On Thu, Dec 12, 2019 at 04:38:45PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: Vivek Goyal <vgo...@redhat.com>
>
> Doing posix locks with-in guest kernel are not sufficient if a file/dir
> is being shared by multiple guests. So we need the notion of daemon doing
> the locks which are visible to rest of the guests.
>
> Given posix locks are per process, one can not call posix lock API on host,
> otherwise bunch of basic posix locks properties are broken. For example,
> If two processes (A and B) in guest open the file and take locks on different
> sections of file, if one of the processes closes the fd, it will close
> fd on virtiofsd and all posix locks on file will go away. This means if
> process A closes the fd, then locks of process B will go away too.
>
> Similar other problems exist too.
>
> This patch set tries to emulate posix locks while using open file
> description locks provided on Linux.
>
> Daemon provides two options (-o posix_lock, -o no_posix_lock) to enable
> or disable posix locking in daemon. By default it is enabled.
>
> There are few issues though.
>
> - GETLK() returns pid of process holding lock. As we are emulating locks
> using OFD, and these locks are not per process and don't return pid
> of process, so GETLK() in guest does not reuturn process pid.
>
> - As of now only F_SETLK is supported and not F_SETLKW. We can't block
> the thread in virtiofsd for arbitrary long duration as there is only
> one thread serving the queue. That means unlock request will not make
> it to daemon and F_SETLKW will block infinitely and bring virtio-fs
> to a halt. This is a solvable problem though and will require significant
> changes in virtiofsd and kernel. Left as a TODO item for now.
>
> Signed-off-by: Vivek Goyal <vgo...@redhat.com>
> ---
> tools/virtiofsd/passthrough_ll.c | 190 +++++++++++++++++++++++++++++++
> 1 file changed, 190 insertions(+)
>
> diff --git a/tools/virtiofsd/passthrough_ll.c
> b/tools/virtiofsd/passthrough_ll.c
> index fbcc222860..fc79d5ac43 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -68,6 +68,13 @@
> #include "seccomp.h"
>
> #define HAVE_POSIX_FALLOCATE 1
> +
> +/* Keep track of inode posix locks for each owner. */
> +struct lo_inode_plock {
> + uint64_t lock_owner;
> + int fd; /* fd for OFD locks */
> +};
> +
> struct lo_map_elem {
> union {
> struct lo_inode *inode;
> @@ -96,6 +103,8 @@ struct lo_inode {
> struct lo_key key;
> uint64_t refcount; /* protected by lo->mutex */
> fuse_ino_t fuse_ino;
> + pthread_mutex_t plock_mutex;
> + GHashTable *posix_locks; /* protected by lo_inode->plock_mutex */
> };
>
> struct lo_cred {
> @@ -115,6 +124,7 @@ struct lo_data {
> int norace;
> int writeback;
> int flock;
> + int posix_lock;
> int xattr;
> const char *source;
> double timeout;
> @@ -138,6 +148,8 @@ static const struct fuse_opt lo_opts[] = {
> { "source=%s", offsetof(struct lo_data, source), 0 },
> { "flock", offsetof(struct lo_data, flock), 1 },
> { "no_flock", offsetof(struct lo_data, flock), 0 },
> + { "posix_lock", offsetof(struct lo_data, posix_lock), 1 },
> + { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
> { "xattr", offsetof(struct lo_data, xattr), 1 },
> { "no_xattr", offsetof(struct lo_data, xattr), 0 },
> { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
> @@ -486,6 +498,17 @@ static void lo_init(void *userdata, struct
> fuse_conn_info *conn)
> fuse_log(FUSE_LOG_DEBUG, "lo_init: activating flock locks\n");
> conn->want |= FUSE_CAP_FLOCK_LOCKS;
> }
> +
> + if (conn->capable & FUSE_CAP_POSIX_LOCKS) {
> + if (lo->posix_lock) {
> + fuse_log(FUSE_LOG_DEBUG, "lo_init: activating posix locks\n");
> + conn->want |= FUSE_CAP_POSIX_LOCKS;
> + } else {
> + fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling posix locks\n");
> + conn->want &= ~FUSE_CAP_POSIX_LOCKS;
> + }
> + }
> +
> if ((lo->cache == CACHE_NONE && !lo->readdirplus_set) ||
> lo->readdirplus_clear) {
> fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling readdirplus\n");
> @@ -773,6 +796,19 @@ static struct lo_inode *lo_find(struct lo_data *lo,
> struct stat *st)
> return p;
> }
>
> +/* value_destroy_func for posix_locks GHashTable */
> +static void posix_locks_value_destroy(gpointer data)
> +{
> + struct lo_inode_plock *plock = data;
> +
> + /*
> + * We had used open() for locks and had only one fd. So
> + * closing this fd should release all OFD locks.
