Re: [PATCH RFC] virhook: Adding inotify support to virhook.

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Hi guys,

As I mentioned, we are working in a project that introduces a hook for QEMU.
And when someone installs the RPM/DEB package with this hook,
we need to restart the libvirtd service everytime. It is really
annoying for users.

In my opinion, we can include an #if and #else to compile with inotify support.
But, I don't see any good reason to add.

Julio Cesar Faracco

2016-09-12 21:21 GMT-03:00 Julio Faracco <jcfaracco@xxxxxxxxx>:
> Libvirtd only support hooks when the daemon is started. Hooks cannot be
> loaded when the daemon is already running. So, to load a hook you need to
> restart the service everytime. Now, the inotify support enables the option
> of create a hook and run it even if libvirtd was started.
>
> Cc: Carlos Castilho <ccasti@xxxxxxxxxx>
> Signed-off-by: Julio Faracco <jcfaracco@xxxxxxxxx>
> ---
>  daemon/libvirtd.c        |   1 +
>  src/libvirt_private.syms |   1 +
>  src/util/virhook.c       | 165 ++++++++++++++++++++++++++++++++++++++++++++++-
>  src/util/virhook.h       |  10 +++
>  4 files changed, 175 insertions(+), 2 deletions(-)
>
> diff --git a/daemon/libvirtd.c b/daemon/libvirtd.c
> index 95c1b1c..56175d1 100644
> --- a/daemon/libvirtd.c
> +++ b/daemon/libvirtd.c
> @@ -1622,6 +1622,7 @@ int main(int argc, char **argv) {
>                  0, "shutdown", NULL, NULL);
>
>   cleanup:
> +    virHookCleanUp();
>      virNetlinkEventServiceStopAll();
>      virObjectUnref(remoteProgram);
>      virObjectUnref(lxcProgram);
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index 6a77e46..c8ad816 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -1648,6 +1648,7 @@ virHashValueFree;
>  virHookCall;
>  virHookInitialize;
>  virHookPresent;
> +virHookCleanUp;
>
>
>  # util/virhostdev.h
> diff --git a/src/util/virhook.c b/src/util/virhook.c
> index facd74a..d5fc928 100644
> --- a/src/util/virhook.c
> +++ b/src/util/virhook.c
> @@ -26,6 +26,7 @@
>  #include <sys/types.h>
>  #include <sys/wait.h>
>  #include <sys/stat.h>
> +#include <sys/inotify.h>
>  #include <unistd.h>
>  #include <stdlib.h>
>  #include <stdio.h>
> @@ -45,6 +46,10 @@ VIR_LOG_INIT("util.hook");
>
>  #define LIBVIRT_HOOK_DIR SYSCONFDIR "/libvirt/hooks"
>
> +#define virHookInstall(driver) virHooksFound |= (1 << driver);
> +
> +#define virHookUninstall(driver) virHooksFound ^= (1 << driver);
> +
>  VIR_ENUM_DECL(virHookDriver)
>  VIR_ENUM_DECL(virHookDaemonOp)
>  VIR_ENUM_DECL(virHookSubop)
> @@ -109,6 +114,8 @@ VIR_ENUM_IMPL(virHookLibxlOp, VIR_HOOK_LIBXL_OP_LAST,
>
>  static int virHooksFound = -1;
>
> +static virHookInotifyPtr virHooksInotify = NULL;
> +
>  /**
>   * virHookCheck:
>   * @driver: the driver name "daemon", "qemu", "lxc"...
> @@ -153,6 +160,121 @@ virHookCheck(int no, const char *driver)
>      return ret;
>  }
>
> +/**
> + * virHookInotifyEvent:
> + * @fd: inotify file descriptor.
> + *
> + * Identifies file events at libvirt's hook directory.
> + * Install or uninstall hooks on demand. Acording file manipulation.
> + */
> +static void
> +virHookInotifyEvent(int watch ATTRIBUTE_UNUSED,
> +                    int fd,
> +                    int events ATTRIBUTE_UNUSED,
> +                    void *data ATTRIBUTE_UNUSED)
> +{
> +    char buf[1024];
> +    struct inotify_event *e;
> +    int got;
> +    int driver;
> +    char *tmp, *name;
> +
> +    VIR_DEBUG("inotify event in virHookInotify()");
> +
> +reread:
> +    got = read(fd, buf, sizeof(buf));
> +    if (got == -1) {
> +        if (errno == EINTR)
> +            goto reread;
> +        return;
> +    }
> +
> +    tmp = buf;
> +    while (got) {
> +        if (got < sizeof(struct inotify_event))
> +            return;
> +
> +        VIR_WARNINGS_NO_CAST_ALIGN
> +        e = (struct inotify_event *)tmp;
> +        VIR_WARNINGS_RESET
> +
> +        tmp += sizeof(struct inotify_event);
> +        got -= sizeof(struct inotify_event);
> +
> +        if (got < e->len)
> +            return;
> +
> +        tmp += e->len;
> +        got -= e->len;
> +
> +        name = (char *)&(e->name);
> +
> +        /* Removing hook file. */
> +        if (e->mask & (IN_DELETE | IN_MOVED_FROM)) {
> +            if ((driver = virHookDriverTypeFromString(name)) < 0) {
> +                VIR_DEBUG("Invalid hook name for %s", name);
