Improve file saving strategy

- The TempFile class guarantees to generate a file name, we are not limited to
  100 tries of a predictable scheme anymore, which could break if LyX
  frequently crashes.
- The temp file name generation has no race condition against another LyX
  instance in the same directory anymore.
- Symlinks survive saving again (regression of 10364082c8).
This commit is contained in:
Georg Baum 2014-06-09 11:08:24 +02:00
parent 47721216f0
commit bf782ee02a
5 changed files with 56 additions and 25 deletions

View File

@ -1284,25 +1284,8 @@ bool Buffer::save() const
// we first write the file to a new name, then move it to its
// proper location once that has been done successfully. that
// way we preserve the original file if something goes wrong.
string const savepath = fileName().onlyPath().absFileName();
int fnum = 1;
string const fname = fileName().onlyFileName();
string savename = "tmp-" + convert<string>(fnum) + "-" + fname;
FileName savefile(addName(savepath, savename));
while (savefile.exists()) {
// surely that is enough tries?
if (fnum > 100) {
Alert::error(_("Write failure"),
bformat(_("Cannot find temporary filename for:\n %1$s.\n"
"Even %2$s exists!"),
from_utf8(fileName().absFileName()),
from_utf8(savefile.absFileName())));
return false;
}
fnum += 1;
savename = "tmp-" + convert<string>(fnum) + "-" + fname;
savefile.set(addName(savepath, savename));
}
TempFile tempfile(fileName().onlyPath(), "tmpXXXXXX.lyx");
FileName savefile(tempfile.name());
LYXERR(Debug::FILES, "Saving to " << savefile.absFileName());
if (!writeFile(savefile))
@ -1310,6 +1293,7 @@ bool Buffer::save() const
// we will set this to false if we fail
bool made_backup = true;
bool const symlink = fileName().isSymLink();
if (lyxrc.make_backup) {
FileName backupName(absFileName() + '~');
if (!lyxrc.backupdir_path.empty()) {
@ -1321,7 +1305,7 @@ bool Buffer::save() const
// Except file is symlink do not copy because of #6587.
// Hard links have bad luck.
made_backup = fileName().isSymLink() ?
made_backup = symlink ?
fileName().copyTo(backupName):
fileName().moveTo(backupName);
@ -1333,8 +1317,13 @@ bool Buffer::save() const
//LYXERR(Debug::DEBUG, "Fs error: " << fe.what());
}
}
if (made_backup && savefile.moveTo(fileName())) {
// If we have no symlink, we can simply rename the temp file.
// Otherwise, we need to copy it so the symlink stays intact.
if (!symlink)
tempfile.setAutoRemove(false);
if (made_backup &&
(symlink ? savefile.copyTo(fileName(), true) : savefile.moveTo(fileName()))) {
markClean();
return true;
}

View File

@ -217,9 +217,26 @@ void FileName::erase()
}
bool FileName::copyTo(FileName const & name) const
bool FileName::copyTo(FileName const & name, bool keepsymlink) const
{
LYXERR(Debug::FILES, "Copying " << name);
FileNameSet visited;
visited.insert(*this);
return copyTo(name, keepsymlink, visited);
}
bool FileName::copyTo(FileName const & name, bool keepsymlink,
FileName::FileNameSet & visited) const
{
LYXERR(Debug::FILES, "Copying " << name << " keep symlink: " << keepsymlink);
if (keepsymlink && name.isSymLink()) {
FileName const target(fromqstr(name.d->fi.symLinkTarget()));
if (visited.find(target) != visited.end()) {
LYXERR(Debug::FILES, "Found circular symlink: " << target);
return false;
}
return copyTo(target, true);
}
QFile::remove(name.d->fi.absoluteFilePath());
bool success = QFile::copy(d->fi.absoluteFilePath(), name.d->fi.absoluteFilePath());
if (!success)
@ -231,6 +248,7 @@ bool FileName::copyTo(FileName const & name) const
bool FileName::renameTo(FileName const & name) const
{
LYXERR(Debug::FILES, "Renaming " << name);
bool success = QFile::rename(d->fi.absoluteFilePath(), name.d->fi.absoluteFilePath());
if (!success)
LYXERR0("Could not rename file " << *this << " to " << name);
@ -240,6 +258,7 @@ bool FileName::renameTo(FileName const & name) const
bool FileName::moveTo(FileName const & name) const
{
LYXERR(Debug::FILES, "Moving " << name);
QFile::remove(name.d->fi.absoluteFilePath());
bool success = QFile::rename(d->fi.absoluteFilePath(),

View File

@ -16,6 +16,7 @@
#include "support/strfwd.h"
#include <ctime>
#include <set>
namespace lyx {
@ -123,7 +124,9 @@ public:
/// \return true when file/directory is writable (write test file)
/// \warning This methods has different semantics when system level
/// copy command, it will overwrite the \c target file if it exists,
bool copyTo(FileName const & target) const;
/// If \p keepsymlink is true, the copy will be written to the symlink
/// target. Otherwise, the symlink will be destroyed.
bool copyTo(FileName const & target, bool keepsymlink = false) const;
/// remove pointed file.
/// \return true on success.
@ -136,6 +139,8 @@ public:
bool renameTo(FileName const & target) const;
/// move pointed file to \param target.
/// If \p target exists it will be overwritten (if it is a symlink,
/// the symlink will be destroyed).
/// \return true on success.
bool moveTo(FileName const & target) const;
@ -212,6 +217,12 @@ public:
private:
friend bool equivalent(FileName const &, FileName const &);
/// Set for tracking of already visited file names.
/// Uses operator==() (which may be case insensitive), and not
/// equvalent(), so that symlinks are not resolved.
typedef std::set<FileName> FileNameSet;
/// Helper for public copyTo() to find circular symlink chains
bool copyTo(FileName const &, bool, FileNameSet &) const;
///
struct Private;
Private * const d;

View File

@ -74,5 +74,10 @@ FileName TempFile::name() const
}
void TempFile::setAutoRemove(bool autoremove)
{
d->f.setAutoRemove(autoremove);
}
} // namespace support
} // namespace lyx

View File

@ -46,6 +46,13 @@ public:
* This is empty if the file could not be created.
*/
FileName name() const;
/**
* Set whether the file should be automatically deleted in the
* destructor.
* Automatic deletion is the default, but it can be switched off if
* the file should be kept, because it should be renamed afterwards.
*/
void setAutoRemove(bool autoremove);
private:
///
struct Private;