fastannotate: remove support for flock() locking

We've seen enough weirdness in CI with flock for remotefilelog that
I'm now of the opinion we should just stop using flock() everywhere
until someone has a concrete need for the extra performance *and* a
way to only use it when safe (even if that's just default-to-off.)

Differential Revision: https://phab.mercurial-scm.org/D6861

hgext/fastannotate/__init__.py

@@ -1,193 +1,170
 # Copyright 2016-present Facebook. All Rights Reserved.
 #
 # fastannotate: faster annotate implementation using linelog
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 """yet another annotate implementation that might be faster (EXPERIMENTAL)
 
 The fastannotate extension provides a 'fastannotate' command that makes
 use of the linelog data structure as a cache layer and is expected to
 be faster than the vanilla 'annotate' if the cache is present.
 
 In most cases, fastannotate requires a setup that mainbranch is some pointer
 that always moves forward, to be most efficient.
 
 Using fastannotate together with linkrevcache would speed up building the
 annotate cache greatly. Run "debugbuildlinkrevcache" before
 "debugbuildannotatecache".
 
 ::
 
     [fastannotate]
     # specify the main branch head. the internal linelog will only contain
     # the linear (ignoring p2) "mainbranch". since linelog cannot move
     # backwards without a rebuild, this should be something that always moves
     # forward, usually it is "master" or "@".
     mainbranch = master
 
     # fastannotate supports different modes to expose its feature.
     # a list of combination:
     # - fastannotate: expose the feature via the "fastannotate" command which
     #   deals with everything in a most efficient way, and provides extra
     #   features like --deleted etc.
     # - fctx: replace fctx.annotate implementation. note:
     #     a. it is less efficient than the "fastannotate" command
     #     b. it will make it practically impossible to access the old (disk
     #        side-effect free) annotate implementation
     #     c. it implies "hgweb".
     # - hgweb: replace hgweb's annotate implementation. conflict with "fctx".
     # (default: fastannotate)
     modes = fastannotate
 
     # default format when no format flags are used (default: number)
     defaultformat = changeset, user, date
 
     # serve the annotate cache via wire protocol (default: False)
     # tip: the .hg/fastannotate directory is portable - can be rsynced
     server = True
 
     # build annotate cache on demand for every client request (default: True)
     # disabling it could make server response faster, useful when there is a
     # cronjob building the cache.
     serverbuildondemand = True
 
     # update local annotate cache from remote on demand
     client = False
 
     # path to use when connecting to the remote server (default: default)
     remotepath = default
 
     # minimal length of the history of a file required to fetch linelog from
     # the server. (default: 10)
     clientfetchthreshold = 10
 
-    # use flock instead of the file existence lock
-    # flock may not work well on some network filesystems, but they avoid
-    # creating and deleting files frequently, which is faster when updating
-    # the annotate cache in batch. if you have issues with this option, set it
-    # to False. (default: True if flock is supported, False otherwise)
-    useflock = True
-
     # for "fctx" mode, always follow renames regardless of command line option.
     # this is a BC with the original command but will reduced the space needed
     # for annotate cache, and is useful for client-server setup since the
     # server will only provide annotate cache with default options (i.e. with
     # follow). do not affect "fastannotate" mode. (default: True)
     forcefollow = True
 
     # for "fctx" mode, always treat file as text files, to skip the "isbinary"
     # check. this is consistent with the "fastannotate" command and could help
     # to avoid a file fetch if remotefilelog is used. (default: True)
     forcetext = True
 
     # use unfiltered repo for better performance.
     unfilteredrepo = True
 
     # sacrifice correctness in some corner cases for performance. it does not
     # affect the correctness of the annotate cache being built. the option
     # is experimental and may disappear in the future (default: False)
     perfhack = True
 """
 
 # TODO from import:
 # * `branch` is probably the wrong term, throughout the code.
 #
 # * replace the fastannotate `modes` configuration with a collection
 #   of booleans.
 #
 # * Use the templater instead of bespoke formatting
 #
 # * rename the config knob for updating the local cache from a remote server
 #
-# * move `flock` based locking to a common area
-#
 # * revise wireprotocol for sharing annotate files
 #
 # * figure out a sensible default for `mainbranch` (with the caveat
 #   that we probably also want to figure out a better term than
 #   `branch`, see above)
 #
 # * format changes to the revmap file (maybe use length-encoding
 #   instead of null-terminated file paths at least?)
 from __future__ import absolute_import
 
 from mercurial.i18n import _
 from mercurial import (
-    configitems,
     error as hgerror,
     localrepo,
     registrar,
 )
 
 from . import (
     commands,
-    context,
     protocol,
 )
 
 # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
 # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
 # be specifying the version(s) of Mercurial they are tested with, or
 # leave the attribute unspecified.
 testedwith = 'ships-with-hg-core'
 
 cmdtable = commands.cmdtable
 
 configtable = {}
 configitem = registrar.configitem(configtable)
 
 configitem('fastannotate', 'modes', default=['fastannotate'])
 configitem('fastannotate', 'server', default=False)
-configitem('fastannotate', 'useflock', default=configitems.dynamicdefault)
 configitem('fastannotate', 'client', default=False)
 configitem('fastannotate', 'unfilteredrepo', default=True)
 configitem('fastannotate', 'defaultformat', default=['number'])
 configitem('fastannotate', 'perfhack', default=False)
 configitem('fastannotate', 'mainbranch')
 configitem('fastannotate', 'forcetext', default=True)
 configitem('fastannotate', 'forcefollow', default=True)
 configitem('fastannotate', 'clientfetchthreshold', default=10)
 configitem('fastannotate', 'serverbuildondemand', default=True)
 configitem('fastannotate', 'remotepath', default='default')
 
-def _flockavailable():
-    try:
-        import fcntl
-        fcntl.flock
-    except (AttributeError, ImportError):
-        return False
-    else:
-        return True
 
 def uisetup(ui):
     modes = set(ui.configlist('fastannotate', 'modes'))
     if 'fctx' in modes:
         modes.discard('hgweb')
     for name in modes:
         if name == 'fastannotate':
             commands.registercommand()
         elif name == 'hgweb':
             from . import support
             support.replacehgwebannotate()
         elif name == 'fctx':
             from . import support
             support.replacefctxannotate()
             commands.wrapdefault()
         else:
             raise hgerror.Abort(_('fastannotate: invalid mode: %s') % name)
 
     if ui.configbool('fastannotate', 'server'):
         protocol.serveruisetup(ui)
 
-    if ui.configbool('fastannotate', 'useflock', _flockavailable()):
-        context.pathhelper.lock = context.pathhelper._lockflock
-
 def extsetup(ui):
     # fastannotate has its own locking, without depending on repo lock
     # TODO: avoid mutating this unless the specific repo has it enabled
     localrepo.localrepository._wlockfreeprefix.add('fastannotate/')
 
 def reposetup(ui, repo):
     if ui.configbool('fastannotate', 'client'):
         protocol.clientreposetup(ui, repo)

hgext/fastannotate/context.py

@@ -1,826 +1,811
 # Copyright 2016-present Facebook. All Rights Reserved.
 #
 # context: context needed to annotate a file
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import collections
 import contextlib
 import hashlib
 import os
 
 from mercurial.i18n import _
 from mercurial import (
     error,
     linelog as linelogmod,
     lock as lockmod,
     mdiff,
     node,
     pycompat,
     scmutil,
     util,
 )
 from mercurial.utils import (
     stringutil,
 )
 
 from . import (
     error as faerror,
     revmap as revmapmod,
 )
 
 # given path, get filelog, cached
 @util.lrucachefunc
 def _getflog(repo, path):
     return repo.file(path)
 
 # extracted from mercurial.context.basefilectx.annotate
 def _parents(f, follow=True):
     # Cut _descendantrev here to mitigate the penalty of lazy linkrev
     # adjustment. Otherwise, p._adjustlinkrev() would walk changelog
     # from the topmost introrev (= srcrev) down to p.linkrev() if it
     # isn't an ancestor of the srcrev.
     f._changeid
     pl = f.parents()
 
     # Don't return renamed parents if we aren't following.
     if not follow:
         pl = [p for p in pl if p.path() == f.path()]
 
     # renamed filectx won't have a filelog yet, so set it
     # from the cache to save time
     for p in pl:
         if not '_filelog' in p.__dict__:
             p._filelog = _getflog(f._repo, p.path())
 
     return pl
 
 # extracted from mercurial.context.basefilectx.annotate. slightly modified
 # so it takes a fctx instead of a pair of text and fctx.
 def _decorate(fctx):
     text = fctx.data()
     linecount = text.count('\n')
     if text and not text.endswith('\n'):
         linecount += 1
     return ([(fctx, i) for i in pycompat.xrange(linecount)], text)
 
