passthrough_ll: add flock()

Conditionally enable flock() locking on underlying filesystem, based on the
flock/no_flock options.  Default is "no_flock", meaning locking will be
local to the fuse filesystem and won't be propagated to the filesystem
passed through.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/example/passthrough_ll.c b/example/passthrough_ll.c
index ad1185b2c98243221997e6f18cb0b700e0d8fe65..ba0f4afed664b8f04adfdddf7b2886673d7de5af 100644 (file)
--- a/example/passthrough_ll.c
+++ b/example/passthrough_ll.c
@@ -51,6 +51,7 @@
 #include <err.h>
 #include <inttypes.h>
 #include <pthread.h>
+#include <sys/file.h>
 
 /* We are re-using pointers to our `struct lo_inode` and `struct
    lo_dirp` elements as inodes. This means that we must be able to
@@ -79,6 +80,7 @@ struct lo_data {
        pthread_mutex_t mutex;
        int debug;
        int writeback;
+       int flock;
        const char *source;
        struct lo_inode root; /* protected by lo->mutex */
 };
@@ -90,6 +92,10 @@ static const struct fuse_opt lo_opts[] = {
          offsetof(struct lo_data, writeback), 0 },
        { "source=%s",
          offsetof(struct lo_data, source), 0 },
+       { "flock",
+         offsetof(struct lo_data, flock), 1 },
+       { "no_flock",
+         offsetof(struct lo_data, flock), 0 },
 
        FUSE_OPT_END
 };
@@ -131,6 +137,11 @@ static void lo_init(void *userdata,
                        fprintf(stderr, "lo_init: activating writeback\n");
                conn->want |= FUSE_CAP_WRITEBACK_CACHE;
        }
+       if (lo->flock && conn->capable & FUSE_CAP_FLOCK_LOCKS) {
+               if (lo->debug)
+                       fprintf(stderr, "lo_init: activating flock locks\n");
+               conn->want |= FUSE_CAP_FLOCK_LOCKS;
+       }
 }
 
 static void lo_getattr(fuse_req_t req, fuse_ino_t ino,
@@ -888,6 +899,17 @@ static void lo_fallocate(fuse_req_t req, fuse_ino_t ino, int mode,
        fuse_reply_err(req, err);
 }
 
+static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
+                    int op)
+{
+       int res;
+       (void) ino;
+
+       res = flock(fi->fh, op);
+
+       fuse_reply_err(req, res == -1 ? errno : 0);
+}
+
 static struct fuse_lowlevel_ops lo_oper = {
        .init           = lo_init,
        .lookup         = lo_lookup,
@@ -917,6 +939,7 @@ static struct fuse_lowlevel_ops lo_oper = {
        .write_buf      = lo_write_buf,
        .statfs         = lo_statfs,
        .fallocate      = lo_fallocate,
+       .flock          = lo_flock,
 };
 
 int main(int argc, char *argv[])