> + */
> + close(plock->fd);
> + free(plock);
> +}
> +
> static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
> struct fuse_entry_param *e)
> {
> @@ -826,6 +862,9 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t
> parent, const char *name,
> newfd = -1;
> inode->key.ino = e->attr.st_ino;
> inode->key.dev = e->attr.st_dev;
> + pthread_mutex_init(&inode->plock_mutex, NULL);
> + inode->posix_locks = g_hash_table_new_full(
> + g_direct_hash, g_direct_equal, NULL, posix_locks_value_destroy);
>
> pthread_mutex_lock(&lo->mutex);
> inode->fuse_ino = lo_add_inode_mapping(req, inode);
> @@ -1192,6 +1231,11 @@ static void unref_inode_lolocked(struct lo_data *lo,
> struct lo_inode *inode,
> if (!inode->refcount) {
> lo_map_remove(&lo->ino_map, inode->fuse_ino);
> g_hash_table_remove(lo->inodes, &inode->key);
> + if (g_hash_table_size(inode->posix_locks)) {
> + fuse_log(FUSE_LOG_WARNING, "Hash table is not empty\n");
> + }
> + g_hash_table_destroy(inode->posix_locks);
> + pthread_mutex_destroy(&inode->plock_mutex);
> pthread_mutex_unlock(&lo->mutex);
> close(inode->fd);
> free(inode);
> @@ -1548,6 +1592,136 @@ out:
> }
> }
>
> +/* Should be called with inode->plock_mutex held */
> +static struct lo_inode_plock *lookup_create_plock_ctx(struct lo_data *lo,
> + struct lo_inode *inode,
> + uint64_t lock_owner,
> + pid_t pid, int *err)
> +{
> + struct lo_inode_plock *plock;
> + char procname[64];
> + int fd;
> +
> + plock =
> + g_hash_table_lookup(inode->posix_locks,
> GUINT_TO_POINTER(lock_owner));
> +
> + if (plock) {
> + return plock;
> + }
> +
> + plock = malloc(sizeof(struct lo_inode_plock));
> + if (!plock) {
> + *err = ENOMEM;
> + return NULL;
> + }
> +
> + /* Open another instance of file which can be used for ofd locks. */
> + sprintf(procname, "%i", inode->fd);
> +
> + /* TODO: What if file is not writable? */
> + fd = openat(lo->proc_self_fd, procname, O_RDWR);
> + if (fd == -1) {
> + *err = -errno;
I think the errno is positive value, so the minus isn't needed?
*err = errno;
Otherwise looks good to me.