 # extracted from mercurial.context.basefilectx.annotate. slightly modified
 # so it takes an extra "blocks" parameter calculated elsewhere, instead of
 # calculating diff here.
 def _pair(parent, child, blocks):
     for (a1, a2, b1, b2), t in blocks:
         # Changed blocks ('!') or blocks made only of blank lines ('~')
         # belong to the child.
         if t == '=':
             child[0][b1:b2] = parent[0][a1:a2]
     return child
 
 # like scmutil.revsingle, but with lru cache, so their states (like manifests)
 # could be reused
 _revsingle = util.lrucachefunc(scmutil.revsingle)
 
 def resolvefctx(repo, rev, path, resolverev=False, adjustctx=None):
     """(repo, str, str) -> fctx
 
     get the filectx object from repo, rev, path, in an efficient way.
 
     if resolverev is True, "rev" is a revision specified by the revset
     language, otherwise "rev" is a nodeid, or a revision number that can
     be consumed by repo.__getitem__.
 
     if adjustctx is not None, the returned fctx will point to a changeset
     that introduces the change (last modified the file). if adjustctx
     is 'linkrev', trust the linkrev and do not adjust it. this is noticeably
     faster for big repos but is incorrect for some cases.
     """
     if resolverev and not isinstance(rev, int) and rev is not None:
         ctx = _revsingle(repo, rev)
     else:
         ctx = repo[rev]
 
     # If we don't need to adjust the linkrev, create the filectx using the
     # changectx instead of using ctx[path]. This means it already has the
     # changectx information, so blame -u will be able to look directly at the
     # commitctx object instead of having to resolve it by going through the
     # manifest. In a lazy-manifest world this can prevent us from downloading a
     # lot of data.
     if adjustctx is None:
         # ctx.rev() is None means it's the working copy, which is a special
         # case.
         if ctx.rev() is None:
             fctx = ctx[path]
         else:
             fctx = repo.filectx(path, changeid=ctx.rev())
     else:
         fctx = ctx[path]
         if adjustctx == 'linkrev':
             introrev = fctx.linkrev()
         else:
             introrev = fctx.introrev()
         if introrev != ctx.rev():
             fctx._changeid = introrev
             fctx._changectx = repo[introrev]
     return fctx
 
 # like mercurial.store.encodedir, but use linelog suffixes: .m, .l, .lock
 def encodedir(path):
     return (path
             .replace('.hg/', '.hg.hg/')
             .replace('.l/', '.l.hg/')
             .replace('.m/', '.m.hg/')
             .replace('.lock/', '.lock.hg/'))
 
 def hashdiffopts(diffopts):
     diffoptstr = stringutil.pprint(sorted(
         (k, getattr(diffopts, k))
         for k in mdiff.diffopts.defaults
     ))
     return node.hex(hashlib.sha1(diffoptstr).digest())[:6]
 
 _defaultdiffopthash = hashdiffopts(mdiff.defaultopts)
 
 class annotateopts(object):
     """like mercurial.mdiff.diffopts, but is for annotate
 
     followrename: follow renames, like "hg annotate -f"
     followmerge: follow p2 of a merge changeset, otherwise p2 is ignored
     """
 
     defaults = {
         'diffopts': None,
         'followrename': True,
         'followmerge': True,
     }
 
     def __init__(self, **opts):
         opts = pycompat.byteskwargs(opts)
         for k, v in self.defaults.iteritems():
             setattr(self, k, opts.get(k, v))
 
     @util.propertycache
     def shortstr(self):
         """represent opts in a short string, suitable for a directory name"""
         result = ''
         if not self.followrename:
             result += 'r0'
         if not self.followmerge:
             result += 'm0'
         if self.diffopts is not None:
             assert isinstance(self.diffopts, mdiff.diffopts)
             diffopthash = hashdiffopts(self.diffopts)
             if diffopthash != _defaultdiffopthash:
                 result += 'i' + diffopthash
         return result or 'default'
 
 defaultopts = annotateopts()
 
 class _annotatecontext(object):
     """do not use this class directly as it does not use lock to protect
     writes. use "with annotatecontext(...)" instead.
     """
 
     def __init__(self, repo, path, linelogpath, revmappath, opts):
         self.repo = repo
         self.ui = repo.ui
         self.path = path
         self.opts = opts
         self.linelogpath = linelogpath
         self.revmappath = revmappath
         self._linelog = None
         self._revmap = None
         self._node2path = {} # {str: str}
 
