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QFileSystemEngine/Unix: implement getting the size of block devices

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Implemented for Linux, macOS, and FreeBSD. This works only on open files
because of the need to ioctl().

Before:
"/dev/system/stuff2" : 0

After:
"/dev/system/stuff2" : 68719476736              [Linux]
"/dev/ada1" : 42949672960                       [FreeBSD]
"/dev/disk0" : 500277792768                     [macOS]
"/dev/disk2" : 39306240                         [macOS]

With:
    if (f.open(QIODevice::ReadOnly | QIODevice::Unbuffered))
        qDebug() << f.fileName() << ':' << f.size();

[ChangeLog][QtCore][QFile] For open block devices on Unix systems,
size() now returns the size of the underlying device. Previously, it
would always return 0.

Change-Id: I8a96935cf6c742259c9dfffd17e9402bdbd6b963
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
This commit is contained in:
Thiago Macieira 2024-08-06 14:14:49 -07:00
parent 731b1159f9
commit 3b9f5c82f5
1 changed files with 34 additions and 0 deletions
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34
src/corelib/io/qfilesystemengine_unix.cpp
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@ -36,6 +36,11 @@
# define _PATH_TMP "/tmp"
#endif
#if __has_include(<sys/disk.h>)
// BSDs (including Apple Darwin)
# include <sys/disk.h>
#endif
#if defined(Q_OS_DARWIN)
# include <QtCore/private/qcore_mac_p.h>
# include <CoreFoundation/CFBundle.h>
@ -362,6 +367,33 @@ inline void QFileSystemMetaData::fillFromStatxBuf(const struct statx &)
//static
bool QFileSystemEngine::fillMetaData(int fd, QFileSystemMetaData &data)
{
auto getSizeForBlockDev = [&](mode_t st_mode) {
#ifdef BLKGETSIZE64
// Linux
if (quint64 sz; (st_mode & S_IFMT) == S_IFBLK && ioctl(fd, BLKGETSIZE64, &sz) == 0)
data.size_ = sz; // returns byte count
#elif defined(BLKGETSIZE)
// older Linux
if (ulong sz; (st_mode & S_IFMT) == S_IFBLK && ioctl(fd, BLKGETSIZE, &sz) == 0)
data.size_ = sz * 512; // returns 512-byte sector count
#elif defined(DKIOCGETBLOCKCOUNT)
// Apple Darwin
qint32 blksz;
if (quint64 count; (st_mode & S_IFMT) == S_IFBLK
&& ioctl(fd, DKIOCGETBLOCKCOUNT, &count) == 0
&& ioctl(fd, DKIOCGETBLOCKSIZE, &blksz) == 0)
data.size_ = count * blksz;
#elif defined(DIOCGMEDIASIZE)
// FreeBSD
// see Linux-compat implementation in
// http://fxr.watson.org/fxr/source/compat/linux/linux_ioctl.c?v=FREEBSD-13-STABLE#L282
// S_IFCHR is correct: FreeBSD doesn't have block devices any more
if (QT_OFF_T sz; (st_mode & S_IFMT) == S_IFCHR && ioctl(fd, DIOCGMEDIASIZE, &sz) == 0)
data.size_ = sz; // returns byte count
#else
Q_UNUSED(st_mode);
#endif
};
data.entryFlags &= ~QFileSystemMetaData::PosixStatFlags;
data.knownFlagsMask |= QFileSystemMetaData::PosixStatFlags;
@ -371,6 +403,7 @@ bool QFileSystemEngine::fillMetaData(int fd, QFileSystemMetaData &data)
if (ret != -ENOSYS) {
if (ret == 0) {
data.fillFromStatxBuf(statxBuffer);
getSizeForBlockDev(statxBuffer.stx_mode);
return true;
}
return false;
@ -380,6 +413,7 @@ bool QFileSystemEngine::fillMetaData(int fd, QFileSystemMetaData &data)
if (QT_FSTAT(fd, &statBuffer) == 0) {
data.fillFromStatBuf(statBuffer);
getSizeForBlockDev(statBuffer.st_mode);
return true;
}