Hello
I have trouble figuring the whole story about how to cope with FUSE
directory filehandles in the NetBSD implementation.
libfuse makes a special use of filehandles exposed to filesystem for
OPENDIR, READDIR, FSYNCDIR, and RELEASEDIR. For that four operations,
the fh is a pointer to a struct fuse_dh, in which the fh field is
exposed to the filesystem. All other filesystem operations pass the fh
as is from kernel to filesystem back and forth.
That means that a fh obtained by OPENDIR should never be passed to
operations others than (READDIR, FSYNCDIR and RELEASEDIR). For instance,
when porting ltfs to NetBSD, I experienced that passing a fh obtained
from OPENDIR to SETATTR would crash.
glusterfs implementation differs from libfuse because it seems the
filesystem is always passed as is: there is nothing like libfuse struct
fuse_dh. It will therefore happily accept fh obtained by OPENDIR for any
operation, something that I do not expect to happen in libfuse based
filesystems.
My real concern is SETLK on directory. Here glusterfs really wants a fh
or it will report an error. The NetBSD implementation passes the fh it
got from OPENDIR, but I expect a libfuse based filesystem to crash in
such a situation. For now I did not find any libfuse-based filesystem
that implements locking, so I could not test that.
Could someone clarify this? What are the FUSE operations that should be
sent to filesystem on that kind of program?
int fd;
/* NetBSD calls FUSE LOOKUP and OPENDIR */
if ((fd = open("/gfs/tmp", O_RDONLY, 0)) == -1)
err(1, "open failed");
/* NetBSD calls FUSE SETLKW */
if (flock(fd, LOCK_EX) == -1)
err(1, "flock failed");
--
Emmanuel Dreyfus
http://hcpnet.free.fr/pubz
manu@xxxxxxxxxx
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