     @property
     def linelog(self):
         if self._linelog is None:
             if os.path.exists(self.linelogpath):
                 with open(self.linelogpath, 'rb') as f:
                     try:
                         self._linelog = linelogmod.linelog.fromdata(f.read())
                     except linelogmod.LineLogError:
                         self._linelog = linelogmod.linelog()
             else:
                 self._linelog = linelogmod.linelog()
         return self._linelog
 
     @property
     def revmap(self):
         if self._revmap is None:
             self._revmap = revmapmod.revmap(self.revmappath)
         return self._revmap
 
     def close(self):
         if self._revmap is not None:
             self._revmap.flush()
             self._revmap = None
         if self._linelog is not None:
             with open(self.linelogpath, 'wb') as f:
                 f.write(self._linelog.encode())
             self._linelog = None
 
     __del__ = close
 
     def rebuild(self):
         """delete linelog and revmap, useful for rebuilding"""
         self.close()
         self._node2path.clear()
         _unlinkpaths([self.revmappath, self.linelogpath])
 
     @property
     def lastnode(self):
         """return last node in revmap, or None if revmap is empty"""
         if self._revmap is None:
             # fast path, read revmap without loading its full content
             return revmapmod.getlastnode(self.revmappath)
         else:
             return self._revmap.rev2hsh(self._revmap.maxrev)
 
     def isuptodate(self, master, strict=True):
         """return True if the revmap / linelog is up-to-date, or the file
         does not exist in the master revision. False otherwise.
 
         it tries to be fast and could return false negatives, because of the
         use of linkrev instead of introrev.
 
         useful for both server and client to decide whether to update
         fastannotate cache or not.
 
         if strict is True, even if fctx exists in the revmap, but is not the
         last node, isuptodate will return False. it's good for performance - no
         expensive check was done.
 
         if strict is False, if fctx exists in the revmap, this function may
         return True. this is useful for the client to skip downloading the
         cache if the client's master is behind the server's.
         """
         lastnode = self.lastnode
         try:
             f = self._resolvefctx(master, resolverev=True)
             # choose linkrev instead of introrev as the check is meant to be
             # *fast*.
             linknode = self.repo.changelog.node(f.linkrev())
             if not strict and lastnode and linknode != lastnode:
                 # check if f.node() is in the revmap. note: this loads the
                 # revmap and can be slow.
                 return self.revmap.hsh2rev(linknode) is not None
             # avoid resolving old manifest, or slow adjustlinkrev to be fast,
             # false negatives are acceptable in this case.
             return linknode == lastnode
         except LookupError:
             # master does not have the file, or the revmap is ahead
             return True
 
     def annotate(self, rev, master=None, showpath=False, showlines=False):
         """incrementally update the cache so it includes revisions in the main
         branch till 'master'. and run annotate on 'rev', which may or may not be
         included in the main branch.
 
         if master is None, do not update linelog.
 
         the first value returned is the annotate result, it is [(node, linenum)]
         by default. [(node, linenum, path)] if showpath is True.
 
         if showlines is True, a second value will be returned, it is a list of
         corresponding line contents.
         """
 
         # the fast path test requires commit hash, convert rev number to hash,
         # so it may hit the fast path. note: in the "fctx" mode, the "annotate"
         # command could give us a revision number even if the user passes a
         # commit hash.
         if isinstance(rev, int):
             rev = node.hex(self.repo.changelog.node(rev))
 
         # fast path: if rev is in the main branch already
         directly, revfctx = self.canannotatedirectly(rev)
         if directly:
             if self.ui.debugflag:
                 self.ui.debug('fastannotate: %s: using fast path '
                               '(resolved fctx: %s)\n'
                               % (self.path,
                                  stringutil.pprint(util.safehasattr(revfctx,
                                                                     'node'))))
             return self.annotatedirectly(revfctx, showpath, showlines)
 
         # resolve master
         masterfctx = None
         if master:
             try:
                 masterfctx = self._resolvefctx(master, resolverev=True,
                                                adjustctx=True)
             except LookupError: # master does not have the file
                 pass
             else:
                 if masterfctx in self.revmap: # no need to update linelog
                     masterfctx = None
 
         #                  ... - @ <- rev (can be an arbitrary changeset,
         #                 /                not necessarily a descendant
         #      master -> o                 of master)
         #                |
         #     a merge -> o         'o': new changesets in the main branch
         #                |\        '#': revisions in the main branch that
         #                o *            exist in linelog / revmap
         #                | .       '*': changesets in side branches, or
         # last master -> # .            descendants of master
         #                | .
         #                # *       joint: '#', and is a parent of a '*'
         #                |/
         #     a joint -> # ^^^^ --- side branches
         #                |
         #                ^ --- main branch (in linelog)
 
         # these DFSes are similar to the traditional annotate algorithm.
         # we cannot really reuse the code for perf reason.
 
