Whenever we encounter a directory with an st_dev that differs from that
of its parent, we set the FUSE_ATTR_SUBMOUNT flag so the guest can
create a submount for it.
Make this behavior optional, so submounts are only announced to the
guest with the announce_submounts option. Some users may prefer the
current behavior, so that the guest learns nothing about the host mount
structure.
Signed-off-by: Max Reitz <mre...@redhat.com>
---
tools/virtiofsd/helper.c | 1 +
tools/virtiofsd/passthrough_ll.c | 67 ++++++++++++++++++++++++++++----
2 files changed, 60 insertions(+), 8 deletions(-)
diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c
index 7bc5d7dc5a..8c5b923604 100644
--- a/tools/virtiofsd/helper.c
+++ b/tools/virtiofsd/helper.c
@@ -178,6 +178,7 @@ void fuse_cmdline_help(void)
" (0 leaves rlimit unchanged)\n"
" default: min(1000000, fs.file-max -
16384)\n"
" if the current rlimit is
lower\n"
+ " -o announce_submounts Announce sub-mount points to the
guest\n"
);
}
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 2c48c03b4c..fe7b9fbbb6 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -40,6 +40,7 @@
#include "fuse_virtio.h"
#include "fuse_log.h"
#include "fuse_lowlevel.h"
+#include "standard-headers/linux/fuse.h"
#include <assert.h>
#include <cap-ng.h>
#include <dirent.h>
@@ -159,6 +160,7 @@ struct lo_data {
int timeout_set;
int readdirplus_set;
int readdirplus_clear;
+ int announce_submounts;
struct lo_inode root;
GHashTable *inodes; /* protected by lo->mutex */
struct lo_map ino_map; /* protected by lo->mutex */
@@ -187,6 +189,7 @@ static const struct fuse_opt lo_opts[] = {
{ "cache=always", offsetof(struct lo_data, cache), CACHE_ALWAYS },
{ "readdirplus", offsetof(struct lo_data, readdirplus_set), 1 },
{ "no_readdirplus", offsetof(struct lo_data, readdirplus_clear), 1 },
+ { "announce_submounts", offsetof(struct lo_data, announce_submounts), 1 },
FUSE_OPT_END
};
static bool use_syslog = false;
@@ -582,22 +585,52 @@ static void lo_init(void *userdata, struct fuse_conn_info
*conn)
}
}
+/**
+ * Call fstatat() and set st_rdev whenever a directory's st_dev
+ * differs from the rparent's st_dev (@parent_dev). This will
+ * announce submounts to the FUSE client (unless @announce_submounts
+ * is false).
+ */
+static int do_fstatat(int dirfd, const char *pathname, struct stat *statbuf,
+ int flags, dev_t parent_dev, uint32_t *fuse_attr_flags)
+{
+ int res = fstatat(dirfd, pathname, statbuf, flags);
+ if (res == -1) {
+ return res;
+ }
+
+ if (statbuf->st_dev != parent_dev && S_ISDIR(statbuf->st_mode) &&
+ fuse_attr_flags)
+ {
+ *fuse_attr_flags |= FUSE_ATTR_SUBMOUNT;
+ }
+
+ return 0;
+}
+
static void lo_getattr(fuse_req_t req, fuse_ino_t ino,
struct fuse_file_info *fi)
{
int res;
struct stat buf;
struct lo_data *lo = lo_data(req);
+ struct lo_inode *inode = lo_inode(req, ino);
+ uint32_t fuse_attr_flags = 0;
(void)fi;
- res =
- fstatat(lo_fd(req, ino), "", &buf, AT_EMPTY_PATH |
AT_SYMLINK_NOFOLLOW);
+ res = do_fstatat(inode->fd, "", &buf, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW,
+ inode->parent_dev, &fuse_attr_flags);
+ lo_inode_put(lo, &inode);
if (res == -1) {
return (void)fuse_reply_err(req, errno);
}
- fuse_reply_attr(req, &buf, lo->timeout);
+ if (!lo->announce_submounts) {
+ fuse_attr_flags &= ~FUSE_ATTR_SUBMOUNT;
+ }
+
+ fuse_reply_attr_with_flags(req, &buf, lo->timeout, fuse_attr_flags);
}
static int lo_fi_fd(fuse_req_t req, struct fuse_file_info *fi)
@@ -793,11 +826,16 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t
parent, const char *name,
goto out_err;
}
- res = fstatat(newfd, "", &e->attr, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW);
+ res = do_fstatat(newfd, "", &e->attr, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW,
+ dir->key.dev, &e->attr_flags);
if (res == -1) {
goto out_err;
}
+ if (!lo->announce_submounts) {
+ e->attr_flags &= ~FUSE_ATTR_SUBMOUNT;
+ }
+
inode = lo_find(lo, &e->attr);
if (inode) {
close(newfd);
@@ -1043,11 +1081,17 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino,
fuse_ino_t parent,
goto out_err;
}
- res = fstatat(inode->fd, "", &e.attr, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW);
+ res = do_fstatat(inode->fd, "", &e.attr,
+ AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW,
+ parent_inode->key.dev, &e.attr_flags);
if (res == -1) {
goto out_err;
}
+ if (!lo->announce_submounts) {
+ e.attr_flags &= ~FUSE_ATTR_SUBMOUNT;
+ }
+
pthread_mutex_lock(&lo->mutex);
inode->nlookup++;
pthread_mutex_unlock(&lo->mutex);
@@ -1082,14 +1126,21 @@ static struct lo_inode *lookup_name(fuse_req_t req,
fuse_ino_t parent,
{
int res;
struct stat attr;
+ struct lo_data *lo = lo_data(req);
+ struct lo_inode *dir = lo_inode(req, parent);
+
+ if (!dir) {
+ return NULL;
+ }
- res = fstatat(lo_fd(req, parent), name, &attr,
- AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW);
+ res = do_fstatat(dir->fd, name, &attr,
+ AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW, dir->key.dev, NULL);
+ lo_inode_put(lo, &dir);
if (res == -1) {
return NULL;
}
- return lo_find(lo_data(req), &attr);
+ return lo_find(lo, &attr);
}
static void lo_rmdir(fuse_req_t req, fuse_ino_t parent, const char *name)
--
2.26.2
