaveFile:
         from .. import platform
         self.fd.close()
         if exc_type is not None:
-            truncate_and_unlink(self.tmppath)
+            safe_unlink(self.tmppath)
             return
         os.replace(self.tmppath, self.path)
         platform.sync_dir(os.path.dirname(self.path))

src/borg/remote.py

@@ -25,7 +25,7 @@ from .helpers import get_limited_unpacker
 from .helpers import replace_placeholders
 from .helpers import sysinfo
 from .helpers import format_file_size
-from .helpers import truncate_and_unlink
+from .helpers import safe_unlink
 from .helpers import prepare_subprocess_env
 from .logger import create_logger, setup_logging
 from .helpers import msgpack
@@ -1150,7 +1150,7 @@ class RepositoryCache(RepositoryNoCache):
                 fd.write(packed)
         except OSError as os_error:
             try:
-                truncate_and_unlink(file)
+                safe_unlink(file)
             except FileNotFoundError:
                 pass  # open() could have failed as well
             if os_error.errno == errno.ENOSPC:

src/borg/repository.py

@@ -18,7 +18,7 @@ from .helpers import Error, ErrorWithTraceback, IntegrityError, format_file_size
 from .helpers import Location
 from .helpers import ProgressIndicatorPercent
 from .helpers import bin_to_hex
-from .helpers import secure_erase, truncate_and_unlink
+from .helpers import secure_erase, safe_unlink
 from .helpers import Manifest
 from .helpers import msgpack
 from .locking import Lock, LockError, LockErrorT
@@ -1342,7 +1342,7 @@ class LoggedIO:
             if segment > transaction_id:
                 if segment in self.fds:
                     del self.fds[segment]
-                truncate_and_unlink(filename)
+                safe_unlink(filename)
                 count += 1
             else:
                 break
@@ -1450,7 +1450,7 @@ class LoggedIO:
         if segment in self.fds:
             del self.fds[segment]
         try:
-            truncate_and_unlink(self.segment_filename(segment))
+            safe_unlink(self.segment_filename(segment))
         except FileNotFoundError:
             pass