         # 1st DFS calculates merges, joint points, and needed.
         # "needed" is a simple reference counting dict to free items in
         # "hist", reducing its memory usage otherwise could be huge.
         initvisit = [revfctx]
         if masterfctx:
             if masterfctx.rev() is None:
                 raise error.Abort(_('cannot update linelog to wdir()'),
                                   hint=_('set fastannotate.mainbranch'))
             initvisit.append(masterfctx)
         visit = initvisit[:]
         pcache = {}
         needed = {revfctx: 1}
         hist = {} # {fctx: ([(llrev or fctx, linenum)], text)}
         while visit:
             f = visit.pop()
             if f in pcache or f in hist:
                 continue
             if f in self.revmap: # in the old main branch, it's a joint
                 llrev = self.revmap.hsh2rev(f.node())
                 self.linelog.annotate(llrev)
                 result = self.linelog.annotateresult
                 hist[f] = (result, f.data())
                 continue
             pl = self._parentfunc(f)
             pcache[f] = pl
             for p in pl:
                 needed[p] = needed.get(p, 0) + 1
                 if p not in pcache:
                     visit.append(p)
 
         # 2nd (simple) DFS calculates new changesets in the main branch
         # ('o' nodes in # the above graph), so we know when to update linelog.
         newmainbranch = set()
         f = masterfctx
         while f and f not in self.revmap:
             newmainbranch.add(f)
             pl = pcache[f]
             if pl:
                 f = pl[0]
             else:
                 f = None
                 break
 
         # f, if present, is the position where the last build stopped at, and
         # should be the "master" last time. check to see if we can continue
         # building the linelog incrementally. (we cannot if diverged)
         if masterfctx is not None:
             self._checklastmasterhead(f)
 
         if self.ui.debugflag:
             if newmainbranch:
                 self.ui.debug('fastannotate: %s: %d new changesets in the main'
                               ' branch\n' % (self.path, len(newmainbranch)))
             elif not hist: # no joints, no updates
                 self.ui.debug('fastannotate: %s: linelog cannot help in '
                               'annotating this revision\n' % self.path)
 
         # prepare annotateresult so we can update linelog incrementally
         self.linelog.annotate(self.linelog.maxrev)
 
         # 3rd DFS does the actual annotate
         visit = initvisit[:]
         progress = self.ui.makeprogress(('building cache'),
                                         total=len(newmainbranch))
         while visit:
             f = visit[-1]
             if f in hist:
                 visit.pop()
                 continue
 
             ready = True
             pl = pcache[f]
             for p in pl:
                 if p not in hist:
                     ready = False
                     visit.append(p)
             if not ready:
                 continue
 
             visit.pop()
             blocks = None # mdiff blocks, used for appending linelog
             ismainbranch = (f in newmainbranch)
             # curr is the same as the traditional annotate algorithm,
             # if we only care about linear history (do not follow merge),
             # then curr is not actually used.
             assert f not in hist
             curr = _decorate(f)
             for i, p in enumerate(pl):
                 bs = list(self._diffblocks(hist[p][1], curr[1]))
                 if i == 0 and ismainbranch:
                     blocks = bs
                 curr = _pair(hist[p], curr, bs)
                 if needed[p] == 1:
                     del hist[p]
                     del needed[p]
                 else:
                     needed[p] -= 1
 
             hist[f] = curr
             del pcache[f]
 
             if ismainbranch: # need to write to linelog
                 progress.increment()
                 bannotated = None
                 if len(pl) == 2 and self.opts.followmerge: # merge
                     bannotated = curr[0]
                 if blocks is None: # no parents, add an empty one
                     blocks = list(self._diffblocks('', curr[1]))
                 self._appendrev(f, blocks, bannotated)
             elif showpath: # not append linelog, but we need to record path
                 self._node2path[f.node()] = f.path()
 
         progress.complete()
 
         result = [
             ((self.revmap.rev2hsh(fr) if isinstance(fr, int) else fr.node()), l)
             for fr, l in hist[revfctx][0]] # [(node, linenumber)]
         return self._refineannotateresult(result, revfctx, showpath, showlines)
 
