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revlog: avoid possible collision between directory and temporary index...
revlog: avoid possible collision between directory and temporary index Since 6.4, we create a temporary index file to write the split data without overwriting the inline version too early. However, the store encoding does not prevent these new `.i.s` file to collide with a directory with the same name. While the odds for such a collision to happens are fairly low, the collision would prevent Mercurial from working. The store encoding have a mitigation solution in place to prevent such collisions from happening for `.i` and `.d` files, but not for other extensions. We cannot update this encoding scheme to solve the issue since it would diverge from older version of Mercurial. Instead, we create an alternative directory tree dedicated to such files. The use of the `.i` extension combined with store encoding will prevent collisions there.

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concurrency_checker.py
38 lines | 1.5 KiB | text/x-python | PythonLexer
from ..i18n import _
from .. import error
def get_checker(ui, revlog_name=b'changelog'):
"""Get a function that checks file handle position is as expected.
This is used to ensure that files haven't been modified outside of our
knowledge (such as on a networked filesystem, if `hg debuglocks` was used,
or writes to .hg that ignored locks happened).
Due to revlogs supporting a concept of buffered, delayed, or diverted
writes, we're allowing the files to be shorter than expected (the data may
not have been written yet), but they can't be longer.
Please note that this check is not perfect; it can't detect all cases (there
may be false-negatives/false-OKs), but it should never claim there's an
issue when there isn't (false-positives/false-failures).
"""
vpos = ui.config(b'debug', b'revlog.verifyposition.' + revlog_name)
# Avoid any `fh.tell` cost if this isn't enabled.
if not vpos or vpos not in [b'log', b'warn', b'fail']:
return None
def _checker(fh, fn, expected):
if fh.tell() <= expected:
return
msg = _(b'%s: file cursor at position %d, expected %d')
# Always log if we're going to warn or fail.
ui.log(b'debug', msg + b'\n', fn, fh.tell(), expected)
if vpos == b'warn':
ui.warn((msg + b'\n') % (fn, fh.tell(), expected))
elif vpos == b'fail':
raise error.RevlogError(msg % (fn, fh.tell(), expected))
return _checker