> +                return;
> +            }
> +
> +            virHookUninstall(driver);
> +        }
> +
> +        /* Creating hook file. */
> +        if (e->mask & (IN_CREATE | IN_CLOSE_WRITE | IN_MOVED_TO)) {
> +            if ((driver = virHookDriverTypeFromString(name)) < 0) {
> +                VIR_DEBUG("Invalid hook name for %s", name);
> +                return;
> +            }
> +
> +            virHookInstall(driver);
> +        }
> +    }
> +}
> +
> +/**
> + * virHookInotifyInit:
> + *
> + * Initialize inotify hooks support.
> + * Enable hooks installation on demand.
> + *
> + * Returns 0 if inotify was successfully installed, -1 in case of failure.
> + */
> +static int
> +virHookInotifyInit(void) {
> +
> +    if (VIR_ALLOC(virHooksInotify) < 0)
> +        goto error;
> +
> +    if ((virHooksInotify->inotifyFD = inotify_init()) < 0) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("cannot initialize inotify"));
> +        goto error;
> +    }
> +
> +    if ((virHooksInotify->inotifyWatch =
> +            inotify_add_watch(virHooksInotify->inotifyFD,
> +                              LIBVIRT_HOOK_DIR,
> +                              IN_CREATE | IN_MODIFY | IN_DELETE)) < 0) {
> +        virReportSystemError(errno, _("Failed to create inotify watch on %s"),
> +                             LIBVIRT_HOOK_DIR);
> +        goto error;
> +    }
> +
> +    if ((virHooksInotify->inotifyHandler =
> +            virEventAddHandle(virHooksInotify->inotifyFD,
> +                              VIR_EVENT_HANDLE_READABLE,
> +                              virHookInotifyEvent, NULL, NULL)) < 0) {
> +        VIR_DEBUG("Failed to add inotify handle in virHook.");
> +        goto error;
> +    }
> +
> +    return 0;
> +
> +error:
> +    virHookCleanUp();
> +    return -1;
> +}
> +
> +
>  /*
>   * virHookInitialize:
>   *
> @@ -174,10 +296,14 @@ virHookInitialize(void)
>              return -1;
>
>          if (res == 1) {
> -            virHooksFound |= (1 << i);
> +            virHookInstall(i);
>              ret++;
>          }
>      }
> +
> +    if (virHookInotifyInit() < 0)
> +        VIR_INFO("Disabling hooks inotify support.");
> +
>      return ret;
>  }
>
> @@ -309,7 +435,12 @@ virHookCall(int driver,
>      if (output)
>          virCommandSetOutputBuffer(cmd, output);
>
> -    ret = virCommandRun(cmd, NULL);
> +    ret = virHookCheck(driver, virHookDriverTypeToString(driver));
> +
> +    if (ret > 0) {
> +        ret = virCommandRun(cmd, NULL);
> +    }
> +
>      if (ret < 0) {
>          /* Convert INTERNAL_ERROR into known error.  */
>          virReportError(VIR_ERR_HOOK_SCRIPT_FAILED, "%s",
> @@ -322,3 +453,33 @@ virHookCall(int driver,
>
>      return ret;
>  }
> +
> +/**
> + * virHookCall:
> + *
> + * Release all structures and data used in virhooks.
> + *
> + * Returns: 0 if the execution succeeded
> + */
> +int
> +virHookCleanUp(void)
> +{
> +    if (!virHooksInotify)
> +        return -1;
> +
> +    if ((virHooksInotify->inotifyFD >= 0) &&
> +        (virHooksInotify->inotifyWatch >= 0))
> +        if (inotify_rm_watch(virHooksInotify->inotifyFD,
> +                             virHooksInotify->inotifyWatch) < 0)
> +            virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("Cannot remove inotify watcher."));
> +
> +    if (virHooksInotify->inotifyHandler >= 0)
> +        virEventRemoveHandle(virHooksInotify->inotifyHandler);
> +
> +    VIR_FORCE_CLOSE(virHooksInotify->inotifyFD);
> +    VIR_FREE(virHooksInotify);
> +
> +    virHooksFound = -1;
> +
> +    return 0;
> +}
> diff --git a/src/util/virhook.h b/src/util/virhook.h
> index 205249c..47a32c7 100644
> --- a/src/util/virhook.h
> +++ b/src/util/virhook.h
> @@ -100,6 +100,14 @@ typedef enum {
>      VIR_HOOK_LIBXL_OP_LAST,
>  } virHookLibxlOpType;
>
> +struct _virHookInotify {
> +    int inotifyFD;
> +    int inotifyWatch;
> +    int inotifyHandler;
> +};
> +
> +typedef struct _virHookInotify *virHookInotifyPtr;
> +
>  int virHookInitialize(void);
>
>  int virHookPresent(int driver);
> @@ -107,4 +115,6 @@ int virHookPresent(int driver);
>  int virHookCall(int driver, const char *id, int op, int sub_op,
>                  const char *extra, const char *input, char **output);
>
> +int virHookCleanUp(void);
> +
>  #endif /* __VIR_HOOKS_H__ */
> --
> 2.7.4
>

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