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lxc_fuse: Implement support for FUSE3

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Plenty of projects switch from FUSE to FUSE3. This commit enables
libvirt to compile with newer fuse-3.1 which allows users to have
just one fuse package on their systems, allows us to set
O_CLOEXEC on the fuse session FD. In general, FUSE3 offers more
features, but apparently we don't need them right now. There is a
rewrite guide at [1] but I've took most inspiration from sshfs
[2].

1: https://github.com/libfuse/libfuse/releases/tag/fuse-3.0.0
2: https://github.com/libfuse/sshfs

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
This commit is contained in:
Michal Privoznik 2020-04-13 13:17:47 +02:00
parent 7664955086
commit d881cefe60
1 changed files with 71 additions and 2 deletions
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73
src/lxc/lxc_fuse.c
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@ -28,6 +28,9 @@
#if WITH_FUSE
# define FUSE_USE_VERSION 26
# include <fuse.h>
# if FUSE_USE_VERSION >= 31
# include <fuse_lowlevel.h>
# endif
#endif
#include "lxc_fuse.h"
@ -48,15 +51,19 @@ struct virLXCFuse {
virThread thread;
char *mountpoint;
struct fuse *fuse;
# if FUSE_USE_VERSION < 31
struct fuse_chan *ch;
# else
struct fuse_session *sess;
# endif
virMutex lock;
};
static const char *fuse_meminfo_path = "/meminfo";
static int
lxcProcGetattr(const char *path,
struct stat *stbuf)
lxcProcGetattrImpl(const char *path,
struct stat *stbuf)
{
g_autofree char *mempath = NULL;
struct stat sb;
@ -90,6 +97,40 @@ lxcProcGetattr(const char *path,
return 0;
}
# if FUSE_USE_VERSION >= 31
static int
lxcProcGetattr(const char *path,
struct stat *stbuf,
struct fuse_file_info *fi G_GNUC_UNUSED)
{
return lxcProcGetattrImpl(path, stbuf);
}
# else
static int lxcProcGetattr(const char *path, struct stat *stbuf)
{
return lxcProcGetattrImpl(path, stbuf);
}
# endif
# if FUSE_USE_VERSION >= 31
static int
lxcProcReaddir(const char *path,
void *buf,
fuse_fill_dir_t filler,
off_t offset G_GNUC_UNUSED,
struct fuse_file_info *fi G_GNUC_UNUSED,
enum fuse_readdir_flags unused_flags G_GNUC_UNUSED)
{
if (STRNEQ(path, "/"))
return -ENOENT;
filler(buf, ".", NULL, 0, 0);
filler(buf, "..", NULL, 0, 0);
filler(buf, fuse_meminfo_path + 1, NULL, 0, 0);
return 0;
}
# else
static int
lxcProcReaddir(const char *path,
void *buf,
@ -106,6 +147,7 @@ lxcProcReaddir(const char *path,
return 0;
}
# endif
static int
lxcProcOpen(const char *path,
@ -292,7 +334,11 @@ lxcFuseDestroy(struct virLXCFuse *fuse)
{
VIR_LOCK_GUARD lock = virLockGuardLock(&fuse->lock);
# if FUSE_USE_VERSION >= 31
fuse_unmount(fuse->fuse);
# else
fuse_unmount(fuse->mountpoint, fuse->ch);
# endif
g_clear_pointer(&fuse->fuse, fuse_destroy);
}
@ -335,6 +381,23 @@ lxcSetupFuse(struct virLXCFuse **f,
fuse_opt_add_arg(&args, "-ofsname=libvirt") == -1)
goto error;
# if FUSE_USE_VERSION >= 31
fuse->fuse = fuse_new(&args, &lxcProcOper, sizeof(lxcProcOper), fuse->def);
if (fuse->fuse == NULL)
goto error;
if (fuse_mount(fuse->fuse, fuse->mountpoint) < 0)
goto error;
fuse->sess = fuse_get_session(fuse->fuse);
if (virSetInherit(fuse_session_fd(fuse->sess), false) < 0) {
virReportSystemError(errno, "%s",
_("Cannot disable close-on-exec flag"));
goto error;
}
# else
fuse->ch = fuse_mount(fuse->mountpoint, &args);
if (fuse->ch == NULL)
goto error;
@ -344,6 +407,7 @@ lxcSetupFuse(struct virLXCFuse **f,
if (fuse->fuse == NULL) {
goto error;
}
# endif
*f = g_steal_pointer(&fuse);
ret = 0;
@ -352,8 +416,13 @@ lxcSetupFuse(struct virLXCFuse **f,
return ret;
error:
# if FUSE_USE_VERSION < 31
if (fuse->ch)
fuse_unmount(fuse->mountpoint, fuse->ch);
# else
fuse_unmount(fuse->fuse);
fuse_destroy(fuse->fuse);
# endif
g_free(fuse->mountpoint);
virMutexDestroy(&fuse->lock);
goto cleanup;