From patchwork Thu Feb 25 20:32:25 2021
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Subject: =?utf-8?q?D10077=3A_rhg=3A_Don=E2=80=99t_attempt_to_read_persisten?=
 =?utf-8?q?t_nodemap_without_=2Ehg/requires_opt-in?=
From: phabricator <phabricator@mercurial-scm.org>
X-Patchwork-Id: 48392
Message-Id: <differential-rev-PHID-DREV-ym7nyk7xazjtzmvrk2bc-req@mercurial-scm.org>
To: Phabricator <phabricator@mercurial-scm.org>
Cc: mercurial-devel@mercurial-scm.org
Date: Thu, 25 Feb 2021 20:32:25 +0000

SimonSapin created this revision.
Herald added a reviewer: hg-reviewers.
Herald added a subscriber: mercurial-patches.

REPOSITORY
  rHG Mercurial

BRANCH
  default

REVISION DETAIL
  https://phab.mercurial-scm.org/D10077

AFFECTED FILES
  rust/hg-core/src/revlog/nodemap_docket.rs

CHANGE DETAILS




To: SimonSapin, #hg-reviewers
Cc: mercurial-patches, mercurial-devel

diff --git a/rust/hg-core/src/revlog/nodemap_docket.rs b/rust/hg-core/src/revlog/nodemap_docket.rs
--- a/rust/hg-core/src/revlog/nodemap_docket.rs
+++ b/rust/hg-core/src/revlog/nodemap_docket.rs
@@ -1,4 +1,5 @@
 use crate::errors::{HgError, HgResultExt};
+use crate::requirements;
 use bytes_cast::{unaligned, BytesCast};
 use memmap::Mmap;
 use std::path::{Path, PathBuf};
@@ -38,6 +39,14 @@
         repo: &Repo,
         index_path: &Path,
     ) -> Result<Option<(Self, Mmap)>, RevlogError> {
+        if !repo
+            .requirements()
+            .contains(requirements::NODEMAP_REQUIREMENT)
+        {
+            // If .hg/requires does not opt it, don’t try to open a nodemap
+            return Ok(None);
+        }
+
         let docket_path = index_path.with_extension("n");
         let docket_bytes = if let Some(bytes) =
             repo.store_vfs().read(&docket_path).io_not_found_as_none()?
@@ -88,6 +97,8 @@
                 Err(HgError::corrupted("persistent nodemap too short").into())
             }
         } else {
+            // Even if .hg/requires opted in, some revlogs are deemed small
+            // enough to not need a persistent nodemap.
             Ok(None)
         }
     }