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osdep: Add runtime OFD lock detection

Build time check of OFD lock is not sufficient and can cause image open
errors when the runtime environment doesn't support it.

Add a helper function to probe it at runtime, additionally. Also provide
a qemu_has_ofd_lock() for callers to check the status.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Fam Zheng Kevin Wolf
Fam Zheng authored and Kevin Wolf committed Aug 11, 2017
1 parent d0d5d0e commit ca749954b09b89e22cd69c4949fb7e689b057963
Showing with 57 additions and 10 deletions.
  1. +1 −0 include/qemu/osdep.h
  2. +56 −10 util/osdep.c
@@ -357,6 +357,7 @@ int qemu_dup(int fd);
int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive);
int qemu_unlock_fd(int fd, int64_t start, int64_t len);
int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive);
bool qemu_has_ofd_lock(void);

#if defined(__HAIKU__) && defined(__i386__)
#define FMT_pid "%ld"
@@ -38,14 +38,6 @@ extern int madvise(caddr_t, size_t, int);
#include "qemu/error-report.h"
#include "monitor/monitor.h"

#ifdef F_OFD_SETLK
#define QEMU_SETLK F_OFD_SETLK
#define QEMU_GETLK F_OFD_GETLK
#else
#define QEMU_SETLK F_SETLK
#define QEMU_GETLK F_GETLK
#endif

static bool fips_enabled = false;

static const char *hw_version = QEMU_HW_VERSION;
@@ -82,6 +74,10 @@ int qemu_madvise(void *addr, size_t len, int advice)
}

#ifndef _WIN32

static int fcntl_op_setlk = -1;
static int fcntl_op_getlk = -1;

/*
* Dups an fd and sets the flags
*/
@@ -149,6 +145,54 @@ static int qemu_parse_fdset(const char *param)
return qemu_parse_fd(param);
}

static void qemu_probe_lock_ops(void)
{
if (fcntl_op_setlk == -1) {
#ifdef F_OFD_SETLK
int fd;
int ret;
struct flock fl = {
.l_whence = SEEK_SET,
.l_start = 0,
.l_len = 0,
.l_type = F_WRLCK,
};

fd = open("/dev/null", O_RDWR);
if (fd < 0) {
fprintf(stderr,
"Failed to open /dev/null for OFD lock probing: %s\n",
strerror(errno));
fcntl_op_setlk = F_SETLK;
fcntl_op_getlk = F_GETLK;
return;
}
ret = fcntl(fd, F_OFD_GETLK, &fl);
close(fd);
if (!ret) {
fcntl_op_setlk = F_OFD_SETLK;
fcntl_op_getlk = F_OFD_GETLK;
} else {
fcntl_op_setlk = F_SETLK;
fcntl_op_getlk = F_GETLK;
}
#else
fcntl_op_setlk = F_SETLK;
fcntl_op_getlk = F_GETLK;
#endif
}
}

bool qemu_has_ofd_lock(void)
{
qemu_probe_lock_ops();
#ifdef F_OFD_SETLK
return fcntl_op_setlk == F_OFD_SETLK;
#else
return false;
#endif
}

static int qemu_lock_fcntl(int fd, int64_t start, int64_t len, int fl_type)
{
int ret;
@@ -158,7 +202,8 @@ static int qemu_lock_fcntl(int fd, int64_t start, int64_t len, int fl_type)
.l_len = len,
.l_type = fl_type,
};
ret = fcntl(fd, QEMU_SETLK, &fl);
qemu_probe_lock_ops();
ret = fcntl(fd, fcntl_op_setlk, &fl);
return ret == -1 ? -errno : 0;
}

@@ -181,7 +226,8 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive)
.l_len = len,
.l_type = exclusive ? F_WRLCK : F_RDLCK,
};
ret = fcntl(fd, QEMU_GETLK, &fl);
qemu_probe_lock_ops();
ret = fcntl(fd, fcntl_op_getlk, &fl);
if (ret == -1) {
return -errno;
} else {

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