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[PULL 10/12] virtiofsd: Announce sub-mount points
From: |
Dr. David Alan Gilbert (git) |
Subject: |
[PULL 10/12] virtiofsd: Announce sub-mount points |
Date: |
Mon, 2 Nov 2020 19:56:55 +0000 |
From: Max Reitz <mreitz@redhat.com>
Whenever we encounter a directory with an st_dev or mount ID that
differs from that of its parent, we set the FUSE_ATTR_SUBMOUNT flag so
the guest can create a submount for it.
We only need to do so in lo_do_lookup(). The following functions return
a fuse_attr object:
- lo_create(), though fuse_reply_create(): Calls lo_do_lookup().
- lo_lookup(), though fuse_reply_entry(): Calls lo_do_lookup().
- lo_mknod_symlink(), through fuse_reply_entry(): Calls lo_do_lookup().
- lo_link(), through fuse_reply_entry(): Creating a link cannot create a
submount, so there is no need to check for it.
- lo_getattr(), through fuse_reply_attr(): Announcing submounts when the
node is first detected (at lookup) is sufficient. We do not need to
return the submount attribute later.
- lo_do_readdir(), through fuse_add_direntry_plus(): Calls
lo_do_lookup().
Make announcing submounts 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.
(announce_submounts is force-disabled when the guest does not present
the FUSE_SUBMOUNTS capability, or when there is no statx().)
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201102161859.156603-6-mreitz@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
tools/virtiofsd/helper.c | 1 +
tools/virtiofsd/passthrough_ll.c | 22 ++++++++++++++++++++++
2 files changed, 23 insertions(+)
diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c
index ae1b22e4a6..75ac48dec2 100644
--- a/tools/virtiofsd/helper.c
+++ b/tools/virtiofsd/helper.c
@@ -190,6 +190,7 @@ void fuse_cmdline_help(void)
" retain/discard O_DIRECT flags
passed down\n"
" to virtiofsd from guest
applications.\n"
" default: no_allow_direct_io\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 34d107975f..ec1008bceb 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>
@@ -167,6 +168,7 @@ struct lo_data {
int readdirplus_set;
int readdirplus_clear;
int allow_direct_io;
+ int announce_submounts;
bool use_statx;
struct lo_inode root;
GHashTable *inodes; /* protected by lo->mutex */
@@ -207,6 +209,7 @@ static const struct fuse_opt lo_opts[] = {
{ "no_readdirplus", offsetof(struct lo_data, readdirplus_clear), 1 },
{ "allow_direct_io", offsetof(struct lo_data, allow_direct_io), 1 },
{ "no_allow_direct_io", offsetof(struct lo_data, allow_direct_io), 0 },
+ { "announce_submounts", offsetof(struct lo_data, announce_submounts), 1 },
FUSE_OPT_END
};
static bool use_syslog = false;
@@ -601,6 +604,20 @@ static void lo_init(void *userdata, struct fuse_conn_info
*conn)
fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling readdirplus\n");
conn->want &= ~FUSE_CAP_READDIRPLUS;
}
+
+ if (!(conn->capable & FUSE_CAP_SUBMOUNTS) && lo->announce_submounts) {
+ fuse_log(FUSE_LOG_WARNING, "lo_init: Cannot announce submounts, client
"
+ "does not support it\n");
+ lo->announce_submounts = false;
+ }
+
+#ifndef CONFIG_STATX
+ if (lo->announce_submounts) {
+ fuse_log(FUSE_LOG_WARNING, "lo_init: Cannot announce submounts, there "
+ "is no statx()\n");
+ lo->announce_submounts = false;
+ }
+#endif
}
static void lo_getattr(fuse_req_t req, fuse_ino_t ino,
@@ -877,6 +894,11 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent,
const char *name,
goto out_err;
}
+ if (S_ISDIR(e->attr.st_mode) && lo->announce_submounts &&
+ (e->attr.st_dev != dir->key.dev || mnt_id != dir->key.mnt_id)) {
+ e->attr_flags |= FUSE_ATTR_SUBMOUNT;
+ }
+
inode = lo_find(lo, &e->attr, mnt_id);
if (inode) {
close(newfd);
--
2.28.0
- [PULL 00/12] migration queue, Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 02/12] migration: Postpone the kick of the fault thread after recover, Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 03/12] virtiofsd: Seccomp: Add 'send' for syslog, Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 01/12] migration: Unify reset of last_rb on destination node when recover, Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 05/12] virtiofsd: Fix the help message of posix lock, Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 04/12] tools/virtiofsd: Check vu_init() return value (CID 1435958), Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 06/12] virtiofsd: Check FUSE_SUBMOUNTS, Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 07/12] virtiofsd: Add attr_flags to fuse_entry_param, Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 08/12] meson.build: Check for statx(), Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 09/12] virtiofsd: Add mount ID to the lo_inode key, Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 10/12] virtiofsd: Announce sub-mount points,
Dr. David Alan Gilbert (git) <=
- [PULL 11/12] tests/acceptance/boot_linux: Accept SSH pubkey, Dr. David Alan Gilbert (git), 2020/11/02
- [PULL 12/12] tests/acceptance: Add virtiofs_submounts.py, Dr. David Alan Gilbert (git), 2020/11/02
- Re: [PULL 00/12] migration queue, Peter Maydell, 2020/11/03