Mercurial > hg
view mercurial/diffhelper.py @ 50316:87f0155d68aa stable
revlog: improve the robustness of the splitting process
The previous "in-place" splitting, preserving the splitting on transaction
failure had a couple of issue in case of transaction rollback:
- a race windows that could still lead to a crash and data loss
- it corrupted the `fncache`.
So instead, we use a new approach that we summarized as "we do a backup of the
inline revlog pre-split, and we restore this in case of failure".
To make readers live easier, we don't overwrite the inline index file until
transaction finalization. (once the transaction get into its finalization phase,
it is not expected to rollback, unless some crash happens).
To do so, we write the index of the split index in a temporary file that we use
until transaction finalization. We also keep a backup of the initial inline file
to be able to rollback the split if needed.
As a result, transaction rollback cancel the split and no longer corrupt
fncache. We also no longer have a small inconsistency windows where the
transaction could be unrecoverable.
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
---|---|
date | Mon, 20 Mar 2023 11:52:17 +0100 |
parents | d44e3c45f0e4 |
children |
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# diffhelper.py - helper routines for patch # # Copyright 2009 Olivia Mackall <olivia@selenic.com> and others # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from .i18n import _ from . import ( error, ) MISSING_NEWLINE_MARKER = b'\\ No newline at end of file\n' def addlines(fp, hunk, lena, lenb, a, b): """Read lines from fp into the hunk The hunk is parsed into two arrays, a and b. a gets the old state of the text, b gets the new state. The control char from the hunk is saved when inserting into a, but not b (for performance while deleting files.) """ while True: todoa = lena - len(a) todob = lenb - len(b) num = max(todoa, todob) if num == 0: break for i in range(num): s = fp.readline() if not s: raise error.ParseError(_(b'incomplete hunk')) if s == MISSING_NEWLINE_MARKER: fixnewline(hunk, a, b) continue if s == b'\n' or s == b'\r\n': # Some patches may be missing the control char # on empty lines. Supply a leading space. s = b' ' + s hunk.append(s) if s.startswith(b'+'): b.append(s[1:]) elif s.startswith(b'-'): a.append(s) else: b.append(s[1:]) a.append(s) def fixnewline(hunk, a, b): """Fix up the last lines of a and b when the patch has no newline at EOF""" l = hunk[-1] # tolerate CRLF in last line if l.endswith(b'\r\n'): hline = l[:-2] else: hline = l[:-1] if hline.startswith((b' ', b'+')): b[-1] = hline[1:] if hline.startswith((b' ', b'-')): a[-1] = hline hunk[-1] = hline def testhunk(a, b, bstart): """Compare the lines in a with the lines in b a is assumed to have a control char at the start of each line, this char is ignored in the compare. """ alen = len(a) blen = len(b) if alen > blen - bstart or bstart < 0: return False for i in range(alen): if a[i][1:] != b[i + bstart]: return False return True