docs: clarify on-disk order and size of log entry fields
The order of the fields of a log entry on disk is CRC32 first, the docs had the size first.
I tried to make this list similar to the HashIndex struct description.
the movement of the start of the hashing window stops at (file_size - window_size), thus THAT would be the factor in that formula, not just file_size.
for medium and big files, window_size is much smaller than file_size, so guess we can just say "approximately" for the general case.
a file map can be:
- created internally inside chunkify by calling sparsemap, which uses
SEEK_DATA / SEEK_HOLE to determine data and hole ranges inside a
seekable sparse file.
Usage: borg create --sparse --chunker-params=fixed,BLOCKSIZE ...
BLOCKSIZE is the chunker blocksize here, not the filesystem blocksize!
- made by some other means and given to the chunkify function.
this is not used yet, but in future this could be used to only read
the changed parts and seek over the (known) unchanged parts of a file.
sparsemap: the generate range sizes are multiples of the fs block size.
the tests assume 4kiB fs block size.
We know use only "target chunk size" when speaking of the chunk size
that is expected to happen most of the time. This removes statistical
and mathematical inacurracies that could be troublesome for mathematical
people.
Fixes#5336
locking: fix ExclusiveLock race condition bug, fixes#4923
- ExclusiveLock is now based on os.rename instead of os.mkdir.
- catch FileNotFoundError observed under race condition in ExclusiveLock.release()
and .kill_stale_lock()
- added TestExclusiveLock.test_race_condition() which reveals issue #4923
- updated docs
- locking: use "raise LockTimeout from None" for prettier traceback
Co-authored-by: Thomas Portmann <thomas@portmann.org>
Co-authored-by: Thomas Waldmann <tw@waldmann-edv.de>
You can now control the files cache mode using this option:
--files-cache={ctime,mtime,size,inode,rechunk,disabled}*
(only some combinations are supported)
Previously, only these modes were supported:
- mtime,size,inode (default of borg < 1.1.0rc4)
- mtime,size (by using --ignore-inode)
- disabled (by using --no-files-cache)
Now, you additionally get:
- ctime alternatively to mtime (more safe), e.g.:
ctime,size,inode (this is the new default of borg >= 1.1.0rc4)
- rechunk (consider all files as changed, rechunk them)
Deprecated:
- --ignore-inodes (use modes without "inode")
- --no-files-cache (use "disabled" mode)
The tests needed some changes:
- previously, we use os.utime() to set a files mtime (atime) to specific
values, but that does not work for ctime.
- now use time.sleep() to create the "latest file" that usually does
not end up in the files cache (see FAQ)
