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author | Filippo Cucchetto <filippocucchetto@gmail.com> | 2018-10-21 10:36:17 +0200 |
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committer | Liang Qi <liang.qi@qt.io> | 2018-11-12 13:01:15 +0000 |
commit | 104200d688650db02f1447f73a499784115d897d (patch) | |
tree | 692ebf030b770ff677ef5db309b20b56803b1d54 /src/corelib/io | |
parent | ac4f075274414aac1b6cf2e8e854f0f21fee0761 (diff) |
Fix QFileSystemWatcher::removePath after move operations
Foreword:
- During a file or directory move the inotify id for an
entity is not changed.
- QFileSystemWatcher implementation uses a QMultiHash for
mapping an id to its path.
Suppose this filesystem hypothetical directory structure
- A
|--> B
and user watches both A and B directories.
Suppose that the B directory gets moved by calling "mv B B1".
The user receives a directoryChanged event for parent directory
A and scan filesystem for changes. During this scan the
user notices:
- a new directory B1
- a deleted directory B
The user simply invoke QFileSystemWatcher::addPath(B1) and
QFileSystemWatcher::removePath(B).
With the actual implementation the second operation could fail:
- The call QFileSystemWatcher::addPath(B1) insert a duplicated
records in the QFileSystemWatcher::idToPath
multihash ( {0, "A"}, {1, "A/B"} {1, "A/B1"}
- The call QFileSystemWatcher::removePath(B) fails because
- it first retrieves the the id for path B ---> pathToId("A/B") <-- return 1
- Then it calls idToPath.take with the id obtain in the
previous step <--- idToPath.take(1)
This last operation could take the record {1, "A/B1"} instead
of the {1, "A/B"} (because both have the same key) meaning that
the next check "x != path" evaluates to true (making the
removePath function fail).
This patch fixes the problem in the following way:
- Use idToPath.equal_range in order to obtain all paths with
the given id
- Remove the correct record that match (id, path)
- Prevent the removal of the inotify watch if another record
with the same id is still present in the multihash (like a
simple reference counting).
Change-Id: I9c8480b2a869d91e500af5c4aded596b9aa53b46
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Diffstat (limited to 'src/corelib/io')
-rw-r--r-- | src/corelib/io/qfilesystemwatcher_inotify.cpp | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/src/corelib/io/qfilesystemwatcher_inotify.cpp b/src/corelib/io/qfilesystemwatcher_inotify.cpp index 3b7135e582..a5e629b646 100644 --- a/src/corelib/io/qfilesystemwatcher_inotify.cpp +++ b/src/corelib/io/qfilesystemwatcher_inotify.cpp @@ -330,13 +330,24 @@ QStringList QInotifyFileSystemWatcherEngine::removePaths(const QStringList &path while (it.hasNext()) { QString path = it.next(); int id = pathToID.take(path); - QString x = idToPath.take(id); - if (x.isEmpty() || x != path) + + // Multiple paths could be associated to the same watch descriptor + // when a file is moved and added with the new name. + // So we should find and delete the correct one by using + // both id and path + auto path_range = idToPath.equal_range(id); + auto path_it = std::find(path_range.first, path_range.second, path); + if (path_it == idToPath.end()) continue; - int wd = id < 0 ? -id : id; - // qDebug() << "removing watch for path" << path << "wd" << wd; - inotify_rm_watch(inotifyFd, wd); + const ssize_t num_elements = std::distance(path_range.first, path_range.second); + idToPath.erase(path_it); + + // If there was only one path associated to the given id we should remove the watch + if (num_elements == 1) { + int wd = id < 0 ? -id : id; + inotify_rm_watch(inotifyFd, wd); + } it.remove(); if (id < 0) { |