     def canannotatedirectly(self, rev):
         """(str) -> bool, fctx or node.
         return (True, f) if we can annotate without updating the linelog, pass
         f to annotatedirectly.
         return (False, f) if we need extra calculation. f is the fctx resolved
         from rev.
         """
         result = True
         f = None
         if not isinstance(rev, int) and rev is not None:
             hsh = {20: bytes, 40: node.bin}.get(len(rev), lambda x: None)(rev)
             if hsh is not None and (hsh, self.path) in self.revmap:
                 f = hsh
         if f is None:
             adjustctx = 'linkrev' if self._perfhack else True
             f = self._resolvefctx(rev, adjustctx=adjustctx, resolverev=True)
             result = f in self.revmap
             if not result and self._perfhack:
                 # redo the resolution without perfhack - as we are going to
                 # do write operations, we need a correct fctx.
                 f = self._resolvefctx(rev, adjustctx=True, resolverev=True)
         return result, f
 
     def annotatealllines(self, rev, showpath=False, showlines=False):
         """(rev : str) -> [(node : str, linenum : int, path : str)]
 
         the result has the same format with annotate, but include all (including
         deleted) lines up to rev. call this after calling annotate(rev, ...) for
         better performance and accuracy.
         """
         revfctx = self._resolvefctx(rev, resolverev=True, adjustctx=True)
 
         # find a chain from rev to anything in the mainbranch
         if revfctx not in self.revmap:
             chain = [revfctx]
             a = ''
             while True:
                 f = chain[-1]
                 pl = self._parentfunc(f)
                 if not pl:
                     break
                 if pl[0] in self.revmap:
                     a = pl[0].data()
                     break
                 chain.append(pl[0])
 
             # both self.linelog and self.revmap is backed by filesystem. now
             # we want to modify them but do not want to write changes back to
             # files. so we create in-memory objects and copy them. it's like
             # a "fork".
             linelog = linelogmod.linelog()
             linelog.copyfrom(self.linelog)
             linelog.annotate(linelog.maxrev)
             revmap = revmapmod.revmap()
             revmap.copyfrom(self.revmap)
 
             for f in reversed(chain):
                 b = f.data()
                 blocks = list(self._diffblocks(a, b))
                 self._doappendrev(linelog, revmap, f, blocks)
                 a = b
         else:
             # fastpath: use existing linelog, revmap as we don't write to them
             linelog = self.linelog
             revmap = self.revmap
 
         lines = linelog.getalllines()
         hsh = revfctx.node()
         llrev = revmap.hsh2rev(hsh)
         result = [(revmap.rev2hsh(r), l) for r, l in lines if r <= llrev]
         # cannot use _refineannotateresult since we need custom logic for
         # resolving line contents
         if showpath:
             result = self._addpathtoresult(result, revmap)
         if showlines:
             linecontents = self._resolvelines(result, revmap, linelog)
             result = (result, linecontents)
         return result
 
     def _resolvelines(self, annotateresult, revmap, linelog):
         """(annotateresult) -> [line]. designed for annotatealllines.
         this is probably the most inefficient code in the whole fastannotate
         directory. but we have made a decision that the linelog does not
         store line contents. so getting them requires random accesses to
         the revlog data, since they can be many, it can be very slow.
         """
         # [llrev]
         revs = [revmap.hsh2rev(l[0]) for l in annotateresult]
         result = [None] * len(annotateresult)
         # {(rev, linenum): [lineindex]}
         key2idxs = collections.defaultdict(list)
         for i in pycompat.xrange(len(result)):
             key2idxs[(revs[i], annotateresult[i][1])].append(i)
         while key2idxs:
             # find an unresolved line and its linelog rev to annotate
             hsh = None
             try:
                 for (rev, _linenum), idxs in key2idxs.iteritems():
                     if revmap.rev2flag(rev) & revmapmod.sidebranchflag:
                         continue
                     hsh = annotateresult[idxs[0]][0]
                     break
             except StopIteration: # no more unresolved lines
                 return result
             if hsh is None:
                 # the remaining key2idxs are not in main branch, resolving them
                 # using the hard way...
                 revlines = {}
                 for (rev, linenum), idxs in key2idxs.iteritems():
                     if rev not in revlines:
                         hsh = annotateresult[idxs[0]][0]
                         if self.ui.debugflag:
                             self.ui.debug('fastannotate: reading %s line #%d '
                                           'to resolve lines %r\n'
                                           % (node.short(hsh), linenum, idxs))
                         fctx = self._resolvefctx(hsh, revmap.rev2path(rev))
                         lines = mdiff.splitnewlines(fctx.data())
                         revlines[rev] = lines
                     for idx in idxs:
                         result[idx] = revlines[rev][linenum]
                 assert all(x is not None for x in result)
                 return result
 
