Add a helper API for setting up a NBD device with qemu-nbd

Add a virFileNBDDeviceAssociate method, which given a filename
will setup a NBD device, using qemu-nbd as the server.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2013-04-22 15:06:16 +01:00
parent 1eeff53d7d
commit 8aabd597b3
3 changed files with 150 additions and 0 deletions

View File

@ -1298,6 +1298,7 @@ virFileLoopDeviceAssociate;
virFileMakePath; virFileMakePath;
virFileMakePathWithMode; virFileMakePathWithMode;
virFileMatchesNameSuffix; virFileMatchesNameSuffix;
virFileNBDDeviceAssociate;
virFileOpenAs; virFileOpenAs;
virFileOpenTty; virFileOpenTty;
virFileReadAll; virFileReadAll;

View File

@ -653,6 +653,138 @@ cleanup:
return lofd; return lofd;
} }
# define SYSFS_BLOCK_DIR "/sys/block"
static int
virFileNBDDeviceIsBusy(const char *devname)
{
char *path;
int ret = -1;
if (virAsprintf(&path, SYSFS_BLOCK_DIR "/%s/pid",
devname) < 0) {
virReportOOMError();
return -1;
}
if (access(path, F_OK) < 0) {
if (errno == ENOENT)
ret = 0;
else
virReportSystemError(errno,
_("Cannot check NBD device %s pid"),
devname);
goto cleanup;
}
ret = 1;
cleanup:
VIR_FREE(path);
return ret;
}
static char *
virFileNBDDeviceFindUnused(void)
{
DIR *dh;
char *ret = NULL;
struct dirent *de;
if (!(dh = opendir(SYSFS_BLOCK_DIR))) {
virReportSystemError(errno,
_("Cannot read directory %s"),
SYSFS_BLOCK_DIR);
return NULL;
}
errno = 0;
while ((de = readdir(dh)) != NULL) {
if (STRPREFIX(de->d_name, "nbd")) {
int rv = virFileNBDDeviceIsBusy(de->d_name);
if (rv < 0)
goto cleanup;
if (rv == 0) {
if (virAsprintf(&ret, "/dev/%s", de->d_name) < 0) {
virReportOOMError();
goto cleanup;
}
goto cleanup;
}
}
errno = 0;
}
if (errno != 0)
virReportSystemError(errno, "%s",
_("Unable to iterate over NBD devices"));
else
virReportSystemError(EBUSY, "%s",
_("No free NBD devices"));
cleanup:
closedir(dh);
return ret;
}
int virFileNBDDeviceAssociate(const char *file,
enum virStorageFileFormat fmt,
bool readonly,
char **dev)
{
char *nbddev;
char *qemunbd;
virCommandPtr cmd = NULL;
int ret = -1;
const char *fmtstr = NULL;
if (!(nbddev = virFileNBDDeviceFindUnused()))
goto cleanup;
if (!(qemunbd = virFindFileInPath("qemu-nbd"))) {
virReportSystemError(ENOENT, "%s",
_("Unable to find 'qemu-nbd' binary in $PATH"));
goto cleanup;
}
if (fmt > 0)
fmtstr = virStorageFileFormatTypeToString(fmt);
cmd = virCommandNew(qemunbd);
/* Explicitly not trying to cope with old qemu-nbd which
* lacked --format. We want to see a fatal error in that
* case since it would be security flaw to continue */
if (fmtstr)
virCommandAddArgList(cmd, "--format", fmtstr, NULL);
if (readonly)
virCommandAddArg(cmd, "-r");
virCommandAddArgList(cmd,
"-n", /* Don't cache in qemu-nbd layer */
"-c", nbddev,
file, NULL);
/* qemu-nbd will daemonize itself */
if (virCommandRun(cmd, NULL) < 0)
goto cleanup;
*dev = nbddev;
nbddev = NULL;
ret = 0;
cleanup:
VIR_FREE(nbddev);
VIR_FREE(qemunbd);
virCommandFree(cmd);
return ret;
}
#else /* __linux__ */ #else /* __linux__ */
int virFileLoopDeviceAssociate(const char *file, int virFileLoopDeviceAssociate(const char *file,
@ -665,6 +797,17 @@ int virFileLoopDeviceAssociate(const char *file,
return -1; return -1;
} }
int virFileNBDDeviceAssociate(const char *file,
enum virStorageFileFormat fmt ATTRIBUTE_UNUSED,
bool readonly ATTRIBUTE_UNUSED,
char **dev ATTRIBUTE_UNUSED)
{
virReportSystemError(ENOSYS,
_("Unable to associate file %s with NBD device"),
file);
return -1;
}
#endif /* __linux__ */ #endif /* __linux__ */

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@ -29,6 +29,7 @@
# include <stdio.h> # include <stdio.h>
# include "internal.h" # include "internal.h"
# include "virstoragefile.h"
typedef enum virFileCloseFlags { typedef enum virFileCloseFlags {
VIR_FILE_CLOSE_PRESERVE_ERRNO = 1 << 0, VIR_FILE_CLOSE_PRESERVE_ERRNO = 1 << 0,
@ -114,6 +115,11 @@ int virFileUpdatePerm(const char *path,
int virFileLoopDeviceAssociate(const char *file, int virFileLoopDeviceAssociate(const char *file,
char **dev); char **dev);
int virFileNBDDeviceAssociate(const char *file,
enum virStorageFileFormat fmt,
bool readonly,
char **dev);
int virFileDeleteTree(const char *dir); int virFileDeleteTree(const char *dir);
int virFileReadLimFD(int fd, int maxlen, char **buf) ATTRIBUTE_RETURN_CHECK; int virFileReadLimFD(int fd, int maxlen, char **buf) ATTRIBUTE_RETURN_CHECK;