Reviewed-by: Masayoshi Mizuma <m.miz...@jp.fujitsu.com>
Thanks,
Masa
> + free(plock);
> + return NULL;
> + }
> +
> + plock->lock_owner = lock_owner;
> + plock->fd = fd;
> + g_hash_table_insert(inode->posix_locks,
> GUINT_TO_POINTER(plock->lock_owner),
> + plock);
> + return plock;
> +}
> +
> +static void lo_getlk(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info
> *fi,
> + struct flock *lock)
> +{
> + struct lo_data *lo = lo_data(req);
> + struct lo_inode *inode;
> + struct lo_inode_plock *plock;
> + int ret, saverr = 0;
> +
> + fuse_log(FUSE_LOG_DEBUG,
> + "lo_getlk(ino=%" PRIu64 ", flags=%d)"
> + " owner=0x%lx, l_type=%d l_start=0x%lx"
> + " l_len=0x%lx\n",
> + ino, fi->flags, fi->lock_owner, lock->l_type, lock->l_start,
> + lock->l_len);
> +
> + inode = lo_inode(req, ino);
> + if (!inode) {
> + fuse_reply_err(req, EBADF);
> + return;
> + }
> +
> + pthread_mutex_lock(&inode->plock_mutex);
> + plock =
> + lookup_create_plock_ctx(lo, inode, fi->lock_owner, lock->l_pid,
> &ret);
> + if (!plock) {
> + pthread_mutex_unlock(&inode->plock_mutex);
> + fuse_reply_err(req, ret);
> + return;
> + }
> +
> + ret = fcntl(plock->fd, F_OFD_GETLK, lock);
> + if (ret == -1) {
> + saverr = errno;
> + }
> + pthread_mutex_unlock(&inode->plock_mutex);
> +
> + if (saverr) {
> + fuse_reply_err(req, saverr);
> + } else {
> + fuse_reply_lock(req, lock);
> + }
> +}
> +
> +static void lo_setlk(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info
> *fi,
> + struct flock *lock, int sleep)
> +{
> + struct lo_data *lo = lo_data(req);
> + struct lo_inode *inode;
> + struct lo_inode_plock *plock;
> + int ret, saverr = 0;
> +
> + fuse_log(FUSE_LOG_DEBUG,
> + "lo_setlk(ino=%" PRIu64 ", flags=%d)"
> + " cmd=%d pid=%d owner=0x%lx sleep=%d l_whence=%d"
> + " l_start=0x%lx l_len=0x%lx\n",
> + ino, fi->flags, lock->l_type, lock->l_pid, fi->lock_owner,
> sleep,
> + lock->l_whence, lock->l_start, lock->l_len);
> +
> + if (sleep) {
> + fuse_reply_err(req, EOPNOTSUPP);
> + return;
> + }
> +
> + inode = lo_inode(req, ino);
> + if (!inode) {
> + fuse_reply_err(req, EBADF);
> + return;
> + }
> +
> + pthread_mutex_lock(&inode->plock_mutex);
> + plock =
> + lookup_create_plock_ctx(lo, inode, fi->lock_owner, lock->l_pid,
> &ret);
> +
> + if (!plock) {
> + pthread_mutex_unlock(&inode->plock_mutex);
> + fuse_reply_err(req, ret);
> + return;
> + }
> +
> + /* TODO: Is it alright to modify flock? */
> + lock->l_pid = 0;
> + ret = fcntl(plock->fd, F_OFD_SETLK, lock);
> + if (ret == -1) {
> + saverr = errno;
> + }
> + pthread_mutex_unlock(&inode->plock_mutex);
> + fuse_reply_err(req, saverr);
> +}
> +
> static void lo_fsyncdir(fuse_req_t req, fuse_ino_t ino, int datasync,
> struct fuse_file_info *fi)
> {
> @@ -1649,6 +1823,19 @@ static void lo_flush(fuse_req_t req, fuse_ino_t ino,
> struct fuse_file_info *fi)
> {
> int res;
> (void)ino;
> + struct lo_inode *inode;
> +
> + inode = lo_inode(req, ino);
> + if (!inode) {
> + fuse_reply_err(req, EBADF);
> + return;
> + }
> +
> + /* An fd is going away. Cleanup associated posix locks */
> + pthread_mutex_lock(&inode->plock_mutex);
> + g_hash_table_remove(inode->posix_locks,
> GUINT_TO_POINTER(fi->lock_owner));
> + pthread_mutex_unlock(&inode->plock_mutex);
> +
> res = close(dup(lo_fi_fd(req, fi)));
> fuse_reply_err(req, res == -1 ? errno : 0);
> }
> @@ -2111,6 +2298,8 @@ static struct fuse_lowlevel_ops lo_oper = {
> .releasedir = lo_releasedir,
> .fsyncdir = lo_fsyncdir,
> .create = lo_create,
> + .getlk = lo_getlk,
> + .setlk = lo_setlk,
> .open = lo_open,
> .release = lo_release,
> .flush = lo_flush,
> @@ -2466,6 +2655,7 @@ int main(int argc, char *argv[])
> struct lo_data lo = {
> .debug = 0,
> .writeback = 0,
> + .posix_lock = 1,
> .proc_self_fd = -1,
> };
> struct lo_map_elem *root_elem;
> --
> 2.23.0
>
>