             # run the annotate and the lines should match to the file content
             self.ui.debug('fastannotate: annotate %s to resolve lines\n'
                           % node.short(hsh))
             linelog.annotate(rev)
             fctx = self._resolvefctx(hsh, revmap.rev2path(rev))
             annotated = linelog.annotateresult
             lines = mdiff.splitnewlines(fctx.data())
             if len(lines) != len(annotated):
                 raise faerror.CorruptedFileError('unexpected annotated lines')
             # resolve lines from the annotate result
             for i, line in enumerate(lines):
                 k = annotated[i]
                 if k in key2idxs:
                     for idx in key2idxs[k]:
                         result[idx] = line
                     del key2idxs[k]
         return result
 
     def annotatedirectly(self, f, showpath, showlines):
         """like annotate, but when we know that f is in linelog.
         f can be either a 20-char str (node) or a fctx. this is for perf - in
         the best case, the user provides a node and we don't need to read the
         filelog or construct any filecontext.
         """
         if isinstance(f, bytes):
             hsh = f
         else:
             hsh = f.node()
         llrev = self.revmap.hsh2rev(hsh)
         if not llrev:
             raise faerror.CorruptedFileError('%s is not in revmap'
                                              % node.hex(hsh))
         if (self.revmap.rev2flag(llrev) & revmapmod.sidebranchflag) != 0:
             raise faerror.CorruptedFileError('%s is not in revmap mainbranch'
                                              % node.hex(hsh))
         self.linelog.annotate(llrev)
         result = [(self.revmap.rev2hsh(r), l)
                   for r, l in self.linelog.annotateresult]
         return self._refineannotateresult(result, f, showpath, showlines)
 
     def _refineannotateresult(self, result, f, showpath, showlines):
         """add the missing path or line contents, they can be expensive.
         f could be either node or fctx.
         """
         if showpath:
             result = self._addpathtoresult(result)
         if showlines:
             if isinstance(f, bytes): # f: node or fctx
                 llrev = self.revmap.hsh2rev(f)
                 fctx = self._resolvefctx(f, self.revmap.rev2path(llrev))
             else:
                 fctx = f
             lines = mdiff.splitnewlines(fctx.data())
             if len(lines) != len(result): # linelog is probably corrupted
                 raise faerror.CorruptedFileError()
             result = (result, lines)
         return result
 
     def _appendrev(self, fctx, blocks, bannotated=None):
         self._doappendrev(self.linelog, self.revmap, fctx, blocks, bannotated)
 
     def _diffblocks(self, a, b):
         return mdiff.allblocks(a, b, self.opts.diffopts)
 
     @staticmethod
     def _doappendrev(linelog, revmap, fctx, blocks, bannotated=None):
         """append a revision to linelog and revmap"""
 
         def getllrev(f):
             """(fctx) -> int"""
             # f should not be a linelog revision
             if isinstance(f, int):
                 raise error.ProgrammingError('f should not be an int')
             # f is a fctx, allocate linelog rev on demand
             hsh = f.node()
             rev = revmap.hsh2rev(hsh)
             if rev is None:
                 rev = revmap.append(hsh, sidebranch=True, path=f.path())
             return rev
 
         # append sidebranch revisions to revmap
         siderevs = []
         siderevmap = {} # node: int
         if bannotated is not None:
             for (a1, a2, b1, b2), op in blocks:
                 if op != '=':
                     # f could be either linelong rev, or fctx.
                     siderevs += [f for f, l in bannotated[b1:b2]
                                  if not isinstance(f, int)]
         siderevs = set(siderevs)
         if fctx in siderevs: # mainnode must be appended seperately
             siderevs.remove(fctx)
         for f in siderevs:
             siderevmap[f] = getllrev(f)
 
