Re: [libvirt] [PATCH 4/7] Add a helper API for setting up a NBD device with qemu-nbd

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; 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(a)redhat.com&gt; --- src/libvirt_private.syms | 1 + src/util/virfile.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++ src/util/virfile.h | 4 ++ 3 files changed, 129 insertions(+) diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index 5cad990..0607bae 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -1253,6 +1253,7 @@ virFileDirectFdFlag; virFileFclose; virFileFdopen; virFileLoopDeviceAssociate; +virFileNBDDeviceAssociate; virFileRewrite; virFileTouch; virFileUpdatePerm; diff --git a/src/util/virfile.c b/src/util/virfile.c index 4a9fa81..095559e 100644 --- a/src/util/virfile.c +++ b/src/util/virfile.c @@ -631,6 +631,119 @@ cleanup: 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; + } + + 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; + } + } + } + + virReportSystemError(EBUSY, "%s", + _("No free NBD devices")); + +cleanup: + closedir(dh); + return ret; +} + + +int virFileNBDDeviceAssociate(const char *file, + char **dev, + bool readonly) +{ + char *nbddev; + char *qemunbd; + virCommandPtr cmd = NULL; + int ret = -1; + + if (!(nbddev = virFileNBDDeviceFindUnused())) + goto cleanup; + + if (!(qemunbd = virFindFileInPath("qemu-nbd"))) { + virReportSystemError(ENOENT, "%s", + _("Unable to find 'qemu-nbd' binary in $PATH")); + goto cleanup; + } + + cmd = virCommandNew(qemunbd); + 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__ */ int virFileLoopDeviceAssociate(const char *file, @@ -643,4 +756,15 @@ int virFileLoopDeviceAssociate(const char *file, return -1; } +int virFileNBDDeviceAssociate(const char *file, + char **dev ATTRIBUTE_UNUSED, + bool readonly ATTRIBUTE_UNUSED) +{ + virReportSystemError(ENOSYS, + _("Unable to associate file %s with NBD device"), + file); + *dev = NULL;

+ return -1; +} + #endif /* __linux__ */ diff --git a/src/util/virfile.h b/src/util/virfile.h index c885b73..6c9179b 100644 --- a/src/util/virfile.h +++ b/src/util/virfile.h @@ -108,4 +108,8 @@ int virFileUpdatePerm(const char *path, int virFileLoopDeviceAssociate(const char *file, char **dev); +int virFileNBDDeviceAssociate(const char *file, + char **dev, + bool readonly); + #endif /* __VIR_FILES_H */