         # the changeset in the main branch, could be a merge
         llrev = revmap.append(fctx.node(), path=fctx.path())
         siderevmap[fctx] = llrev
 
         for (a1, a2, b1, b2), op in reversed(blocks):
             if op == '=':
                 continue
             if bannotated is None:
                 linelog.replacelines(llrev, a1, a2, b1, b2)
             else:
                 blines = [((r if isinstance(r, int) else siderevmap[r]), l)
                           for r, l in bannotated[b1:b2]]
                 linelog.replacelines_vec(llrev, a1, a2, blines)
 
     def _addpathtoresult(self, annotateresult, revmap=None):
         """(revmap, [(node, linenum)]) -> [(node, linenum, path)]"""
         if revmap is None:
             revmap = self.revmap
 
         def _getpath(nodeid):
             path = self._node2path.get(nodeid)
             if path is None:
                 path = revmap.rev2path(revmap.hsh2rev(nodeid))
                 self._node2path[nodeid] = path
             return path
 
         return [(n, l, _getpath(n)) for n, l in annotateresult]
 
     def _checklastmasterhead(self, fctx):
         """check if fctx is the master's head last time, raise if not"""
         if fctx is None:
             llrev = 0
         else:
             llrev = self.revmap.hsh2rev(fctx.node())
             if not llrev:
                 raise faerror.CannotReuseError()
         if self.linelog.maxrev != llrev:
             raise faerror.CannotReuseError()
 
     @util.propertycache
     def _parentfunc(self):
         """-> (fctx) -> [fctx]"""
         followrename = self.opts.followrename
         followmerge = self.opts.followmerge
         def parents(f):
             pl = _parents(f, follow=followrename)
             if not followmerge:
                 pl = pl[:1]
             return pl
         return parents
 
     @util.propertycache
     def _perfhack(self):
         return self.ui.configbool('fastannotate', 'perfhack')
 
     def _resolvefctx(self, rev, path=None, **kwds):
         return resolvefctx(self.repo, rev, (path or self.path), **kwds)
 
 def _unlinkpaths(paths):
     """silent, best-effort unlink"""
     for path in paths:
         try:
             util.unlink(path)
         except OSError:
             pass
 
 class pathhelper(object):
     """helper for getting paths for lockfile, linelog and revmap"""
 
     def __init__(self, repo, path, opts=defaultopts):
         # different options use different directories
         self._vfspath = os.path.join('fastannotate',
                                      opts.shortstr, encodedir(path))
         self._repo = repo
 
     @property
     def dirname(self):
         return os.path.dirname(self._repo.vfs.join(self._vfspath))
 
     @property
     def linelogpath(self):
         return self._repo.vfs.join(self._vfspath + '.l')
 
     def lock(self):
         return lockmod.lock(self._repo.vfs, self._vfspath + '.lock')
 
-    @contextlib.contextmanager
-    def _lockflock(self):
-        """the same as 'lock' but use flock instead of lockmod.lock, to avoid
-        creating temporary symlinks."""
-        import fcntl
-        lockpath = self.linelogpath
-        util.makedirs(os.path.dirname(lockpath))
-        lockfd = os.open(lockpath, os.O_RDONLY | os.O_CREAT, 0o664)
-        fcntl.flock(lockfd, fcntl.LOCK_EX)
-        try:
-            yield
-        finally:
-            fcntl.flock(lockfd, fcntl.LOCK_UN)
-            os.close(lockfd)
-
     @property
     def revmappath(self):
         return self._repo.vfs.join(self._vfspath + '.m')
 
 @contextlib.contextmanager
 def annotatecontext(repo, path, opts=defaultopts, rebuild=False):
     """context needed to perform (fast) annotate on a file
 
     an annotatecontext of a single file consists of two structures: the
     linelog and the revmap. this function takes care of locking. only 1
     process is allowed to write that file's linelog and revmap at a time.
 
     when something goes wrong, this function will assume the linelog and the
     revmap are in a bad state, and remove them from disk.
 
     use this function in the following way:
 
         with annotatecontext(...) as actx:
             actx. ....
     """
     helper = pathhelper(repo, path, opts)
     util.makedirs(helper.dirname)
     revmappath = helper.revmappath
     linelogpath = helper.linelogpath
     actx = None
     try:
         with helper.lock():
             actx = _annotatecontext(repo, path, linelogpath, revmappath, opts)
             if rebuild:
                 actx.rebuild()
             yield actx
     except Exception:
         if actx is not None:
             actx.rebuild()
         repo.ui.debug('fastannotate: %s: cache broken and deleted\n' % path)
         raise
     finally:
         if actx is not None:
             actx.close()
 
 def fctxannotatecontext(fctx, follow=True, diffopts=None, rebuild=False):
     """like annotatecontext but get the context from a fctx. convenient when
     used in fctx.annotate
     """
     repo = fctx._repo
     path = fctx._path
     if repo.ui.configbool('fastannotate', 'forcefollow', True):
         follow = True
     aopts = annotateopts(diffopts=diffopts, followrename=follow)
     return annotatecontext(repo, path, aopts, rebuild)